Effects of dietary digestible amino acids and a novel exogenous sfericase protease on growth performance of broilers.

Two experiments (Exp.) were conducted to evaluate the effects of a novel exogenous sfericase protease on growth performance and ileal digestibility of broiler chickens until day 35 of age. In Exp. 1, 1350 one-day-old male chicks (Cobb 500) were allocated in 54 floor pens and fed one of the three dietary treatments, with 18 replicates of 25 birds each in a completely randomized design. Diets consisted of positive control [PC; commercially relevant ME and balanced amino acids (AA)]; negative control (NC; with reduction of 6% dig. Lys and proportional reductions for adjacent AA compared to the PC), and NC supplemented with sfericase protease [30,000 New Feed Protease units (NFP)/kg]. On day 35, ileal digesta was collected to determine apparent ileal digestibility of dry matter and nitrogen (N). In Exp. 2, 1620 one-day-old male chicks (Cobb 500) were allocated in 54 floor pens having three treatments and 18 replicates of 30 birds each in a completely randomized design from day 1-35. Broilers were fed a control basal diet (Control); Control supplemented with sfericase at 30,000 NFP/kg and at 60,000 NFP/kg. In Exp. 1, from day 1-35, body weight gain (BW gain) and feed conversion ratio (FCR) of broilers improved 3.4 and 2.5% when diets were supplemented with sfericase, respectively, whereas the digestibility of N increased by 2.7% compared to the NC. In Exp. 2, diets with usual protein and AA levels and supplemented with 30,000 NFP/kg had 2.3 and 1.75% improved BW gain and FCR from day 1-35, respectively. When diets were supplemented with 60,000 NFP/kg, BW gain and FCR were enhanced by 3.9 and 3.2%, respectively compared to the Control. In conclusion, these results demonstrate that the novel sfericase protease could be successfully used in corn-soy diets with protein and AA reductions or in feed formulations with usual digestible AA levels to enhance growth performance of broilers.