OKPARA, MORGAN OBINNA DEPARTMENT OF ANIMAL SCIENCE, FACULTY OF AGRICULTURE NWANKWO ONYEKACHI.A.

Transcription

1 1 OKPARA, MORGAN OBINNA LAYING AND PHYSICAL CHARACTERISTICS OF SHAVER BROWN AND NERA BLACK HENS IN HOT HUMID ENVIRONMENT DEPARTMENT OF ANIMAL SCIENCE, FACULTY OF AGRICULTURE NWANKWO ONYEKACHI.A.

2 2 TITLE PAGE LAYING AND PHYSICAL CHARACTERISTICS OF SHAVER BROWN AND NERA BLACK HENS IN HOT HUMID ENVIRONMENT BY OKPARA, MORGAN OBINNA PG/MSc/09/5054 A THESIS SUBMITTED TO THE DEPARTMENT OF ANIMAL SCIENCE, FACULTY OF AGRICULTURE IN FUFILLMENT OF THE REQUIREMENT FOR THE AWARD OF MASTER OF SCIENCE DEGREE OF THE UNIVERSITY OF NIGERIA, NSUKKA. AUGUST, 2012

3 3 CERTIFICATION This is to certify that the work embodied in this project report for the degree of Master of Science of the University of Nigeria, Nsukka was carried out by Mr. Okpara, Morgan Obinna at the Poultry Farm of the Animal Science Department of this University. The work presented herein is original and has not been submitted in part or full for any other degree of this or any other university.. DR. A.O. ANI Project Supervisor Date.. DR. A.E. ONYIMONYI (Esq.) JP Head of Department... Date.. EXTERNAL EXAMINER Date

4 4 DEDICATION This work is dedicated to my beloved family and to God Almighty, our Father in heaven.

5 5 ACKNOWLEDGEMENT I wish to sincerely record in the pages of history the unalloyed cooperation I received from my research supervisor Dr. A.O. Ani. He sponsored the research and provided a fertile ground for the successful completion of the work. I am grateful to the Head of Animal Science Department, Dr. A.E. Onyimonyi. I would also like to express my profound gratitude to Professor A.G. Ezekwe, Professor S.O.C. Ugwu, Dr. N.S. Machebe, Dr. (Mrs) H.M. Ndofor- Foleng, Miss N.C.P. Uberu and Mr. C.O. Osita. I thank Dr. C.C. Ogbu for his assistance in the statistical analysis of the data and for his invaluable contribution during and after the research work. I thank Dr. E.C. Akanno of the Center for Genetic improvement of Livestock, Department of Animal and Poultry Science, University of Guelph, Ontario Canada, for his contribution towards my academic and mental emancipation during the study. The Farm Manager, Mr. S.C. Chime provided a very conducive environment on the farm for my study to sail through. My thanks are due to Mr. Mark Nnamani for assisting and guiding me during the study. Finally, I thank the Almighty GOD for His grace and blessings without which this programme would have been impossible. To Him I say Thus Far the Lord has helped me. Many thanks to all and may GOD bless all of you.

6 6 TABLE OF CONTENTS Title Page i Certification ii Dedication iii Acknowledgement iv Table of contents v List of Tables viii List of figures ix Abstract x CHAPTER ONE Introduction 1.1 Background Statement of problem Objectives of study Justification of study CHAPTER TWO Literature Review 2.1 Classification of chickens Exotic breed of laying birds The reproductive system of the laying hen The Ovary The Oviduct Ovulation Egg formation Oviposition Sequential laying Sequence/Clutch length Pause days Ovpiosition time Time interval between successive eggs and lag Total egg production Rate/Intensity of lay Egg quality Egg weight Physical characteristics of hens Climatic condition

7 CHAPTER THREE Materials and Methods 3.1 Location and duration of study Experimental birds Management of hens Parameters measured Oviposition time Total egg production Clucth/sequence length Pause days Egg weight Egg quality Average daily feed intake Percentage egg production Physical characteristics Temperature Experimental design Statistical analysis CHAPTER FOUR Results and discussion 4.1 Results Egg laying characteristics of Shaver brown hens Oviposition time Total egg production Clutch length Pause days Egg weight Intensity/ Rate of lay Hen housed egg production (HHEP) Hen day egg production (HDEP) Egg laying characteristics of Nera black hens Oviposition time Total egg production Clutch length Pause days Egg weight Intensity/ Rate of lay Hen housed egg production (HHEP) Hen day egg production (HDEP)

8 Effect of temperature on performance of Shaver brown and Nera black hens Interaction of strain and temperature on Performance Physical characteristics of hens Comparison between strains for performance and egg quality traits Discussion Climatic data for Nsukka Egg laying characteristics of Shaver brown and Nera black hens Oviposition time Total egg production and other egg productionindices Clutch length Pause days Egg weight Effect of temperature on performance of Shaver brown and Nera black hens Interaction of strain and temperature on performance Physical characteristics Comparison between strains for performance and egg quality traits CHAPTER FIVE Summary and conclusion References Appendices

9 9 LIST OF TABLES Table 1: Times of egg laying in hens Table 2: Mean weekly environmental temperatures and relative humidity during the period of the study Table 3: Frequency distribution of egg production of Shaver brown hens.. 30 Table 4: Frequency distribution of mean clutch length of Shaver brown hens 32 Table 5: Effect of egg position and clutch size on egg weight of Shaver brown hens 33 Table 6: Frequency distribution of pause days of Shaver brown hens 34 Table : Effect of oviposition interval on egg weight of Shaver brown hens.. 36 Table 8: Frequency distribution of egg laying of Shaver brown and Nera black hens during the day Table 9: Classification of experimental hens Table 10: Frequency distribution of egg production of Nera black hens.. 42 Table 11: Frequency distribution of mean clutch length of Nera black hens.. 44 Table 12: Effect of egg position and clutch size on egg weight of Nera black hens 45 Table 13: Frequency distribution of pause days of Nera black hens Table 14: Effect of oviposition interval on egg weight of Nera black hens.. 49 Table 15: Comparison between strains for performance and egg quality traits 52 Table 16: Effect of temperature on performance of Shaver brown hens.. 63 Table 1: Effect of temperature on performance of Nera black hens 54 Table 18: Effect of interaction of strain and temperature on performance 56

10 10 LIST OF FIGURES Figure 1: Figure 2: Figure 3: Frequency distribution of egg laying of Shaver brown hens at different oviposition intervals during the day Frequency distribution of egg laying of Nera black hens at different oviposition intervals during the day Average weekly temperatures (Indoor and Outdoor) and relative humidity of the study area

11 11 ABSTRACT A total of one hundred and fifty Shaver brown and Nera black hens in their 14 th week of lay were used in a study conducted to determine the laying and physical characteristics of Shaver brown and Nera black hens under humid tropical environment. Hens were housed individually in separate cages. The hens were supplied water ad libitum and fed layers mash containing 16.5% crude protein and 2650 kcal/kg of metabolizable energy for 10 weeks. The hens were also divided into three classes based on their laying performance as follows: good layers, intermediate layers and poor layers and their physical conditions appraised. Temperature readings were taken 3-hourly at time intervals of 0900h, 1200h, 1500h, and 1800h using a standard air thermometer and the mean daily temperatures noted. The climatic data taken during the period of the experiment showed that the study area had the natural day-length of 13 to 14 hours; mean maximum weekly indoor and outdoor temperatures of C to C and C to C, respectively; mean minimum weekly indoor and outdoor temperatures of C to C and C to C, respectively; relative humidity of 3.1% to 6.6% and mean total monthly rainfall of 81.33mm. Results showed that the peak of lay was between 000h and 0800h and declined gradually throughout late afternoon hours until no egg was laid between 100h and 1800h. For Shaver brown hens, about 86.24% and 13.6% of the eggs were laid in the morning and afternoon hours respectively, while 88.5% and 11.25% of the eggs were laid in the morning and afternoon hours respectively, for Nera black hens. Mean egg weight of 0.05g±1.0 and 0.10g±0.92 for eggs laid between 0600h and 000h for Shaver brown and Nera black hens, respectively were the heaviest (P<0.05) of all the mean egg weights observed in all oviposition intervals. For Shaver brown hens, first eggs laid in a clutch were significantly greater (P<0.05) than subsequent eggs laid in a clutch, while the first eggs in a clutch for Nera black were greater than other eggs in the clutch, although the differences were not significant (P>0.05). Hens with the longest clutches and shortest number of pause days produced the greatest number of eggs. The total number of pause days observed were 1410 and 1329 for Shaver brown and Nera black hens, respectively. Observations made on physical characteristics of the hens revealed that good layers had smooth combs and wattles, moist and enlarged vents with flexible pubic bone, soft abdomen and worn out feathers. Intermediate layers had similar features with good layers except that the eye rings, beaks and shanks were slightly bleached. Poor layers had dry combs and wattles, tight and hard abdomen and closed pubic bones. The Effect of ambient temperature on performance parameters showed that for Shaver brown hens, hen day egg production, average daily feed intake, egg shell weight, egg shape index, albumin height, yolk height, yolk height and Haugh units were significantly reduced (P<0.05) with increasing temperatures. All performance parameters measured for Nera black hens were significantly reduced (P<0.05) with increasing temperatures. Likewise, there was significant interaction (P<0.05) of strain and temperature on average daily feed intake and yolk height. The results of the present study indicate that although heat stress had effect on performance, Shaver brown and Nera black hens are adapted to humid tropical environment and can lay 86.24% and 88.5% eggs, respectively in the morning hours, with overall production rate of 66.43% and 68.36% respectively, for Shaver brown and Nera black hens.

12 12 CHAPTER ONE INTRODUCTION 1.1 BACKGROUND OF THE STUDY The growth in global demand for poultry products is tremendous as the market for these products is growing very fast. Poultry is probably the fastest route to achieve any appreciable improvement in the nutritional standard of the populace because of its short generation interval, quick turnover rate and relatively low capital investment (Smith, 2001; Ani and Okeke, 2011). Gueye (2000) asserted that 85% of rural households in Sub-Saharan Africa keep chickens or other types of poultry. Poultry are equally important to other smallholders in Asia, Latin America and other parts of the world (Mallia, 1999; FAO, 2003; Islam and Jabbar, 2005; Kyrsgarrd, 200). Increased egg production is one sure way of achieving the target of providing quality animal protein at a minimum cost to the consumers (Oluyemi and Roberts, 2000). Advances in genetic selection make today s commercial layers quite different from those of years ago. Body weight is less, age at housing is earlier, total egg number has increased, egg mass is greater and feed conversion has improved considerably (Miles and Jacob, 2000; Minivielle et al., 2006). Total egg production is affected both by the physical and laying characteristics of the hen. Laying characteristics of hens have been assessed by evaluating such indices as rate of lay, oviposition time, clutch/sequence length, number of pause days, lag time, hen housed egg production (HHEP), and hen day egg production (HDEP). Physical characteristics of laying hens on the other hand, consist of those features that can be seen easily on their body such as condition of combs, wattles, eyes, beaks, pubic bones, abdomen and vent. They are used to determine whether a hen is laying or not (Gillespie, 199; Reddy et al., 2004; Daghir, 2008; Ani and Nnamani, 2011). Apart from egg laying characteristics which are cyclic and genetically influenced, egg production is affected by nutrition, variations in temperature, light intensity, day- length, relative humidity, disease and level of management. Hens lay sequentially (Wolford et al., 199; Spradbrow, 199; Gillespie, 199; Miles and Jacob, 2000; Smith, 2003; Van Der Molen, 2004; Jakowski and Kaufman, 2004; Reddy et al., 2004; Clauer, 2005; Poultryhelp, 2005). Hens vary in their laying habits. The number of eggs in a sequence varies between one to forty and

13 13 occasionally even more. Even if flock uniformity is high, not all hens in the flock lay at the same rate. While some hens may be laying at a very high rate of production, others may not even be laying at all (Miles and Jacob, 2000; Ani and Nnamani, 2011). The longer the clutch length, the more eggs a hen lays in a given period (Etches, 1996; Reddy et al., 2004; Jakowski and Kaufman, 2004 ). According to Butcher and Miles (2000), the exotic hen is capable of laying eggs per annum, each weighing about 58 grammes under tropical condition. The success of birds as a class is largely due to the fact that they have evolved physiological mechanisms that cause them to lay eggs at a time of season, when such factors as weather and food supply are optimal (Koelkebeck, 2001). According to Daghir (2008), humid environment is very suitable for poultry production. Although all livestock are subject to environmental stress in the tropics, poultry appears to be less susceptible than mammals. One reason may be that with higher body temperature than mammals, birds spend less production energy than other livestock in homeostatic regulations (adjustments). Under suitable tropical housing and management practices, poultry performance in the tropics has in many instances compared favourably with the performance standards of the same breeds reared in temperate environments. In acclimatizing to hot climate, animals normally make physiological adjustments (Hahn et al., 2003). As the seasons change, two major kinds of changes occur in the environments: changes in temperature and changes in length of daylight. Hormones enable the animal to respond physiologically to these seasonal changes (Hahn et al., 2003). The pineal body in chicken s brain controls its body temperature and its sense of environmental temperature. Normal body temperature lies between C and C being at its highest around 1600h and its lowest around midnight (Hahn et al., 2003; Daghir, 2008). Egg production is intimately linked with daylight hours. The light rays received through the eyes affect the pituitary gland, which releases hormone into the bloodstream thus stimulating the ovaries into action. As the day-length hours shorten, egg production correspondingly decreases. By midwinter in temperate environment, it is usually nonexistent. To ensure continued production, hens in temperate regions must have a minimum of 16 hours of light per day. As the hours of natural day-length decreases, artificial lighting can be gradually introduced for longer periods to make up the difference (Clauer, 2005; Hanson, 2005). Environmental condition of the area in which the hens are laying affects their sequence length. 1.2 STATEMENT OF PROBLEM

14 14 Advances in genetic selection make today s commercial layers quite different from those of years ago. Body weight is less, age at housing is earlier, total egg number has increased, egg mass is greater and feed conversion ratio has improved considerably (Miles and Jacob, 2000; Minivielle et al., 2006). Although management and feeding practices are the key determining factors of egg production, the breed of laying hen affects egg production. The rate of adaptation and quality of egg production of different exotic breeds of hen vary when exposed to a variety of climate and environments. According to Miles and Jacob (2000), some hens may be laying at a very high production rate while others may not be laying at all. The climatic conditions of Nsukka in particular and those of South Eastern Nigeria in general depict a typical tropical climate (Egbunike, 2002). Findings by Okonkwo and Akubuo (200) have revealed an average annual minimum and maximum temperature ranges of 22 0 C C and 33 0 C -3 o C, respectively. These ranges appear to fall outside the zone of thermo neutrality of laying hens which is 18 0 C - 22 o C as recently defined by Imik et al. (2009). As such, adverse effects of heat stress are suspected to clasp egg production parameters of laying hens in the tropics. Most African diets (including Nigerian) are deficient in animal protein which results in poor and stunted growth as well as increase in spread of diseases and consequently death (Apantaku et al., 2003). Apart from low egg production and poor performing breeds, other problems associated with poultry production in Nigeria are diseases and pests, poor weight gain/feed conversion, feeding and management problems and lack of capital (Eekeren et al.,1995; Isiaka 1998; Apantaku et al., 2003). Moreover, the environment to which poultry birds are exposed affect performance of the birds (Abeke et al., 1998; Isiaka, 1998). The optimal laying temperature is between C (Imik et al., 2009), while a relative humidity above 5 percent will cause a reduction in egg laying (Hahn et al., 2003). When the temperature rises above 28 0 C, the production and quality of eggs decrease as seasonal temperature increase can reduce egg production by 10 percent (Oluyemi and Roberts, 2000; Smith, 2001). Lastly, egg production clearly requires planning for costs as well as for profit generation and for meeting market demand without which a commercial egg production venture may suffer serious setbacks. 1.3 OBJECTIVES OF THE STUDY The study was aimed at evaluating the laying and physical characteristics of Shaver brown and Nera black hens in hot humid environment.

15 15 The specific objectives of the study were as follows: 1. To determine the oviposition time, and clutch size of Shaver brown and Nera black hens in hot humid environment. 2. To determine position of eggs in a clutch and their relationship to egg weight in hot humid environment. 3. To determine the comparative performance of Shaver brown and Nera black hens in hot humid environment. 4. To establish the relationship between performance and environmental temperature.

16 JUSTIFICATION OF THE STUDY With the increasing importation and utilization of exotic hybrids in commercial egg production in Nigeria, it is imperative to study the egg laying characteristics of these birds under the local condition. Information obtained would help assess the level of adaptability of Shaver brown and Nera black hens to humid tropical environment. Knowledge of laying distribution is necessary in recommending frequency of egg collection to management and poultry farmers. More eggs crack if they are not collected at frequent intervals. When buying birds at the point of lay, a careful observation of the physical features will enable a farmer to choose or buy only birds that have the potential of good layers. The ultimate objective of the poultry farmer is the realization of profit, and in order to do this, he must understand the interactions between body conformation, body function and environment. In the tropical context, environment (mainly temperature and humidity) plays a very important role as it imposes extra stress in the ability of the chicken to grow and function optimally. Solutions to the problems bedeviling poultry production in Nigeria depend mostly on research and this requires effective research approach to make meaningful impact on poultry productivity. At this juncture therefore, conducting research on the laying and physical characteristics of two strains of exotic breed of hen has become imperative so as to obtain information that would help in assessing their level of adaptability to humid tropical environment and also, to establish proven production basis which will determine their suitability and adaptability for massive commercial and small scale egg productions.

17 1 CHAPTER TWO LITERATURE REVIEW 2.1 CLASSIFICATION OF CHICKEN There are approximately 15 varieties of chickens grouped into 12 classes and approximately 60 breeds (Daghir, 2008; Obioha, 1992). A class is a group of breeds originating in the same geographical area. The names themselves Asiatic, American, Mediterranean, indicate the region where the breeds originated. Breed means a group which possesses a given set of physical features, such as body shape, skin colour, carriage or station, and number of toes. Variety is a category of breed and is based on feather colour, comb or presence of beard or muff. Thus the Plymouth Rock may be Barred, White, Buff or one of other several colours. The Rhode Island Red may be either a single or rose comb. In each case, the body shape and physical features should be identical. Breed and Variety tell little about the qualities of good producing stock. Strain however, does. A strain is a group of breeding population within a variety or cross that has been bred and developed to possess certain desirable characteristics. Many commercial strains exist such as Babcock, Dekalb, Hyline, and Shaver that have been bred for specific purposes mainly for egg production (Daghir, 2008). 2.2 Exotic breeds of laying birds The first exotic chickens to be imported into Nigeria probably came around the early fifties but their full commercial potential was not realized until the late fifties after their successful adaptation and performance. The earliest breeds which were imported then included Rhode Island Red, Barred Plymouth Rock, New Hampshire and White Leghorn. Although these came as straight breeds, their ancestors were composite of different blood lines which had been developed in the native or adapted countries from several generations of crosses. Subsequent importation included several hybrids developed from inbred lines and cross-breeding processes aimed at developing strains for growth or egg production. The more common hybrids in tropical Africa today according to Daghir (2008) and Obioha (1992) include: A UNITED STATES 1 Hyline / B 11

18 18 2 Hyline Harco (Obioha, 1992) 4 Babcock Babcock 380 B UNITED KINGDOM 1. Rangers/Sykes 2. Thornbers Thornbers 909 C FRANCE 1. Warren Sex-Linked D CANADA 1. Shaver Star Cross 2. Shaver Star Cross 444T 3. Brown Eggs Shaver 59 ( intensive and alternative) E ISRAEL 1 Yarkon 2 Yaafa 3 Kabir (Obioha, 1992). These Layers have variable performance capabilities, and because of the rapid genetic turnover by breeders, new strains appear in the market practically everyday (Obioha, 1992). The best chicken breeds include commercial white-type hybrids, which produce white-shelled eggs and are the most economical feed to egg converter. Commercial red plumage coloured birds (e.g. Rhode Island Reds, New Hampshire) or sex linked hybrids produce large, brown-shelled eggs. These birds have meaty carcasses and produce a good supply of eggs. The hybrids that lay more eggs tend to be docile than those that lay white eggs. All poultry breeds lay eggs, but they are not equally efficient (Clauer, 2005). 2.3 The Reproductive System Of Hen There are two main parts of the reproductive system of hen: the ovary and the oviduct. Only the left ovary and the oviduct develop in a bird (Imai, 2003; Pineda and Dooley, 2003). Pesek (1999) noted that right ovary regressed probably as an adaptive mechanism to reduce weight necessary to aid flight. The ovary is attached underneath the backbone, about midway between the neck and tail. When a female chick is hatched, the ovary begins to

19 19 convert ova to egg yolks at the appropriate time. For this to happen, the pullet (young female chicken) must have reached the correct stage of physical development. Then if the appropriate light stimulation is present, hormones cause ova to develop in sequence to yolks. Yolks are released from the ovary into the body cavity when they reach the correct size (Smith, 1998). The ovulated yolk is retrieved by the infindubulum, the first part of the oviduct. Completion of the egg will require approximately 24 or more hours. Passage through the magnum, isthmus and uterus of the oviduct results in the addition of egg white, shell membrane and shell. Soon after an egg is laid (oviposition), the process starts again. Another yolk is released, and the next egg formed. Some chicken and ducks can lay an egg everyday for more than 300 consecutive days. Other birds, may lay only a few eggs, yet others may lay only every second day (Smith, 1998) The Ovary The ovary is located in the body (abdominal cavity), ventral to the aorta, posterior to the vena cava, and cranial to the kidney. At hatch, the ovary of a chick contains many thousands of follicles (oocytes) each of which has the potential to become the yolk of an egg. Given the opportunity, hens from highly selected strains may lay eggs during their life expectancy of -10 years (Zakaria, 2001; Etches, 1996). At the time of sexual maturity, (18 to 20 weeks of age), 4 to 6 oocytes increase in diameter and the follicular hierarchy begins to be established. During subsequent ovulation cycle, only the largest follicle will ovulate followed in successive days by the 2 nd, 3 rd, 4 th largest ones, each of which enlarges to assume the size of the ovulated predecessor (Etches, 1996). Cassey et al. (2004) noted that in hens, the ovarian follicles committed to ovulation are arranged in an orderly follicular hierarchy. The ovary of the mature hen contains a hierarchy of yellow yolky follicles and several thousand smaller follicles from which the large yolk follicles are recruited. Esminger (1991) observed that at the time of hatching, the female chick s left ovary contains approximately 3,600 to 4,000 tiny ova from which fully-sized yolks may develop when the hen matures. Austic and Nesheim (1990) reported that the ovary of a hen contains 5 to 6 large yellow developing yolks (follicles) and a large number of small large number of small white follicles which represent immature underdeveloped yolks. Each of the follicles contains an oocyte and it is attached to the ovary by a slender stalk called the stigma.

20 20 In the hierachy, Zakaria (2001) explained that sizes range from microscopic to size of the follicle that is destined to ovulate next. This follicle weighs about 15g; the next member of this size hierarchy weighs about 12g and the third about 10g. Below these sizes, there may be several follicles less than 1mg, and eventually down to a multitude of follicles of microscopic size. Only a follicle reaches ovulatory size each day. After ovulation of the longest follicle, the smaller follicles move up one notch size and re-establish the hierarchy as it existed just before ovulation. Zakaria (2001) also threw some light into mechanisms involved in establishing and maintaining follicular size hierarchy for prolonged period of time. He indicated that the hen must be able to distribute hypophyseal hormones circulation in the bloodstream in such a way that some follicles get a larger quantity of formed ones, so that they can grow faster and become large, and other follicles receive a small quantity. The net result of the rationing system is that they establish and maintain a follicular size hierarchy in which the position of the individual follicle is determined by the amount of hormone stimulating it. According to Etches (1996), most follicles therefore never ovulate, but it would appear that most participate in the production of steroid hormones from the ovary. At an early stage of follicular development that has not yet been identified, the small ovarian follicles begin to produce oestrogen. As sexual maturity approaches, the production of these hormones stimulates deposition of calcium in the medullary bone, development of yolk precursors by the liver, development of the reproductive tract and development of other secondary characteristics. These secondary characteristics include the comb, spurs, softening and spreading of pubic bones and deposition of pigments in the beak, the shanks and around the vent. Each of these secondary sexual characteristics can be, and is used to indicate both the onset and maintenance of lay The Oviduct An intimate anatomic relationship exists between the ovary and oviduct. The term oviduct is used to describe the complete tubular genitalia of the hen. It is large, convoluted tube occupying a large part of the abdominal cavity. It weighs about 60g in sexually mature chicken and extends from ovary to cloaca (Zakaria, 2001). It has good blood supply and muscular walls that are in nearly continuous movement during the time egg formation is taking place. The oviduct is about 50-5cm long (Zakaria, 2001; Esminger, 1991). Austin and Neshein (1990) noted that large variations occur in the size of the oviduct depending on the

21 21 stage of the reproductive cycle. The size changes are dependent upon the levels of the gonadtrophic hormones being secreted by anterior pituitary and oestrogen production in the ovary. The oviduct is divided into five clearly defined functional regions. Starting from the ovarian end, they are infundubulum, the magnum, the isthmus, uterus or the shell gland and vagina. І The infundubulum (the funnel) picks up the ovulated egg. It is also the site of fertilization. ІІ The magnum is where the albumen is secreted ІІІ The isthmus is where the shell membrane is secreted ІV The uterus secretes the shell, adds fluid to the egg (plumping) and stratifies the albumen V The vagina stores sperm and aids in the expulsion of the full formed egg Ovulation Ovulation is the release of the ovum from the ovarian follicles. It occurs through the rupture of the follicles along streak called stigma (a specialized region of the follicle wall) (Zakaria, 2001; Etches, 1996). Ovulatory Cycle The ovulatory cycle of hens is hormonally controlled by the subtle interaction of the gonadotropins and ovarian steroid hormones. The ovulatory cycle of hens is defined as the interval between consecutive ovulations. By subtraction of the consecutive times of ovulation, the length of the ovulatory cycle reveals that they vary from a minimum of hours to a maximum of hours within sequences of 2 to 6 eggs (Etches, 1996). The last ovulation of a sequence is separated by approximately 40 hours from the first ovulation of the next sequence because one full day elapses during which ovulation does not occur. The minimum length of the ovulatory cycle of hens maintained under 14 hours of light (14L: 10D) is therefore, 24 hours. This minimum is achieved by only a small proportion of hens when the rate of lay is very high during peak production. In practice, it is technically difficult to establish times of ovulation directly. Ovulation of the second and all subsequent ova in a sequence however occurs minutes after oviposition of the preceding egg and this relationship is used to establish the time of ovulation (Etches, 1996).

22 22 An ovulatory cycle extends from the oviposition of the first egg of the next clutch. Generally, the laying cycle of hen is governed by the lightning schedule. If the hen is given hours of light per day, the first egg of the clutch is usually laid early in the morning. As a rule, ovulation occurs shortly after oviposition (5-60 mins), and approximately 26 hours are required before newly ovulated ovum acquires its integuments and is ready to be laid as an egg (Zakaria, 2001). Because ovulation does not occur until after oviposition and because the completion of the formation of the eggs requires at least 24 hours, each succeeding egg in the clutch is laid later than the first egg of the clutch, the last egg of the clutch is laid early in the afternoon. The hens with the longest clutches ovulate very shortly after oviposition and takes less time (some only 24 hours) to complete the egg (Etches, 1996). Under ordinary daylight conditions, ovulation occurs in the morning hours and almost never after 3.00 pm. The ovulated egg spends about 3.5 hours in the magnum portion of the oviduct where it acquires the albumen coat, 1.25 hours in the isthmus where the soft shell membranes are formed and 21 hours in the uterus where the calciferous shell is applied. A total of hours is therefore required for egg formation. The succeeding egg is ovulated minutes after the egg is oviposited (Jakowski and Kaufman, 2004). Hormonal Control of Ovulation The mechanisms controlling ovulation luteinizing hormone (LH) release, oviposition and the eggs rate of travel through the oviduct have been worked out in part, but some details remain unknown (Jakowski and Kaufman, 2004). Zakaria (2001) reported that the interval between ovulation of two successive eggs is usually 24 to 28 hours. But the important questions are, how is ovulation triggered? Why would a hen ovulate consecutively for several days and then skip a day? And how are the intervals between ovulations kept at the stated hours? According to Pineda and Dooley (2003), ovulation is brought about by the release of the ovulatory (Luteinizing ) hormone from the pituitary gland governed by a timing mechanism that is influenced by day length and the ovarian hormones. Pesek (1999) suggested that follicular growth and maturation in the hen depends on a constant output of follicle stimulating hormone (FSH) by the pituitary with based levels of luteinizing hormone (LH). At the specific times during the ovulatory cycle, there is an increased release of the LH which causes ovulation. An excitation hormone acts via the neural pathway (hypolothamus) to trigger the LH release. The threshold for the action of the

23 23 excitation hormone undergoes diurnal fluctuations. If the level of the excitation hormone reaches the threshold level necessary for LH release, the gonadotropin is released and ovulation follows. Since successive follicles mature at intervals of 24 hours plus a lag (at a later time each day), the increase in excitation hormone will follow a similar time course. As a result, the neural components would be stimulated at a progressively later time each day until eventually the peak level of the excitation hormone would occur at a time when the neural threshold would also be elevated. Because the given concentration of the excitation hormone was not sufficiently high to trigger the LH release, no ovulation would occur on that day and there would be no pause in the ovulatory cycle. Luteinizing hormone would be stimulated again the next day when the neural threshold for LH had decreased and ovulation would again resume. The excitation hormone is generally assumed to be progesterone. Zakaria (2001) indicated that it is very challenging to disentangle the hypothalamohypophyseal-ovarian relationship in the hen because all the changes are compressed into hours ovulating cycle. Jakowski and Kaufman (2004) explained that there is experimental evidence to show that the oviductal nervous system participates in signaling instructions to the pituitary gland, and that instruction not to release amounts of gonadotropic hormones adequate for ovulation may originate in the oviduct. Such signaling systems are frequently involved in phenomena controlled by hormones and that they are part of the neuroendocrine feedback mechanisms. In the hen, it seems to operate as follows: If a yolk is present in the magnum, a nerve conducted signal goes from the oviduct preventing new ovulations from occurring. Thus, no ovulatory dose of gonadotropic hormones would be released until the oviduct is ready for the next egg. Soon after the egg leaves the oviduct and enters the uterus (shell gland), these signals stop and the pituitary gland now releases the amount of gonadotropic hormones needed to accomplish ovulation, some 8 to 12 hours later that is, after the hard shelled egg is laid. As soon as the next ovum enters the oviduct, the ovulation blocking signal action again becomes effective and holds further ovulation in check. According to Hanson (2005), day length, temperature and humidity influence reproduction. In areas where the climate is stable and day length is constant, rainfall may trigger reproductive behaviour. Biological clocks known as Circannual Cycles control the release of the hormones that regulate reproduction, metabolism and behaviour. Light stimulates a part of the brain- the hypothalamus, to produce releasing factors. These releasing factors stimulate the anterior pituitary to secrete hormones known as gonadotropins.

24 24 Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH) are two gonadotropins produced by the anterior pituitary which affect the ovaries. FSH and, to a lesser degree, LH, are responsible for normal ovarian follicular growth. As the follicle increases in size, they produce increasing amounts of oestrogen and progesterone. Progesterone acts on LH which triggers ovulation. Once ovulation occurs, progesterone secretion increases rapidly Egg Formation According to Daghir (2008) and Obioha (1992), the egg is formed from an interaction of hormonal, structural and nutritional process. The yolk forms in the ovary, its protein being synthesized in and transported from the kidney and liver. The fat in the yolk is mainly dietary or demobilized from fat deposits. Both fat and protein are transported by the blood. The yolk material contains 35% fat, 1% protein and 50% water (Latour et al., 2003). According to Latour et al. (2003), the formation of the egg involves the transport of large quantities of material across numerous biological membranes, and the formation of many new substances, particularly specific proteins and lipids. The size and the composition of the egg are affected by numerous genetic environmental and physiologic factors. The passage of the egg down the oviduct is made possible by peristalsis, probably aided to some extent by cilliary action. According to BFREPA (2003), the original purpose of an egg was a protective development chamber for an embryo to eventually produce a day old chick. Genetics and nutrition have led to current layer strains, aimed more specifically at producing eggs for human consumption. 2.4 Oviposition Oviposition (laying of the hen s egg) is the expulsion of the fully calcified egg from the reproductive tract. It requires coordination of the muscular activity of the shell gland with the behavioural repertoire during which the hen investigates and selects a nest. Except for the last oviposition of a sequence, expulsion of the egg is initiated by the pre-ovulatory endocrine events that are associated with ovulation (Zakaria, 2001; Novo et al., 199; Etches, 1996). Oviposition is under both hormonal and neural control. The time of oviposition may be determined by ovulation via changes in the ruptured follicle. The post ovulatory (ruptured) follicle is necessary for oviposition because its removal delays oviposition (Novo et al., 199). It is not known precisely how oviposition is initiated, but both hormonal and neural mechanisms are involved (Reddy et al., 2004). Whatever the stimulus, contraction of the

25 25 uterine musculature forces the egg into the vaginal region. This may be under neural control, for stimulation of the central/nervous system can affect it, but hormones are also involved. Oviposition may also be regulated by the balance of the circulating steroid sex hormones. Oluyemi and Roberts (2000) observed that progesterone is involved in ovulation. Progesterone acts on the hormone-releasing factors in the hypothalamus to cause the release for LH from the anterior pituitary which causes release of yolk from the ovary (Imai, 2003). Johnson (1990) noted that in birds, ovulation and oviposition are processes controlled by LH and sex steroids, including progesterone. Surges of LH and progesterone have been observed between 4 and hours before ovulation in laying chicken, quails and ducks and 2-8 hours before ovulation in laying turkey hens Sequential Laying Chickens lay eggs in sequence or clutches. Normally the egg laying pattern follows certain rules. The first rule is that egg of a sequence is laid within 1-2 hours after daylight. Secondly, each egg in a sequence is laid later in the day. Thirdly, the last egg of a sequence is typically laid about 9-10 hours after daylight as shown in Table 1.

26 26 Table 1: Sequence of egg laying in hens after daylight Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day (Robinson and Renema, 1999a; Etches, 1996).

27 2 Table 1 shows times of successive ovipositions under 14L:10D photoperiod. The last ovulation of a sequence is followed by a day during which ovulation does not occur. According to Etches (1996), birds can lay eggs for period of about 12 months without stopping. Birds can lay up to 358 eggs in one year Clutch/Sequence Length The number of eggs laid by a hen on consecutive days before a pause is known as a clutch. A clutch is terminated a day an egg is not laid. A prolific hen lays five or more eggs in a clutch, the clutches being separated by not more than a day of rest (pause). Clutches of eggs are not uncommon and many hens have laid 365 eggs in a year (Butcher and Miles, 2000). A hen laying 20, 30, or more eggs in one clutch accomplishes this by two means. Shortening the interval between oviposition and ovulation to a few minutes (hens with very long clutches ovulate even before the egg is laid) and/or shortening the time the egg spends in the shell gland to as little as 18hours (Jakowski and Kaufman, 2004). According to Robinson and Renema (1999b), the tendency of some hens to lay short clutches (1 to 2 eggs) and others to lay longer clutches (6 and up to 100 or more) is a heritable characteristic. Sequence length varies within birds of the same species depending on the cross and probably, environmental conditions of the area in which the birds are laying. Robinson and Renema (1999b), working on broiler breeder hens, observed that hens have slow rate of follicular maturation (26-28hours or more) lay shorter (2-3 days) sequence. On the other hand, hens that lay very long sequence typically have maturation rates of 24 hours or less. Sequence length changes throughout the egg production year with the longest sequence seen at the time of peak production at about weeks of age. All hens lay one characteristically long sequence of eggs known as the Prime Sequence which in broiler breeders is usually about 20 eggs in a length (Robinson and Renema, 1999b) Pause (Skip days) Pause is defined as the time between two clutches in which the hen is considered a low producer. Pause may be due to environmental or genetic factors. The number of eggs in a clutch and the number of pause days between clutches can be regular or irregular. Robinson and Renema (1999b) illustrated this using data on white leghorn pullets: Hen two-egg cycle Hen three-egg cycle

28 28 Hen Regular Sequence, Regular Skip Hen Irregular Sequence, Regular Skip Hen Irregular Sequence, Irregular Skip 0 represents an egg while - represents a pause day Oviposition Time Oviposition time is the actual time of the day in which an egg is laid. Under optimal lighting conditions (usually hours), a hen usually lays its first egg in the sequence in the early hours of the morning and subsequent eggs are laid progressively later in the day. The time of the day during which the hen lay most of their eggs is referred to as oviposition peak period. This period falls in the morning hours in the domestic fowl. The actual time of the day when eggs are laid depends on the length of the sequence and the position of the egg in the sequence and also on the number of hours of daylight. Time of laying may also be influenced by feeding schedule (Herren, 1994). If hens receive no light cues by being kept under continuous light with natural daylight excluded and are fed only from 8am-4pm, most of the eggs will be laid within those hours. On the other hand, if feeding is from 8pm to 4am, the hens will adjust to the new schedule by laying most of their eggs during the new feeding period (Herren, 1994) Time Interval between successive eggs and lag The difference between interval length of one egg and 24 hours is termed lag. The lag or the interval between successively laid eggs in a sequence appears to be greater for the first two or last two laid eggs of the sequence than those of the intervening eggs, length of the sequence not withstanding. With average hens laying about 3-4 eggs per clutch, the interval is about 26 hours. Such hens may lay first egg of clutch at 9am, the second at 11am, and third at 1pm and perhaps fourth at 3-4 pm. As hens do not normally ovulate after 2pm, no ovulation will occur on fourth day resulting in no egg laid on fifth day and a four-egg clutch will be terminated. The oviposition interval by most hens range from hours (Zakaria, 2001). Robinson and Renema (1999b) also reported that lag is greater between the first and second egg in the clutch, then decreases towards the end of the cycle. However, negative lag occurs in the middle of long cycles and under such condition the interval between eggs is less than 24 hours. Lag again increases towards the end of a sequence. This interval between eggs and the rhythm of lay mainly

29 29 represents difference in time of ovulation. Lag does not represent difference in time of day of one oviposition with respect to its predecessor Total Egg Production Total egg production is an attribute of the number and length of clutches, the duration of the laying period, the rate of lay, number of pause days and length of broody period. Total egg production is often calculated by a method which includes the effect of mortality. The method involves dividing the total number of eggs laid during a period by the number of hens or pullets housed at the beginning of the period. This gives a value known as hen-housed average or production index. The problem in this method is that high mortality during the period will lower the value even though the surviving hens may have laid exceedingly well. Reddy et al. (2004) modified the hen-housed method by replacing it with survivor egg production as one of egg production indices. Survivor egg production is calculated by dividing the total number of eggs laid by the number of surviving birds. It can be expressed in percentage. According to Ani and Nnamani (2011), if a hen lays in clutches of single eggs, the most she can lay in a thirty-day period is 15 eggs. If she lays 2-egg clutches, her maximum record in 30 days is 20 eggs, an increase of 33.5%, where she lays in 3-egg clutches throughout the month, she could make a total of 23 eggs which is a further increase of 15% over the 2-egg clutch. In order for the hen to be able to produce 300 or more eggs annually, the clutch length must be 5 or more eggs. Imai (2003) estimated that hens laying at 60% for nine months will produce as many eggs as a hen laying at 90% for six months Rate/Intensity of Lay The number of eggs produced in a given period of time is dependent on sequence length. If a hen lays more egg in a given time, then, her rate of lay is high. If the hen lays more number of eggs per clutch, the hen is usually a better layer than the hen that lays fewer number of eggs. Although rate of lay is a lowly heritable trait, family selection for this trait can bring about improvement (Reddy et al., 2004). Butcher and Miles (2000) had observed that a hen may lay approximately 250 eggs per annum. Only a few hens lay everyday for 100 or more consecutive days. The rate of lay depends primarily on the ability of the ovary to produce ova and this has a direct bearing on

30 30 the stage of life of a hen. Based on individual competence, the laying period of a hen can be divided into 3 phases Phase 1: Onset of lay Phase 2: Main period of lay Phase 3: Remaining of the pullet year Phase 1 lasts about one or two months and during which the hens attain their peak production. The onset of lay corresponds to the seventh month of age and is characterized by (і) Laying of soft-shelled eggs (іі) Irregular laying with long intervals between eggs and laying of more than one egg in one day in which one or both may be abnormal. Phase 2 is characterized by regular egg production and falls within 11 months of age of bird. Phase 3 is a relatively short period during which egg laying rapidly comes to an end (Latour, 2003; Etches, 1996). 2.5 Egg quality The quality of an egg is defined by its internal and external attributes. The internal attributes consist of quality of the albumen and yolk parts, while the external quality is dependent on the egg shell quality which is related to the existence of cracked shell or stains (Berardinelli et al., 2005). In general, exterior and internal egg quality standards are based on shell cleanliness, shell soundness, shell texture, shell shape, relative viscosity of the albumen, freedom from foreign matter in the albumen, shape and firmness of the yolk, and freedom from yolk defect (Kemps et al., 2006). Internal egg quality Internal egg quality involves functional, aesthetic and microbiological properties of the egg yolk and albumen. The proportions of components for fresh egg are 32% yolk, 58% albumen and 10% shell (Robinson and Renema, 1999b). The egg white is formed by four structures. Firstly, the chalaziferous layer or chalazae, immediately surround the yolk, accounting for 3% of the white. Next is the inner thin layer, which surrounds the chalazae and accounts for 1% of the white. Third is the firm or thick layer, which provides an envelope or jacket that holds the inner thin white and the yolk. It adheres to the shell membrane at each end of the egg and accounts for 5% of the albumen. Finally, the outer thin layer lies just inside the shell membranes, except where the thick white is attached to the shell, and accounts for 23% of the egg white (USDA, 2000). External egg quality

31 31 Exterior egg quality is judged on the basis of texture, colour, shape, soundness and cleanliness according to USDA (2000) standards. It has been always recognized that the hen has the most extraordinary method of obtaining and depositing calcium (Ca) in the entire animal kingdom. An egg has an average of 2.3 g of calcium in the shell, and almost 25 mg in the yolk (Etches, 1996). A modern hen laying 330 eggs per cycle will deposit 6 g of calcium; assuming a 50% calcium retention rate from the diet, the hen will consume 1.53 kg of calcium per cycle (Etches, 1996) Egg weight This is a highly heritable trait which can be improved by selection. Birds which mature early tend to lay smaller eggs than those that mature late. The mature egg is approximately gms (Reddy et al., 2004). Egg weight is influenced by breed, nutrition, season and disease condition. It is also influenced by the type of housing (Reddy et al., 2004). 2.6 Physical Characteristics According to Daghir (2008) and Gillespie (199), in order to determine whether or not the hen is laying, it is advisable to examine the condition of the comb, wattles, eyes, beaks, pubic bones, abdomen and vent. A laying hen has large bright, red, soft and waxy comb and wattles. The eyes are bright and prominent. The beak is bleached. The eyelids and eyerings are bleached. The pubic bones are flexible and spread wide enough for two to four fingers to be placed between them. The abdomen is full, soft and pliable. The vent is moist, bleached and enlarged (Gillespie, 199). A non-laying hen has a small, pale, scaly and shrunken comb. The beak is yellow, and the eyes are dull and sunken. The eyelids and eyerings are also yellow. The pelvis bones are stiff and close together with room for less than two fingers between them. The abdomen is full and hard. The vent is dry, puckered and yellow (Gillespie, 199; Obioha, 1992). Past production is indicated by the amount of yellow pigment left in the body and the time of moult. Moulting is the process of losing the feathers from the body or wings. Producing a large number of eggs bleaches the yellow pigment from the hen s body. The beak, eye ring, ear lobes and shanks are bleached white. The feathers are worn and soiled. The pigment bleaches from the hen s body in a definite order as laying progresses. The pigment leaves the vent first. It becomes fully bleached after about one week of laying. The eye ring is next to bleach, requiring about seven to ten days to become fully bleached. The beak bleaches next,

32 32 starting at the base and progressing to the tip. This takes 4 to 6 weeks. The shanks are last to bleach. The shank bleaches in this order (1) front of shanks (2) rear of shanks (3) tops of toes (4) hock joints. It requires 4 to 6 months for the shanks to be fully bleached (Gillespie, 199). When the hen stops laying, the pigments return to the body parts in the same order in which it left. Return of the colour takes about one half of the time required for bleaching. A hen that has been a poor layer will show yellow pigment in the body parts mentioned above. A high rate of lay is indicated by the shape and refinement of the head, the width and depth of the body, the abdominal capacity, the softness and pliability of the skin, the shape of the shanks. A hen with a high rate of lay has a moderately deep and broad head (Daghir, 2008; Gillespie, 199). The face is free of wrinkles and the comb and wattle are fine and smooth textured. The hen has large body capacity; the abdomen is soft and pliable. The shanks are flat or wedge shaped. A hen with poor rate of lay has a long shallow head and a back that is narrow and tapering. The pubic bones are narrow and thick while the abdomen is hard. The skin is tight and thick. The shanks are narrow and round. Obioha (1992) divided layers into good and poor layers as follows: Good layers Poor layers Appearance of: Comb: Large, full, plump, smooth and waxy Limp covered with white scales, dry, shriveled Eye: bright Dull Beak: white and well bleached Yellow colour at base of beak and extending towards the tip Eye ring and Earlobe: white and well bleached Yellow or tinted Vent: white or well bleached, large, soft, moist, oval, sometimes over-hanging Yellow or tinted, small, hard, dry, round sometimes appear contracted Wattles: Prominent, soft, smooth Rough and dry Face: bright red Yellow tint

33 33 Head: alert, healthy Dull, listless Moulting: sheds feathers late and rapidly Sheds early and slowly Pubic bone: thin, pliable, and relatively wide apart about 2 or more fingers Thick, blunt and relatively close together, less than 2 fingers, rigid. Abdomen: loose, pliable, soft, full when in laying condition. Deep from pubic bones to the rear of keel about 4 fingers width Tight, hard, tucked up. Rear end of the keel rather close to the pubic bone less than 3 fingers width Activity: active, alert Inactive, tired Plumage: worn, soiled, close New, glossy, loose 2. Climatic Condition For many years, researchers have been investigating the effect of high environmental temperature and relative humidity on the performance of different poultry species, including turkeys (McKee and Sams, 199), young chickens (Henken et al., 1983), broilers (Cooper and Washburn, 1998), broiler breeders (McDaniel et al., 1995) and laying hens (Emery et al., 1984; Muiruri and Harrison, 1991; Whitehead et al., 1998), and have found that high environmental temperatures have deleterious effects on productive performance. In laying hens, heat stress depresses body weight (Scott and Balnave, 1988), egg production (Muiruri and Harrison, 1991; Whitehead et al., 1998), egg weight (Balnave and Muheereza, 199), and shell quality (Emery et al., 1984; Mahmoud et al., 1996) and is generally accompanied by suppression of feed intake which could be the cause of decline in production. Heat stress in poultry is prompted by combinations of environmental temperature and humidity that prevent the birds thermoregulatory processes from effectively dissipating the heat produced during metabolism. Poultry birds are said to be thermally stressed when ambient temperature exceeds body temperature such that peripheral physiologic responses of the bird can no longer match the external changes (Ezekwe, 2011).

34 34 During heat stress, the environmental parameters of ambient temperature (AT) and relative humidity (RH) in general and temperature humidity index (THI) in particular, have been reported to be an invaluable tool in the presumptive diagnosis of the animal state of health, and is also relevant in evaluating the adaptability of the animal (Tao and Xin, 2003; Karaman et al., 200). Altan et al. (2003) reported that high ambient temperature and relative humidity, increases heat stress and are responsible for the increase in rectal/body temperature. Chronic heat stress results in behavioural changes, depressed feed intake (Daghir, 2008; Oguz et al., 2010) and a wide range of metabolic activities (Sahin et al., 2002), including elevation of body temperature, electrolyte, acid-base and hormonal imbalances (Holik, 2009); and tissue damage (Sinkalu et al., 2008). Egg production and shell quality in laying hens will be depressed (Asli et al., 200; Ajakaiye et al., 2011). The ideal temperature (conventionally referred to as the zone of thermoneutrality) under which performance of laying hens is not adversely affected by temperature has been identified by Holik (2009) and Imik et al. (2009) as C. Temperatures outside the critical limits of the thermoneutral zone such as those prevailing in most humid tropical regions of the world have been reported to constitute heat stress (CTA, 198; Ensminger et al., 1990; Kucuk, 2003; Hoilk, 2009; Tuleun et al., 2010; Whitehead and Mitchell, 2010). Egg quality and production as a whole is affected by temperature which is manifested by the effect it has on the physiology and metabolism of the hen. During hot weather, there is a reduction of carbonate ions in the blood which lowers the buffering capacity and may lead to poor buffering of hydrogen ions produced during shell formation. This explains why there is a low egg production in hot weather and also why eggs laid during hot weather have thin shells (Ajakaiye et al., 2011; Asli, 200). It was also noted by Kirunda et al. (2001) that the specific gravity of eggs declined at the onset of warm weather. High temperature could prevent the reproductive tract of laying hens from probably getting enough nutrient supply as a result of low blood supply and therefore reducing nutrients reaching the tract for normal egg formation (Ezekwe, 2011). Excessively high relative humidity makes adaptation to extremes of temperature more difficult. An increase in relative humidity decrease loss of heat by evaporation at high temperatures and decreases thermal isolation of the animal at low temperatures (Leeson, 1986).

35 35 CHAPTER THREE MATERIALS AND METHODS 3.1 Location and Duration of Study The study was carried out in the Poultry Unit of the Department of Animal Science Teaching and Research Farm, University of Nigeria, Nsukka. It lasted for a period of ten weeks (1 st July 9 th September, 2011). During this period, hens were observed daily and egg collection was done hourly between 0600h and 1800h for the first eight weeks, while the subsequent two weeks were used to appraise their physical characteristics. The study was conducted in late rainy season. 3.2 Experimental Birds One hundred and fifty 36 weeks old hens, comprising seventy-five Shaver brown and seventy-five Nera black hens each in their 12 th week of lay were used. The hens were selected from a flock of laying hens in the farm. Each hen was housed in individual battery cage as observations were made on individuals. 3.3 Management of Hens The hens were housed in an open-sided building with a block wall of 90cm high and wire netting to the roof. Feeding containers used were v-shaped, long and detachable feeders and water containers used were U shaped. Hens were fed commercial layers mash containing 16.5% crude protein, 2650 kcal/kg of metabolizable energy, 4% crude fat, 6.5% crude fibre, 3.6% calcium and 0.4% phosphorus. Each hen received about 125g of layers mash daily and ad libitum supply of water. The water supplied to the birds was medicated with an anti-stress (Vitalyte) for a period of one week at the start of the experiment. Eggs were collected daily and recorded for each hen. As a general flock prophylactic management strategy, routine vaccinations and other health operations were carried out as at when due. Wood shavings were spread under the battery cages to absorb moisture and ease regular removal of poultry droppings from the laying house, usually weekly. The surroundings of the experimental birds were kept as tidy as possible.

36 36 Dead birds were promptly removed and taken to the Faculty of Veterinary Medicine University of Nigeria, Nsukka for autopsy when the need arose. No supplemental light was provided during the period of the study. 3.4 Parameters Measured Oviposition Time Oviposition time was recorded hourly during the period of the study Total Egg Production Total egg production was determined by adding all the eggs produced by each of the two strains of hen during the study Clutch/Sequence Length This was determined for each hen by counting the number of eggs laid until a day was skipped Pause Days Days in which no egg was laid by the hens were obtained by adding together such number of days Egg Weight (g) Egg weight was taken for every egg collected for the hens in relation to oviposition time weighing was done for all eggs within one hour of collection. Electronic balance (D & G sensitive scale) was used and the measurement expressed in grammes Egg Quality Sixteen (16) eggs per strain were selected at random weekly for egg quality determination. The indices evaluated were as follows: i. Egg Shell Weight (g) Eggs were carefully broken and dried after which the egg shells were weighed singly using a weighing balance. ii. Egg Shell Thickness (mm) This was determined by pulling off the shell immediately the egg was broken and the shell was air-dried for a day (24 hours) after which the egg shell thickness was determined with the help of a micrometer screw guage.

37 3 iv. Egg Shape Index The egg shape index was calculated as the proportion of egg length to diameter v. Albumin Height and Diameter (mm/cm) The eggs after weighing were broken into a piece of flat glass positioned on a flat surface. The albumin height was measured using a tripod micrometer. Albumin diameter was taken as the maximum cross sectional diameter of the albumin using a pair of calipers and read on a ruler calibrated in millimeter. vi. Yolk Height and Diameter (mm/cm) The eggs after weighing were broken into a piece of flat glass positioned on a flat surface. The Yolk height was measured using a tripod micrometer. Yolk diameter was taken as the maximum cross sectional diameter of the yolk using a pair of calipers and read on a ruler calibrated in millimeter. vii. Albumin Index The albumin index was calculated as the proportion of yolk height to diameter. viii. Yolk Index The yolk index was calculated as the proportion of yolk height to diameter. ix. Haugh Unit This was calculated from the values obtained from the albumin height and egg weight by using the formula: Haugh s unit = 100log (H+.5-1.W 0.3 ) 3.4. Average Daily Feed Intake Average Daily feed Intake (g): Feed Offered (g) Feed not eaten (g) Number of Hens Percentage Egg Production Percentage egg production for each strain of hen was calculated using the formula as shown below: No of eggs laid by each breed for 8 weeks 100 % egg production No of hens for each breed 5 housed x No of days 1 Other egg production indices were obtained using the formulae as shown below:

38 38 a. Hen housed egg production (HHEP): It was obtained by dividing the total number of eggs by each strain of hen by the number of hens housed in the laying cages. This does not take mortality into account. Hen housed egg production (HHEP) = No of eggs laid No of hens housed b. Hen day egg production (HDEP): It was obtained by dividing the total number of eggs by each strain of hen by the number of hen days. No of eggs laid Hen day egg production (HDEP) = No of hen days 3.5 Physical Characteristics By visual observation, the conditions of the head, comb, wattles, eyes, beaks, pubic bones, shanks, abdomen, plumage and vent were appraised and noted for all the hens. Palpation of palpable physical structures of each hen was made. The hens were divided into three classes according to their egg production rate and physical characteristics as follows: good layers, intermediate layers and poor layers. 3.6 Temperature Temperature readings were taken 3-hourly at time intervals of 0900h, 1200h, 1500h and 1800h using a standard air thermometer and the mean daily temperatures noted 3. Experimental design The experiment had a completely randomized design with the following model; Yijk = μ + ai + bj + Ɛijk Where Yijk = Observed value of dependent variable μ = Overall mean ai = Effect of laying and physical characteristics of the ith individual of Shaver brown hens bj = Effect of laying and physical characteristics of the jth individual of Nera black hens Ɛijk = Random error associated with observation

39 Statistical Analysis Descriptive statistics such as means and standard error of the means, percentages for the different parameters were calculated. Data were subjected to analysis of variance (ANOVA) in a completely randomized design (CRD) using SPSS Package (2003) windows version 8.0. Significantly different means where separated using Duncan s New Multiple Range Test (Duncan, 1955). The statistical procedures used were as described by Steel et al. (199).

40 40 CHAPTER FOUR RESULTS The climatic data (Table 2 and Figure 1) taken during the period of the experiment showed that the study area had the natural day-length of 13 to 14 hours; mean maximum weekly indoor and outdoor temperatures of C to C and C to C, respectively; mean minimum weekly indoor and outdoor temperatures of C to C and C to C, respectively; relative humidity of 3.1% to 6.6% and mean total monthly rainfall of 81.33mm.

41 41 Table 2: Mean weekly environmental temperatures and relative humidity recorded during the period of study TEMPERATURES ( 0 C) WEEK INDOOR OUTDOOR RELATIVE HUMIDITY MINIMUM MAXIMUM MINIMUM MAXIMUM Thermo neutral zone for poultry is C (Imik et al., 2009).

42 Temperature Relative humidity humidity o C IT Indoor Outdoor o C 30 RH Weeks Figure 1: Average weekly temperatures (indoor and outdoor) and relative humidity of the study area

43 Results Egg Laying Characteristics of Shaver Brown Hens Oviposition time As shown in Table 3, more eggs (86.24%) were laid in the morning hours (0600h 1159h), while 13.6% of egg were laid in the afternoon hours (1200h 100h). Oviposition reached peak between 0630h to 030h and declined in the early afternoon hours between 1130h 1230h until eight eggs were laid between 1530h 1630h (late afternoon hours).

44 44 Table 3: Frequency distribution of egg laying of Shaver brown and Nera black hens during the day Oviposition Interval Strain Number of eggs laid 6:00am-6:59am Shaver brown 46 Nera black 520 :00am-:59 am 8.00am-8:59 am 9:00am-9:59 am 10:00am-10:59 am 11:00am-11:59 am 12:00pm-12:59pm 1:00pm-1:59pm 2:00pm-2:59pm 3:00pm-3-59pm 4:00pm-4:59pm 5:00pm-6:00pm Shaver brown Nera black Shaver brown Nera black Shaver brown Nera black Shaver brown Nera black Shaver brown Nera black Shaver brown Nera black Shaver brown Nera black Shaver brown Nera black Shaver brown Nera black Shaver brown Nera black Shaver brown Nera black

45 Table 4: Frequency distribution of egg production of Shaver brown hens Hen code No. Number observed Relative freq.(%) Hen code No. Number observed Relative freq.(%) Hen code No. Number observed 45 Relative freq.(%)

46 Total egg production The distribution pattern of egg production is shown in Table 4. Result shows that a total of 290 eggs were laid by Shaver Brown hens during the experimental period. The average number of eggs produced by a hen was Egg production by individual hen ranged from Therefore, the least number of eggs produced by a single hen within the experimental period was 1 and the highest number of eggs produced were 55 eggs Clutch Length The distribution pattern of the mean clutch length is shown in Table 5. During the experimental period, clutch lengths of 1 to 1 were observed. Clutch length of 10 occurred most frequently and clutch length of 1 occurred only once throughout the period. The data obtained on clutch length shows that about 56% of the clutch lengths were of 10 cycle lengths and below. The effect of egg position and clutch size on egg weight is shown in Table 6. The first eggs in a clutch for Shaver brown hens in general were heavier (P<0.05) than eggs produced later in a clutch. Egg weight across various clutch sizes varied significantly (P<0.05) for Shaver Brown hens from 2-egg clutch to the 1-egg clutch. 1-egg clutch had the highest (P<0.05) egg weight of 66.01g, while 10-egg clutch had the (P<0.05) least egg weight of 56.45g.

47 4 Table 5: Frequency distribution of mean clutch length of Shaver brown hens Hen code No. Clutch length Relative freq.(%) Hen code No. Clutch length Relative freq.(%) Hen code No. Clutch length Relative freq.(%)

48 48 Table 6: Effect of egg position and clutch size on egg weight of Shaver brown hens Effect of egg position on egg weight Egg weight and its relationship to clutch size Position of eggs Egg weight (g) Clutch size Egg weight (g) a ab 2-egg clutch bc ab 3-egg clutch ab ab 4-egg clutch 63.4 bc ab 5-egg clutch de ab 6-egg clutch de ab -egg clutch 61.4 cd ab 8-egg clutch a ab 9-egg clutch ef ab 10-egg clutch fg ab 11-egg clutch bc ab 12-egg clutch cd ab 13-egg clutch bc ab 14-egg clutch g ab 15-egg clutch bc ab 16-egg clutch bc ab 1-egg clutch ab SEM a,b,c,d,e,f,g: Mean values in a column with different superscripts are significantly different (P<0.05) SEM: standard error of means

49 49 Table : Frequency distribution of pause days of Shaver Brown hens Hen code No. Pause days Relative freq.(%) Hen code No. Pause days Relative freq.(%) Hen code No. Pause days Relative freq.(%)

50 50

51 51 Table 8: Effect of oviposition interval on egg weight of Shaver brown hens Oviposition time interval Egg weight (g) Sig. 6.00am-6.59am 0.05±1.0 a *.00am-.59am 68.9±1.52 a * 8.00am-8.59am 68.81±0.63 a * 9.00am-9.59am 6.85±0.68 ab * 10.00am-10.59am 66.0±0.48 bc * 11.00am-11.59am 65.63±0.58 bc * 12.00pm-12.59pm 63.2±0.49 c * 1.00pm-1.59pm 58.22±1.29 d * 2.00pm-2.59pm 53.61±0.63 e * 3.00pm-6.00pm 51.50±0.43 e * Overall mean 63.43±0.5 a,b,c,d,e: Mean values in a column with different superscripts are significantly different (p<0.05); *=(p<0.05)

52 Pause Days The distribution pattern of the number of pause days is shown in Table 6. The total number of pause days for all birds were 1410 days. Of these, pause days of 8 and 19 occurred most frequently and pause days of 1, 14 and 22 were the least Egg Weight The mean egg weight for Shaver Brown hens (Table ) was ±0.5(P<0.05) and ranged from 43 89g. Eggs laid in the morning hours were significantly (P<0.05) heavier than those laid later in the day. The difference in mean egg weight (P<0.05) between eggs laid from 0600h to 000h and those laid from 1500h to 1800h was 18.55g. The first eggs in a clutch in general were heavier than eggs produced later in a clutch Intensity/ Rate of lay As shown in Table 4, the 56 days used to appraise the laying characteristics of Shaver Brown hens, the 5 hens laid 290 eggs, giving overall production rate of 66.43%. Good layers laid 1915 eggs representing 56% of eggs laid, intermediate layers laid 84 eggs accounting for 3.3% and poor layers laid 28 eggs or 6.6% of the eggs laid.

53 Hen housed egg production (HHEP): The mean number of eggs produced by each hen for the period of the study was eggs for good layers; eggs for intermediate layers and 5.60 eggs for poor layers (Table 3). For the 5 Shaver brown hens altogether, the mean number of eggs produced by each hen was 3.20 eggs during the 56 days of the study Hen day egg production (HDEP): The mean number of eggs laid daily by good layers was eggs, intermediate and poor layers and 0.5 eggs respectively (Table 3). The general mean was eggs daily.

54 54 Table 9: classification of experimental hens Strain No. of hens PCLAL No. of eggs Clutch length Shaver brown 42 Good (56%) (38-56) ( ) Nera black 50 Good (66.6%) Shaver brown 28 Intermediate (3.33%) Nera black 16 Intermediate (21.33%) Shaver brown 5 Poor (6.6%) Nera black 9 Poor (38-56) (19-3) (19-3) 5.60 (0-18) ( ) 2.6 ( ) 3.45 ( ) 5.94 ( ).08 Pause days 11.5 (5-18) 8.58 (2-1) 25.5 (19-3) (19-35) (49-55) Physical characteristics White shanks, bleached beak, white cloaca. Bleaching shank, bleaching beak, bleaching cloaca Dry cloaca (12.00%) ( ) (40-56) PCLAL = Performance class of layers and % Lay

55 Egg Laying Characteristics of Nera Black Hens Oviposition time As shown in Table 3 and Figure 1, more eggs (88.5%) were laid in the morning hours (0600h 1159h) while 11.25% of eggs were laid in the afternoon hours (1200h 100h). Oviposition reached peak between 0630h to 030h and declined in the early afternoon hours between 1230h to 1330h until ten eggs were laid between 1530h to 1630h (late afternoon hours).

56 56