249 The Effects of Breed and Early Supplementation on Bovine Intramuscular Fat Deposition, Adipogenic and Lipogenic Gene Expression

Abstract

Abstract Wagyu cattle are known to deposit greater amounts of intramuscular fat, which can directly increase quality grade and carcass value. Supplementation can positively influence animal production and overall nutrient acquisition when used strategically. The objectives of this study were to evaluate 1) the effect of breed and early supplementation on intramuscular and subcutaneous fat deposition in Wagyu and Hereford cross calves, and 2) changes in adipogenic and lipogenic gene expression in longissimus muscle (LM) biopsies from Wagyu and Hereford cross calves during an early supplementation period. Angus cows (n = 34) were artificially inseminated with semen from a Wagyu bull. A Hereford bull was utilized as a clean-up bull. From this breeding, Wagyu cross steers (n = 8) and Hereford cross steers (n = 9) were produced and were placed on study on day 100 of age. At this time, calves were allowed access to four SuperSmart Feeder stalls and were individually supplemented with steam-rolled corn at 0.5% body weight (BWT). Calves were ultrasounded on day 0, day 43, and day 86 of the study to evaluate intramuscular fat deposition and backfat thickness. An longissimus muscle (LM) biopsy was taken on day 0 and day 86 of the study to evaluate gene expression. Supplemented steers tended (P < 0.10) to have more backfat than non-supplemented steers. Intramuscular fat amount differed (P < 0.05) by breed, while ribeye area tended (P < 0.10) to differ by breed. Wagyu exhibited a greater (P < 0.05) amount of intramuscular fat at the beginning and at the end of the study. Breed did not (P > 0.05) influence backfat thickness. Neither breed nor supplementation affected (P > 0.05) average daily gain or final body weights. Platelet-derived growth factor alpha (PDGRFA) and SREBP cleavage-activating protein (SCAP) differed (P < 0.05) between biopsy phases. Fatty acid binding protein-4 (FABP4) and stearoyl-coA desaturase-1 (SCD1) did not differ (P > 0.05) between breed or biopsy phase. In conclusion, changes in gene expression could indicate enhanced preadipocyte proliferation during this stage of calf development. Overall, supplementation altered backfat deposition but did not alter intramuscular fat levels. Opposingly, sire breed influenced intramuscular fat levels at an early age. A deeper understanding of the physical and molecular effects of supplementation and sire breed could provide additional avenues for manipulating adipose tissue.