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

## TL;DR

Early threonine supplementation can help mitigate the negative effects of delayed feed access on broiler growth and gut development.

## Contribution

The study introduces in ovo threonine feeding as a novel strategy to counteract the adverse effects of post-hatch feed deprivation in broilers.

## Key findings

- Immediate feed access resulted in the best performance and gut morphology in broilers.
- In ovo threonine feeding partially mitigated the negative effects of delayed feed access.
- Hydrogel with or without threonine improved body weight in broilers with delayed feed access.

## Abstract

Broiler chickens travel long distances from the hatchery to the farms. This lag time may affect not just later performance, but also the development of the immune system. Threonine (Thr) is an essential amino acid that has key role in immune defense. Thus, the study aimed to examine the effects of some early nutritional practices such as in ovo feeding or provision of hydrogel on the morphology of the gut, histology of the liver, and the possible changes in white blood cell counts, with or without adding Thr in an early stage of life. Our results confirmed that birds without a feed deprivation period had the best performance and gut morphology, while threonine supplementation could partly compensate for the loss attributed to the post-hatch delay in feed access. There were no effects of early threonine feeding on the rate of white blood cells and histological parameters of the liver. The use of Hydrogel® with or without Thr fortification during the post-hatch period improved the body weight at slaughter; thus, it can be recommended for use with broilers with delayed feed access.

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.