Abstract
In this study, the effects of synbiotic inclusion at the intra-amniotic stage in layer chicks were evaluated with different parameters, such as performance, immunological function, intestinal development, and cecal microflora content. A total of 1,200 eggs with fertile embryos were allocated into four treatment groups. For every treatment, five replicates were used, and 60 eggs were included in each replicate. The following four treatment groups were established: the non-injected group, 0.9% physiological saline injection (saline) group, 1 × 106 CFU/egg Lactobacillus plantarum injection (probiotic) group, and 1 × 106 CFU/egg L. plantarum + 2 mg/egg Astragalus polysaccharide injection (synbiotic) group. In ovo injection was carried out at 18.5 days of incubation. The results showed that in ovo injection of probiotics or synbiotics did not affect the hatching or growth performance of the chicks but significantly increased their feed intake (FI), body weight (BW), and the feed conversion ratio (FCR). Additionally, in ovo injection of synbiotics enhanced the levels of serum interleukin-2 (IL-2), interferon-γ (IFN-γ), and secretory immunoglobulin A (SIgA) in intestinal lavage fluid and the histomorphological development of the small intestine. Our results also indicated that intra-amniotic synbiotic injection significantly increased Lactobacillus and Bifidobacterium colonization while decreasing the relative abundance of Escherichia coli in the chicken cecum (P < 0.05). In summary, in ovo injection of synbiotics had positive impacts on the performance, immunological function, gut development, and microbiota of growing chicks.
Highlights
At the initial stages of hatching, the immune system of the chick is immature and inefficient
The initial egg weights (EWs) ranged from 60.54 to 60.68 g, with no significant differences observed between the initial weight of the eggs and the weights of 18 embryonic eggs among all the groups (P > 0.05)
In contrast to the period between 8 and 21 days, no significant differences in feed intake (FI), body weight gain (BWG), or feed conversion ratio (FCR) were observed among the treatments before day 7 post-hatch (P > 0.05)
Summary
At the initial stages of hatching, the immune system of the chick is immature and inefficient. In ovo injection has been reported to be an effective way to deliver nutrients into the amniotic cavity to compensate for the energy deficiencies that occur during the hatching process [3]. In ovo Injection of Synbiotics hatched chicks to various pathogens, administering Lactobacillus before hatching may be used as a strategy to enhance the immune-reactivity of hatchlings while reducing their susceptibility to pathogens [4]. Beneficial bacteria quickly colonize the intestines of hatchlings to help them establish a good balance of gut microflora, which can competitively inhibit pathogenic microorganisms in the intestine and promote disease resistance [5]. Different studies have reported beneficial influences of probiotics on chick growth performance, intestinal microflora, and immune function [12, 13]
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