Early feeding in the hatcher influences physiological indicators of nutritional status and hydration in broiler chicks during the immediate post-hatch period.

As early feeding (EF) is considered a promising strategy to improve broiler welfare, performance and health, new approaches to implement EF are becoming increasingly popular in the poultry industry. EF provided in the hatcher, commonly referred to as in-hatcher feeding, can offer a solution for the feed and water deprivation period experienced by chicks in traditional hatchery systems. However, in-hatcher feeding is still developing and scientific research regarding its impact on performance, health and welfare is limited. Therefore, the present study was designed to determine specific short-term physiological responses to EF in broiler chicks hatched in a hatcher, focusing on stress indicators and indicators for inferring time to first feed and water intake. A total of 320 Ross 308 broiler chicks, housed in 32 hatching baskets (10 chicks per basket; 8 replicates per treatment), were randomly assigned to one of four post-hatch feeding treatments until 48 h post-hatch: immediate access to feed and water (FW), to feed only (F), to water only (W), or deprived of both feed and water (D). At 4, 14, 24, 36, and 48 h post-hatch, blood and tissue samples (proventriculus and residual yolk) were collected to assess chick body weight (BW), residual yolk weight, plasma osmolality, plasma arginine vasotocin (AVT), plasma corticosterone (CORT) and ghrelin mRNA. Data were analysed using mixed models with the hatching basket as the experimental unit. From 24 h - 48 h post-hatch, BW differed between treatments with FW consistently showing the highest BW when compared to the other treatments (p < 0.001). An age-related increase in plasma osmolality was observed in water deprived treatments (D and F) from 24 - 48 h post-hatch, while levels in W and FW decreased slightly (p < 0.001). In D, AVT levels increased sharply from 24 h post-hatch onwards, whereas FW consistently showed lower levels compared to D (p = 0.005). Similarly, plasma CORT concentrations were lower in FW compared to D (p = 0.010) at 36 and 48 h post-hatch. Ghrelin mRNA expression did not differ between treatments during the first 14 h post-hatch but was consistently lower in FW when compared to D, F and W (p < 0.001) thereafter. Conversely, no treatment effects were observed for residual yolk weight. In conclusion, the physiological and neuroendocrine responses observed between 14 and 24 h post-hatch suggest a transition in metabolic and hydration status that is consistent with the onset of feeding and drinking during this time window. Additionally, higher body weights and reductions in corticosterone levels were only observed when both feed and water were provided.