Physiological adaptations in adipose tissue of Brahman vs Angus heifers

Nonpregnant yearling Brahman (n = 12) and Angus (n = 12) heifers were equally allocated to two dietary treatments in a replicated study to examine responses in lipid metabolism to nutritional treatments consisting of a moderate energy diet (2.0 Mcal ME/kg) fed at maintenance and a 2.5 x maintenance high-energy diet (2.4 Mcal ME/kg) fed for 30 d. In vitro lipogenesis and the activities of lipoprotein lipase (LPL) and hormone-sensitive lipase (HSL) were determined in perianal subcutaneous adipose tissue biopsies at the start and end of the trial. At the start of the trial, breeds had similar (P > .10) rates of lipogenesis and LPL activity. Brahman had greater (P < .05) HSL activity than Angus at the start of the trial and tended (P < .07) to have greater HSL activity at the end. Diet did not influence (P > .10) HSL activity. Heifers on the high-energy, higher-intake diet had greater lipogenesis (P < .001) and LPL activity (P < .01) than those on the moderate-energy diet. Inclusion of body condition score (BCS) nested within breed as a covariate explained breed differences for lipogenesis (P < .05). Thus, by including the covariate, the two breeds had similar (P > .10) rates of lipogenesis at the end of the trial. When adjusted for BCS nested within breed, Brahman had greater (P < .05) LPL activity than Angus.