Adiposity, lipogenesis, and fatty acid composition of subcutaneous and intramuscular adipose tissues of Brahman and Angus crossbred cattle

The objective of this study was to demonstrate differences in aspects of adipose tissue cellularity, lipid metabolism, and fatty and cholesterol composition in Angus and Brahman crossbred cattle. We hypothesized that in vitro measures of lipogenesis would be greater in three-fourths Angus progeny than in three-fourths Brahman progeny, especially in intramuscular (i.m.) adipose tissue. Progeny (n = 227) were fed a standard, corn-based diet for approximately 150 d before slaughter. Breed was considered to be the effect of interest and was forced into the model. There were 9 breed groups including all 4 kinds of threefourths Angus calves: Angus bulls x Angus-sired F-1 cows (n = 32), Angus bulls x Brahman-sired F-1 cows (n = 20), Brahman-sired F-1 bulls x Angus cows (n = 24), and Angus-sired F-1 bulls x Angus cows (n = 20). There were all 4 kinds of three-fourths Brahman calves: Brahman bulls x Brahman-sired F-1 cows (n = 21), Brahman bulls x Angus-sired F-1 cows (n = 43), Brahman-sired F-1 bulls x Brahman cows (n = 26), and Angus-sired F-1 bulls x Brahman cows (n = 13). Additionally, F-2 calves (one-half Brahman and onehalf Angus) were produced only from Brahman-sired F-1 bulls x Angus-sired F-1 cows (n = 28). Contrasts were calculated when breed was an important fixed effect, using the random effect family(breed) as the error term. Most contrasts were nonsignificant (P > 0.10). Those that were significant (P < 0.05) included cholesterol concentration of subcutaneous (s.c.) adipose tissue (three-fourths Angus > F-2, three-fourths Brahman > F-2, and three-fourths crossbred progeny combined > F-2), s.c. adipocyte volume (three-fourths Angus > F-2 and three-fourths bloods combined > F-2), lipogenesis from acetate in s.c. adipose tissue (three-fourths Brahman calves from Brahman dams > three-fourths Brahman calves from F-1 dams), and percentage 18:3n-3 in s.c. adipose tissue (three-fourths Brahman calves from Brahman-sired F-1 dams < threefourths Brahman calves from Angus-sired F-1 dams). Intramuscular adipocyte volume (P < 0.001) was less in three-fourths Brahman cattle than in three-fourths Angus cattle. Additionally, several differences were observed in i.m. adipose tissue that were consistent with this being a less-developed adipose tissue in three-fourths Brahman cattle than in three-fourths Angus cattle.