Effect of energy intake on protein and energy metabolism of boars of high genetic potential for lean growth

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Abstract
Two experiments were conducted each using one batch of six Landrace littermate, entire male, pedigree pigs in a Latin-square change-over study of the effects of energy intake on nitrogen and energy metabolism over the range 33 to 88 kg live weight. One animal from each litter was slaughtered at 33 kg body weight to obtain initial body composition data. Five feeding levels (80, 100, 120, 140 and 160g/kg M0·63) were used during five consecutive metabolism trials each of 11-days duration, excreta being collected during the last 7 days. The pigs were housed in individual metabolism cages and the diets were offered in liquid form (approx. 300 g dry matter (DM) per kg) twice daily at 09.00 and 16.00 h. Heat production was measured for 1 day during each balance period in an open-circuit respiration chamber. The average daily gain, nitrogen retention, heat production and energy retention increased linearly (P < 0·001) with increasing metabolizable energy (ME) intake. The relationship between energy intake and protein deposition was linear up to levels above the normal ad libitum consumption of energy. Protein deposition potential of these high genetic potential pigs was at least 200 g/day, and tended to be constant between 35 and 85 kg live weight. From the combined results of experiments 1 and 2, the energy requirement for maintenance was 0·982 MJ ME per kg M0·63 per day and the decrease in protein deposition was approximately 6 g/MJ reduction in ME within the range of practical energy intakes.