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%.

Growth trials were conducted to determine the effects of Cr as chromium picolinate at various protein levels on performance of growing pigs. The effects of continued supplementation on sow fecundity and body weight changes through two parities also were examined. In Trial 1, 48 crossbred pigs (40.9 kg initial weight) were assigned to one of three diets (0, 250, or 500 ppb of added Cr). The only observed difference was an overall trend for an improvement in gain:feed when Cr was added to the diet (P < .10). In Trial 2, 105 crossbred pigs (14.5 kg initial weight) were assigned to one of seven treatments involving a combination of two factors: 1) lysine level at 100 or 120% of NRC (1988) requirement estimate and 2) added Cr level (0, 100, 200, 500, or 1,000 ppb). A Cr x lysine interaction (P < .02) for gain:feed existed that demonstrated that the addition of 200 ppb of Cr resulted in improved gain:feed at the 100% of requirement lysine level but not at the 120% of requirement lysine level. The addition of 200 ppb Cr also reduced backfat (P < .04) and increased longissimus muscle area (P < .04) regardless of lysine level in the diet.(ABSTRACT TRUNCATED AT 250 WORDS)

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The objective of this study was to determine the effects of addition of spray-dried plasma protein (SDPP) and Cu to nonmedicated diets on growth performance and intestinal morphology in weaned pigs reared in sanitary or nonsanitary environments. Weanling pigs (n = 192, 18 +/- 2 d of age, 6.0 +/- 0.2 kg of BW) were assigned to 8 treatments arranged factorially, including 2 dietary levels of SDPP (0 or 6% for the initial 10 d), 2 levels of added dietary Cu (0 or 200 ppm for the entire 35-d experiment), and 2 pen sanitation conditions (sanitized or nonsanitized before pig placement). The nonsanitary pen condition was created by 3 applications of swine manure slurry to all pen surfaces in 1 room and not washing or disinfecting. In an identical adjacent room, sanitary pens were washed and disinfected before weaning. There were 4 pigs per pen, and feed and water were available ad libitum. Growth performance was determined at the end of each diet formulation phase (d 10, 20, and 35 after weaning). On d 10, 1 pig per pen was euthanized, and cross sections of duodenum, jejunum, and ileum were collected for microscopic assessment of mucosal morphology. During the initial postweaning period, SDPP, and Cu supplementation improved ADG and ADFI (P < 0.001). A trend for an interaction of sanitation x dietary SDPP (P = 0.07) was observed for G:F, with a positive response to the supplement in nonsanitary pens but no response in sanitary pens. There were no interactions of SDPP and Cu for any performance variables (P > 0.30). By d 35, there were no main or interaction effects of treatment on ADG or G:F (P > 0.17). Pen sanitation condition produced morphological effects, with shorter villous length and less crypt depth observed in each intestinal segment for pigs reared in the nonsanitary pens (P < 0.05), but these effects must be considered conditional based on the potential confounding influence of separate nursery rooms. In the duodenum, reduced crypt depth with Cu supplementation (P = 0.01) and a tendency for greater villous length with SDPP supplementation (P = 0.09) were observed. In this study, SDPP and Cu supplementation improved pig growth performance during the initial 10-d postweaning. These modifications to nonmedicated diets acted independently with regard to their impacts on postweaning performance and, therefore, could have additive effects.

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