Dynamics of body protein deposition and changes in body composition following sudden changes in amino acid intake: II. Entire male pigs

¹ Department of Animal and Poultry Science, University of Guelph, Guelph, ON, Canada, N1G 2W1

^* To whom correspondence should be addressed. E-mail: cdelange{at}uoguelph.ca.

	Abstract

A study was conducted to evaluate the extent and dynamics of whole body protein deposition (Pd) and changes in chemical and physical body composition following a period of AA intake restriction in entire male pigs with high lean tissue growth potentials. Fifty-eight entire male pigs (initial BW 15.8 ± 0.9 kg) were allotted to 1 of 3 dietary AA levels between 15 and 38 kg BW: Control (15% above requirements; NRC, 1998), AA-15% (15% below requirements), and AA-30% (30% below requirements). Thereafter, pigs were fed diets not limiting in AA content. Throughout the experiment, pigs were scale-fed at 90% of estimated voluntary daily DE intake. Representative pigs were slaughtered at 15, 38, 53, 68 or 110 kg BW to monitor changes in body composition. Between 15 and 38 kg BW, restriction of AA intake reduced BW gain (P < 0.01; 794, 672 and 648 g/d; Control, AA-15% and AA-30%, respectively). At 38 kg BW, AA intake restriction increased whole-body lipid (LB) content (P < 0.01; 11.3, 14.3, 17.5% of empty BW), and the LB to whole-body protein (PB) ratio (LB/PB; P < 0.02; 0.68, 0.88, 1.10; Control, AA-15% and AA-30%, respectively). Relationships between PB vs whole body water and PB vs whole body ash were not affected by dietary treatments (P > 0.10). At 110 kg BW and based on BW, PB and LB/PB, complete compensatory growth (CG) was achieved. Body weight gain between 38 and 110 kg BW was inversely related to previous dietary AA levels (1,100, 1,166, 1,180 g/d; P < 0.01; Control, AA-15% and AA-30%, respectively). For pigs on Control, and based on N-balance data, Pd increased with BW, from 172 at 40 kg BW to 226 g/d at 82 kg BW. At 40 kg BW, Pd was greater (P < 0.05) for pigs on AA-15% (205 g/d) and AA-30% (191 g/d) than pigs on Control (172 g/d). These findings indicate that pigs with high-lean-tissue growth potentials are more likely to express compensatory Pd and their genetically determined upper limit to Pd (PdMax) following a period of AA intake restriction. This study confirms previous findings that BW effects on PdMax are small in growing pigs between 40 and 80 kg BW. It is suggested that CG and compensatory Pd following a period of AA intake restriction is constrained by the pig's PdMax and is driven by a target LB/PB. Combined with previous observations in our laboratory, these results suggest that CG following a period of AA intake restriction tends to occur only when pigs are within the energy dependent phase of lean tissue growth and not when the genetically determined upper limit to lean tissue growth, or PdMax, determines growth performance.

Key Words: Amino acid intake, body composition, compensatory growth, pigs