This trial was done to determine broiler live performance to 42 days, under a hot climate in India. 2080 VenCobb 400 broilers were allocated in 4 groups with 26 birds per floor pen and 20 replicates per group: negative control group (NC), positive control group (PC), direct-fed microbial group (DFM) at Log 5 CFU/g of feed and Bacitracine group (BMD) at 500 g/T of feed. The DFM product was composed with 3 species of sporulated Bacillus: Bacillus amyloliquefaciens, bacillus licheniformis and bacillus pumilus. The room temperature reached a peak of 31.64 to 33.29°C from 4 to 6 weeks old. PC, DFM and BMD groups were fed with a challenging feed formula: 5 to 10% of DDGS, 8 to 10% of mustard cake extract and 5 % of medium quality meat and bone meal (which is still usually used in India). NC group was with a classical and non-challenging corn and soybean-based diet.
The body weight at 42 days was 2.707 kg in NC group, but only 2.144 kg in PC group, due to the feed challenge. It reached 2.205 kg in BMD group and 2.254 kg in DFM group, significantly higher than PC group (p=0.001).
The broilers were vaccinated against Newcastle disease during the trial at 7 and 21 days. The humoral vaccine response was evaluated by HI-test at 42 days. The response was 5.05 Log2 in NC group, 4.75 Log2 in PC group, 4.10 Log2 in BMD group and 5.85 Log 2 in DFM group, significantly higher with DFM (p=0.001). The cell-mediated immunity was also evaluated by basophilic hypersensitivity test. The response was respectively 70.05, 72.65, 65.65 and 95.20 significantly stronger with DFM (p=0.004).
The ileal microbial count in CFU/g was evaluated at 42 days. The quantity of E. coli was respectively 3.942, 3,849, 3.968 and 3.510, significantly lower with DFM (p=0.019). The quantity of Clostridium perfringens was respectively 3.515, 3.748, 3.510 and 3.158, also significantly lower with DFM (p=0.015). This direct-fed microbial enabled to improve the growth performances under a natural heat stress, helped to improve the vaccine response and reduce the pressure of potentially pathogenic bacteria like E. coli and Clostridium in the gut.
Keywords: broiler, direct-fed microbial, hot climate, feed challenge, performances