|ELSASSER, THEODORE - Retired ARS Employee|
Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/16/2020
Publication Date: 7/3/2020
Publication URL: https://handle.nal.usda.gov/10113/7007529
Citation: Proszkowiec-Wegla, M.K., Schreier, L.L., Kahl, S., Miska, K.B., Russell, B.A., Elsasser, T.H. 2020. Effect of early neonatal development and delayed feeding post-hatch on expression of tight junction- and gut barrier-related genes in small intestine of broiler chickens. Poultry Science. https://doi.org/10.1016/j.psj.2020.06.023.
Interpretive Summary: Gastrointestinal tract plays an important role not only in digestion and absorption of digested nutrients, but also forms a physical barrier and first line of protection between the host and the gut environment. A proper barrier between host and gut environment is essential for optimal health and production efficiency of food producing animals, including chickens. The gut barrier is formed by layer of mucus protecting gut epithelial cells and epithelial cells connected by tight junction. In the current broiler production systems, chicks are deprived of food and water for up to 72 hours due to uneven hatching, hatchery procedures such as sexing, sorting, selection and vaccination, and transportation time to destination farms. Lack of access to feed during the first 48-72 hours results in lower body and organ weight, higher feed conversion ratio (amount of feed required for 1kg of body weight gain) and mortality, delayed growth rate and gastrointestinal tract development. Little is known about the effects of early neonatal development and delayed feeding immediately post-hatch on gut barrier function in chickens. Therefore, the aim of the present study was to characterize mRNA and protein expression pattern of gut barrier- and tight junction-related genes in small intestine of broiler chickens during early development and delayed access to feed post-hatch. To mimic commercial settings, newly hatched chicks were subjected to 48 hours delay in feeding or fed immediately after hatch. We have determined that delayed access to feed immediately post-hatch: 1) changes the expression patter of gut barrier- and tight junction-related genes, 2) affects histology of the gut and 3) changes mucin type in the gastrointestinal tract. In summary, we have shown, for the first-time, developmental changes in expression of gut barrier- and tight junction-related genes in broiler chickens. Our results suggest that delayed access to feed post-hatch may affect the structure and/or function of tight junction, changing gut barrier function and in consequences can have deteriorating effect of gut and overall health, and well-being of broiler chickens.
Technical Abstract: Gut plays a key role not only in the digestion and absorption of nutrients, but also forms a physical barrier and first line of defense between the host and the luminal environment. A functional gut barrier (mucus and epithelial cells with tight junctions (TJ)) is essential for optimal health and efficient production in poultry. In current broiler system, chicks are deprived of food and water up to 72 h due to uneven hatching, hatchery procedures and transportation. Post-hatch (PH) feed delay results in lower BW, higher FCR and mortality, and delay PH gut development. Little is known about the effects of early neonatal development and delayed feeding immediately PH on gut barrier function in chickens. Therefore, the aim of the present study was to characterize gene and protein expression pattern of gut barrier- and TJ-related protein genes in small intestine of broiler chickens during early development and delayed access to feed PH. Newly hatched chicks received feed and water immediately after hatch or were subjected to 48 h delayed access to feed to mimic commercial hatchery setting and operations. Birds were sampled (n=6) at -48, 0, 4, 24, 48, 72, 96, 144, 192, 240, 288 and 336 h PH, and jejunum and ileum were collected, cleaned of digesta and snap frozen in liquid nitrogen or fixed in paraformaldehyde. The relative mRNA levels of gut barrier- and TJ-related protein genes were measured by quantitative PCR and analyzed by two-way ANOVA. In both tissues, changes (P<0.05) in gene expression pattern of gut barrier- and TJ-related genes were detected due to delayed access to feed PH and development. Most changes in TJ-related gene expression were observed in ileum. No significant (P>0.05) changes in protein expression for claudin 1 and 5 were observed due to delayed access to feed in ileum and jejunum. Histological differences and changes in mucin staining due to age and treatment were observed. These results suggest that delayed access to feed PH may affect TJ structure and/or function and therefore, gut barrier function and overall health of chicken small intestine.