Effects of bacillus subtilis and protease enzyme added to broiler mixed feeds on growth performance

This study was conducted to determine the effects of Bacillus subtilis probiotics and protease enzyme added to mixed feeds on total live weight, daily live weight gain, feed consumption, and feed conversion ratio in broilers. In the study, 234 mixed-sex Ross 308 broiler chicks were used. At the start of the experiment, the chicks were divided into 1 control and 2 test groups so that their live weights would be similar, each group was divided into 6 subgroups with 13 animals each, and in this way, the chicks were fed for 40 days. While the traditional broiler mixed feed was given to the control group (K), the Bacillus subtilis strain containing 1g per 100 kg feed (1x108 cfu/g) was added to the test (P) group. For the PE test group, in addition to the test K group feeds, Bacillus subtilis strain + 12.5 g protease enzyme was added in a way that it would add 1 g per 100 kg concentrate feed (1x108 cfu/g). The live weights of the chicks were determined on days 7,14,21,28,35, and 40, and their feed consumption was recorded daily. At the end of the trial (40th day), the lowest average live weight was seen in the group with Bacillus subtilis and protease enzyme added (test 2) (p<0.05). While the live weight gain values were found similar in the control and groups containing only Bacillus subtilis (p>0.05), the lowest live weight gain occurred in the group containing Bacillus subtilis + protease enzyme (p<0.05). At the end of the research, when looking at feed consumption and feed conversion ratio, there was no significant difference in all groups (p>0.05). In conclusion, in this study; the use of Bacillus subtilis alone in broiler mixed feeds has had a positive effect on daily live weight gain, especially between 7-21 days, and feed consumption and feed conversion ratio between 14-21 days (p<0.05), during the trial period, the growth performance was adversely affected in the group where the probiotic + protease enzyme was combined in diets. Keywords: Bacillus subtilis, broiler chicken, feed consumption, growth performance, protease.