The present study was conducted to evaluate the effects of in-ovo injection and early feeding on performance, intestinal morphology, ileum microbiota, digestive enzyme activities, and immune system development in broiler chickens. 1,800 Ross 308 eggs were divided into 6 treatment groups with 10 replicates of 30 eggs in a completely randomized 3 × 2 factorial design. The experimental treatments included six groups as follows: NI-NF: Non-injected eggs and as hatches chicks with 48 h delayed access to feed (negative control); NI-YF: Non-injected eggs and as hatched chicks with immediate nutrient gel access; SL-NF: In-ovo saline injection and delayed feed access; SL-YF: In-ovo saline injection and as hatched chicks with immediate nutrient gel access; PB-NF: In-ovo probiotic injection (100 μL per egg) and delayed feed access; PB-YF: In-ovo probiotic injection and as hatched chicks with immediate nutrient gel access. Hatchability did not differ among treatments (P = 0.721). Chicks from probiotic-injected eggs (PB-NF and PB-YF) exhibited higher body weight at hatch than those from non-injected (NI-NF, NI-YF) and saline-injected (SL-NF, SL-YF) eggs (P = 0.043). At 48 h post-hatch, the PB-YF group recorded the greatest body weight (P = 0.004). During 11-24 days, PB-YF birds showed the highest BWG, differing from all other groups (P = 0.004). From 25-42 days, PB-YF, SL-YF, and NI-YF maintained higher BWG values compared with NI-NF and SL-NF (P = 0.017). At all ages, chicks with early feeding access (NI-YF, SL-YF, and PB-YF) exhibited significantly greater villus height compared with their delayed-fed counterparts (NI-NF, SL-NF, and PB-NF) (P < 0.05). At 10 days, the PB-NF group exhibited the lowest C. perfringens and E. coli population, significantly lower than NI-NF and SL-NF (P = 0.034; P = 0.001). At 10 days, PB-YF group chicks exhibited the highest amylase, lipase and protease activity (P < 0.05). A significant interaction between in ovo probiotic injection and early feeding was detected for IgM, IgA, IL-10, and IL-6 at 3 and 10 days of age (P < 0.05). At day 3, the PB-YF group showed the lowest corticosterone level (P = 0.001), while no significant difference was detected at day 10 (P = 0.128). In conclusion, in ovo probiotic injection improved early survival, immunity, and initial growth, whereas early feeding provided more persistent advantages throughout the production period; together, these strategies acted synergistically to optimize broiler health, gut development, and overall performance.
Hassanlou et al. (Thu,) studied this question.