Efficacy of high available phosphorus corn in laying hen diets

Total and water-soluble phosphorus excretion from swine fed low-phytate soybeans

A study was conducted to evaluate the impact of feeding soybean meal (SBM) from low-phytate (LP) or traditional phytate (TP) soybeans on performance and excretions from growing swine. Ninety-six crossbred barrows (initial BW = 18 +/- 0.3 kg) were allocated by BW to 24 pens and fed 1 of 4 treatment diets: TP SBM without supplemental phytase; TP SBM plus 500 phytase units of phytase/kg, as-fed basis [Ronozyme P (CT) 2500; DSM Nutritional Products, Basel, Switzerland]; LP SBM (USDA-ARS breeding line CX1834-1) without supplemental phytase, and LP SBM plus phytase. All diets within a feeding phase were formulated to be isocaloric and have similar available Lys and nonphytin P content. Pens were assigned randomly to treatments at the beginning of each of the 4 feeding phases. An indigestible marker was added to the mash feed. Individual pig weights and fecal samples were collected, and feed disappearance by pen was recorded weekly. No phytase inclusion or SBM source effects were observed for pen ADG, ADFI, or G:F (P > 0.05). Total tract apparent digestibility of DM and OM was not different among treatment groups (P > 0.05). Apparent digestibility of P was greater for pigs fed diets containing the LP SBM (48.9 vs. 42.4%; P < 0.01) and less when diets included phytase (44.3 vs. 47.0%; P < 0.0001). Total P (tP) and water-soluble P (WSP) excreted were affected by dietary treatment (tP: 20.0, 18.0, 16.8, and 13.8 g/kg of feces DM, P < 0.01; and WSP: 10.9, 10.1, 9.1, and 8.5 g/kg, P < 0.01, for TP SBM without supplemental phytase, TP SBM plus 500 phytase units of phytase/kg, LP SBM without supplemental phytase, and LP SBM plus phytase diets, respectively). Inclusion of phytase decreased tP and WSP excreted (P < 0.01), as did use of LP SBM (P < 0.01). Diet effects on the fraction of excreted tP that was WSP were observed (P < 0.01); however, there was not a significant effect of SBM source. Inclusion of exogenous phytase in diets increased the proportion of tP that was excreted as WSP from 55% in diets without phytase to 59% in diets containing phytase. The findings suggest that there is a need for LP soybeans as a dietary component to minimize environmental impacts.

Performance and nutrient utilization of laying hens fed low-phosphorus corn-soybean and wheat-soybean diets supplemented with microbial phytase

Two experiments were conducted with laying hens (Lohmann Brown) in an individual cage system and with single feeding conditions. Experiment 1 (n = 24) was a performance trial (22 to 61 wk) to evaluate phytase effects on performance and nutrient utilization in corn-soybean meal (CSM1) and wheat-soybean meal (WSM1) basal diets (0.12% NPP; 3.1% Ca) supplemented (300 U/kg) with an experimental microbial phytase (CSM2 and WSM2) or 1.5 g/kg inorganic P (CSM3 and WSM3). Experiment 2 (n = 16) was also conducted as a performance trial (22 to 61 wk) only using CSM diets with dietary treatments similar to those in experiment 1. In addition, parallel N and P balance experiments in 2 age periods (26 and 33 wk, respectively) were conducted. In experiment 1, no significant (P < 0.05) differences in mortality, feed intake, egg production, egg weight, or body weight were observed. Tibia bone mineral composition was significantly affected by microbial phytase. Microbial phytase in the low-P CSM diet significantly (P < 0.05) improved the feed conversion ratio. In experiment 2, only feed conversion ratio was significantly improved by microbial phytase. The phytase supplementation had no significant effect on P excretion, P balance, P utilization, N balance, N utilization, or AMEn in the balance experiments.