Comparative Efficacy of a Novel Multi-Strain Bacillus-Based Direct Fed Microbial and Each One of its Single Strains for The Control of Necrotic Enteritis Caused by Clostridium Perfringens in Broiler Chickens

The use of Bacillus species as probiotic supplements is expanding rapidly and these products demonstrate immune stimulation, antimicrobial activities, enzyme production and competitive exclusion as the most prevalent modes of action (Grant et al., 2018; Hmani et. al., 2017; Reis et al., 2017).

The objective of this study was to evaluate the effect of a multi-strain Bacillus-based directly fed microbial (DFM) and its three single strains on performance of broilers challenged with a commercial Eimeria vaccine and a field isolate of Clostridium perfringens known to cause necrotic enteritis (NE) originating from a commercial broiler operation.

The experiment consisted of 2250 day of hatch Cobb 500 male chicks distributed in 45 pens with 50 chicks per pen. The five treatments were replicated in nine blocks, randomized within blocks of five pens each. T1 (control group; challenged birds without DFM); T2 (DSM32324 strain at 8 X 10⁵CFU/g of feed); T3 (DSM32325 strain at 5 X 10⁵ CFU/g of feed); T4 (DSM25840 strain at 3 X 10⁵ CFU/g of feed) and T5 (the three strains combined at 1.6 X 10⁶CFU/g of feed). The standard diet was corn soy based pelleted feed and was, together with water, provided ad libitum. All birds were spray vaccinated with Eimeria vaccine on day of hatch. On Days 19, 20, and 21, all pens were challenged with a field isolated C. perfringens. Each pen received the same amount of C. perfringens (1.0 X 10⁸CFU) (Mathis 2018). On day 21, five birds per pen were sacrificed and examined for the degree of NE lesions. The NE lesion scoring was as follows: 0 for normal looking intestines and up to 3 for extreme NE lesions. Weight gain (WG), feed intake and feed conversion ratio (FCR) were recorded on day 21, 35 and 42. NE lesion scores and % NE mortality were calculated on day 21.

The groups supplemented with DFM’s had significantly improved FCR ranging from 1.841-1.898 compared to the control group (1.957) (P < 0.05), the multi-strain DFM showing the lowest value (1.841). Furthermore, DFM treatments significantly reduced NE lesion scores (0.5-0.7) and NE related mortality (0.4-1.6%) compared to the control group (1.0 and 4.2% respectively) (P < 0.05).

In conclusion, the results of this study showed that inclusion of both the multi-strain Bacillus based DFM or its single strains decreased the degree of NE lesion scores and mortality and improved FCR in a sub-clinical NE model. It is hypothesised that the mode of action for this novel probiotic involves antimicrobial activities and competitive exclusion against pathogens.