Effect of low-phytate barley or phytase supplementation to a barley-soybean meal diet on phosphorus retention and excretion by grower pigs.
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.
Htoo
J K
JK
Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada T6G 2P5.
Sauer
W C
WC
Yáñez
J L
JL
Cervantes
M
M
Zhang
Y
Y
Helm
J H
JH
Zijlstra
R T
RT
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
D010758:Phosphorus; D010833:Phytic Acid; D010832:6-Phytase