Effect of constant or weekly varied eggshell temperature during incubation on broiler performance up until slaughter age

After hatching in conventional systems, broiler chickens have a delay to nutrition thatcan last for 72h, depending on length of the hatch window, internal hatchery proceduresand transport duration. Previous research on early life feeding strategies has shownnegative effects on bodyweight (BW) gain after delayed nutrition (DN), compared withearly 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 thehypothesis that DN chickens have an increased growth rate, as a result of compensatorygrowth. Data from 3 independent experiments were used. In these studies, broilerswere subjected to either EN or DN with different durations of DN (38 to 72 h) and daysto 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, decreasedfrom 114 to 176% post placement to 102 – 112 % at slaughter (35 d). Growth curves of DNand EN chickens were analysed to study whether compensatory growth could explain thedifferences in BW between EN and DN. Absolute average daily gain (aADG) was higher inEN 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 rADGseems insufficient to catch up with EN broilers. EN chickens have higher aADG untilslaughter, however, rADG is lower, showing that growth rate is influenced by feedingstrategy. Previous literature describes interactions between compensatory growth andnutrient composition of diets on nitrogen and fat retention. This may give reason forfuture work to evaluate effects of early life feeding strategy on carcass traits.