Effects of protease supplementation of low protein and/or energy diets on growth performance and blood parameters in broiler chickens under heat stress condition

AbstractThe effects of feeding low dietary crude protein (CP) and/or metabolisable energy (ME) with or without supplemental protease on growth performance, carcase characteristics and physiological responses in broiler chickens were investigated under cyclic heat stress condition. A total of 350 day-old male broiler chicks were fed with one of the following seven experimental diets: (1) recommended-CP and recommended-ME (RPE, served as control); (2) recommended-CP and low-ME (RPLE); (3) recommended-CP and low-ME with protease (RPLEP); (4) low-CP and recommended-ME (LPRE); (5) low-CP and recommended-ME with protease (LPREP); (6) low-CP and low-ME (LPE) and (7) low-CP and low-ME with protease (LPEP). From 22 to 42 d of age, half of the chickens from each dietary group were exposed to 34 ± 1 °C for 7 h daily (heat stress), whereas the other half were raised at constant 23 ± 2 °C (normal temperature). Supplementation of protease to RPLE, LPRE and LPE diets had no significant effects on feed intake (FI), weigh...