OYEAGU CHIKA ETHELBERT PG/M.Sc/10/58000

Transcription

1 RESPONSE OF NERA BLACK AND SHAVER BROWN HENS TO SELF- COMPOUNDED AND COMMERCIAL FEEDS IN NSUKKA, ENUGU STATE. BY OYEAGU CHIKA ETHELBERT PG/M.Sc/10/58000 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 FEBRUARY, 2014.

2 2 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. Oyeagu, Chika Ethelbert 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 Date Project Supervisor..... DR. A.E. ONYIMONYI (Esq.) JP Date Head of Department.. EXTERNAL EXAMINER Date

3 3 DEDICATION This work is dedicated to God Almighty; He is the reason for my living. God! To you be all glory.

4 4 ACKNOWLEDGEMENT I sincerely acknowledge 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 the Departmental technologists, Mr. S. I. Onuorah, Mrs. O.J. Odo, Miss. E.N. Ezeaku and Miss. O. M. Ezeh for their assistance and co-operation during my laboratory analysis. 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 my lovely family members who gave me all the needed support throughout the period of this programme. Many thanks to all my friends who assisted me in one way or the other for the success of this research work, May GOD bless all of you. Finally, I thank the Almighty GOD for His grace and blessings without which this programme would have been impossible. To Him I say Thank you JESUS.

5 5 TABLE OF CONTENTS Title Page i Certification ii Dedication iii Acknowledgement iv Table of contents v List of Tables vi Abstract vii CHAPTER ONE INTRODUCTION 1.1 Background of the study Statement of problem Objectives of study Justification of study CHAPTER TWO 2.0 LITERATURE REVIEW Classification of chicken Exotic breeds of laying birds The physical (External) and internal measures of egg quality Egg quality Eggshell quality Eggshell integrity Eggshell texture Eggshell shape

6 Eggshell colour Eggshell cleanliness Internal egg quality Yolk quality Albumin quality Factors affecting internal egg quality indices Age of the hen Genetics Age and storage of the egg Diseases Blood spots Meat spots Bacterial or fungal contamination Round worms in eggs Off odors/flavours Factors affecting egg production Breeds of laying hen Age of laying hen Nutritional factors Management factors Environmental factor Parasites Diseases Avian physiology of egg production Male reproductive system 30

7 Testes and sperm Vas deferens The female reproductive system Ovary Oviduct Nutritional Requirement for Laying Hens Water Carbohydrate Protein Fat Vitamins Minerals 39 CHAPTER THREE MATERIALS AND METHODS Location and duration of experiment Experimental diets Experimental animals and management Experimental design and data collection Experimental design Data collection Chemical and data analysis 46 CHAPTER FOUR RESULTS AND DISCUSSION Response of Nera Black (NB) Hens to different commercial layers diets 47

8 Effect of feed type on laying performance of Nera Black (NB) Hens Effect of feed type on external egg parameters of Nera Black (NB) Hens Effect of feed type on internal egg parameters of Nera Black (NB) Hens Cost implication of feeding different layers diets to Nera Black (NB) Hens Response of Shaver Brown (SB) Hens to different layers Diets Effect of feed type on laying performance of Shaver Brown (SB) Hens Effect of feed type on external egg parameters of Shaver Brown (SB) Hens Effect of feed type on internal egg parameters of Shaver Brown (SB) Hens Cost Implication of feeding different layers diets to Shaver Brown (SB) Hens Comparative performance of Nera Black (NB) and Shaver Brown (SB) hens fed control and commercial layers diets Effect of feed type and strain type on performance traits of Nera Black and Shaver Brown Hens Effect of feed type and strain type on the external egg parameters of Nera Black and Shaver Brown Hens

9 Effect of feed type and strain type on the internal egg parameters of Nera Black and Shaver Brown Hens Effect of feed type and strain type on cost of feeding control diets and commercial layers diets to Nera Black and Shaver Brown Hens 66 CHAPTER FIVE SUMMARY, CONCLUSION AND RECOMMENDATION Summary Conclusion Recommendation 70 References Appendices

10 10 LIST OF TABLES Table 1: Percentage compositions of experimental diets Table 2: Determined Compositions of the Experimental Diet Table 3: Effect of Feed type on Laying Performance of Nera Black (NB) Hens Table 4: Effect of Feed type on External Egg Parameters of Nera Black (NB) Hens Table 5: Effect of Feed type on Internal Egg Parameters of Nera Black (NB) Hens 51 Table 6: Cost implication of feeding different Layers Diets to Nera Black (NB) Hens Table 7: Effect of Feed type on Laying Performance of Shaver Brown (SB) Hens Table 8: Effect of Feed type on External Egg Parameters of Shaver Brown (SB) Hens Table 9: Effect of Feed type on Internal Egg Parameters of Shaver Brown (SB) Hens Table 10: Cost implication of feeding different Layers Diets to Shaver Brown (SB) Hens

11 11 Table 11: Effect of Feed type and Strain type on Performance Traits.. 61 Table 12: Effect of Feed type and Strain type on the External Egg Parameters of Nera Black and Shaver Brown Hens 63 Table 13: Effect of Feed type and Strain type on the Internal Egg Parameters of Nera Black and Shaver Brown Hens 65 Table 14: Effect of feed type and strain type on the cost of feeding control and Commercial Layers Diets to Shaver Brown (SB) Hens 67

12 12 ABSTRACT A study was conducted to determine the response of Nera Black (NB) and Shaver Brown (SB) hens to self-compounded layers diet (A) and four commercial layers diets (B, C, D, and E). Two hundred and forty 28 weeks old laying hens comprising one hundred and twenty (120) Nera Black (NB) hens and one hundred and twenty (120) Shaver Brown (SB) hens were used for the study. Each Strain was divided into five (5) groups of 24 hens each and each group (for each strain) was randomly assigned to one of the five diets (A, B, C, D, and E, respectively). Each diet constituted a treatment and this was replicated three (3) times with eight (8) birds per replicate. Two hens were housed in a cage measuring cm and four (4) of such cages constitute a replicate. Each hen in each group received about 130g of layers mash daily and ad libitum supply of water for twelve (12) weeks. Eggs were collected daily and recorded for each hen. Three (3) eggs were collected at random from each replicate every two weeks for external and internal assessment of the eggs for three months. Results showed that for the Nera black hens, final body weight (FBW), hen day production (HDP), average daily feed intake (ADFI) and feed conversion ratio (FCR) were significantly (P<0.05) influenced by treatments, while treatments had no significant (P>0.05) effect on average body weight gain. Average egg weight, egg shell thickness and egg shell weight were significantly (P<0.05) affected by treatments while egg diameter, egg length and egg shape index were not significantly (P>0.05) influenced by treatments. Birds that consumed control diet (A) had significantly (P<0.05) higher average egg weight than those fed the commercial diets which had similar mean egg weight. Haugh unit, yolk height, yolk diameter, yolk index albumin height and albumin diameter were significantly (P<0.05) affected by treatments, while yolk weight, albumin weight, albumin length and albumin index were not significantly (P>0.05) influenced by treatments. Although dozens of eggs produced per bird and revenue from dozens of eggs produced were not significantly (P>0.05) influenced by feed type, total feed consumed, cost of feed consumed, cost per dozen of egg and gross profit were significantly (P<0.05) influenced by treatments. For the Shaver brown hens, the final body weight, average body weight gain and hen day production were not significantly (P>0.05) influenced by dietary treatments, while average daily feed intake and feed conversion ratio were significantly (P<0.05) affected by treatments. Average egg weight and egg shell thickness were significantly (P<0.05) influenced by treatments, while no significant (P>0.05) differences existed among treatments in egg shell weight, egg diameter, egg length and egg shape index. Haugh unit, yolk weight, yolk diameter, albumin weight, albumin height, albumin diameter, albumin length and albumin index were not significantly (P>0.05) influenced by dietary treatments while yolk height and yolk index were significantly (P<0.05) affected. There were significant (P<0.05) feed x strain interactions in hen day production, average daily feed intake (ADFI) and feed conversion ratio (FCR). Nera Black hens which consumed control diet (A) and commercial diet (D) had significantly (P<0.05) higher hen day production% value than Shaver Brown hens that consumed the same feeds. Shaver Brown hens which consumed commercial diets B and E had significantly (P<0.05) higher egg shell thickness value than Nera Black hens that consumed the same feeds. Nera Black birds that consumed the control diet produced more (P<0.05) dozens of eggs than the shaver brown birds that consumed the same diet. Nera Black birds also consumed more (P<0.05) of commercial diet C than the shaver brown birds. It was concluded that the Nera Black hens performed better than the Shaver Brown hens in terms of dozens of eggs produced, cost per dozen of egg produced, revenue from dozens of eggs produced and gross profit, while the use of self-compounded diet resulted in better performance than the use of commercial diets in the present study.

13 13 CHAPTER ONE INTRODUCTION 1.1 Background of the study Developing countries like Nigeria is facing a big problem of protein malnutrition. Animal protein is essential in human nutrition in order to solve the problem of kwashiorkor which is a resultant effect of malnutrition (Oladeebo et al., 2007). Food and Agricultural Organization (FAO) has recommended about 36 g daily animal protein intake for an adult of 60kg of the populace (FAO, 2006). Poultry products especially eggs and table birds are major sources of animal protein (Alabi and Samuel, 2002). However, egg production in Nigeria is grossly inadequate because of the wide gap between demand and supply of the product. The situation whereby egg buyers had to make orders several days before such orders could be met is an evidence (Ajibefun and Daramola, 1999) of short egg supply. The increased egg production is one way of achieving the target of providing quality animal protein at a minimum cost to the consumers (Oluyemi and Roberts, 2000). Advances in genetics and selection has made present commercial layers quite different from their predecessors. Body weight is less, total number of egg has increased, egg mass is greater, and feed conversion has improved considerably (Miles and Jacob, 2000; Minvielle et al., 2006). Success in the advances in genetic selection for increased production depends on the availability of feed. Therefore, the types of feed used in feeding the birds also play a significant role in the performance of laying hen. The effects of feed on the performance of the birds stand out as the most reliable method of assessing the quality of a feed (Afolayan et al., 2009).

14 14 The birds can only perform economically well and profitable if it consumes on daily basis the appropriate amount of energy, protein, vitamins and minerals (Oluyemi and Roberts, 2000). Thus, all the essential nutrients must be present in their ration for proper growth, production and maintenance of the body. Different studies have shown that layers fed high quality rations perform better than their counterparts reared with low quality feed (Oluyemi and Roberts, 2000; Smith, 2001). Abeke et al. (2003) stated that the proliferation of small feed mills run sometimes by illiterates and semi literate individuals has compounded the problem of poor feed quality in the market. Egg and broiler meat production is still at subsistence, small or medium scale level in Nigeria, in spite of its roles in income, food and gross domestic products. This shortfall could be attributed to inadequate and high cost of feed which is not even readily available (Payne and Wilson, 1999). These lapses paved way for commercial poultry feed manufacturers to source for unconventional, unwholesome and stale feed ingredients in order to maximize profit, undermining the fact that qualitative feed enhances good performances of egg and broiler meat production (Idahor et al., 2010). This situation is thriving in many major cities across Nigeria because of lack of government control of feed quality standards. Farmers are therefore left at the mercy of these quacks for supply of feeds and in many cases these feeds are very poor in quality (Abeke et al., 2008). Thus, this current situation cannot be left to continue. Efforts should be made by all and sundry within and outside the Nigerian feed industry to check this unwholesome development. According to Atteh (2002), Adebayo et al. (2002) and Kehinde (2006), feed alone accounts for over seventy percent of total cost of producing broilers and eggs. However, farmers may not have a direct influence on the feed cost when feed is purchased from the commercial

15 15 feed millers. Therefore, many farmers change from one commercial feed to another in search of a better feed (Ogundipe et al., 1986) while a good number have decided to be producing their own feeds. As a matter of fact, feed costs as well as the quality of the feeds are among the factors which dictate farmer s preference for commercial or self-compounded feeds (Adebayo et al., 2002; Umeh and Odo, 2002). Many farmers also believe that self made feeds are cheaper than the commercial feeds (Adesehinwa et al., 1996; Adebayo et al., 2002). It becomes very necessary to conduct a study which aims at determining the egg production performance of two strains of laying hens ( Nera black and Shaver brown pullets ) fed self-compounded and four commercial feeds in Nsukka, Enugu State. Inference drawn from such a study will enable researchers to make valuable recommendations to poultry farmers on the feed type (Home made, and Commercial feed) and strain (Nera Black and Shaver Brown hens) that would give the optimum egg production in order to increase the level of animal protein intake in the diet of the Nigerian populace. 1.2 STATEMENT OF PROBLEM One of the major hindrances to commercial egg production is the poor quality of feed for layers. Afolayan et al. (2009) stated that the type of feed used in feeding the birds play an important role in the performance of the laying hen. This shows that the availability of a nutritionally balanced feed is very important in poultry production. Most poultry farmers are ignorant about the nutrient requirements of poultry and how feed ingredients can be manipulated to satisfy these requirements of poultry and therefore heavily rely on any commercial feed in the locality (Lorgyer et al., 2007).

16 16 In Nigeria, feed manufacturers often market feeds whose chemical composition differs markedly from the label content. The problems associated with analyzing these feeds to finding their true chemical composition are numerous, which include lack of facilities, cost and the distance where the feed analysis will take place. This has resulted in many farmers sustaining heavy losses from feeding these substandard rations to poultry through delay in the attainment of market weight and prolonged feeding of layers before the first set of eggs are laid (Asaniyan and Laseinde, 2005). According to Payne and Wilson (1999), the poor development of commercial egg production is attributed to inadequate and high cost of feed which is not even readily available. It is, therefore, necessary that before a standard diet for poultry can be formulated, adequate knowledge of the nutrient requirement and the nutrient composition of the different ingredients among others must be known. However, feeding trials on animals must be carried out before making recommendation(s) to the farmer. This is in line with the observation of Idahor et al. (2010) that it is necessary to analyze for nutrients contained in these commercial poultry feeds prior to usage, to ascertain their potencies. 1.3 OBJECTIVES The present study was aimed at investigating the response of Nera black and Shaver brown hens to homemade and commercial feeds in Nsukka. The specific objectives of the study were as follows: 1. To evaluate egg production performances of Nera black and Shaver brown hens fed control layers mash and some commercial layers feeds in Nsukka, Enugu State, Nigeria.

17 17 2. To determine the effect of interaction between strain and diet on the performance of laying hens in Nsukka, Enugu State, Nigeria. 3. To determine the cost implication of feeding control layers diet and some commercial layers diets to hens in Nsukka, Enugu State, Nigeria. 1.4 JUSTIFICATION OF STUDY In Nigeria, the rate at which food is being produced is not commensurate with the population growth. According to Federal Office of Statistic (FOS) (1996) as cited in Ojo (2003), food production increases at the rate of 2.5% while food demand increases at a rate more than 3.5% due to high rate of population growth of 2.83%. This study tend to properly guide the farmers in their choice of layers diet and strain of commercial laying hen for a profitable business, considering the fact that the total cost of production and profit after sales are the two major concerns of poultry farmers (Afolayan et al., 2009). However, poultry is one the most important sources of animal protein (eggs and meat), employment opportunities (Ajibefun and Daramola, 1999) and income (Olarinde and Kuponiyi, 2004).

18 CLASSIFICATION OF CHICKEN CHAPTER TWO 2.0 LITERATURE REVIEW There are approximately 175 varieties of chickens grouped into 12 classes and approximately 60 breeds (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 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.

19 19 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 Obioha (1992) include: A UNITED STATES 1 Hyline / B 11 2 Hyline Harco (Obioha, 1992) 4 Babcock Babcock 380 B UNITED KINGDOM 1. Rangers/Sykes 2. Thornbers Thornbers 909 C FRANCE 5 Warren Sex-Linked D CANADA 1. Shaver Star Cross

20 20 2. Shaver Star Cross 444T 3. Brown Eggs Shaver 579 ( intensive and alternative) E ISRAEL 6 Yarkon 7 Yaafa 8 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 whiteshelled 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). 2.2 PHYSICAL (EXTERNAL) AND INTERNAL MEASURES OF EGG QUALITY Egg Quality Kramer (1951) cited by Koelkebeck (2006) defined quality as the sum of characteristics of a given food item which influence the acceptability or preference for that food by the consumer. Based on this definition, it is clear that egg quality will mean different things to

21 21 different people and the consumer s perception of quality is likely to vary depending on their intended use of the egg and their own preferences. This is clearly illustrated by a brief review of the regulatory requirements for eggs sold around the world. Under the European Union Egg Marketing Regulations, enforced in all European Union Countries, eggs are classed as either class A or class B eggs (Council of the European Union, 2006; European Commission, 2003) and only eggs graded class A can be sold for direct human consumption or retail (Council of the European Union, 2006). In Nigeria, both class A and B eggs can be sold for direct human consumption or retail but the only difference is that class A eggs command or attract higher price more than the class B eggs. In contrast, Coutts and Wilson (1990) pointed out that, little attention has been focused on internal egg quality factors, such as yolk or albumen quality. However, shell eggs intended to be traded must: a) Be visibly clean; and b) Have no cracks that are visible on candling (or equivalent) unless they have been treated by a process that destroys pathogenic organisms; and c) Have no evidence of embryo development or putrefaction, and no significant blood clots; and d) Not have been incubated; and e) Be handled and stored under conditions that minimize condensation on the surface of the eggs. Eggs which do not meet these minimum requirements can only be sold for human consumption if they have been pasteurized (or undergone an equivalent process) and meet the

22 22 microbiological criteria. Thus, grading system for shell eggs may vary from country to country or region to region but eggshell quality and interior quality are important factors in determining egg quality (Jacob et al. 2000) Eggshell Quality The vast majority of eggs are sold in their shell and a consumer s first impression of any egg purchased is based on their perception of shell quality. The Egg Producers Federation of New Zealand (Inc) (EPF) Code of Practice (EPF and NZFSA, 2002) lists five main categories, defects associated with eggshell integrity, texture, shape, colour and cleanliness Egg Shell Integrity Defects considered under the category of egg shell integrity include gross cracks, hairline cracks, star cracks and thin shelled or shell-less eggs. As cracked eggs cannot be made available for retail sale in New Zealand for instance (Food Standards Australia New Zealand, 2006), high number of cracked eggs will have a negative impact on the profitability of any egg producer. One of the most obvious reasons for egg shell cracks is mechanical damage caused by either the birds themselves or as a result of poor management practices such as infrequent collection of eggs, rough handling, poor quality of diet and poor design and/or maintenance of the cage floor. Egg shell strength ultimately affects the soundness of the shell, with weaker shelled eggs more prone to cracks and breakages and subsequently microbial contamination. Shell strength can be affected by a wide range of factors including: Bird Strain: As a result of genetic selection, different strains of laying hen vary significantly in egg shell quality, egg size, and production (Curtis et al., 1995) and there are clear

23 23 differences between modern commercial birds and traditional breeds of laying fowl (Hocking et al., 2003). Selection for one characteristics such as production or egg weight can affect other characteristics of the hen such as egg shell quality (Poggenpoel et al., 1996). Egg Size: Smaller eggs have stronger shells than larger ones, as hens have a finite capacity to deposit calcium in the shell and as a result, the same amount of calcium is spread over a larger area (Butcher and Miles, 2003a). Age of Birds: Older birds tend to lay bigger eggs and have a higher egg output, which impacts on shell strength as described by (Butcher and Miles, 2003a). Young birds with immature shell glands may produce shell-less eggs or eggs with thin shells. Delaying the onset of sexual maturity by one to two weeks will prevent this (Coutts and Wilson, 1990). Stress: A single stress or disturbance to a flock of laying hens can be enough to desynchronise the process of egg formation for several days, during which time, a number of different egg quality faults may be seen (Natalie, 2008). For example; any factor which results in oviposition prior to completion of shell deposition will result in soft or thin-shelled eggs. Activities which create disturbances in and around the layer shed should be minimized (Coutts and Wilson, 1990). If an egg is retained in the shell gland, any subsequent egg laid may spend less time than normal in the shell gland, resulting in insufficient shell deposition and a soft shelled or shell-less egg (Natalie, 2008). Solomon (1991) noted that once an imperfect mammillary layer hen formed (as a result of stress experienced before the egg reaches the shell gland), subsequent layers are disorganized and thin or soft shelled eggs are a common phenomenon after stress.

24 24 Elevated Environmental Temperature: High (above 25 o C) environmental temperature may affect the feed and therefore calcium intake of the bird, thus resulting in decreased availability of calcium for shell deposition (Jones 2006). In a high environmental temperature, the laying hens will try to overcome heat stress by panting (Koelkebeck, 2006). As egg shells are made up of 95% calcium carbonate (CaCO 3 ), this decrease in blood P H and a subsequent decrease in Ca 2+ ions for shell formation lead to an increase in the number of thin or soft shelled eggs produced. Arima et al (1976) cited by Jones, 2006) found that the egg quality of older hens was more severely affected by increased temperature than younger hens. Nutrition and Water Quality: The provision of adequate dietary minerals and vitamins is essential for good eggshell quality. Similarly, as water quality varies from country to country and region, the role of drinking water in mineral and trace element supply should not be overlooked. Calcium and Phosphorus are essential macro minerals with calcium forming a significant component of the shell formation during the dark period (Boorman et al, 1989). Coetzee (2002) investigated the effect of calcium levels in drinking water on shell integrity in South African laying hens and demonstrated that birds supplied an additional 200 mg of calcium per litre of drinking water laid eggs with mean shell strength of 42.6±9.0 mm. This was in comparison to those receiving un-supplemented water, whose eggs had mean shell strength of 38.9±7.0 mm. Vitamin D also plays an important role in the proper utilization of calcium and phosphorus and sufficient amount of this vitamin should be included in the feed. Thorough mixing of the fed is essential if each bird in the flock is to receive, a similar amount of any given nutrient. This is particularly true for layer hen diet which frequently contains raw material with a wide range of different densities (Jones 2006).

25 25 Mycotoxicosis: Jewers (1990) reported that thin rubbery shells which break more readily than normal have been observed during field outbreaks of ochratoxicosis. Similarly, in an outbreak of T-2 toxicosis, egg breakages increased from a normal 3 to 15% with a further 18% of eggs broken in transit to customers (Jewers, 1990). Zaghini et al (2005) reported that birds fed diets containing 2.5ppm (part per million) of aflatoxin B 1 had lower egg shell weights than those fed the control diet or diets supplemented with mannanoligosaccharides. Genetics: Clunies et al (1992, cited by Jones, 2006) found that hens laying thick-shelled eggs retained more dietary calcium than those laying thin-shelled eggs. Although there was no difference in egg production between thick and thin shell layers, both egg and shell weight were greater for the thick shelled eggs. Disease: Infectious bronchitis (IB), a viral disease caused by a coronavirus which attacks the mucus membranes of the respiratory and reproductive tracts (Butcher and Miles, 2003a; Cavanagh and Naqi, 2003; Jones, 2006) may result in egg defects. These include, pale shell eggs, and eggs with poor shell structure and integrity (Butcher and Miles, 2003a; Cavanagh and Naqi, 2003; Beyer, 2005;Jones, 2006). Similarly, birds affected by egg drop syndrome (EDS), caused by an adenovirus, initially produce pale eggs, quickly followed by thin-soft-shelled or shell-less eggs (McFerran and Adair, 2003) Eggshell Texture Rough or sand-paper shells, pimples, pinholes and mottled or glassy-shells are all egg shell defects associated with egg shell texture. These defects are frequently a result of bird age, but may also be caused by other factors (Coutts and Wilson, 1990; Natalie, 2008).

26 26 Disease: Certain disease such as IB, infectious Laryngotracheitis (ILT) (Beyer, 2005; Coutts and Wilson, 1990), and avian encephalomyelitis (AE) (Coutts and Wilson, 1990) have been implicated in the production of rough or sand-paper eggshells. Mycotoxicosis: As discussed above, ochratoxicosis may result in rubbery-shelled eggs (Jewers, 1990). Genetics: The production egg with calcium deposits on the shell (or pimple) is thought to be hereditary (Butcher and Miles, 2003a; Coutts and Wilson, 1990). Management: Overcrowding of birds, change in the lighting programme, poor shed ventilation and inadequate water supply can contribute to increased incidence of shell defect associated with egg texture (Coutts and Wilson, 1990) Eggshell Shape Misshapen eggs have a shape which differs from the smooth normal shape (for example, flat sided eggs and body checked eggs. This can be caused by a number of factors: Age of Bird: As with shell soundness, young birds with immature shell glands may produce misshapen eggs (Coutts and Wilson, 1990). Stress: Body checked eggs, marked by grooves and ridges, occur when the shell of the egg breaks in the shell gland during the formation process (i.e hours before the egg is laid). Although the damage can be partly repaired, a bulge forms around the egg (Solomon, 1991; Natalie, 2008). Flat sided eggs occur where two eggs are in the shell glan at the same time (Natalie, 2008). Both defects may be caused by overcrowding, frights or other disturbances and

27 27 poor lighting patterns (Koelkebeck, 2006; Coutts and Wilson, 1990). Jones (2006) stated that proper handling can reduce the incidence of body checks. Disease: As the albumen of the egg and surrounding membrane provide the structure on which the egg shell is deposited, if the albumen quality is very poor, there is no sound foundation on which to build the shell (Natalie, 2008). As a result, those diseases which result in poor albumen quality often cause an increase in the number of misshapen eggs. Examples of these are IB (Infectious Bronchitis) (Jones, 2006; Butcher and Miles, 2003a; Cavanagh and Naqi, 2003), Egg Drop Syndrome (EDS) (McFerran and Adair, 2003; Coutts and Wilson, 1990) and certain Newcastle Disease (NCD) or Avian Influenza (AI) (Butcher and Miles, 2003a; Coutts and Wilson, 1990) Eggshell Colour The colour of the egg shell is determined primarily by the genetics of the hen, with white feathered hens laying white eggs and brown feathered hens laying brown eggs (Jacob et al, 2000). During the process of eggshell formation in brown egg layers, the epithelial cells lining the surface of the shell gland synthesize and accumulate pigments, such as biliverdin-ix, its zinc chelate and protoporphyrin-ix (Butcher and Miles, 2003b). In the final three or four hours of shell formation, these pigments are transferred to the viscous, protein rich cuticle. The quantity of pigment in the cuticle determines the colour of the egg (Butcher and Miles, 2003b). As the cuticle is depositing onto the eggshell at the same time that shell deposition reaches a plateau approximately 90 minutes prior to oviposition), pigment distribution is not uniform throughout the shell, with very little pigment contained in the shell itself (Butcher and

28 28 Miles, 2003b). Thus, any factor which causes a disruption, either in the ability of the epithelial cells to synthesize pigment or in the deposition of the cuticle, will affect the colour of the egg shell. These factors include: Stress: Epinephrine, a stress hormone, will cause a delay in oviposition and cessation of shell gland cuticle formation, which can cause pale shelled eggs to be produced. Stressors may include, among others, high cage density, loud noise, and handling (Butcher and Miles, 2003b). Age of Bird: As birds age increases, the intensity of pigment decreases. This may be due to decreasing production of pigment or increased surface area over which available pigment is distributed (Butcher and Miles, 2003b). Chemotherapeutic Agents: Certain drugs have been shown to affect egg shell colour. For example, nicarbazin (an anticoccidial drug) fed at a level of 5mg per day can result in the production of pale eggs within 24 hours, while higher doses can lead to complete depigmentation (Butcher and Miles, 2003b). Chlortetracycline ( ppm) may also result in yellow egg shells (Beyer, 2005; Natalie, 2008). Diseases: Viruses, which affect the mucus membranes of the respiratory and reproductive tract, such as NCD and IB, not only cause a decrease in egg production, but also cause the shell to become abnormally thin and pale (Beyer, 2005; Butcher and Miles, 2003b) Eggshell Cleanliness Cleanliness is probably the easiest aspect of egg shell quality to control, and good management plays an important role. Most eggs are clean when laid and subsequently become contaminated with faecal material or other contaminants. Defects listed in the EPF code of

29 29 practice (EPF and NZFSA, 2002), which fall into this category, cage marks, stained eggs and fly marks. Although, fungus or mildew on shells is listed as a defect, it is only likely to occur in poor condition (Coutts and Wilson, 1990). Management: Good management practices will help reduce the number of dirty eggs. These practices include frequent collection of eggs, as well as regular replacement of litter material in the nest boxes or regular maintenance and cleaning of cage floors and roll out trays. It is found that; fly stains, water stains and grease or oil stains may occur, and can be prevented by good shed and equipment maintenance or management (Coutts and Wilson, 1990). Nutrition and/or Bird Health: Any factor which causes diarrhea in the birds, (for example high dietary salt levels), will also result in an increase in the number of dirty eggs collected. Blood smears on eggs can be minimized by good pullet management, including weight for age, lighting and beak trimming if necessary (Coutts and Wilson, 1990) Internal Egg Quality Unlike external (shell) quality, internal quality of the egg begins to decline as soon as the egg is laid. Thus although factors associated with the management and nutrition of the hen do play a role in Internal egg quality, egg handling and storage practices do have a significant impact on the quality of the egg reaching the consumer. Similarly, although the shell provides a unique package for the distribution of the egg contents to the consumer, it is in fact that internal quality of the egg that is most important to the consumer. These aspects of internal quality are significantly more difficult to observe or evaluate in the intact egg, even with the use of candling.

30 30 In addition to the, obvious, nutritional quality of the egg, internal egg quality is extremely important because of it s many functional and aesthetic properties. For example, eggs are used as thickening agents in custards and puddings, egg whites are used as smoothing agents to give icings a desirable texture and egg yolks add colour and richness to food (Koelkebeck, 1999). The EPF Code of Practice (EPF and NZFSA, 2002) lists a total of nine internal defects and these can be broadly categorized into three groups; namely: defects affecting yolk quality, defects affecting albumin quality and defects affecting overall quality Yolk Quality al. 2000). Yolk quality is determined by the colour, texture, firmness and smell of the yolk (Jacob et Yolk Colour: Although yolk colour is a key factor in any consumer survey relating to egg quality (Jacob et al., 2000), consumer preferences for yolk colour are highly subjective and vary widely from country to country. The primary determination of yolk colour is the xanthophyll (plant pigment) content of the diet consumed. It is possible to manipulate the yolk colour of eggs by the addition of natural or synthetic xanthophylls to layer hen feeds. This ability to readily manipulate egg yolk colour can be an advantage in meeting market demands. however, the ease with which yolk colour can be manipulated can lead to unwanted colour changes. For example, the inclusion of higher than recommended levels or incorrect ratios of pigments can lead to orange red yolks (Coutts and Wilson, 1990). Similarly, diphenyl para phenylenediamine (DPPD), an antioxidant, has been reported to cause excessive deposition of pigments in the egg yolk (Coutts and Wilson, 1990).

31 31 The inclusion of more than 5% cotton seed meal in a layer diet will result in olive or salmon coloured yolks (Beyer, 2005), while the inclusion of certain weeds or weed seeds may result in green yolks (Beyer, 2005; Coutts and Wilson, 1990). Similarly, inadvertent omission of xanthophylls from the diet will also result in a heterogeneous feed, and subsequent variation in the amount of xanthophylls consumed by each hen in the flock, this will result in egg yolk colour not being uniform throughout the flock. Pale yolks can result from any factor which alters or prevents the absorption of pigments from the diet or the deposition of these pigments in the yolk. These factors could include; - Worms (Coutts and Wilson, 1990) - Any factor which inhibits liver function, subsequent lipids metabolism and deposition of pigment in the yolk. For example, mycotoxicosis caused by aflatoxin BI (Zaghini et al., 2005) and - coccidiosis, although this is rare in adult hens. Mottled yolks (with many pale spots and blotches which vary in colour size and shape), occur when the contents of the albumen and yolk mix as a result of degeneration and increase permeability of the vitelline membrane (Jacob et al., 2000). Factors affecting mottling were reviewed in detail by Cunningham and Sanford (1974). Dietary factors which may cause mottled yolks include; - The presence of nicarbazin (an anticoccidalagent) in the feed has shown by numerous authors to cause mottling (Jones et al., 1990).

32 32 - Worming drugs such as phenothiazine (Coutts and Wilson, 1990), dibutyltin dialaurate (Jacob et al., 2000). It was observed that yolk defects were not recorded when peperazine was fed at the manufacturer s recommendations. Similarly, they only observed defects when dibutyltin dialaurate was fed at the recommended level but over a much longer period. - Gossypol from cotton and meal (Jacob et al., 2000). - Certain antioxidants such as gallic acid (from grapes, tea and oak bark) and tannic acid (Coutts and Wilson, 1990), or tannins from grains such as sorghum (Jacob et al., 2000). - Calcium deficient diets (Jacob et al., 2000). Storage time and temperature has also been shown to affect the degree of egg yolk mottling (Jacob et al., 2000; Coutts and Wilson, 1990). Jones (2006) stated that as the internal temperature of the egg increase above 7 0 C, the protein structures of the thick albumen and vitelline membrane breakdown faster. As the membrane degenerates during storage, water enters the yolk causing mottling and after prolonged storage, albumen proteins also enter the yolk increasing the severity of mottling (Jacob et al., 2000). In order to reduce the rate of breakdown of the vitelline membrane, eggs should be collected regularly, reducing the time they are exposed to higher environmental temperatures and contaminants, and stored at temperatures of C and humidity of 50 60%. Yolk Firmness: The yolk of a freshly laid egg is round and firm (Jacob et al., 2000). However, as the egg ages and the vitelline membrane degenerates, water from the albumen moves into the yolk and give the yolk a flattened shape.

33 33 Yolk texture: Rubbery yolks may be caused by severe chilling and freezing of intact eggs, the consumption of crude cottonseed oil or the seeds of some weeds (Jacob et al., 2000) Albumin Quality Albumin quality is related to the consistency, appearance and the functional properties, albumen quality is measured in terms of Haugh Units (HU) calculated from the height of the albumen and the weights of the egg (Coutts and Wilson, 1990). A minimum measurement in HU for eggs reaching the consumer is 60. However, most eggs leaving the farm should be between 75 and 85 HU (Coutts and Wilson, 1990). 2.3 FACTORS AFFECTING INTERNAL EGG QUALITY INDICES Age of the Hen: HU will decrease with increasing bird age value, with HU decreasing by around 1.5 to 2 units (Coutts and Wilson, 1990) for each mouth in lay. Doyon et al., (1986, cited by Jones, 2006) stated that HU decreases at a fairly constant rate of units per day of lay as the hen ages. It was found that in an ideal situation, HU should be on average 102 at 20 weeks of age, falling to an average of 74 HU by weeks of age Genetics: Strain of bird has also been shown to play a role in albumin consistency, with some strains consistently producing eggs with thin albumin. Curtis et al., (1985, cited by Jones, 2006) reported that brown egg layers produced eggs with higher HU, while other authors (Williams, (1992) cited by Jones (2006); Hill (1981) cited by Jones ( 2006) reported that HU values were more variable within the brown egg layers compared with those that lay white eggs. High producing birds tend to lay eggs with relatively lower amounts of thick albumin and, although this can be influenced by selective breeding, egg numbers are usually considered more important.

34 Age and Storage of the Egg: As the egg ages and CO 2 (carbon dioxide) is lost through the shell, the contents of the egg become more alkaline, causing the albumin to become transparent and increasingly watery (Natalie, 2008). At higher temperatures, loss of CO 2 is faster and the albumin quality deteriorates faster. Decreasing shed temperatures in the hotter months, combined with regular collection of eggs will help to reduce deterioration of the albumin before collection (Jones, 2006; Coutts and Wilson, 1990). Eggs stored at ambient temperatures and humidity lower than 70% will lose HU in few days from point of lay. By 35 days, these eggs will lose up to 30 HU. Storage of eggs at temperatures of C and humidity of 50 60% will reduce the rate of degeneration of thick albumen proteins consequently, egg albumin quality will be maintained for longer (Jones, 2006). Oiling of eggs can also help to reduce CO 2 losses and thus help maintain internal egg quality (Beyer, (2005); Koelkebeck, (1999); Coutts and Wilson, (1990) but it is not a substitute for cold storage (Jacob et al., 2000) Diseases: Diseases such as certain strains of EDS, IB (Jacob et al., 2000; Coutts and Wilson, 1990), NCD and ILT (Jacob et al., 2000) can cause a decrease in albumin consistency Blood Spots: Blood spots may vary from indistinguishable spots on the surface of the yolk to heavy contamination throughout the yolk (Coutts and Wilson, 1990). Although blood spots are normally closely associated with the yolk (Natalie, 2008), occasionally blood may be diffused through the albumin (Coutts and Wilson, 1990). Blood spots occure when small blood vessels in the ovary rupture when the yolk is released (Natalie, 2008). Vitamin Deficiency: Vitamin K plays an important role in blood clotting. Vitamin K deficiency can result in an increased occurrence of blood spots (Bains, 1999).

35 35 Genetics: Some strains of birds appear to be predisposed to blood spots (Coutts and Wilson,, 1990) although the incidence is low (Bayer, 2005). Disease: Avian encephalomyelitis has been reported as a cause of blood spots (Coutts and Wilson, 1990). Mycotoxicosis: Jewers (1990) reported an increase in blood spots from essentially 0 to 3% in birds affected with T 2 toxicosis. Bains (1990) suggested that mycotoxicosis may reduce vitamin K absorption and this may explain the elevated incidence of blood spots in hens affected by T 2 toxicosis Meat Spots: These are usually associated with the albumin (Natalie, 2008) rather than the yolk and often consist of small pieces of body tissue (Coutts and Wilson, 1990). However, some may consist of partially broken down blood spots (Coutts and Wilson, 1990) or pigments. The occurrence of blood spots varies with strain of bird, increases with age of bird and is reported to be higher in brown egg layers (Coutts and Wilson, 1990) Bacterial or Fungal Contamination: Solomon (1991) suggested that while pores on the surface of the egg do represent possible ports of entry for bacteria, particularly as the cuticle hardens just after oviposition, these are of secondary importance to the structural defects that are likely route for bacteria to enter the egg. Bacteria and fungal contamination of eggs usually results in black, red, or green rot. The egg looks and smells putrid when broken out of the shell (Bayer, 2005; Coutts and Wilson, 1990). Bacterial and fungal contamination of eggs, resulting from faecal contamination of the egg, can be prevented by good management practices including regular replacement of nesting materials or good cage maintenance as appropriate (Beyer, 2005; Coutts and Wilson, 1990). Bacterial

36 36 contamination of the egg contents may also occur as a result of an infection in the oviduct of the hen and any affected hens should be culled (Coutts and Wilson, 1990). Proper handling and storage of eggs following collection will minimize the opportunity for bacterial or fungal contamination. However, improper washing procedures, high storage temperatures and humidity will increase the incidence of bacterial or fungal contamination (Coutts and Wilson, 1990). Careful attention should be paid to feed source, as salmonella spp. can be transmitted through the feed Roundworms in Eggs: Coutts and Wilson (1990) reported that where roundworm infestation of the intestinal tract occurs, worms may migrate from the cloaca into the oviduct and become enclosed in the egg. This can be prevented by good flock management Off Odors/Flavors: Although off odours and flavours are rare if eggs are stored correctly (Coutts and Wilson, 1990), eggs readily absorb strong odours or flavours. Storage of eggs in close proximity to fish oils and meals, sour milk, strongly scented or decaying fruits and vegetables, mould, disinfectants and kerosene is likely to result in the development of off odours or flavours (Coutts and Wilson, 1990). However, eggs that have been oiled are less likely to absorb foreign odours (Coutts and Wilson, 1990). Old eggs and eggs stored at high temperatures are more likely to exhibit off odours or flavours. Other sources of off odours or flavours include strongly flavoured feed ingredients such as fish meal or fish oil, some vegetables (including onions, turnips and excessive amounts of cabbage) and rapeseed or canola (Coutts and Wilson, 1990).