PALMITATE ESTERIFICATION AND GLYCEROPHOSPHATE ACYLTRANSFERASE ACTIVITY IN ADIPOSE-TISSUE OF GROWING LAMBS

The purposes of this study were to determine the effects of BW in grow ing lambs on rates of palmitate esterification (PE) and activity of gl ycerophosphate acytransferase (GPAT) in subcutaneous and intermuscular adipose tissue in vitro and to determine the relationship between the se in vitro measurements and carcass lipid accretion. At 37, 49, 60, a nd 71 kg of live weight, nine, nine, eight, and seven Columbia-Ramboui llet-cross ewe lambs, repectively, were slaughtered and adipose tissue was dissected for glycerolipid biosynthesis assays. One-half of each carcass was boned, and carcass soft tissue lipid was measured. In both adipose tissues, PE and GPAT activity were highest at 37 kg (P = .000 1); the greatest accumulation of carcass fat occurred between 37 and 4 9 kg (P = .0001). Differences in PE and GPAT were less well marked bet ween 49-, 60-, and 71-kg lambs, but both were generally decreased with increased BW. Significant R(2) from regression of mass and percentage of carcass fat on either PE, GPAT, or steady-state glycerolipid synth esis (GLS) were from .29 to .44 (PE), .40 to .58 (GPAT), .50 to .75 (G LS), and .60 to .77 (PE, GPAT, and GLS combined). Changes in PE, GPAT, and GLS with BW were consistent with changes in rates of carcass fat accretion, which indicated a close relationship between glycerolipid b iosynthesis in vitro and lipid deposition in vivo in growing-finishing lambs.