Body weight is affected by early life feeding strategy and hatch moment in broiler chickens

After hatching in conventional systems, broiler chickens have a delay to nutrition that can last for 72h, depending on length of the hatch window, internal hatchery procedures and transport duration. Previous research on early life feeding strategies has shown negative effects on bodyweight (BW) gain after delayed nutrition (DN), compared with early nutrition (EN). However, it is not known whether DN chickens can (partially)compensate for their lower BW between hatch and slaughter. In this study, we tested the hypothesis that DN chickens have an increased growth rate, as a result of compensatory growth. Data from 3 independent experiments were used. In these studies, broilers were subjected to either EN or DN with different durations of DN (38 to 72 h) and days to slaughter (14 to 35 d). In all experiments, DN groups had lower BW compared withEN which was sustained until slaughter. Relative differences in BW, however, decreased from 114 to 176% post placement to 102 – 112 % at slaughter (35 d). Growth curves of DN and EN chickens were analysed to study whether compensatory growth could explain the differences in BW between EN and DN. Absolute average daily gain (aADG) was higher in EN chickens from start until slaughter. To analyse the growth curve independent of BW, relative ADG (rADG) between two ages was calculated as follows: Differences in rADG between DN and EN chickens were greater in the first 14 d (DN:63%, EN: 47%; P < 0.001), but smaller in the remaining grow-out period (14 – 28 d:DN: 18%, EN: 16%; 28 – 35 d: DN: 8%, EN: 7%; both P <0 .001). Based on these results,it seems that DN broilers compensate for their lag in BW during the first 14 d postplacement. As differences in absolute BW were still present at 35 d, the increase in rADG seems insufficient to catch up with EN broilers. EN chickens have higher aADG until slaughter, however, rADG is lower, showing that growth rate is influenced by feeding strategy. Previous literature describes interactions between compensatory growth and nutrient composition of diets on nitrogen and fat retention. This may give reason for future work to evaluate effects of early life feeding strategy on carcass traits.