The effect of microbial phytase and feed restriction on protein, fat and ash deposition in growing-finishing pigs

Abstract

Forty-eight 35-kg-bodyweight barrows were assigned to treatments in a 2 × 2 factorial arrangement. Main factors were feed intake level (ad libitum or restricted) and supplementation of microbial phytase (with or without). Restricted pigs rece ived 80% of the feed consumed by the corresponding ad libitum group. Phytase-supplemented diets contained 584 phytase units kg-1. Body weight, fat, protein and ash were estimated every 2 wk by dual-energy X-ray absorptiometry. Plasma alpha-amino N concentrations were measured every 30 min during the 6 first postprandial hours at 90 and 132 d of age. Microbial phytase addition reduced feed intake by 6.8% (P < 0.05). Phytase did not affect (P > 0.05) feed, energy and protein efficiencies, but it reduced protein deposition (P < 0.05) and tended to reduce ADG (P < 0.09). Ninety day-old pigs receiving phytase had higher plasma levels of alpha-amino N during the first postprandial hours (P < 0.01) as compared to control pigs. At 132 d of age these effects disappeared. Supplemental phytase may improve alpha-amino acid absorption in growing pigs but the phytase effect on protein deposition suggest that these effect is not necessarily associated with better growth performance when nutrient requirements are satisfied. Key words: Pigs, phytase, feed intake, amino acids, protein deposition