EFFECTS OF DIETARY-FAT AND L-METHIONINE ON THE HEPATIC-METABOLISM OF VERY-LOW-DENSITY LIPOPROTEINS IN THE PRERUMINANT CALF, BOS SPP

The effects of triglycerides (TG) from tallow (1.21 and 2.13 g TG/kg of body weight (BW) per meal, diets R and B respectively) and from tallow plus cream (2.50 g TG/kg of BW per meal, diet L) with or without L-methionine (2.6 g/kg dry matter) on hepatic apparent secretion of very low density lipoproteins (VLDL) were investigated in 3 groups of 4 preruminant calves fitted with chronic catheters and with electromagnetic blood-flow probes implanted in their hepatic vessels. Increasing TG concentrations stimulated the apparent VLDL secretion by the liver (1.02, -0.36 and -1.51 mg VLDL mass/min per kg of BW in diets L, B and R, respectively). L-Methionine increased this secretion when associated with the lipid-restricted (diet R; 0.25 and -1.51 mg VLDL/min per kg of BW) and basal (diet B; 0.35 and -0.36 mg VLDV/min per kg of BW) diets (non-significant). However, the VLDL apparent secretion decreased with the lipid-enriched diet (diet L), which suggests an insufficient dose of L-methionine compared with the level of TG intake, and a possible competition between liver and intestine for utilization of L-methionine for the synthesis of TG-rich lipoproteins.