Nutritional influences on the ultra-structural development of the small intestinal epithelium of the perinatal turkey embryo and poult

The transition from a lipid-rich in-ovo environment to a carbohydrate- and protein-rich diet is perhaps the biggest challenge that hatchlings must overcome during early life. Because amniotic fluid swallowing naturally prepares the embryonic digestive tract for post-hatch feed intake, amniotic fluid supplementation of the late-term avian embryo (i.e. in-ovo feeding---IOF) has been shown to stimulate enteric maturation of poultry and alleviate the stress of hatching. Moreover, rapidly dividing cells (e.g. intestinal epithelial cells) preferentially metabolize preformed nucleotides; hence, dietary nucleotide supplementation can improve post-hatch enteric maturation. Thus, our working hypothesis was that nutritional strategies influencing in-ovo nutrition and post-hatch dietary feed intake enhance the enteric development in perinatal turkey embryos and poults. Our study was among the first to characterize the ultra-structural changes in the small intestinal mucosa of the perinatal turkey embryo and poult (Chapter II). Furthermore, electron microscopy revealed that microbial colonization in the avian digestive tract begins prior to hatch, as early as 17E. Molecular profiling of these bacteria confirmed that some of the species include Bacillus, Lactobacilli, Pseudomonas and several uncultured bacteria (Chapter III). We showed that IOF accelerates the ultra-structural maturation of the jejunum mucosa of turkey embryos and poults around the time of hatch, and these effects are associated with elevated plasma triiodothyronine (T3) levels, a potent stimulator of morphological development of the mucosa (Chapter IV). Finally, we showed that dietary nucleotide supplementation to IOF turkey poults enhances the enteric maturation after hatch and the positive effects of nucleotide supplementation appear to be associated with stimulation of feed intake post-hatch. Therefore, we concluded that: (1) profound ultra-structural adaptations of the intestinal mucosa coincide with the swallowing of the amniotic fluid by the embryo; (2) microflora colonization of the avian gut begins well before hatch, (3) IOF stimulates ultra-structural maturation of the small intestine at hatch and these effects involve up-regulation of genes mediating epithelial cell proliferation as well as higher T 3 levels. (4) Dietary nucleotide supplementation of IOF turkey poults enhances enteric maturation post-hatch, which coincide with a consistent stimulation of poults appetite by dietary nucleotide supplementation.