The Hatching Time of Broiler Chickens Modifies Not Only the Production Traits but Also the Early Bacteriota Development of the Ceca

SIMPLE SUMMARY: Chicken meat is one of the main protein sources of animal origin worldwide and its production has been increasing steadily. These chickens have huge growth potential and a short production period, so all the factors that affect the vitality of day-old birds are getting more and more important. An other important issue in animal production is the decreased use of antibiotics to stabilize the bacteriota composition of the gut. In this article, the effects of parent flocks with different ages and the hatching time of the chickens were evaluated according to the production parameters, hatchability, and gut bacteriota composition of chickens. From the results, it can be concluded that the live weight of day-old chickens is crucial because it determines the growth rate of birds for the whole fattening period. Different parent flocks had no effect, but the hatching time modified the bacterium composition of the ceca at day 11. The reason for this could be the differences in the bacteriota colonization in the hatcher and the feed and water access between the early- and late-hatched chickens. ABSTRACT: This trial was carried out to find out the effects of the parent flock and hatching time of broiler chickens on the production traits and bacteriota development of animals. Two sets of 730 hatching eggs were collected from two different parent flocks with ages of 25 and 50 weeks. In the hatchery, both groups were divided into two subgroups: those hatched during the first 10 and the subsequent 10 h of the hatching window. A feeding trial was carried out afterwards, using the four treatments in six replicate floor pens and feeding commercial starter, grower, and finisher diets that contained all the nutrients according to the breeder’s recommendations. The day-old chickens of the older parent flock and those hatched later were heavier, and this advantage remained until the end of the production period. The different ages and origins of the parent flocks failed to modify the microbiological parameters of the chicken’s ceca; however, the hatching time significantly influenced the different bacteriota diversity indices: the late-hatched chickens showed higher Bacteroidetes and lower Firmicutes and Actinobacteria abundances at day 11. These treatments resulted in differences in the main families, Ruminococcaceae, Lactobacillaceae, and Bacteroidaceae. These differences could not be found at day 39.