The Physiological Responses to Dietary Administration of Zinc Bacitracin and Bacillus Mixture on Low-Weight Day-Old Chicks

This study investigated the responses of low-weight day-old chicks to zinc bacitracin and Bacillus mixture on growth performance, hematology, intestinal selected microbiota populations, and carcass characteristics. A total of 192 unsexed Lohman MB-202 day-old broiler chicks were randomly allotted to four dietary treatment groups of 48 chicks each (6 replicates of 8 chicks) and fed for 35 days. The four treatments were CONT (basal diet without supplementation), AGP (basal diet with 0.04% zinc bacitracin), PROB (basal diet supplemented with 0.5% Bacillus mixture), and PROB+AGP (basal diet supplemented with 0.5% Bacillus mixture and 0.04% zinc bacitracin). There were no significant differences in final body weight, feed intake, and feed conversion ratio of broilers. The relative weight of thymus was higher (P= 0.01) in AGP than that in PROB and PROB+AGP birds. Birds in PROB+AGP had lower (P= 0.04) values of alanine aminotransferase (ALT) enzyme compared to those in CONT and AGP groups, but the difference was not significant when compared with birds in PROB group. Serum creatinine was lower (P< 0.01) in PROB+AGP than in CONT and AGP birds. Birds in AGP group tended (P = 0.09) to have higher globulin concentration in the serum compared to other birds. There was also a tendency (P = 0.07) for PROB+AGP birds to have higher albumin to globulin ratio compared with other birds. There was more lactic acid bacteria in ileal digesta (P = 0.05) in PROB+AGP than in AGP birds, but the difference was not significant when compared to CONT and PROB birds. Birds in AGP group had higher (P = 0.05) relative breast weight compared to other birds. In conclusion, Bacillus mixture did not affect performance and hematological parameters, but increased the intestinal population of lactic acid bacteria in broiler chicks.