Production Performance and Flock Uniformity of Broilers Supplemented with an Exogenous Protease

Poultry rely on enzymatic digestion more so than any other livestock species due to their very short digesta transit time and because their large intestines lack the bacteria that aids other species in digestion. Because of this, their ability to digest nutrients in the feed is not absolute. Recently, along with phytase and non-starch polysaccharide-degrading enzymes, protease has become a standard component in broiler diets to improve nutrient digestibility and utilization. However, there are several other known mechanisms which support the observed benefits of protease in broiler nutrition. These include improvements in energy digestibility, degradation of protein-based anti-nutrients, enhancement of gut physiology, improvement in intestinal integrity, and beneficial effects on gut microbiota (Ghazi et al., 2002; Wu et al., 2014). Singly or collectively, these mechanisms may impart positive impact on animal health and performance. To this end, a study was conducted to evaluate the effects of protease supplementation on animal performance and flock uniformity in broiler diets.

A total of 960-d-old male Cobb chickens were randomly assigned to receive 1 of 4 dietary treatments: 1) Treatment 1, a standard diet based on corn and soybean meal (T1), 2) Treatment 2, same as T1 but reduced by 2.5% digestible AA and 20 kcal/kg ME + 0.0125% Protease (T2), 3) Treatment 3, same as T1 but reduced by 5.0% digestible AA and 20 kcal/kg ME (T3), 4) Treatment 4, same as T3 + 0.0125% Protease (T4). A completely randomized design consisting of 4 treatments, 12 replicate pens, and 20 birds in each pen was used. Flock uniformity was measured by weighing birds individually at the start (d 0) and at the end of the study (d 42) and was expressed as coefficient of variation (CV) in live weight, with increased CV values synonymous with decreased uniformity. Relative to T1 and T3, protease supplementation in T2 and T4 diets increased (P < 0.05) body weight gain (BWG) (2.453 vs. 2.509 and 2.365 vs. 2.422 kg) and decreased (P < 0.05) FCR (1.758 vs. 1.736 and 1.799 vs. 1.770) at d 42, respectively. Compared with T1, reducing the levels of digestible AA and ME in T3 adversely affected BWG and FCR at d 42; however, protease supplementation in T4 diet allowed birds to restore performance that was not significantly different to those birds fed with T1 (standard diet). There was no significant difference among the treatment groups in terms of mortality. Flock uniformity was significantly improved (P < 0.05) by protease supplementation in T2 diet relative to T1 (4.85 vs. 7.65) but had no effect in birds fed with T3 and T4 diets (8.55 vs 6.78). There was no difference in flock uniformity between birds fed T1, T3, and T4 diets. Since flock uniformity is known to be influenced by the concentration of AA in broiler diets, the 5% reduction in digestible AA might have been too much relative to the level of AA uplift that the protease can provide, hence, no significant effect was observed between T3 and T4. Overall, protease supplementation may improve or restore losses in animal performance when used in nutrient reduced broiler diets. In addition, it may also help promote better flock uniformity, thus, reducing potential economic losses due to increased number of downgrades at harvest.