Housing systems interacting with sex and genetic line affect broiler growth and carcass traits

Abstract

Housing systems used in the production of poultry meat vary worldwide dependent on climate, land availability, and other resources essential for production. Reported here are comparisons between pen and cage rearing (the housing system, denoted HS: ), line crosses LC: ), two native Chinese lines (EM males were mated to Y1 and Y2 and their offspring denoted as EMY1 and EMY2), and sex in determining broiler traits. At hatch, 320 males and 320 females from each LC (giving a total of 1,280 chicks) were randomly assigned within each subgroup to 16 battery pens. There were 4 replicates for each combination of LC by sex. On d 28, half of the chicks were transferred to indoor floor pens, and the others were raised in single cages from d 29 to 91. Weekly body weights, livability, and feed conversion ratios ( FCR: ) were obtained to d 91, the age at which the broilers were slaughtered for carcass measurements. The caged males and females were heavier (P < 0.05) than their penned counterparts (2,292 vs 2,219 g). Except for females from line EMY1 (94.9%), the livability for each unit from 1 to 28 d, and 29 to 91 d was greater than 95%. Penned EMY2 broilers had the highest FCR (3.02), whereas penned EMY1 broilers had the lowest FCR (2.96) among the housing systems by LC combinations (P < 0.05). Caged chickens had thicker subcutaneous fat (7.24 mm), a higher percentages of abdominal fat (5.01%) and liver mass (3.13%) , but lower eviscerated carcass (60.63%) and breast muscle weights (pectoralis major and minor, 17.10%). Males were heavier and had higher percentages of leg muscle (boneless drum plus thigh, 24.22%) and heart muscle (1.08%) than the females (P < 0.05). However, the females had thicker subcutaneous fat (7.19 mm) and higher percentages of carcass weight (87.28%), breast muscle (18.11%), abdominal fat (6.54%), and liver mass (3.15%) than males. Penned females had the highest percentage of breast muscle (18.94%), and caged females had the highest percentage of liver mass (3.72%). Females of EMY1 had the highest percentage of breast muscle (18.40%). Generally, the housing system employed and the sex of the broilers greatly affect the carcass traits.

Keywords: breeding; carcass composition; chicken; feed conversion ratio; housing system.