Relevance of navel quality of day-old chick on organ development, initial performance, and bacterial presence.

This study aimed to evaluate effects of day-old chick navel quality on the absorption of the residual yolk sac, visceral development, macroscopic organ alterations, yolk sac bacterial presence and performance of broilers up to 14 d of age. A total of 372 male Ross 308 day-old chicks were classified as first or second-grade based on navel quality. First-grade chicks were chicks with the yolk sac completely retracted and a fully healed dry navel, without any further abnormality. Second-grade chicks were chicks with incomplete healed navels, based on the presence of residual yolk membrane or a black button on the navel larger than 2 mm. Necropsies were performed at d 0 (placement) and on d 3 and 5 post-pulling and swabs were taken from the yolk sac for bacteriological culture. In addition, weights the yolk sac, proventriculus, gizzard, small intestine, caeca, pancreas, liver, and heart were determined daily from d 0 to 5. First-grade chicks showed greater absorption of the residual yolk sac, as well as higher weights for the small intestine and pancreas up to 24 h after placement than the second-grade chicks. Chick quality had no significant effect on the relative weights of the proventriculus, gizzard, caeca, or heart during the first 5 d post-hatch. At placement, second-grade chicks presented bacterial growth in the yolk sac content, predominantly by Enterococcus faecalis. At d 5, both groups exhibited bacterial growth, with the detection of Escherichia coli and three Enterococcus species. First-grade chicks showed higher body weight, weight gain, and better feed conversion at seven and 14 d of age than second-grade chicks. In the first week after placement, high mortality was observed, mainly due to infection with Enterococcus faecalis and Escherichia coli, but no significant effect of day-old chick navel quality was observed. In conclusion, navel quality at hatch did not significantly influence chick mortality in the presence of yolk sac infections caused by Enterococcus spp. and E. coli. However, it was associated with greater body weight gain and higher feed efficiency during the first days of rearing.