Effects of quantitative nutrient allocation on myopathies of the Pectoralis major muscles in broiler chickens at 32, 43, and 50 days of age

An experiment was conducted to determine if myopathies of the Pectoralis major muscles are influenced by differences in growth trajectory achieved through a controlled feeding program. Male Yield Plus × Ross 708 broiler chicks were placed into 28 pens (25 birds/pen) equipped with plastic slats to prevent coprophagy. All birds received identical starter (1 to 10 d), grower (11 to 32 d), finisher (33 to 42 d), and withdrawal (43 to 50 d) diets that were formulated to meet or exceed nutrient recommendations of the primary breeder. Each pen of birds was randomly assigned to one of 4 pair-feeding programs (TRT 1: ad libitum; TRT 2: 95% of TRT 1 intake; TRT 3: 90% of TRT 1 intake; and TRT 4: 85% of TRT 1 intake) with 7 replicate pens per treatment. Feed intake and mortality were recorded daily. Individual BW was recorded at 31, 42, and 49 d of age. Blood samples were collected from 4 birds per pen at 31, 41, and 48 d of age and subsequently analyzed for plasma creatine kinase (CK) and lactate dehydrogenase (LDH). At 32, 43, and 50 d of age, 4 birds per pen were euthanized for necropsy. The right breast fillet of each bird was visually scored for white striping (WS) and wooden breast (WB). Linear decreases (P ≤ 0.01) in feed intake, BW gain, feed conversion ratio, and mortality were observed with decreasing feed allocation. Linear decreases (P ≤ 0.01) in severity were observed for WS and WB at 33, 43, and 50 d with decreasing feed allocation. Severity of WB at 33 and 43 d, as well as that of WS at 43 and 50 d, decreased (P ≤ 0.05) quadratically with decreasing feed allocation. Reduced feed allocation produced quadratic decreases (P ≤ 0.05) in CK and LDH concentrations at 31, 41, and 48 days. These results indicate that the incidence of breast fillet myopathies in broilers may be reduced through controlled feeding programs.