Immediate access to feed and water in the hatcher influences early metabolic and thermoregulatory status in broiler chicks but is associated with breed-specific differences in later walking ability.

Providing newly hatched chicks with immediate access to feed and water (i.e. early feeding, EF) has gained increasing interest as a management strategy to improve gut health, performance and welfare in broilers. However, the effects of EF on both short- and long-term welfare status have not yet been thoroughly investigated. This study aimed to evaluate the impact of EF in hatchery-hatched chicks on animal-based welfare indicators, providing a more comprehensive understanding of the potential benefits and consequences of implementing EF strategies in the hatcher. A total of 960 Ross 308 (fast-growing) and 960 Hubbard Redbro (slower-growing) broilers, hatched in a hatcher, were randomly allocated to three treatment groups: T0 (immediate feed and water access), T1 (24 h delay to feed and water access), and T2 (48 h delay to feed and water access). Short-term welfare assessments included plasma glucose, body temperature, time of first feed and water intake and plasma arginine vasotocin levels in the first days post-hatch. Fear responses were assessed on day 11 and day 18 using the novel object test. Litter quality, walking ability and femoral head necrosis lesions were scored at the end of the production cycle to determine potential lasting effects of EF. Data were analysed per breed using mixed models. Throughout the production cycle, body weight was higher for T0 compared to T2 in both fast (p < 0.001) and slower-growing (p = 0.009) birds. Similarly, average daily feed intake tended to be higher in T0 compared with T2 in fast-growing broilers (p = 0.070) and was significantly higher in T0 than T2 in slower-growing broilers (p = 0.004), whereas no significant differences in feed conversion rate (FCR) were observed. In both broiler breeds, plasma glucose levels were higher for T0 than T2 on day 1 (p = 0.031) and day 2 (p = 0.005). Body temperature of the fast-growing birds from 10 to 48 h post-hatch was higher for both T1 (p = 0.021) and T0 (p = 0.018) compared to T2. In the slower-growing birds, body temperature was higher for T0 compared to T1 (p = 0.037) and T2 (p = 0.001) between 10 - 48 h post-hatch. In both fast- and slower-growing broilers around 50% of chicks from T0 and T1 had a filled crop at 28 h post-hatch, increasing to approximately 100% at 58 h. Water intake started earlier, with 50% of T0 chicks observed drinking between 16 and 18 h and 100% by 36 h post-hatch. In the fast-growing broilers, plasma arginine vasotocin concentrations at 48 h post-hatch were higher for T2 compared to T1 (p = 0.011) and T0 (p = 0.002). A similar difference was observed in the slower-growing birds, with higher levels for T2 than T1 (p < 0.001). For both the novel object test and litter quality, no significant differences were observed between treatments in either breed. However, on day 46, slower-growing broilers in the T2 group exhibited better gait scores (p = 0.044) and a lower incidence of femoral head lesions (p = 0.032) compared to T0 birds. In conclusion, providing chicks with EF in the hatcher advances the onset of feeding and drinking when compared with commercial hatchery practice. This earlier onset benefits multiple short-term welfare indicators in both fast-and slower-growing broilers chicks, but negatively affects long-term indicators of locomotion in slower-growing birds.