title: Effect of low-phytate barley or phytase supplementation to a barley-soybean meal diet on phosphorus retention and excretion by grower pigs.
abstract: Two studies were conducted to determine the effect of diets containing low-phytate barley or supplemented with phytase on P balance and excretion in grower pigs. In Exp. 1, eight 32-kg barrows were assigned to a repeated, 4 x 4 Latin square design and fed 4 diets that contained 96% barley: normal-phytate hulled barley (HB), low-phytate hulled barley (LPHB), normal-phytate hull-less barley (HLB), and low-phytate hull-less barley (LPHLB). The barley cultivars contained 0.16, 0.05, 0.24, and 0.03% phytate, respectively. Inorganic P (iP) was added to the HB and HLB diets to meet the 1998 National Research Council recommendation of available P (aP, 0.23%), whereas LPHB and LPHLB contained sufficient aP. The diets were fed at 2.5 times the maintenance requirement for ME. The apparent total tract digestibilities (ATTD) of P did not differ between the hulled and hull-less barley diets, but P retention (%) and excretion were greater in pigs fed the hull-less barley diets (P < 0.05). The ATTD of P was greater and P excretion was 35% lower in pigs fed the low-phytate compared with the normal-phytate diets (P < 0.001). The amount of P retained (g/d) was greater (P < 0.001) in pigs fed low-phytate barley, reflecting an ATTD of P of 65 and 49% for low-phytate and normal-phytate barley, respectively (P < 0.001). In Exp. 2, eight 21-kg barrows were assigned to a repeated, 4 x 4 Latin square design and fed 4 diets based on barley and soybean meal (SBM): HB-SBM, HB-SBM + iP, HB-SBM + phytase, and LPHB-SBM. The HB-SBM and HB-SBM + phytase diets were deficient in aP, whereas the HB-SBM + iP and LPHB-SBM diets had adequate aP. The feeding regimen was similar to that of Exp. 1. Adding iP to the HB-SBM diet did not affect the ATTD but increased the amount of P retained (g/d) and excreted (P < 0.001). The ATTD and amount of P retained (g/d) did not differ among pigs fed the HB-SBM + iP, HB-SBM + phytase, and LPHB-SBM diets. However, pigs fed the HB-SBM + phytase and LPHB-SBM diets excreted 32 and 29% less P, respectively, than pigs fed the HB-SBM + iP diet (P < 0.05), confirming that low-phytate barley is as effective as supplemental phytase in improving P digestibility and utilization and decreasing P excretion in grower pigs.
authors.affiliation: Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada T6G 2P5.
authors.forename: J K
authors.initials: JK
authors.lastname: Htoo
authors.forename: W C
authors.initials: WC
authors.lastname: Sauer
authors.forename: J L
authors.initials: JL
authors.lastname: Yáñez
authors.forename: M
authors.initials: M
authors.lastname: Cervantes
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: J H
authors.initials: JH
authors.lastname: Helm
authors.forename: R T
authors.initials: RT
authors.lastname: Zijlstra
mesh_terms: D010832:6-Phytase / Q000008:administration & dosage* / Q000378:metabolism; D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D019587:Dietary Supplements; D004063:Digestion; D004305:Dose-Response Relationship, Drug; D005243:Feces / Q000737:chemistry; D001467:Hordeum; D008297:Male; D009753:Nutritive Value; D010758:Phosphorus / Q000008:administration & dosage* / Q000378:metabolism*; D010833:Phytic Acid / Q000008:administration & dosage* / Q000378:metabolism; D011897:Random Allocation; D013025:Glycine max; D013552:Swine / Q000254:growth & development / Q000378:metabolism*; D015430:Weight Gain
chemical_list: D010758:Phosphorus; D010833:Phytic Acid; D010832:6-Phytase