Factors affecting phosphorus and calcium digestibility in diets for growing-finishing pigs.

In two experiments, we investigated various factors that affect the estimation of the apparent total tract digestibility (ATTD) of DM, Ca, and total P in diets for growing-finishing pigs. In Exp. 1, the effects of age, housing, and calculation method (indicator [Cr2O3] vs 10-d total collection) were determined. Eighteen barrows and gilts (40 to 95 kg BW) were housed in six pens, and ATTD was estimated using the indicator method. Twelve barrows were housed in metabolic crates, and ATTD was estimated using both calculation methods. Dietary treatments were 1) a tapioca-soybean-barley-based diet, 2) Diet 1 supplemented with 400 FTU microbial phytase/kg of diet, and 3) a corn-soybean meal-based diet: In Exp. 2, six barrows (95 to 120 kg BW) were fed a phytase-deficient diet to investigate the effects of coprophagy (40 g fresh feces/kg of diet) and movement. Pigs were fed at 2.8 times maintenance requirement (418 kJ ME/BW.75); water supply was 2.5 L/kg of feed. The ATTD increased as BW increased. Phytase enhanced total P ATTD by an average of 18.1 percentage units. The ATTD of DM was higher and the ATTD of Ca and total P (P < .001) were lower in pigs housed in pens than in pigs housed in metabolic crates. Fecal consumption and movement led to numerical increases in Ca (P = .217) and total P (P = .103) ATTD. Estimates of Ca and total P ATTD using pigs in metabolic crates are lower than estimates in practice.

Efficacy of Natuphos in sorghum-based diets of finishing swine.

The efficacy of a recombinantly derived microbial phytase (Natuphos 5000, BASF Corp.) was evaluated in sorghum-soybean meal-based diets of finishing swine. During the 50- to 80- and 80- to 118-kg BW intervals, diets contained .40 and .39% plant P, respectively; control diets fed during the two weight intervals were supplemented with .08 and .04% inorganic P from dicalcium phosphate. The all plant-P diets were supplemented with 0, 300, or 500 phytase units (FTU) per kilogram of diet. Supplemental P (P = .09) and phytase (linear, P = .01) increased growth rate but did not affect feed efficiency. Dietary treatment did not affect quantitative carcass traits, CP, fat, or moisture content of the loin or taste panel scores of the cooked loin other than a quadratic decrease (P = .02) in connective tissue amount as phytase supplementation increased. Apparent ileal and total tract digestibilities of DM, GE, and N were not affected (P > .25) by phytase supplementation, whereas ileal and total tract digestibilities of Ca and P increased (P < .05 or P < .01) with increasing phytase supplementation. Ultimate load and ash content of the third and fourth metacarpals and metatarsals and serum P levels increased in response to inorganic P and phytase supplementation. Pig performance, carcass traits, and bone traits were essentially equal for the 300 and 500 FTU/kg treatments. These results show that phytase effectively liberates P in sorghum-based diets, and that 300 FTU/kg (or less) will optimize performance and carcass merit of finishing swine.

Nutritional significance of phytic acid and phytase.

In the nutrition of monogastric animals phytate-P represents a poorly available source of phosphorus, especially in the case of diets low in phytase activity. Similarly the bioavailability of different minerals and trace elements is considerably reduced by phytate complexes. High concentrations of Ca increase the anti-nutritive effect of phytic acid on mineral and trace element bioavailability and thus impede the action of phytase. This effect can in part be compensated by an increased supply of vitamin D. There is also evidence for protective functions of phytic acid such as the prevention of the formation of free radicals, the delaying of post prandial glucose absorption, the decrease in plasma cholesterol and triglycerides as well as a change in the carry over of heavy metals. The basic mechanisms by which phytic acid may exert these effects are still not clear. In several studies reported in the literature, evidence for the nutritional significance and ecological importance of microbial phytase for pigs and poultry has been given. As the monogastric organism contains no or only negligible amounts of endogenous phytase in the stomach and small intestine, it is therefore dependent on plant or microbial phytase. Plant phytase, e.g. from rye, triticale, wheat or, in smaller amounts from barley, and supplemented Aspergillus-phytase display cumulative effects.

Efficacy of supplemental 1 alpha-hydroxycholecalciferol and microbial phytase for young pigs fed phosphorus- or amino acid-deficient corn-soybean meal diets.

Young pigs (5 wk of age and 8 kg) were used to test the efficacy of 1 alpha-hydroxycholecalciferol (1 alpha-OH D3) and microbial phytase for improving the utilization of phytate phosphorus (P) and amino acids present in corn-soybean meal (SBM) diets. Phytase supplementation (1,200 units/kg) to a vitamin D3-adequate, P-deficient corn-SBM diet elicited a marked response (P < .05) in weight gain and ash content of fibula, scapula, and metatarsal bones, but dietary addition of 1 alpha-OH D3 (20 micrograms/kg) was without effect. A P- and vitamin D3-adequate, amino acid-deficient corn-SBM diet (15.5% CP) also was supplemented with 1,200 units/kg of phytase to evaluate the efficacy of phytase in improving amino acid utilization. Pigs gained faster (P < .05) and more efficiently (P < .05) when this diet was supplemented with limiting amino acids, and phytase addition also increased (P < .05) weight gain, regardless of whether the diet was deficient or adequate in amino acids. Feed efficiency was improved (P < .05) by phytase addition to the amino acid-deficient diet but not to the amino acid-adequate diet. Pigs fed the low-CP, amino acid-fortified diet gained as fast and as efficiently as those fed a 19.5% CP (1.19% lysine) positive-control diet.

Efficacy of a recombinant-derived phytase in improving the bioavailability of phosphorus in corn-soybean meal diets 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)

Efficacy of low-activity, microbial phytase in improving the bioavailability of phosphorus in corn-soybean meal diets for pigs.

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)