|PAYNE, JASON - University Of Georgia|
|ELLESTAD, LAURA - University Of Georgia|
Submitted to: Poultry Science Association Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/14/2018
Publication Date: 9/1/2018
Citation: Payne, J.A., Proszkowiec-Wegla, M.K., Ellestad, L.E. 2018. Delayed access to feed impacts developmental gene expression in young broiler breast muscle. Poultry Science Association Meeting Abstract. 97:93.
Technical Abstract: In commercial settings, between hatch and placement of chicks, there is a variable length of time where birds do not have access to feed. When this period is prolonged by differences in time of hatch and/or transportation, birds can be left without feed for up to 48h. The objective of this study was to investigate effects of a prolonged delay in access to feed on gene expression in breast muscle. Chicks were given access to feed within 3h of hatch (fed) or were delayed access for 48h (delayed), with six replicate pens per group. Birds were weighed every 2 days from hatch until post-hatch day (D)14, and tissue was collected at hatch, 4 h post-hatch, D1 (24h), D2 (48h), D4, and D8. Total RNA was isolated from breast muscle collected from males in each of 4 different pens for each treatment and analyzed by quantitative PCR for genes regulating growth, development, and metabolism. Data were analyzed by two-way ANOVA, and differences between groups were determined using Tukey's multiple comparison model. After D6, birds from the delayed group were significantly lighter then fed birds through the end of the study (p<.01; n=6). In fed birds, there was a decrease in F-Box only protein 32 (FBXO32) and insulin receptor (INSR) mRNA levels between D1 and D2, while mRNA levels for myostatin (MSTN) and myogenin (MYOG) increased during this time. Alterations in levels of these genes did not occur until D4 in the delayed group, leading to the following differences in mRNA expression in delayed birds as compared to fed birds on D2 (n=4): 28-fold increase in FBXO32, 7-fold decrease in MYOG, 9-fold decrease in MSTN (p<0.05) and 2-fold increase in INSR (p=0.057). An apparent reduction in MSTN mRNA in the delayed group was also observed on D4 (P=0.072). The altered developmental expression of INSR, FBXO32 and MYOG may indicate lower blood glucose, increased protein degradation, and decreased muscle growth due to delayed access to feed, respectively. Reports from knockout models suggest that MSTN is a negative regulator of muscle growth; however, the expression pattern in birds deprived of feed suggest that it may play a different role during early post-hatch development when birds are nutrient deprived. A 48h delay in feeding is sufficient to alter gene expression regulating growth, development, and metabolism in breast muscle, which may contribute to the reduced body weight observed. The lack of differences in gene expression during the first 24h of feed restriction indicate that placement of chicks within this time frame may mitigate detrimental effects on gene expression that contribute to a reduction of body weight gain and alterations in breast muscle development.