Impact of Threonine Supply in Early Ages on Gut Tissue Morphology, Liver Histology, and the Possible Changes in Leukocyte Numbers of Broilers

Delayed feed access post-hatch negatively impacts growth and intestinal development in broilers. Threonine (Thr) is known to support epithelial tissue development. This study evaluated the effects of early feeding strategies, including in ovo Thr administration and hydrogel provision, on broiler performance, gut and liver histomorphology, and leukocyte profiles. Control birds were fed immediately post-hatch, while others experienced a 48 h feed delay. One group received in ovo Thr on day 17 of incubation, while others were given Hydrogel^® with or without Thr during the first 48 h post-hatch. Immediate feed birds showed the best performance (<i>p</i> < 0.05), while early Thr supplementation (in ovo or hydrogel) partially mitigated the negative effects of delayed feed access. On day 21, birds treated with in ovo Thr had 4% higher body weight (BW) than untreated birds (<i>p</i> < 0.05). Birds given hydrogel post-hatch showed no significant BW differences compared to other groups (<i>p</i> > 0.05), but 48 h delayed, non-supplemented birds had 34.3% lower BW than immediate-fed birds (<i>p</i> < 0.05). Compensation was linked to improved gut architecture, though no significant effects were observed on leukocyte profiles or liver histology. In ovo Thr feeding is recommended to mitigate the adverse effects of a two-day delay in feed access for broiler chickens.