Effect of genetic merit for backfat thickness and paternal breed on performance, carcass traits, and gene expression in subcutaneous adipose tissue of feedlot-finished steers

Abstract

• Backfat thickness trait can be selected through genetic merit in Nellore and crossbred steers (½ Aberdeen Angus + ½ Nellore). • Animal performance is not affected by genetic merit for backfat thickness. • The expression of ACACA, ADIPOQ, FASN, PLIN 1, PPARG and SREBF1 genes in subcutaneous adipose tissue is not affected by genetic merit for backfat thickness. This study evaluated selection for backfat thickness based on genetic merit (GMB) in Nellore (N) and crossbred (½ Aberdeen Angus + ½ Nellore, AN) steers, as well as the effects of this selection on animal performance, carcass traits, and gene expression in subcutaneous adipose tissue (SAT). The animals were obtained by mating Nellore cows with Nellore or Aberdeen Angus bulls. Both paternal genetic groups were selected to have positive (+, high GMB) or negative (-, low GMB) expected progeny differences for backfat thickness. Seventy-six animals (14 N+, 20 N-, 20 AN+, and 22 AN-) were reared on pasture and finished in the feedlot. The animals were slaughtered, and SAT samples were collected to investigate the relative expression of the acetyl-CoA carboxylase alpha ( ACACA ), adiponectin, C1Q and collagen domain containing ( ADIPOQ ), fatty acid synthase ( FASN ), perilipin 1 ( PLIN1 ), peroxisome proliferator activated receptor gamma ( PPARG ), and sterol regulatory element binding protein ( SREBF1 ) genes. Carcass weight and yield, conformation, finishing score, fat distribution score, and measurements of backfat thickness and rib eye area were evaluated. There was no effect of GMB on performance or on the relative expression of the genes studied. High GMB steers had greater backfat thickness and higher finishing, conformation and fat distribution scores in the carcass than low GMB animals. The use of high GMB animals provides better carcass finishing without affecting performance. The greater fat deposition in carcasses of high GMB animals is not associated with the relative expression of the genes studied.