Effect on performance parameters of different doses of a novel bacillus CHCC15076 probiotic feed strain for the control of necrotic enteritis in broilers

The use of Bacillus species as probiotic supplements is expanding rapidly and demonstrates immune stimulation, antimicrobial activities, enzyme production and competitive exclusion as the most prevalent modes of action. The objective of this study was to investigate the dosage influence on performance parameters of the novel probiotic strain CHCC15076 in birds recovering from necrotic enteritis (NE) caused by Clostridium perfringens.

The experiment consisted of 1920 day of hatch Cobb 500 male chicks distributed in 48 pens starting with 40 chicks per pen. The treatments were replicated in eight blocks, randomized within blocks of six pens each. Feed and watering were performed ad libitum.

Four different doses (5 x10⁴ CFU/g feed to 3 x10⁶ CFU/g feed) were applied to the feed throughout the trial. Mean weight gain (WG), feed intake, feed conversion ratio (FCR), NE lesion scores and % NE mortality were calculated. On days 19, 20, and 21 all pens except for treatment 1 pens were challenged with a field isolate of C. perfringens known to cause NE. Each pen received the same amount of C. perfringens administrated in the feed. On day 21, three birds from each pen were sacrificed and examined for the degree of presence of NE lesions. The NE lesion scoring was as follows: 0 for normal intestines up to 3 for extreme NE.

Data were analysed with R vs. 3.2.5. Body weight and NE lesion scores were analysed using a regression model (procedure lm from the core package) with treatment group as fixed effect. A logistic regression models (procedure glm of the MASS package) with treatment group as fixed effect was fit to assess the odds of being positive for NE lesions. Residual plots were checked to evaluate model fit. Statistical significance was assessed at P ≤ 0.05. Results for lesion scores at day 21 were significantly improved for the CHCC15076 treated groups at the dose 1x10⁵ CFU/g of feed or higher. Likewise, the NE associated % mortality was improved significantly for all birds receiving CHCC15076.

Conclusions for this trial; Inclusion of the novel Bacillus CHCC15076 probiotic strain decreases the degree of NE lesion scores and mortality, and several of the doses improve the FCR and final slaughter weight. The experiment illustrates the importance of the correct dosage of probiotic for the performance and efficacy of the birds. The mode of action for this novel probiotic involves antimicrobial activities and competitive exclusion against pathogens.