Partial ablation of uropygial gland effect on carcass characteristics of Akar Putra chicken

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1 Partial ablation of uropygial gland effect on carcass characteristics of Akar Putra chicken HasanS.A.Jawad,,,1 L. H. Idris, Z. B. Bakar, and A. B. Kassim Dept. of Veterinary Preclinical Sciences, Faculty of Veterinary Medicine, University of Putra Malaysia; Dept. of Animal Sciences, Faculty of Agriculture, University of Putra Malaysia; and Dept. of Veterinary Anatomy, Histology and Embryology, Faculty of Veterinary Medicine, University of Baghdad, Iraq ABSTRACT This study evaluated the effect of partial with or without eating giblets, and the relative weights uropygialectomy (PU) on carcass traits of male and female Akar Putra chickens. Sixty chicks of each sex were evenly distributed into 5 treatment groups with 3 replicates per group containing 4 males and 4 females each, and reared for 12 wk. Homogeneity of the groups was satisfied with regard to the parity. Experimental treatments consisted of a control treatment (T1), and partial ablation of the uropygial gland was applied on the second, third, fourth, and fifth treatmentsat3,4,5,and6wkofage,respectively.the chickens were fed ad libitum the same diets (1 to 13 d: starter; 14 d to slaughter: finisher). On the last d of the experiment, 12 birds were randomly selected from each treatment group (2 males and 2 females per replicate) and slaughtered to determine carcass characteristics, which included carcass weight, dressing percentage of heart, liver, gizzard, thighs, wings, breast, back, and neck. From the results of the study, it was shown that the partial ablation of the uropygial gland at all ages had certain dependent effects concerning some carcass parameters, as shown by higher breast and back relative weights in males and breast relative weight in females. As a consequence, a positive effect also was noticed regarding the carcass morphology in terms of the increase in dressing percentage with or without eating giblets thus leading to an increase in the body weight and carcass weight. Furthermore, the best result was obtained in the second treatment when PU was applied at 3 wk of age compared with other experimental groups. Moreover, the current study provides a novel and economic alternative to enhance the body performance of poultry in general and Akar Putra chicken particularly. Key words: avian gland, uropygial gland, Akar Putra chicken 2016 Poultry Science 95: INTRODUCTION Akar Putra is a local Malaysian chicken; the cross breeding process happened by chance when wild jungle fowl entered the University of Putra Malaysia grounds and mated with the university s chickens (ayam kampong). Akar Putra has a more robust growth process than its parents because the maturation period is shorter (less than 13 wk); it can lay 120 to 200 eggs per year and has more resistance to diseases (Jawad et al., 2015a). Birds are exposed to terrestrial pressures similar to mammals and reptiles, yet the structure of their integument differs markedly from these animal groups (Menon and Menon, 2000). One of the major differences is the development of the uropygial gland (UG), which, like mammalian sebaceous glands, produces oil (King and McLelland, 1985; Sara et al., 2006). The C 2016 Poultry Science Association Inc. Received July 27, Accepted February 28, Corresponding author: dr.hassan198366@yahoo.com UG is the only subcutaneous gland in the bird s body (Mclelland, 1990). It is described as a preen gland based on its function in preening the bird s feather (Lucas and stettenheim, 1972; King and Mclelland, 1984). Some researchers use an oil gland codename, depending on its oily secretion (Schultz et al., 2002). Nevertheless, it is called uropygial gland because it lies on the base of the tail, dorsally between the fourth caudal vertebrae and pygostile (Lucas and Stettenheim, 1972; Sawad,2006). The function of the gland is still a subject of controversy. There are many accepted functions of gland secretions like conferring water-repellent properties on the feather coat and maintaining the suppleness of it. Furthermore, it is proposed to be associated with pheromone production, control of plumage hygiene, thermal insulation, and defense against predators (Montalti et al., 2000; Vincze et al., 2013). The UG is completely absent in Struthionidae, Rheidae, Casuaridae, and Dromaidae and in a few species of Columbidae and Psittacidae (Johnston, 1988). Montalti and Salibián (2000) mentioned that the oil of the UG is not important to the birds that do not have it. While, Goodwin (1983) mentioned that the UG in 1966

2 PU EFFECT ON CARCASS CHARACTERISTICS 1967 some of the birds is non-active. After that, Brett et al. (2003)and Moyer et al.(2003a) explained that the birds that do not have a UG use dust baths to keep and clean their feathers. MATERIALS AND METHODS Animals and Housing This research was conducted at the poultry farm of Veterinary Medicine Faculty, University of Putra Malaysia (UPM) from December 15, 2014, to March 15, Furthermore, it was approved by the Institutional Animal Care and Use Committee (IACUC) certificate number R070. This study consists of 120 one-day-old local Malaysian chicks (Akar Putra strain). They were randomly assigned to 5 treatment groups by 24 (12 male and 12 female) per treatment, and each treatment consisted of 3 replicates of 8 (4 males and 4 females) birds per replicate. The birds werehousedinwirecageswith8birds(4malesand4females) per pen (5 x4 x1.5 ). The feed was offered ad libitum consisting of the same diets (1 to 13 d: starter; 14 d to slaughter: finisher) with continuous water provided. All the birds were kept under uniform management conditions throughout the experimental period of 12 wk. Partial Uropygialectomy Partial uropygialectomy (PU) was applied with T2, T3, T4, and T5 treatments at 3, 4, 5, and 6 wk of age, respectively. It was conducted based upon the procedure reported by (Jawad et al., 2015a). Carcass Characteristics On the last d of the experiment, 12 birds were randomly selected from each treatment group (2 males and 2 females per replicate) and withdrawn from feed overnight to facilitate gut clearance. After that, the birds were weighed to obtain the live body weight. After recording the weights of the birds, they were slaughtered, defeathered, processed (removal of the head and feet), and eating giblets eradicated (removal of the gastrointestinal tract). The carcasses were immediately dissected to determine the percentage of carcass morphology by measuring the relative weights of eating giblets (heart, liver, and gizzard), thighs, wings, breast, back, and neck. Then, the observations of carcass weight and dressing percentage with and without eating giblets were reported. The variation ration was counted based on the formula reported by (Jawad et al., 2015a). Research Design and Data Analysis This research used a one-way complete random sampling (Steel and Torrie, 1980). Data results were analyzed by one-way analysis of variance (ANOVA). If the treatment significantly affected the chicken, LSD and 150 Duncan (1955) Multiple Range were applied (DRMT) (Genstat, 2003). Differences among treatments were considered significant at P < 0.01 and P < RESULTS The effects of partial ablation of UG on carcass traits descriptive of male and female Akar Putra chickens are presented in Tables 1 and 2. Generally, all PU treatments showed significant results in live body weight, and most of the carcass traits in males and females compared with the control group. The highest live body weight in males was reported in T2 followed by T5, T3, and T4, respectively. However, there was no significant difference among T2, T5, and T3 treatments. Table 1. The effect of partial ablation of the uropygial gland at wk 3 (T2), 4 (T3), 5 (T4), and 6 (T5) of age on male carcass characteristics at the marketing age (Mean ±SE). Parameters T1 T2 T3 T4 T5 Live body weight ± c ± 28.5 a ± a,b ± b ± a,b Carcass weight A ± d ± 28.5 a ± c ± c ± b Carcass weight B ± d ± a ± c 1167 ± c ± b Dressing percentage A ± 0.79 d ± 0.23 a ± 0.43 c ± 0.42 c ± 0.34 b Dressing percentage B ± 0.51 d ± 0.08 a ± 0.27 c ± 0.25 c ± 0.2 b Thighs R.W ± ± ± ± ± 0.22 Breast R.W ± 0.18 b ± 0.1 a ± 0.08 a,b ± 0.09 b ± 0.09 a Back R.W ± b ± a ± b ± 0.02 b ± a Wings R.W ± ± ± ± ± Neck R.W ± ± ± ± ± Hart R.W ± ± ± ± ± Liver R.W ± ± ± ± ± Gizzard R.W ± ± ± ± ± a d Mean values with common superscript in row differ significantly (P < 0.01). R.W.: Means relative weight.

3 1968 JAWADETAL. Table 2. The effect of partial ablation of the uropygial gland at wk 3 (T2), 4 (T3), 5 (T4) and 6 (T5) of age on female carcass characteristics at the marketing age (Mean ±SE). Parameters T1 T2 T3 T4 T5 Live body weight ± c ± a ± c ± b ± b Carcass weight A ± d ± a ± c ± b ± b Carcass weight B ± d ± 21.6 a ± c ± 21.4 b ± b Dressing percentage A ± 0.01 d ± 0.03 a ± 0.56 c ± 0.42 b ± 0.4 b Dressing percentage B ± 0.8 d ± 0.07 a ± 0.39 c ± 0.29 b ± 0.23 b Thigh R.W ± ± ± ± ± Breast R.W ± 0.23 b ± a ± b ± b ± b Back R.W ± ± ± ± ± Wings R.W ± ± ± ± ± Neck R.W ± ± ± ± ± Hart R.W ± ± ± ± ± Liver R.W ± ± ± ± ± Gizzard R.W ± ± ± ± ± a-d Mean values with common superscripts in row differ significantly (P < 0.01). a-b Breast relative weight mean values with common superscript in row differ significantly (P < 0.05). R.W.: Means relative weight. Simultaneously, the T2 treatment in females recorded the highest live body weight followed by T4 and T5, then T3 and the control group. No impactful difference between T4 and T5 or between T3 and T1 were indicated. In males, partially removing the UG at wk 3 resulted in a highly significant difference (P < 0.01) in carcass weight and dressing percentage with and without eating giblets, followed by T5, T4, and T3 in comparison to the T1 control group. On the other hand, the worst result of these traits in males was shown in T3 compared with other PU treatments. In females, the highly significant effects on carcass weight and dressing percentage with and without eating giblets traits were reported in T2, T5, and T3 with no significant impact among them, followed by T4 then the T1 control group. Applying the PU operation at 3 and 6 wk of age provided the heaviest breast and back in males (P < 0.01). Whereas, performing the operation at 4 and 5 wk of age had no significant effect compared with the control group for these traits. Likewise, the breast relative weight of females was found to be significantly (P < 0.05) different as a result of performing the PU operation at wk 3. Overall, the PU operation did not result in any significant effect on the relative weight of male and female wings, neck, heart, liver, and gizzard. However, it had a high impact on the live body weight, carcass weight with or without eating giblets, dressing percentage with or without eating giblets, breast, and back relative weights of both males and females. DISCUSSION First, the present research observed the UG located on the base of the tail, dorsally to the Levator caudal muscle. It can be indicated by palpation above the last sacral vertebra and the first caudle vertebra. These results coincide with those reported by Nicket et al. (1977); Montalti and Saliban (2000); and Gezici (2002) and pointed out by Aslan et al. (2000) who reported that the gland lies on the pygostyl muscle. From investigations of the UG in birds to date, the UG is known to be situated dorsally and medially in the synsacrocaudal region of the bird s body and, when it is present, is always visible to the naked eye (Jacob and Ziswiler, 1982; Martín et al., 2009; Harem et al., 2010). The UG in Akar Putra chickens has a shared basic structure heart shaped with a broad-bean size although some specific differences have been noted. Jacob and Ziswiler (1982) demonstrated the morphological differences between glands in a variety of birds. They found that the largest UG when expressed as a percentage of body weight occurred in the Little Grebe (Tachybaptus ruficollis); it accounted for 0.61% of total body weight. The smallest gland was found to occur in fruit pigeons (genera: Ducula and Ptilinopus), where it represented <0.02% of total body weight. Comparative studies of this sort are important in discovering the selective pressures driving the UG development and these differences between differing groups of birds (Salibian and Montalti, 2009). Calislar (1986) mentioned that the gland had a chicken egg size in pelicans and an almond bean size in ducks. The present experiment found that the UG contains right and left lobes, which have been separated by an interlobular barrier except for the lobe adhesion area in the isthmus in the back third of the gland, and these observations are consistent with Getty (1975). The gland is most commonly a bilobed organ, which varies in both size and shape, depending on the species (Stettenheim, 2000; Salibian and Montalti, 2009). Each lobe contains both the secretory tissue, which produces the oil, and an intricate duct system, which relays the secretion to the papilla, the route to the skin s surface (Jacob and Ziswiler, 1982; King and McLelland, 1985; Salibian and Montalti, 2009). The

4 PU EFFECT ON CARCASS CHARACTERISTICS 1969 UG has a uropygial papilla lying dorso-caudally of the gland and has a uropygial wike. The gland s canals have a single opening at each lobe and possess a pair of canals. Nevertheless, Shawkey et al. (2003) stated that the uropygial papilla in geese was short and wide and held 2 openings for their canals; in chickens the papilla is long and thin, while in turkeys the papilla is wider. On the other hand, some birds, such as the Musk duck, lack the uropygial wike. The papilla is located just above the tail (King and McLelland, 1985; Stettenheim, 2000) and has a characteristic nipple-like appearance (Jacob and Ziswiler, 1982). Most birds also have a tuft of downy feathers (Jacob and Ziswiler, 1982; Stettenheim, 2000) arranged around the papilla, which aids in anointing the bill with the oily secretion (Lucas and Stettenheim, 1972; King and McLelland, 1985; Stettenheim, 2000). Once on the bill, the secretion is spread through the plumage. The papilla is clearly separated from the lobes of the gland by an isthmus formed by very strong connective tissue (Lucas and Stettenheim, 1972). There was a noticeable significant interaction for performing PU on the experimental chickens compared to the control group. The results revealed that partial ablation of the UG at all ages had effects dependent on the evaluated characteristics. Indications about the positive effects of PU on the Akar Putra chicken have been also given in previous studies, which examined its effect on production performance (Jawad et al., 2015a), the anatomy of the digestive system (Jawad et al., 2015b), as well as growth hormone and histology of the digestive system (Jawad et al., 2015c). The results showed that the partial ablation of the UG did not have any serious consequence for the survival of Akar Putra chickens, and no mortality happened during the trial period. That agrees with Jacob (1976) and Chen et al. (2003) who, by considering the physiological role of the UG, suggested it appears that the gland is not necessarily presented in all groups of birds. This fact, observed in a number of species, together with the lack of a clear-cut ecological correspondence, suggests that, when it is present, the function of the gland may be diverse, but not essential. In this regard, it is interesting that the extirpation of the gland was not dangerous for the survival of goslings, hens, or passerine birds. The current research proves that the removing of the UG has a significant effect on the main carcass traits of Akar Putra chickens concerning live body weight, carcass weight with and without eating giblets, dressing percentage with and without eating giblets, and breast and back relative weights. Table 3 shows the variation ratio (%) in male carcass characteristics of PU treatments compared to the control group. Overall, the remarkable variation ratio of carcass weight and dressing percentage with and without eating giblets was indicated in the PU treatments. A higher variation ratio than the control group in the trait of carcass weight with eating giblets was in the T2 = 58.6%, followed by Table 3. The effect of partial ablation of the uropygial gland at wk 3 (T2), 4 (T3), 5 (T4), and 6 (T5) of age on the male carcass variation ratio (%) at the marketing age. Parameters T2 T3 T4 T5 Live body weight Carcass weight A Carcass weight B Dressing percentage A Dressing percentage B Thigh R.W Breast R.W Back R.W Wings R.W Neck R.W Hart R.W Liver R.W Gizzard R.W R.W.: means relative weight. Table 4. The effect of partial ablation of the uropygial gland at wk 3 (T2), 4 (T3), 5 (T4), and 6 (T5) of age on the female carcass variation ratio (%) at the marketing age Parameters T2 T3 T4 T5 Live body weight Carcass weight A Carcass weight B Dressing percentage A Dressing percentage B Thigh R.W Breast R.W Back R.W Wings R.W Neck R.W Hart R.W Liver R.W Gizzard R.W R.W.: Means relative weight. T5 = 45.7%, T3 = 35%, and T4 = 34%. Likewise, the T2 treatment achieved priority in carcass weight without eating giblet with 59%, followed by T5 = 46%, T3 = 34.9%, and T4 = 34.2%. Furthermore, a noticeable variation ratio in the dressing percentage with eating giblets was observed in T2 = 30.4%, followed by T5 = 21.8%, T4 = 17.8%, and T3 = 16.8%. The same superiority order in the dressing percentage without eating giblets trait was shown as follows: T2 = 30.8%, T5 = 22%, T4 = 18%, and T3 = 16.6%. Table 4 highlights a remarkable increase in the variation ratio of female carcass characteristics in the PU treatments. In the carcass weight with eating giblets trait, the variation ratios were as follows: T2 = 121.7%, T5 = 64.6%, T3 = 64.2%, and T4 = 29.1%, while in the

5 1970 JAWADETAL. carcass weight without eating giblets trait, they were: T2 = 122.2%, T5 = 64.7%, T3 = 64.3%, and T4 = 29.1%. A significant outweighing of the T2 treatment variation ratio in the dressing percentage with eating giblets trait was reported, which was 60.3% followed by T5 = 30.5%, T4 = 29.6%, and T3 = 22.6%. The same thing was observed in the dressing percentage characteristic as follows: T2 = 60.7%, T5 = 30.6%, T4 = 29.7%, and T3 = 22.7%. These results agree with Al-Hassani, D.H. et al. (2008) when they tested the effect of removing the UG (uropygialectomy) on the same semen trails of broiler breeder males and they got significant effects of removing the gland on all semen tested trails. Also, they recommended that a uropygialectomy could be used as a tool to improve fertility in a broiler breeders aged 38 to 54 wk. While Montalti et al. (1998, 2000) andmoyeretal.(2003b) supported an idea that surgical removal of the UG did not necessarily have a positive impact on the body performance for all bird species. They gave evidence that the surgical removal of the UG in Columba Livia did not affect the behavior, survival, and body weight gain and feeding rates, over a 2-mo period. In all species of bird examined to date, this gland is present throughout embryonic development; however, it is not necessarily present in the adult (Montalti and Salibian, 2000; Martín et al., 2009; Salibian and Montalti, 2009). This gland may be considered a primitive feature of the group aves because orders that do not possess the gland as adults are possibly exhibiting a form of secondary specialization (Montalti and Salibian, 2000). In this regard, Montalti et al. (2006) measured several biochemical parameters in relation to gland physiology comparing control specimens with gland-removed specimens. No differences were found in serum levels of cholesterol, total lipids, and calcium after 32 to 120 d. Thus, no alteration in 2 basic biochemical parameters associated with the metabolism of lipids and in a critical parameter related to mineral homeostasis was noted 4 mo after ablation of the gland. These results suggest that the UG may not relate, at least physiologically, to the homeostasis of lipids or to the regulation of calcium metabolism. CONCLUSION AND SUGGESTIONS Based on the results and discussion, it can be concluded that stopping the function of the UG by partial surgical removal technique, especially at 3 wk of age, caused an improvement in the carcass characteristics of Akar Putra chickens significantly. It is assumed that the oil of the UG had a positive impact on the body performance after removing the gland. Based on the conclusion, the research team created several suggestions as follows: 1. Developing research about removing the uropygial gland in one-week-old chicks so that it can increase the effect of the uropygial gland oil on body performance. 2. Developing research about the oil of the uropygial gland biochemistry so that the mechanism of enhancing the body performance after removing the gland can be identified. 3. Since the function of this gland is not yet known, research into its existence in different species is imperative to the discovery of the evolutionary drive causing its development. Considering that there are about 10,000 bird species worldwide, it is very interesting that only 16% of birds UG has been investigated anatomically. With such a small number, the information to be gained from further investigations is likely to be substantial and will contribute to the overall understanding of both the structure and function of this gland. ACKNOWLEDGMENTS This paper was supported by University of Putra Malaysia in The authors wish to thank Prof. Saad A. 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