EFFECT OF MICROBIAL PHYTASE ON DIGESTIBILITY AND UTILIZATION OF PHOSPHORUS AND PROTEIN IN PIGS FED WET BARLEY PROTEIN WITH FIBER

Effect of microbial phytase supplementation on apparent ileal and tota l tract digestibility, utilisation of phosphorus (P) and protein in we t barley protein with fibre (WBPF), a by-product of the integrated sta rch-ethanol process, was studied in six ileal cannulated pigs (live we ight 89-120 kg). Three dietary treatments containing microbial phytase either 0, 250 or 500 FTU kg(-1) dry matter (DM) were assigned using a two-period change-over design. WBPF was the sole source of P and prot ein in semi-purified experimental diet. WBPF phosphorus and crude prot ein contents were 5.4 and 237 g kg(-1) DM, respectively. No inositol h exa- or pentaphosphates were found in WBPF, while only 1 g of P was in the form of inositol tetra- or triphosphates. Lysine, threonine, meth ionine and cystine contents in WBPF protein were 2.4, 2.8, 1.3 and 1.8 g 16 g(-1) N, respectively. Microbial phytase supplementation improve d apparent ileal P (p < 0.10) and calcium (p < 0.05) digestibility in WBPF diets with no effect on total tract digestibility. No significant differences were found in the degradation of phytates in WBPF at the ileal or total tract level. Phytase supplementation tended to improve apparent ileal ash digestibility (p < 0.10) and depressed that of ethe r extract in WBPF diets (p < 0.05). Apparent ileal and total tract P d igestibility in WBPF was very high even without microbial phytase supp lementation (ileal digestibility: 58.3% and total tract digestibility: 59.3%). Daily P retention was the same for all treatments. Microbial phytase supplementation had no effect on apparent ileal or total tract crude protein digestibility (means 79.5 and 53.5%, respectively) in W BPF. Apparent ileal cystine digestibility tended to decline after phyt ase supplementation (p < 0.10), but otherwise the amino acid digestibi lities in WBPF were similar. Average apparent ileal digestibilities of lysine, threonine, methionine and cystine in WBPF were 74.1, 73.1, 83 .2 and 81.6%, respectively. No differences were found in daily nitroge n retention between treatments. (C) 1998 Elsevier Science B.V. All rig hts reserved.