Growth performance and nutrient digestibility of broiler chickens as affected by a novel protease

Two experiments evaluated the addition of an exogenous sfericase protease in broiler diets. Experiments were run (Exp1 and Exp2) with 1,848 and 2,100 one-day-old male chicks being allocated into 84 floor pens with 14 replicates of 22 and 25 birds each, respectively. The studies were conducted in completely randomized designs. In Exp1, Standard diets were formulated with energy and AA at marginally lower levels than usual by the Brazilian integration such that broilers were expected to grow at comparatively reduced rates to the industry whereas in Exp2, the Standard diets were formulated using energy and AA as usual by the Brazilian integrations such that broilers were expected to grow comparable to industry rates. Standard diets had ideally balanced amino acids (AA). Matrix diets, in contrast, had reductions of 6% digestible lysine and of 20 kcal AME/kg compared to the Standard. Matrix diets were supplemented with an sfericase protease at 0, 10,000, and 30,000 New Feed Protease units (NFP)/kg. Outcomes showed no interaction between diet and protease in any of the experiments. However, broilers fed Standard diets had higher cumulative body weight gain (BWG) to 35 and 42 d when compared to Matrix fed birds whereas FCR were worse for birds fed the Matrix diets at 35 d in EXP1 and at 35 and 42 d in EXP2. Improvements in FCR were observed when the sfericase protease was added throughout all ages in EXP1 with a beneficial trend (P<0.067) observed in the cumulative FCR at 42 d in EXP2. The ileal digestible crude protein (IDCP) was significantly higher for birds fed Standard feeds in EXP1 with no other differences in digestibility found in any of the experiments. Protease addition led to improvements in ileal digestibility of dry matter (IDM) and IDCP (P < 0.05) compared to no protease addition in EXP1 as well as in ileal digestibility of energy (IDE) when 30,000 protease units were added. The present report demonstrates that the novel sfericase protease was successful in compensate broiler performance when reductions of 6% digestible Lys and 20 kcal/kg AME were imposed. This compensation, however, seemed more notable when birds were fed diets formulated to support moderate rather than maximum growth and having animal protein in the feed formula.

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