A flying start : Adapted hatching and post-hatch feeding in broiler chickens

Conventional hatching practices do not involve provision of feed and water to broiler chickens before placement at the rearing farm. This can pose problems, especially for early hatchlings, which remain feed-restricted for a considerable period due to biological variation in hatch time. The individual requirements of modern fast-growing chickens in order to remain robust and resilient may have changed in recent decades. This thesis studied the effect of hatching time on interval to first feed intake, growth and organ development in chicks hatched on-farm. It also examined the effects of providing hatching chicks with access to feed and water in the hatcher, combined with two different probiotics, on productivity, organ development, immune traits and development of caecal microbiota. Physiological differences between chicks hatched at different times during the hatching window generally levelled out during the production period. Eating-related activities were low immediately post-hatch, and early hatchlings showed compensatory growth as they were lightest at hatch but heaviest at three days of age. Feed deprivation during hatch resulted in depressed feed intake and associated depressed growth, which in some cases was reversed during the growing phase. Supplementation with probiotics had some negative effects on productivity, especially for chicks deprived of feed and water at hatch. There were no long-term differences due to early feeding on microbiota development or immune traits measured. These results suggest that modern broiler chickens are at least partly capable of compensating for setbacks in early life, and that some early effects of feed and water deprivation are transient. However, the studies in this thesis were performed in highly sanitary conditions and at lower stocking densities than in commercial production. Further research is needed to confirm the effects of adapted hatching and post-hatch feeding strategies in conditions that resemble more closely the challenges faced by the modern broiler