Whey protein concentrate and dried skim milk were each evaluated as the major protein source in milk replacer using four treatments (100% skim milk, 67% skim milk and 33% whey protein concentrate, 33% skim milk and 67% whey protein concentrate, and 100% whey protein concentrate). In the first trial, 64 calves were fed only milk replacer from birth to 6 wk of age. In the second trial, 61 calves were fed milk replacer and were allowed ad libitum intake of starter from birth to 6 wk of age. Calves were fed milk replacer at 10% of birth weight for the first 2 wk and at 12% of birth weight thereafter. In trial 1, average daily gains and feed efficiencies were significantly improved for calves that consumed the milk replacers containing 67 and 100% whey protein concentrate over those for calves that were fed the milk replacer containing 100% skim milk. No difference in growth or feed efficiency caused by treatment was detected in trial 2. Average daily gain in trial 2 was correlated with total starter intake. In trial 1, plasma glucose concentrations were correlated with growth rates and were highest for calves fed the milk replacer containing 67% whey protein concentrate. No differences were found for fecal scores or days scoured between trials. When only milk replacer was fed, higher proportions of whey protein concentrate improved calf performance, but, when starter was also provided, no effect of milk replacer was found.

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Effects of nano-selenium (nano-Se) and stocking density (SD) on growth performance, carcass yield, meat quality, and feathering score of broilers were investigated in this study. One-day-old 480 broiler chickens (45.32.4 g body weight) (Ross 308) were randomly divided into 4 treatments each comprising of 8 replicates. In the experiment, treatments consisted of a 2  2 factorial arrangement of dietary Se form (inorganic or nano) and SD (low = 12 birds/m 2 ; LSD, and high = 18 birds/m 2 ; HSD). No interaction was noted between Se form and SD for any trait. Nano-Se had no effect on growth performance, however, HSD decreased the body weight gain (BWG) (P0.05) and feed intake (FI) (P0.001) while feed conversion ratio (FCR) was unaffected. Neither nano-Se nor HSD had any effect on the relative carcass, breast, and thigh yields. Nano-Se improved the water-holding capacity (WHC) of breast meat 72-hpostmortem (P0.05). However, pH, colour, and cooking loss of meat remained unaffected by Se form or SD. There were no differences between nano-or inorganic Se and LSD or HSD regarding feathering scores for back and wing. In conclusion, dietary nano-Se improved the WHC and had no significant effect on other parameters. In addition, HSD may negatively affect the growth performance.

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BACKGROUND White striping (WS) is a myopathy of breast muscle (Pectoralis major) that affects the quality and consumer acceptance of breast fillets of broiler chickens. Previous studies have shown that intermittent dilution of dietary nutrients suppresses the development of WS on the breast muscle of broiler chickens. However, the mechanism by which these interventions reduce the occurrence of WS remains inconclusive. In this study, we adopted intermittent reduction of dietary digestible lysine (dLys) density or metabolizable energy (ME) and amino acid (AA) density using chemical and fatty acid composition of breast fillets, and blood metabolites to understand the mechanism while histopathology and immunohistochemistry of breast muscles were used for confirmation. RESULTS Occurrence of WS was lower in broiler chickens fed 85% dLys diets in comparison with other groups. Crude protein and ether extract in breast meat of 85% dLys groups were greater (P < 0.001) and lower (P = 0.010), respectively. Serum concentrations of lipid metabolites and enzymes were lower in broiler chickens fed 85% dLys diets than control group (P < 0.05). Feeding 85% dLys diets had low degree of myodegeneration and necrosis, inflammation, lipid deposition, infiltration of T‐lymphocyte (CD3+) and macrophages (Iba‐1+), and low expression of heat‐shock protein 70 (HSP70) than other groups (P < 0.001). CONCLUSION Dilution of dietary dLys to 85% of the required quantities reduces the development of WS in broiler chickens by slowing the growth, lipid synthesis, and muscle damage confirmed by lower extent of histopathological lesions. © 2022 Society of Chemical Industry.