|PAYNE, JASON - UNIVERSITY OF GEORGIA|
|ELLESTAD, LAURA - UNIVERSITY OF GEORGIA|
Submitted to: American Journal of Physiology - Regulatory Integrative & Comparative Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/3/2019
Publication Date: 10/9/2019
Citation: Payne, J.A., Proszkowiec-Wegla, M.K., Ellestad, L.L. 2019. Delayed access to feed alters expression of genes associated with carbohydrate and amino acid utilization in newly hatched broiler chicks. American Journal of Physiology - Regulatory Integrative & Comparative Physiology. https://doi.org/10.1152/ajpregu.00117.2019.
Interpretive Summary: 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. The best growth and development of any organism can be achieved only when the energy and nutrient needs are met. Immediately after hatch, chicks depend on lipid-rich nutrients that are stored in yolk sack to provide nutritional support. After chicks are supplied with post-hatch feed they transition to utilization of carbohydrate-rich diets. Little is known about the effects of a delayed feed access post-hatch on expression of genes related to nutrient uptake and utilization in two tissues that are metabolically important, liver and muscle. Therefore, the aim of the present study was to characterize the expression pattern of genes associated with transcriptional and hormonal regulation of sugar and amino acid homeostasis and transport in liver and muscle. during the first two weeks post-hatch in chickens that were fed or had delayed access to feed. To mimic commercial settings, newly hatched chicks were subjected to 48 hours delay in feeding or fed immediately after hatch. We have determined that delay in post-hatch feeding: 1) impacts expression of transcriptional regulators of sugar and lipid metabolism, 2) delays transition from lipid to carbohydrate metabolism, and 3) affects amino acid transporter genes expression. In summary, we have shown, that delayed access to feed post-hatch negatively impacts carbohydrate and amino acid utilization in newly hatched chicks. Delayed transition to sugar utilization and altered nutrient transport and utilization in liver and muscle, following post-hatch feed restriction in broilers, may lead to reduced animal growth and development.
Technical Abstract: Newly hatched chicks must transition from lipid-rich yolk to carbohydrate-rich feed as their primary nutrient source, and post-hatch delays in access to feed can have long-term negative consequences on growth and metabolism. In this study, impacts of delayed access to feed at hatch on expression of genes related to nutrient uptake and utilization in two metabolically important tissues, liver and muscle, were determined in broiler (meat-type) chickens. Hatched chicks were given access to feed within 3h (Fed) or delayed access to feed for 48h (Delayed Fed), and liver and breast muscle were collected from males at hatch and 4h, 1 day (D), 2D, 4D, and 8D post-hatch for analysis of gene expression. Differential expression of carbohydrate response element binding protein and peroxisome proliferator-activated receptor gamma in muscle and liver was observed, with results indicating a transitional delay from lipid to carbohydrate metabolism when hatched chicks were not given immediate access to feed. Extended upregulation of insulin receptor mRNA was observed in both tissues in Delayed Fed birds, suggesting altered sensitivity to circulating levels of the hormone. Developmental delays in expression of cationic amino acid transporters 1 and 2 was also affected in both tissues, and developmental expression of large neutral amino acid transporter 1 in muscle were also apparent when immediate feed access was prevented. These data suggest that delayed transition to carbohydrate use and altered nutrient transport and utilization within liver and breast muscle are key factors negatively affecting growth and metabolism following delayed feed access in broiler chickens.