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 (p < 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 (p < 0.05). Birds given hydrogel post-hatch showed no significant BW differences compared to other groups (p > 0.05), but 48 h delayed, non-supplemented birds had 34.3% lower BW than immediate-fed birds (p < 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.

Slaughter weight and feed efficiency are highly dependent on the length of post-hatch feed deprivation, due to the short fattening time. Late feed access has negative consequences on the development of the intestine, while threonine might be a candidate to support epithelial tissue development. The present study aimed to examine the effects of different early nutrition methods, particularly early Thr supplementation on the performance, gut and liver histomorphology, and the number of different leukocyte types in broiler chicken. Control birds were fed immediately post-hatch, while others had access to solid feed with a 48-hour delay. In one group in ovo threonine, administration was applied at d17 of incubation, while other groups of birds received hydrogel with or without Thr fortification in the first 48h. Our results confirmed that the best performance was achieved in birds that had no delay in feed access. Early Thr supplementation could at least partly compensate for the loss attributed to the post-hatch delay in feed access. The higher ability of compensation can be explained by the better architecture of the gut tissue, while there were no significant effects of Thr supplementation on the rate of leukocytes and liver histology parameters.