Previous experiments at Shinfield (Taylor, Salter and Lister, 1990) have shown an association between serum cholesterol and carcass fatness. This was particularly marked when cholesterol levels had been altered through feeding a hypercholesterolemic diet. In the present experiment, serum cholesterol and fat deposition have been studied in entire and castrated pigs at different planes of nutrition and stages of growth.
In a 2 x 2 factorial experiment (Taylor, Salter, Close, Laswai and Hudson, 1990) 18 castrated and 18 entire male pigs, of initial weight 20 kg, were fed either 2.25 (Low) or 3.4 (High) x maintenance energy requirements, to a scale based on liveweight. Nitrogen and energy balances (including calorimetry) were measured over 7-day periods when the pigs reached approximately 30, 60 and 90 kg. Fasting blood samples were taken on the morning after each balance period and serum was analysed for total- and HDL-cholesterol and triacylglycerol. LDL-cholesterol was calculated as: Total cholesterol - HDL-cholesterol - (triacylglycerol/6). Fat deposition was calculated as the difference between total energy retention and energy retained as protein.