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 e xamine responses in lipid metabolism to nutritional treatments consist ing of a moderate energy diet (2.0 Meal ME/kg) fed at maintenance and a 2.5 x maintenance high-energy diet (2.4 Meal 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 subcutaneou s adipose tissue biopsies at the start and end of the trial. At the st art 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 activi ty at the end. Diet did not influence (P >.10) RSL activity. Heifers o n the high-energy, higher-intake diet had greater lipogenesis (P <.001 ) and LPL activity (P <.01) than those on the moderate-energy; diet. I nclusion of body condition score (BCS) nested within breed as a covari ate explained breed differences for lipogenesis (P <.05). Thus, by inc luding the covariate, the two breeds had similar (P >.10) rates of lip ogenesis at the end of the trial. When adjusted for BCS nested within breed, Brahman had greater (P <.05) LPL activity than Angus.