In pursuit of a better broiler: carcass traits and muscle myopathies in conventional and slower-growing strains of broiler chickens.

Midian N Santos,Elijah G Kiarie,Tina M Widowski,Michele T Guerin,Ira Mandell,Daniel Rothschild,Shai Barbut,Stephanie Torrey,A Michelle Edwards

doi:10.31220/agrirxiv.2021.00037

Abstract

Abstract Selection for accelerated growth rate and high breast yield in broiler chickens have been associated with an increase in myopathies, including wooden breast (WB) and white striping (WS). To investigate effects of growth rate on carcass traits and incidence of myopathies, 14 strains were evaluated, encompassing 2 conventional (CONV; strains B and C: ADG 0-48 >60 g/d) and 12 slower-growing (SL) strains. The latter were categorized based on growth rate: FAST (strains F, G, I and M; ADG 0-62 =53-55 g/d), MOD (strains E, H, O and S; ADG 0-62 =50-51 g/d), and SLOW (strains D, J, K and N; ADG 0-62 <50 g/d). In a randomized incomplete block design, 7,216 mixed-sex birds were equally allocated into 164 pens (44 birds/pen; 30 kg/m 2 ), with each strain represented in 8-12 pens over 2-3 production cycles. From each pen, 4 males and 4 females were processed at 2 Target Weights (TW) based on their expected time to reach 2.1 kg BW (TW 1: 34 d for CONV; 48 d for SL strains) and 3.2 kg BW (TW 2: 48 d for CONV; 62 d for SL strains). Weights and yields for the carcass, breast, drumsticks, thighs and wings were obtained; breast fillets were assessed to determine the presence and severity of WB and WS. At both TWs, breast yield was higher as growth rate increased (P<0.001), with CONV having greater breast yield than other categories. Strain F had the greatest breast yield at both TWs (P<0.001) within the FAST category. At TW 2, CONV had the greatest incidence of WB and WS (P<0.001). However, within FAST, strain F had the greatest incidence of myopathies (P<0.001) at both TWs, exhibiting values as high or greater than CONV birds. The incidence of WB and WS in strains with differing growth rates but high breast meat yield suggests that the latter may play a major role in the occurrence of these myopathies.

Highlights

There has been a significant increase in preference for chicken meat globally, with world per capita consumption rising over 250% over the past 50 yr (FAO, 2019)
The differences in variables measured in this study are described as comparisons between categories (CONV, fastest slower-growing (FAST), moderate slower-growing (MOD), and SLOW) and comparisons of strains within categories at both target weights (TWs)
Selection for improved growth performance in fastgrowing strains of broiler chickens has been associated with changes in body composition and development of muscle disorders including Wooden breast (WB) and White striping (WS) (Petracci et al, 2015; Barbut, 2019)

Summary

Introduction

There has been a significant increase in preference for chicken meat globally, with world per capita consumption rising over 250% over the past 50 yr (FAO, 2019). Chicken is the most consumed meat in North America and the second most consumed meat worldwide after pork (FAO, 2019). The increase in demand for chicken meat is mainly due to its high nutrient content, lack of religious or cultural restrictions, affordability, convenience, and simple.

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