Phytase supplementation of low-phosphorus growing-finishing pig diets improves performance, phosphorus digestibility, and bone mineralization and reduces phosphorus excretion.

Abstract

Two experiments using 413 crossbred growing-finishing pigs were conducted to assess the use of a commercial microbial phytase (Natuphos) in corn-soybean meal diets to improve phytate P bioavailability and thus reduce inorganic P supplementation and fecal P excretion. In Exp. 1 (n = 189), the following diets were used: 1) .50/.40% total P, respectively, for grower and finisher phases, and no phytase; 2) .40/.35% P and no phytase; 3) diet 2 plus 250 U phytase/kg; and 4) diet 2 plus 500 U phytase/ kg. The total Ca level was .58/.48% for diet 1 and .53/.43% Ca for diets 2, 3, and 4 in the grower and finisher phases, respectively. Feeding the low-P diet without supplemental phytase resulted in an overall 18% reduction in ADG (P < .05), 15% reduction in ADFI (P < .05), and 3% poorer feed efficiency (P < .08). Adding 250 to 500 U phytase/kg to the low-P diet restored ADG, ADFI, and feed conversion to levels not significantly different from and within 96% of that observed for pigs fed the adequate-P diet. The overall apparent digestibility of P was linearly (P < .01) improved with addition of 250 and 500 U phytase/kg to the low-P diet, but Ca and DM digestibilities were not affected by phytase or P level. In Exp. 2 (n = 224) the following diets were used: 1) .38/.33% total P, respectively, for grower and finisher phases, and no phytase; 2) .42/.37% P and no phytase; 3) .46/.41% P and no phytase; 4) diet 1 plus 167 U/kg phytase; 5) diet 1 plus 333 U/kg phytase; and 6) diet 1 plus 500 U/kg phytase. All diets contained .41/.36% Ca for grower and finisher phases, respectively. Pigs fed the low-P control diet grew slower (P < .01) and less efficiently (P < .10) than pigs fed diets with added P or phytase. With increasing levels of supplemental phytase or P there was a linear increase (P < .01) in ADG, digestibility of P, and digested P and a quadratic improvement (P < .05) in feed efficiency. Tenth rib mineralization based on shear force and ash were linearly increased (P < .08 to .001) as phytase or P was added to the low-P diet. There were generally no effects of P or phytase level on carcass quality. Using prediction equations derived from the response traits of ADG and P digestibility in Exp. 1 and ADG, P digestibility, and bone shear force in Exp. 2 to added phytase or P, we estimated that 500 U phytase released an amount of phytate P that was approximately equivalent to .87 to .96 g of P from dicalcium-monocalcium phosphate supplements. Fecal P excretion was estimated to be reduced 21.5%.

Effect of microbial phytase and diet fermentation on ileal and total tract digestibility of nutrients and energy in growing pigs

“…The results of experiments studying the effect of phytase on Ca digestibility in pigs are controversial. Some reports showed no effect (Yi et al, 1996;Harper et al, 1997;Sands et al, 2001) while others showed that phytase increased both ileal (Traylor et al, 2001) and total tract (Kemme et al, 1997) Ca digestibility. There are even studies demonstrating a greater effect of added phytase on Ca digestibility than on P digestibility (Johnston et al, 2004).…”

Phosphorus equivalency value of microbial phytase in weanling pigs fed a maize-soyabean meal based diet

“…In the study by Jongbloed et al (1996a) the Ca:tP ratio ranged from 1.94:1 to 2.5:1. Harper et al (1997) in a study with growing-finishing pigs utilized three levels of P and maintained a Ca:tP ratio of approximately 1.2:1 to 1.4:1 in all diets. They reported that 500 U of microbial phytase releases 0.96 g of P per kilogram of diet.…”

“…Several studies have attempted to determine the P equivalency value of phytase in pigs (Jongbloed et al, 1996a;Kornegay and Qian, 1996;Yi et al, 1996;Harper et al, 1997). The range of equivalency values for 500 U/kg phytase is larger ranging from 0.64 g P to 2.47 g P. Factors which may influence these equivalency value estimates include: the basal level of P, the age of the animal, the response criteria used, and perhaps most importantly the ratio of Ca to P. Qian et al (1996) reported a detrimental effect of a widening Ca:tP ratio in excess of 1.2:1 on phytase efficacy in pigs.…”

“…Several studies have attempted to do this (Jongbloed et al, 1996a;Kornegay and Qian, 1996;Yi et al, 1996;Harper et al, 1997). However, in many of these studies diets containing wide Ca:P ratios (Jongbloed et al, 1996a;Kornegay and Qian, 1996;Yi et al, 1996) were fed, which have since been shown to decrease the efficacy of microbial phytase .…”

Effects of Aspergillus fumigatus phytase on phosphorus digestibility, phosphorus excretion, bone strength and performance in pigs

“…It is now generally accepted that active phytase preparations can reduce faecal P excretion into the environment by improvement of phytic-P bioavailability [8,14,15,31,34]. The AFP included in the diet at a level of 500 U/kg strongly increased the P digestibility of growing pigs by 22 [40].…”