Four experiments involving 225 pigs were conducted to assess the efficacy of a microbial phytase (FINASE, Alko Ltd. Biotechnology, Rajamäki, Finland) produced by Aspergillus niger in corn-soybean meal or dextrose-cornstarch-soybean meal-based diets. In two experiments with growing-finishing pigs, fortified corn-soybean meal diets were formulated to be adequate (.50%) or inadequate (.40 or .30%) in P during the growing phase followed by adequate (.40%) or inadequate (.30%) P in the finishing phase. Mono-dicalcium phosphate was the source of supplemental P. Half the diets were supplemented with phytase (500 phytase units/g). Rate and efficiency of gain and bone breaking strength were decreased when P-deficient diets were fed. Phytase supplementation of the low-P diets restored growth rate and feed:gain to levels that approached those of pigs fed the adequate-P control diet. Bone strength was partially restored to that of the controls. In two additional experiments, pigs were fed low-P basal diets in which all the dietary P came from soybean meal or a corn-soybean meal blend. Both diets contained .05% available P. Graded levels of monosodium phosphate were added to these diets, up to .15% added P, to establish a standard curve. Phytase was added to the basal diet at 250, 500, or 1,000 units/g. Growth rate and bone strength improved linearly (P < .01) with added monosodium phosphate and with increasing levels of supplemental phytase. Based on estimates of total and available P intakes, the highest level of phytase (1,000 units/g) increased the bioavailability of the P from 25% in the soybean meal diet to 57% in the phytase-supplemented diet, and from 15% in the corn-soybean diet to 43% in the phytase-supplemented diet. Expressed on the basis of the improvement in phytate P availability, this level of phytase converted approximately one-third of the unavailable P to an available form. The results indicate that the phytase was efficacious in improving the bioavailability of phytate P for pigs.

Three experiments involving 162 pigs were conducted to assess the efficacy of phytase (Natuphos; BASF, Mount Olive, NJ) in low-P, corn-soybean meal-based diets. The phytase was produced by a recombinant Aspergillus niger. The phytase supplement contained 5,000 phytase units (PTU)/g. In Exp. 1 (66 pigs) and 2 (60 pigs), growing-finishing pigs were fed fortified corn-soybean meal diets formulated to be adequate (.50%), marginal (.425%), or inadequate (.35%) in P during the growing phase (23 to 60 kg BW) followed by adequate (.40%), marginal (.35%), or inadequate (.30%) P, respectively, during the finishing phase (to 104 kg BW). Dicalcium phosphate was the source of supplemental P. In addition, the low-P sequence (.35/.30% P) was supplemented with phytase at 250, 500, or 1,000 PTU/kg. Rate and efficiency of gain decreased linearly (P < .01) and bone breaking strength decreased quadratically (P < .01) as the concentration of P was decreased in the diets. Responses in growth and bone traits to increasing levels of phytase activity in the low-P diet were linear (P < .01). The highest level of phytase in the low-P diet restored growth rate and bone breaking strength to levels that approached or met those of pigs fed the adequate P diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Two experiments involving 115 pigs were conducted to assess the efficacy of a microbial phytase (Allzyme Phytase; Alltech, Nicholasville, KY) produced by Aspergillus niger in low-P, corn-soybean meal-based diets. The phytase supplement contained 50 phytase units/g and 1.43% P. In Exp. 1, growing-finishing pigs were fed fortified corn-soybean meal diets formulated to be adequate (.50%) or inadequate (.30%) in P during the growing phase (38 to 57 kg BW) followed by adequate (.40%) or inadequate (.30%) P, respectively, during the finishing phase (to 101 kg BW). Dicalcium phosphate was the source of supplemental P. Half the diets were supplemented with phytase at 500 phytase units/kg. Rate and efficiency of gain and bone breaking strength were decreased (P < .01) when the low-P diet was fed. Adding phytase to the low-P diet restored performance and bone breaking strength (P < .01) to levels that approached those of pigs fed the adequate-P diet. In Exp. 2, growing pigs (13 kg BW), were fed a low-P (.32% total P; .048% available P) based diet supplemented with graded levels of monosodium phosphate to provide 0, .075, and .15% added P or with phytase to supply 250, 500, 1,000, or 2,000 phytase units/kg. Chromic oxide was included as an indigestible marker for determining apparent absorption and fecal excretion of P. Performance and bone strength increased linearly with added monosodium phosphate (P < .01) and with increasing levels of supplemental phytase (P < .05). A portion of these increases from phytase was attributed to the P supplied by the phytase mix (.007, .014, .028, .057%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Dehulled soybean meal prepared from genetically modified, herbicide (glyphosate)-tolerant Roundup Ready soybeans containing the CP4 EPSPS protein and near-isogenic conventional soybeans were assessed in an experiment with growing-finishing pigs. The soybeans were grown in the yr 2000 under similar agronomic conditions except that the Roundup Ready soybeans were sprayed with Roundup herbicide. Both were processed at the same plant. The composition of the two types of soybeans and the processed soybean meal were similar. Corn-soybean meal diets containing conventional or Roundup Ready soybean meal and fortified with minerals and vitamins were fed to 100 cross-bred pigs from 24 to 111 kg BW. Diets contained approximately 0.95% lysine initially and were reduced to 0.80 and 0.65% lysine when pigs reached 55 and 87 kg BW, respectively. There were 10 pens (five pens of barrows and five pens of gilts) per treatment with five pigs per pen. All pigs were scanned at 107 kg mean BW and all barrows were killed at the end of the test for carcass measurements and tissue collection. Rate and efficiency of weight gain, scanned backfat and longissimus area, and calculated carcass lean percentage were not different (P > 0.05) for pigs fed diets containing conventional or Roundup Ready soybean meal. Gilts gained slower, but they were more efficient and leaner (P < 0.05) than barrows. Responses to the type of soybean meal were similar for the two sexes with no evidence of a diet x sex interaction for any of the traits. In most instances, carcass traits of barrows were similar for the two types of soybean meal. Longissimus muscle samples from barrows fed conventional soybean meal tended (P = 0.06) to have less fat than those fed Roundup Ready soybean meal, but water, protein, and ash were similar. Sensory scores of cooked longissimus muscles were not influenced (P > 0.05) by diet. The results indicate that Roundup Ready soybean meal is essentially equivalent in composition and nutritional value to conventional soybean meal for growing-finishing pigs.

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