Bacillus subtilis delivery route: effect on growth performance, intestinal morphology, cecal short-chain fatty acid concentration, and cecal microbiota in broiler chickens

The sub therapeutic use of antibiotic growth promoters (AGPs) to improve growth and health performance of poultry has received strong criticism due to public heath concerns such as anti-microbial resistance, antibiotic residues, and food safety. For these reasons, the poultry industry must evaluate the efficacy of possible alternatives to AGPs as well as the delivery methods that maximizes their effectiveness.
The aim of this study was to clarify knowledge on the effect of the delivery method of a probiotic product (Bacillus subtilis fermentation extract) on the performance and gut parameters of broiler chickens.
To perform the experiment, a total of 450 fertile eggs from Cobb 500 broiler breeders were divided into three groups as follows: in ovo (inject or delivered into the egg) probiotic (n=66), in ovo saline (solution of salt and water) (n=66), and non injection (n=200) and incubated for 21 days. On day 18.5 of incubation, 200 L of either probiotic (10x106cfu) or saline was injected into the amnion (egg). After hatching, chicks were re-assigned to 6 new treatment groups as follows: (1) in ovo probiotic, (2) in ovo saline, (3) in-feed antibiotics, (4) in-water probiotic, (5) in-feed probiotics, and (6) control (corn-wheat-soybean diet) in 6 replicate cages and raised for 28 days.
Of all hatch parameters studied, only percentage pipped eggs was significant (P<0.05) with the non-injection group having higher percentage pipped eggs than the other groups. The treatments did not have an affect on the incidence of necrotic enteritis on day 28 (P>0.05). Necrotic enteritis is the most common and financially devastating bacterial disease of the broiler industry. Also, the probiotic treatments did not have significant effects on growth performance. The ileum villus width of the in ovo probiotic treatment was 18% higher than the in ovo saline group (P=0.05) but this difference was not statistically significant. The jejunum villus height was 23% higher (P=0.000) in thein ovo probiotic group than in the control group. There was no effect of treatment on total cecal short-chain fatty acid concentration and cecal gut microbiota composition and diversity (P>0.05), although few unique bacteria differential abundance were recorded per treatment. In conclusion, although probiotic treatments (irrespective of the delivery route) did not affect growth performance, in ovo delivery of the probiotic product enhanced intestinal morphology, without compromising hatch performance and gut homeostasis