Effect of In ovo Injection of Probiotic, Prebiotic, and Synbiotic on Growth Performance and Gut Health Parameters of Broiler Chicken

Abstract

Due to the claimed public health concerns, use of antibiotics as growth promoters (AGP) in the chicken feed is banned or regulated in several jurisdictions. Therefore, probiotics, prebiotics, and synbiotics are being evaluated as effective alternatives to AGP to improve growth performance and health of poultry. This study aimed to investigate the effects of Bacillus coagulans, Raffinose family oligosaccharides (RFO) and their combination on growth performance and gut health of broilers when injected in ovo. A total of 285 fertilized eggs were divided into 5 groups: i) No-injection group with intact shell, ii) 0.5 ml 0.85% normal saline, iii) Probiotic (B. coagulans) (2×106 CFU/egg) in 0.5 ml 0.85% normal saline, iv) Prebiotic (4.5 mg RFO) in 0.5 ml 0.85% normal saline, and v) Synbiotic (2×106 CFU/egg B. coagulans + 4.5mg RFO) in 0.5 ml 0.85% normal saline. The injection solution was deposited into the amniotic sac on d 17 of incubation. Hatchability of eggs were recorded. Altogether, 48 day-old chicks from each treatment were randomly allocated to 6 replicate floor pens (n=8/pen). All birds were raised on a standard commercial diet and management for 42 days. Body weight and feed intake of birds were measured weekly. Ileum samples were collected on d 0 and d 7 post hatch for total RNA isolation. Expression of immune/cytokines related genes in the ileum were determined using qPCR. The in ovo injection did not affect (P > 0.05) hatchability of eggs across the treatments. There was no significant effect of treatments on body weight, average daily gain and feed intake of broilers in different experimental groups. However, birds from normal saline treatment had significantly better (P < 0.05) feed efficiency and RFO group had the poorest feed efficiency in the first week of post-hatch period. No significant difference (P > 0.05) was found on relative organ weight of birds on d 21 and d 42. At d 7 of age, ileum villus height, crypt depth, and villus height: crypt depth ratio of RFO group were significantly better than other treatments (P < 0.05). On hatch day, expression of IL4 (inducer of T-cells differentiation) was significantly higher (P < 0.001) in the ileum of probiotic group. On d 7, immune-related genes (CD56, ChB6, TLR4, MCN2) and cytokines related gene (IL10) were significantly higher (P < 0.05) in the ileum of saline-treated group, whereas glucose transporter (SGLT1) had lower expression (P < 0.05) in synbiotic group. In conclusion, in ovo injection of probiotic enhances gut immunity of chicken which would be beneficial for gut health. It is interesting to find that in ovo injection of saline also enhanced gut immunity.