Effects of early post-hatch feeding on the growth performance, hormone secretion, intestinal morphology, and intestinal microbiota structure in broilers

This study aimed to investigate the effects of time access to post-hatch feeding on the growth performance, hormone secretion, intestinal morphology, and intestinal microbiota structure of broilers. A total of 900 broilers were randomly allocated to 3 treatment groups, with 6 replicates of 50 broilers each. The 3 treatments were: immediate feeding (Group 2 h), delayed access to feed for 24 h (Group 24 h), and delayed access to feed for 48 h (Group 48 h). The experiment lasted for 50 d. Results revealed that Group 2 h had a higher average daily gain (ADG) and average daily feed intake (ADFI) as well as a lower feed-to-gain ratio (F/G) than Group 48 h during the starter period (P < 0.05). Compared with Group 48 h, broilers in Group 2 h exhibited significantly elevated villus height (VH) and villus height to crypt depth ratio (VH: CD) in the duodenum, increased Occludin, and Claudin-1 mRNA expression in the jejunum but decreased crypt depth (CD) in the duodenum at 50 d (P < 0.05). Meanwhile, broilers in Groups 2 h and 24 h had increased glycogen (Gn) and protein (Pro) levels in breast muscle and TG levels in the liver, as well as a higher concentration of serum T₃, T₄, and IGF-1 compared with Group 48 h at 21 d (P < 0.05). Besides, intestinal microbiota consisted primarily of Firmicutes, Bacteroidetes, and Proteobacteria at the phylum level at 21 d and 50 d; at the genus level, broilers in Group 2 h displayed significantly reduced abundance of Escherichia at 21 d and Bacteroides at 50 d compared with Group 48 h (P < 0.05). Collectively, these findings signal that early post-hatch feeding measures, especially at 21 d, improve hormone secretion, intestinal morphology, and the growth performance of broilers by enhancing intestinal health and modulating the intestinal microbiota.