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Breeding for better welfare: genetic goals for broiler chickens and their parents

Published online by Cambridge University Press:  01 January 2023

MS Dawkins*
Affiliation:
Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK
R Layton
Affiliation:
FAI (Food Animal Initiative), The Field Station, Wytham, Oxford OX2, UK
*
* Contact for correspondence and requests for reprints: [email protected]
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Abstract

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Genetics is key to the improvement of welfare in broiler chickens at both juvenile and adult (breeder) stages but progress is hampered currently by the seemingly conflicting demands of welfare, commercial production, food security and calls for increasing intensification to curb climate change. Animal welfare is therefore most likely to be improved on a commercial scale by future breeding programmes that incorporate multiple goals of different stakeholders as far as possible and give higher priority to animal welfare. These include: i) broilers with high welfare traits; ii) broiler breeders that do not need feed restriction; iii) birds that can be grown in an economically profitable way; iv) birds with low disease levels without the need for routine medication; v) chicken meat that is healthy and good for humans to eat; and (vi) broilers and breeders that thrive in systems that are environmentally sustainable. Progress towards achieving these goals is hampered currently by the assumptions that high juvenile growth rate is incompatible with good welfare and that feed restriction in adults is inevitable with fast-growing juveniles. We challenge these assumptions at both genetic and whole-animal level and argue that the conflict between good welfare and productivity can be reduced by making use of all available genetic variation from existing breeds and other sources and selecting birds in the range of environments they will encounter in commercial production.

Type
Research Article
Copyright
© 2012 Universities Federation for Animal Welfare

References

Ankra-Badu, GA, Le Bihan-Duval, E, Mignon-Grasteau, S, Pitel, F, Beaumont, C, Duclos, MJ, Simon, J, Carre, W, Porter, TE, Vignal, A, Cogburn, LA and Aggrey, SE 2010 Mapping QTL for growth and shank traits in chickens divergently selected for high or low body weight. Animal Genetics 41: 400405Google ScholarPubMed
Arendt, JD 1997 Adaptive intrinsic growth rates: an integration across taxa. Quarterly Review of Biology 72: 149177. http://dx.doi.org/10.1086/419764CrossRefGoogle Scholar
Arnould, C and Leterrier, C 2007 Welfare of chickens reared for meat production. Productions Animales 20: 4145CrossRefGoogle Scholar
Barbato, GF 1991 Genetic architecture of growth curve parameters in chickens. Theoretical Applied Genetics 83: 2432. http://dx.doi.org/10.1007/BF00229222Google ScholarPubMed
Bessei, W 2006 Welfare of broilers: a review. World's Poultry Science Journal 62: 455466. http://dx.doi.org/10.1079/WPS2005108CrossRefGoogle Scholar
Bilcik, B and Estevez, I 2005 Impact of male-male competition and morphological traits on mating strategies and reproductive success in broiler breeders. Applied Animal Behaviour Science 92: 307323. http://dx.doi.org/10.1016/j.applanim.2004.11.007CrossRefGoogle Scholar
Bradshaw, RH, Kirkden, RD and Broom, DM 2002 A review of the aetiology and pathology of leg weakness in broilers in relation to welfare. Avian Poultry Biology Reviews 13: 45103. http://dx.doi.org/10.3184/147020602783698421CrossRefGoogle Scholar
Cogburn, LA, Wang, X, Carre, W, Rejto, L, Porter, TE, Aggrey, SE and Simon, J 2003 Systems-wide chicken DNA microarrays, gene expression profiling, and discovery of functional genes. Poultry Science 82: 939951CrossRefGoogle ScholarPubMed
Cooper, MD and Wrathall, JHM 2010 Assurance schemes as a tool to tackle genetic welfare problems in farm animals: broilers. Animal Welfare 19: 5156Google Scholar
Corr, SA, Gentle, MJ, McCorquodale, CC and Bennett, D 2003 The effect of morphology on walking ability in the modern broiler: a gait analysis study. Animal Welfare 12: 159171Google Scholar
Dawkins, MS 2012 Why Animals Matter: Animal Consciousness, Animal Welfare and Human Well-Being. Oxford University Press: Oxford, UKGoogle Scholar
Dawkins, MS and Bonney, R 2007 The Future of Animal Farming: Renewing the Ancient Contract. Blackwell: Oxford, UKGoogle Scholar
Dawkins, R 1982 The Extended Phenotype. WH Freeman: Oxford, UKGoogle Scholar
D’Eath, RB, Tolkamp, BJ, Kyriazakis, I and Lawrence, AB 2009 ‘Freedom from hunger’ and preventing obesity: the animal welfare implications of reducing food quantity or quality. Animal Behaviour 77: 275288. http://dx.doi.org/10.1016/j.anbehav.2008.10.028CrossRefGoogle Scholar
D’Eath, RB, Conington, J, Lawrence, A, Olsson, IAS and SandØe, P 2010 Breeding for behavioural change in farm animals: practical, economic and ethical considerations. Animal Welfare 19: S17S27Google Scholar
Decuypere, E, Buyse, J and Buys, N 2000 Ascites in broiler chickens: exogenous and endogenous structural and functional causal factors. World's Poultry Science Journal 56: 367377. http://dx.doi.org/10.1079/WPS20000025CrossRefGoogle Scholar
Decuypere, E, Hocking, PM, Tona, K, Onagbesan, O, Bruggeman, V, Jones, EKM, Cassy, S, Rideau, N, Metayer, S, Jego, Y, Putterflam, J, Tesseraud, S, Collin, A, Duclos, M, Trevidy, JJ and Williams, J 2006 Broiler breeder paradox: a project report. World's Poultry Science Journal 62: 443453CrossRefGoogle Scholar
Decuypere, E, Onagbesan, O, Swennen, Q, Buyse, J and Bruggeman, V 2007 The endocrine and metabolic interface of genotype-nutrition interactions in broilers and broiler breeders. World's Poultry Science Journal 63: 115128. http://dx.doi.org/10.1017/S004393390700133XGoogle Scholar
de Jong, IC, van Voorst, S, Ehlhardt, DA and Blokhuis, HJ 2002 Effects of restricted feeding on physiological stress parameters in growing broiler breeders. British Poultry Science 43: 157168. http://dx.doi.org/10.1080/00071660120121355CrossRefGoogle ScholarPubMed
de Jong, IC and Guémené, D 2011 Major welfare issues of broiler breeders. World's Poultry Science Journal 67: 7381. http://dx.doi.org/10.1017/S0043933911000067CrossRefGoogle Scholar
Dunnington, EA and Siegel, PB 1985 Long-term selection for eight-week body weight in chickens: direct and correlated responses. Theoretical Applied Genetics 71: 305313CrossRefGoogle Scholar
Estevez, I 2007 Density allowance for broilers: where to set the limits. Poultry Science 86: 12651272CrossRefGoogle ScholarPubMed
Feldman, MW and Lewontin, RC 1975 The heritability hangup. Science 190: 11631168. http://dx.doi.org/10.1126/science.1198102CrossRefGoogle ScholarPubMed
Flock, DK, Laughlin, KF and Bentley, J 2005 Minimizing losses in poultry breeding and production: how breeding companies contribute to poultry welfare. World's Poultry Science Journal 62: 227237CrossRefGoogle Scholar
Food and Agriculture Organisation 2010 http://faostat.fao.org/site/291Google Scholar
Fortin, D, Gauthier, J and Larochelle, J 2000 Body temperature and resting behaviour of Greater snow goose goslings in the high arctic. The Condor 102: 163171. http://dx.doi.org/10.1650/0010-5422(2000)102[0163:BTARBO]2.0.CO;2CrossRefGoogle Scholar
Gao, Y, Du, ZQ, Feng, CG, Deng, XM, Li, N, Da, Y and Hu, XX 2010 Identification of quantitative trait loci for shank length and growth at different development stages in chicken. Animal Genetics 41: 101104. http://dx.doi.org/10.1111/j.1365-2052.2009.01962.xCrossRefGoogle ScholarPubMed
Godfray, HCJ, Beddington, JR, Crute, IR, Haddad, L, Lawrence, D, Muir, JF, Pretty, J, Robinson, S, Thomas, SM and Toulmin, C 2010 Food security: the challenge of feeding 9 billion people. Science 327: 812818. http://dx.doi.org/10.1126/science.1185383CrossRefGoogle ScholarPubMed
Godin, JGJ and McDonough, HE 2003 Predator preference for brightly colored males in the guppy: a viability cost for a sexually selected trait. Behavioral Ecology 14: 194200. http://dx.doi.org/10.1093/beheco/14.2.1.94CrossRefGoogle Scholar
Gonzalez-Recio, O, Gianola, D, Rosa, GJM and Weigel, KA 2009 Genome-assisted prediction of a quantitative trait measured in parents and progeny: application to food conversion rate in chickens. ASO Genetics Selection Evolution 4: DI 10.1186/1297-9686-41-3Google Scholar
Granevitze, Z, Hillel, J, Chen, GH, Cue, NTK, Feldman, M, Eding, H and Weigend, S 2007 Genetic diversity within chicken populations from different continents and management histories. Animal Genetics 38: 576583. http://dx.doi.org/10.1111/j.1365-2052.2007.01650.xCrossRefGoogle ScholarPubMed
Groenen, MAM, Wahlberg, PF, Cheng, M, Megens, HH, Crooijmans, H-J, Richard, PMA, Besnier, F, Lathrop, M, Muir, WM, Wong, G, Gut, I and Andersson, L 2009 A high density SNP-based linkage map of the chicken genome reveals sequence features correlated with recombination rate. Genome Research 19: 510519. http://dx.doi.org/10.1101/gr.086538.108CrossRefGoogle ScholarPubMed
Grossman, M and Koops, WJ 1988 Multiphasic analysis of growth curves in chickens. Poultry Science 67: 3342CrossRefGoogle ScholarPubMed
Henderson, ND 1970 Genetic influences on behaviour of mice can be obscured by laboratory rearing. Journal of Comparative and Physiological Psychology 72: 505511CrossRefGoogle ScholarPubMed
Hill, WG 2010 Understanding and using quantitative genetic variation. Philosophical Transactions of the Royal Society B365: 7385CrossRefGoogle Scholar
Hocking, PM 2004 Measuring and auditing the welfare of broiler breeders. In: Weeks CA and Butterworth (eds) Measuring and Auditing Broiler Welfare pp 1935. CABI: Wallingford, UKGoogle Scholar
Hocking, PM 2006 High-fibre pelleted rations decrease water intake but do not improve physiological indexes of welfare in food-restricted female broiler breeders. British Poultry Science 47: 1923CrossRefGoogle Scholar
Hocking, PM, Gilbert, AB, Walker, M and Waddington, D 1987 Ovarian follicular structure of white leghorns fed ad libitum and dwarf and normal broiler breeders fed ad libitum or restricted until point of lay. Poultry Science 28: 493506CrossRefGoogle ScholarPubMed
International Chicken Polymorphism Map Consortium 2004 A genetic variation map for chicken with 2.8 million single-nucleotide polymorphisms. Nature 432: 718722Google Scholar
Jacob, F 1977 Evolution and tinkering. Science 196: 11611166CrossRefGoogle ScholarPubMed
Jones, RB and Hocking, PM 1999 Genetic selection for poultry behaviour: big bad wolf or friend in need? Animal Welfare 8: 343359Google Scholar
Jones, EKM, Zaczek, V, MacLeod, M and Hocking, PM 2004 Genotype, dietary manipulation and food allocation affect indices of welfare in broiler breeders. British Poultry Science 45: 725737CrossRefGoogle ScholarPubMed
Julian, RJ 1998 Rapid growth problems: ascites and skeletal deformities in broilers. Poultry Science 77: 7381CrossRefGoogle ScholarPubMed
Julian, RJ 2005 Production and growth related disorders and other metabolic diseases of poultry: a review. Veterinary Journal 169: 350369. http://dx.doi.org/10.1016/j.tvjl.2004.04.015CrossRefGoogle ScholarPubMed
Kasanen, IHE, SØrensen, DB, Forkman, B and SandØe, P 2010 Ethics of feeding: the omnivore dilemma. Animal Welfare 19: 3746Google Scholar
Katanbaf, MN, Dunnington, EA and Siegel, PB 1989 Restricted feeding in early and late feathering chickens 1. Growth and physiological responses. Poultry Science 68: 344351CrossRefGoogle ScholarPubMed
Katanbaf, MN and Hardiman, JW 2010 Primary broiler breeding: striking a balance between economic and well-being traits. Poultry Science 89: 822824. http://dx.doi.org/10.3382/ps.2009-00439CrossRefGoogle ScholarPubMed
Keeling, LJ, Andersson, L, Schütz, K, Kerje, S, Fredriksson, R, Cornwallis, CK, Pizzari, T and Jensen, P 2004 Feather-pecking and victim pigmentation. Nature 431: 645646. http://dx.doi.org/10.1038/431645aCrossRefGoogle ScholarPubMed
Kerr, CL, Hammerstedt, RH and Barbato, GF 2001 Effects of selection for exponential growth rate at different ages on reproduction in chickens. Avian and Poultry Biology Reviews 12: 127136. http://dx.doi.org/10.3184/147020601783698503CrossRefGoogle Scholar
Kestin, SC, Knowles, TG, Tinch, AE and Gregory, N 1992 Prevalence of leg weakness in broiler chickens and its relationship with genotype. The Veterinary Record 131: 190194. http://dx.doi.org/10.1136/vr.13.1.9.190CrossRefGoogle ScholarPubMed
Knowles, TG, Kestin, SC, Haslam, SM, Brown, SN, Green, LE, Butterworth, A, Pope, SJ, Pfeiffer, D and Nicol, CJ 2008 Leg disorders in broiler chickens: prevalence, risk factors and prevention. PLoS One 3(2): e1545CrossRefGoogle ScholarPubMed
Lariviere, JM and Leroy, P 2010 Presumed genotypes from phenotypic traits in traditional Belgian chicken breeds. Archiv für Geflügelkunde 74: 217225Google Scholar
Lawrence, AB 2008 Applied animal behaviour science: past present and future. Applied Animal Behaviour Science 115: 124. http://dx.doi.org/10.1016/j.applanim.2008.06.003CrossRefGoogle Scholar
Lawrence, AB, Conington, J and Simm, G 2004 Breeding and animal welfare: practical and theoretical advantages of multi-trait selection. Animal Welfare 13: S191196Google Scholar
Lyall, J, Irvine, RM, Sherman A McKinley, TJ and Núñez, A 2011 Suppression of avian influenza transmission in genetically modified chickens. Science 331: 223226. http://dx.doi.org/10.1126/science.1198020CrossRefGoogle ScholarPubMed
McGary, S, Estevez, I, Bakst, MR and Pollock, DL 2002 Phenotypic traits as reliable indicators of fertility in male broiler breeders. Poultry Science 81: 102111CrossRefGoogle ScholarPubMed
Mench, JA 2002 Broiler breeders: feed restriction and welfare. World's Poultry Science Journal 58: 2329CrossRefGoogle Scholar
Mercer, JT and Hill, WG 1984 Estimation of genetic parameters for skeletal defects in broiler chickens. Heredity 53: 193203. http://dx.doi.org/10.1038/hdy.1984.75CrossRefGoogle Scholar
Mignon-Grasteau, S, Piles, M, Varona, L, de Rochambeau, H, Poivey, JP, Blasco, A and Beaumont, C 2000 Genetic analysis of growth curve parameters for male and female chickens resulting from selection on shape of growth curve. Journal of Animal Science 78: 25152524CrossRefGoogle ScholarPubMed
Mignon-Grasteau, S, Beaumont, C and Ricard, FH 2001 Genetic analysis of a selection experiment on the growth curve of chickens. Poultry Science 80: 849854CrossRefGoogle ScholarPubMed
Millman, ST, Duncan, IJH and Widowski, TM 2000 Male broiler breeder fowl display high levels of aggression toward females. Poultry Science 79: 12331241CrossRefGoogle ScholarPubMed
Mitchell, M 1997 Ascites syndrome: a physiological and biochemical perspective. World's Poultry Science Journal 53: 6164CrossRefGoogle Scholar
Muir, WM, Wong, GKS, Zhang, Y, Wang, J, Groenen, MAM, Crooijmans, RPMA, Megens, HJ, Zhang, H, Okimoto, R, Vereijken, A, Jungerius, A, Albers, GAA, Lawley, CT, Delany, ME, MacEachern, S and Cheng, HH 2008 Genome-wide assessment of worldwide chicken SNP genetic diversity indicates significant absence of rare alleles in commercial breeds. Proceedings of the National Academy of Sciences USA 105: 1731217317. http://dx.doi.org/10.1073/pnas.0806569105CrossRefGoogle ScholarPubMed
N’Dri, AL, Sellier, N, Tixier-Boichard, M, Beaumont, C and Mignon-Grasteau, S 2007 Genotype by environment interactions in relation to growth traits in slow growing chickens. Genetics Selection Evolution 39: 513528. http://dx.doi.org/10.1186/1297-9686-39-5-513CrossRefGoogle ScholarPubMed
Nie, QH, Fang, MX, Xie, L, Shen, X, Liu, J, Luo, ZP, Shi, JJ and Zhang, XQ 2010 Association of ATGL gene polymorphims with chicken growth and fat traits. Journal of Applied Genetics 51: 185191. http://dx.doi.org/10.1007/BF03195726CrossRefGoogle Scholar
Nielsen, BL, Thodberg, K, Malmkvist, J and Steenfeldt, S 2011 Proportion of insoluble fibre in the diet affects behaviour and hunger in broiler breeders growing at similar rates. Animal 5: 12471258CrossRefGoogle ScholarPubMed
Pakdel, A, Van Arendonk, JAM, Vereijken, ALJ and Bovenhuis, H 2005 Genetic parameters of ascites-related traits in broilers: correlations with feed efficiency and carcase traits. British Poultry Science 46: 4353CrossRefGoogle ScholarPubMed
Puterflam, J, Merlet, F, Faure, JM, Hocking, PM and Picard, M 2006 Effects of genotype and feed restriction on the time-budgets of broiler breeders at different ages. Applied Animal Behaviour Science 98: 100113. http://dx.doi.org/10.1016/j.applanim.2005.08.013CrossRefGoogle Scholar
Rauw, WM, Kanis, E, Noordhuize-Stassen, EN and Grommers, FJ 1998 Undesirable side effects of selection for high production efficiency in farm animals: a review. Livestock Production Science 56: 1533. http://dx.doi.org/10.1016/S0301-6226(98)00147-XCrossRefGoogle Scholar
Remes, V and Martin, TE 2002 Environmental influences on the evolution and developmental rates in passerines. Evolution 56: 25052518CrossRefGoogle ScholarPubMed
Renema, RA, Rustad, ME and Robinson, FE 2007 Implications of changes to commercial broiler and broiler breeder body weight targets over the past 30 years. World's Poultry Science Journal 63: 457472CrossRefGoogle Scholar
Ricklefs, RE 2010 Embryo growth rates in birds and mammals. Functional Ecology 24: 588596. http://dx.doi.org/10.1111/j.1365-2435.2009.01684.xCrossRefGoogle Scholar
Robins, A and Phillips, CJC 2011 International approaches to the welfare of meat chickens. World's Poultry Science Journal 67: 351369CrossRefGoogle Scholar
Robinson, FE, Robinson, NA and Scott, TA 1991 Reproductive performance, growth and body composition of full-fed versus feed restricted broiler breeder hens. Canadian Journal of Animal Science 71: 549556. http://dx.doi.org/10.4141/cjas91-065CrossRefGoogle Scholar
Rodenberg, TB, Bijma, P, Ellen, ED, Bergsma, R, de Vries, S, Bolhuis, JE, Kemp, B and van Arendok, JAM 2010 Breeding amiable animals? Improving farm animal welfare by including social effects in breeding programmes. Animal Welfare 19: S77S82Google Scholar
Roff, DA 2000 Trade-offs between growth and reproduction: an analysis of the quantitative genetic evidence. Journal of Evolutionary Biology 13: 434445. http://dx.doi.org/10.1046/j.1420-9101.2000.00186.xCrossRefGoogle Scholar
Royal Society 2009 Reaping the Benefits: Science and Sustainable Intensification of Global Agriculture. Royal Society: London, UKGoogle Scholar
Sandilands, V, Tolkamp, BJ and Kyriazakis, I 2005 Behaviour of food restricted broilers during rearing and lay: effects of an alternative feed method. Physiology and Behaviour 85: 115123CrossRefGoogle Scholar
Sandilands, V, Tolkamp, BJ, Savory, CJ and Kyriazakis, I 2006 Behaviour and welfare of broiler breeders fed qualitatively restricted diets during rearing: are there viable alternatives to quantitative restriction? Applied Animal Behaviour Science 96: 5367. http://dx.doi.org/10.1016/j.applanim.2005.04.017CrossRefGoogle Scholar
SandØe, P 2010 Breeding for behavioural change in farm animals: practical, economic and ethical considerations. Animal Welfare 19: 1727Google Scholar
Sanotra, GS, Lund, JD, Ersboll, AK, Petersen, JS and Vestergaard, KS 2001 Monitoring leg problems in broilers: a survey of commercial broiler production in Denmark. World's Poultry Science Journal 57: 5569CrossRefGoogle Scholar
Savory, CJ and Maros, K 1993 Influence of degree of food restriction, age and time of day on behavior of broiler breeder chickens. Behavioural Processes 29: 179190. http://dx.doi.org/10.1016/0376-6357(93)90122-8CrossRefGoogle ScholarPubMed
Savory, CJ, Hocking, PM, Mann, JS and Maxwell, MH 1996 Is broiler breeder welfare improved by using qualitative rather than quantitative food restriction to limit growth rate? Animal Welfare 5: 105127Google Scholar
Schekkerman, H, Tulp, I, Piersma, Y and Visser, X 2003 Mechanisms promoting higher growth rate in arctic tern than in temperate shore birds. Oecologia 134: 332342CrossRefGoogle Scholar
Simm, G 1998 Genetic Improvement of Cattle and Sheep. Farming Press: Tonbridge, UKGoogle Scholar
Sizemore, FG and Barbato, GF 2002 Correlated responses in body composition to divergent selection for exponential growth rate to 14 or 42 days of age in chickens. Poultry Science 81: 932938CrossRefGoogle ScholarPubMed
Steinfeld, H, Gerber, P, Wassener, T, Castel, V, Rosales, M and de Haan, C 2006 Livestock's Long Shadow. Environmental Issues and Options. Food and Agricultural Organisation of the United Nations: Rome, ItalyGoogle Scholar
Steward, PA, Muir, WM, Begin, JJ and Johnson, TH 1980 Feed efficiency and gain responses to protein level in two lines of birds selected for oxygen consumption. Poultry Science 59: 26922696CrossRefGoogle Scholar
Thiruvenkadan, AK, Prabakaran, R and Panneerselvam, S 2011 Broiler breeding strategies over the decades: an overview. World's Poultry Science Journal 67: 309336CrossRefGoogle Scholar
UK Government Foresight 2011 The Future of Food and Farming: Challenges and Choices for Global Sustainability. Final Project Report. The Government Office for Science: London, UKGoogle Scholar
Wahlberg, P, Carlborg, O, Foglio, M, Tordoir, X, Syvanen, A-C, Lathrop, M, Gut, IG, Siegel, PB and Andersson, L 2009 Genetic analysis of an F-2 intercross between two chicken lines divergently selected for body-weight. BMC Genomics10: article no 248. http://dx.doi.org/10.1186/1471-2164-10-248CrossRefGoogle Scholar
Wang, YQ, Lehane, C, Ghebremeskel, K and Crawford, MA 2010 Modern organic and broiler chickens sold for human consumption provide more energy from fat than protein. Public Health Nutrition 13: 400408. http://dx.doi.org/10.1017/S1368980009991157CrossRefGoogle ScholarPubMed
Weiner, P and Wilkinson, S 2011 Deciphering the genetic basis of animal domestication. Proceeding of the Royal Society B278: 31613170. http://dx.doi.org/10.1098/rspb.2011.1376Google Scholar
Yang, N and Jiang, RS 2005 Recent advances in breeding for quality chickens. World's Poultry Science Journal 61: 373381CrossRefGoogle Scholar
Zera, AJ and Harshman, LG 2001 The physiology of life history trade-offs in animals. Annual Review of Ecology and Systematics 32: 95126. http://dx.doi.org/10.1146/annurev.ecolsys.32.081501.114006CrossRefGoogle Scholar
Zhang, NB, Tang, H, Kang, L, Ma, YH, Cao, DC, Lu, Y, Hou, M and Jiang, YL 2008 Associations of single nucleotide polymorphisms in BMPR-IB gene with egg production in a synthetic broiler line. Asian-Australian Journal of Animal Sciences 21: 628632CrossRefGoogle Scholar
Zheng, JX, Liu, ZZ and Yang, N 2007 Deficiency of growth hormone receptor does not affect male reproduction in dwarf chickens. Poultry Science 86: 112117CrossRefGoogle Scholar
Zheng, Q, Zhang, Y, Chen, Y, Yang, N, Wang, XJ and Zhu, DH 2009 Systematic identification of genes involved in divergent skeletal muscle growth rates of broiler and layer chickens. Genomics 10: article no 87Google ScholarPubMed