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A Comparison of Leg Health, Carcass Traits, and Muscle Disorders in Strains of Broiler Chickens Selected for Distinct Growth Rates

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Title: A Comparison of Leg Health, Carcass Traits, and Muscle Disorders in Strains of Broiler Chickens Selected for Distinct Growth Rates
Author: Nascimento dos Santos, Midian
Department: Department of Animal Biosciences
Program: Animal and Poultry Science
Advisor: Torrey, StephanieKiarie, Elijah
Abstract: The growth rate of broiler chickens has greatly increased over the past 60 years because of intense genetic selection, improvements in nutrition, and changes to management strategies. However, this increase in performance has resulted in some undesirable consequences that affect the welfare and meat quality of fast-growing broiler chickens. Thus, there has been an increasing interest in the use of slower-growing (SG) strains to mitigate problems associated with fast growth. In this context, the objectives of this thesis were to evaluate leg health, carcass traits, and incidence of muscle myopathies in 2 conventional (CONV) and 12 SG strains classified into 3 categories (FAST, MODERATE, and SLOW), based on their similarities of growth rate. All birds were raised under similar and controlled conditions and evaluated at similar target weights (TW) of 2.1 kg (TW 1) and 3.2 kg (TW 2). Results indicate that growth differences between categories affected most of the variables evaluated (e.g., carcass traits, incidence of myopathies, bone traits, and mobility) although some differences were also found among strains selected for a similar growth rate. Overall, CONV birds had greater breast yield than SG birds, which was accompanied by a greater incidence of myopathies. However, strain F, categorized as FAST, exhibited similar or greater breast yield and incidence of muscle myopathies compared to CONV birds, which was consistently higher than all of the other SG strains. At both TWs, CONV birds had shorter legs, yet similar or greater tibial breaking strength and ash content compared to the SG categories. At TW 2, CONV birds exhibited indicators of poorer leg strength than SLOW birds, although the BW of these categories was similar. However, at both TWs, CONV birds showed indicators of similar walking ability (based on total obstacle crossing) compared to FAST birds, despite the lower BW of CONV vs. FAST birds. The large breast of CONV birds, combined with their shorter legs relative to their heavy body weight, might contribute to their reduced mobility. Altogether, these results indicate that not only differences in genetic potential for growth, but also differences in body conformation influence leg health and meat quality of broiler chickens.
Date: 2021-09
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Related Publications: Santos, M. N., Rothschild, D., Widowski,T.M., Barbut, S., Kiarie, E.G., Mandell, I., Guerin, M.T., Edwards, E.M., and Torrey, S (2021). In Pursuit of a Better Broiler: Carcass traits and muscle myopathies in conventional and slower-growing strains of broiler chickens. Poultry Science .100(9), 1-22.

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