The Effect Of Days On Feed and Beta‐Agonist Administration On The Expression Of Adipocyte‐Specific Regulatory Genes in Skeletal Muscle and Adipose Tissue of Finishing Heifers

Abstract

The development of marbling (Intramuscular fat; IMF) is an economically relevant trait that is mediated at the molecular level of adipose tissue metabolism. The objective of the current research was to evaluate adipose‐specific regulatory genes in skeletal muscle IMF, and adipose depots of finishing heifers. Gastrocnemius Muscle (GM), Longissimus Dorsi Muscle (LM), and subcutaneous adipose tissue (AT) were collected after heifers were on feed for 79, 121, and 163 days and treated with (BAA) or without (Control) beta‐agonist for the final 30d of feeding, respectively. Quantitative Real‐Time PCR was used for gene expression analysis. Pref‐1 expression was highest in the initial slaughter group (P<0.05), and decreased as time on feed increased. LM showed decreased Pref‐1 expression relative to GM indicating an increased IMF adipogenic capacity in this muscle depot. BAA treatment appeared to decrease Pref‐1 expression in both LM and GM. Subcutaneous AT showed increased Pref‐1 expression relative to LM (P<0.05) when treatments within slaughter groups were combined, but when individual tissues and treatments were compared, there was no difference between LM and AT (P>0.05), while the GM showed higher expression (P<0.05) relative to AT and LM. This study showed a temporal Pref‐1 expression pattern that appears to be consistent with the paradigm of late development of the IMF depot.