Effects of Supplementation of Protease to Low Crude Protein Diets on Performance of and Nutrient Digestibility in Heat Stressed Broiler Chickens

Abstract

The effect of supplementation of protease to low crude protein diet on the performance and nutrient digestibility of heat-stressed broiler chickens was investigated in a 35-day experiment. One hundred and sixty-eight 7-day-old broiler chickens were randomly allotted to four treatments with 6 replicates of 7 birds each in a completely randomised design. Diets 1 and 2 contained 23% CP without or with enzyme, while diets 3 and 4 had low 17% CP without or with enzyme at the starter phase. Similarly, normal 21% CP diet without or with enzyme and low 15% CP without or with enzyme supplementation at the finisher phase respectively. At starter phase, final weight, weight gain and feed intake of birds fed 23% CP diets (without or with protease supplementation) were similar to those fed 17% CP without protease. Higher (P<0.05) protein intakes (PI) were recorded in birds fed 23% CP without or with enzyme supplementation when compared to birds on 17% CP. At finisher phase, PI of birds on 21% CP without enzyme was significantly higher (P<0.05) than those on other diets. Highest PER (10.12) was observed in birds on 15% CP with enzyme supplementation while least PER (3.57) was recorded for birds on 21% CP with enzyme. Glucose concentration of birds sampled on day 14 did not differ (P>0.05) significantly within treatments. Lymphocyte values of birds on 17% CP without or with enzyme were similar to those of birds on 23% CP without or with enzyme supplementation. Similar trend was observed in heterophil values and heterophil to lymphocyte ratio of birds on dietary treatments. Lymphocytes of birds on 21% CP without or with enzyme were similar to lymphocyte of birds on 15% CP without or with protease. Diets had no effect on apparent crude protein and gross energy digestibility of birds on dietary treatments. Least dry matter digestibility (28.27%) was recorded in birds fed 21% CP with enzyme supplementation compared to other diets. In conclusion, protease supplementation did not significantly improve performance of heat-stressed birds in both phases. Blood parameters measured were not altered in response to high temperature except lymphocyte counts.