Effects of dietary protease supplementation on behaviour, slaughter performance, meat quality and immune organ indices of broilers

This study was conducted to investigate the effects of protease supplementation on the behaviour, slaughter performance, meat quality, and immune organ indices of broilers. A total of 240 one-day-old Arbor Acres broiler chickens were randomly allocated to four treatments, with six replicates per treatment and 10 broilers per replicate. Chickens were fed corn-soybean meal basal diets supplemented with 0, 4, 8, and 12 IU/g of protease. Compared with 0 IU/g of protease supplementation, 12 IU/g of protease increased the average and minimum time of feeding and drinking behaviour (P < 0.05); increased the average, maximum, and minimum time of preening behaviour (P < 0.05); and decreased feeding, walking, and stretching frequency (P < 0.05). pH24h of breast and thigh muscles had improved (P < 0.05). The shear force of the breast muscle and the cooking loss of the thigh muscle had decreased (P < 0.05). Compared with 0 IU/g of protease, 4 IU/g of protease increased the average and minimum time of lying behaviour (P < 0.05) and decreased stretching, scratching, and aggressive frequency (P