P.A. Kemme

Digestibility of nutrients in growing-finishing pigs is affected by Aspergillus niger phytase, phytate and lactic acid levels. 2. Apparent total tract digestibility of phosphorus, calcium and magnesium and ileal degradation of phytic acid

In growing–finishing pigs, the effects of supplemental microbial phytase, lactic acid and Na phytate in a maize-soybean meal based diet on the apparent total tract digestibility (ATTD) of ash, total P, Ca and Mg and the ileal degradation (AID) of phytic acid were studied. The experimental design was a 2×2×2 factorial arrangement plus a positive control treatment. Six crossbred castrates of 37 kg initial BW, fitted with steered ileo-caecal valve cannulas were used during six collection periods. The dietary treatments consisted of Aspergillus niger phytase (Natuphos®; 0 or 900 FTU kg−1), sodium phytate (0 or 1.5 g P kg−1) or lactic acid (0 or 30 g kg−1). The positive control diet was supplemented with 1.0 g P kg−1 from monocalcium phosphate monohydrate (MCP). The feeding level was 2.3 times maintenance requirement for energy (418 kJ MEW−0.75). Estimates of AID and ATTD were calculated using Cr2O3 as a marker. The addition of MCP to the diet as the only variable had no effect on the AID of phytic acid and the ATTD of ash, Ca and Mg, but enhanced total P ATTD. Both microbial phytase and lactic acid enhanced the ATTD of ash, Ca and Mg and the AID of phytic acid, but there was no interaction. The ATTD of total P was increased by the combination of microbial phytase and lactic acid to a greater extent than was calculated as the sum of the stimulatory effects of the single additions. It is hypothesized that lactic acid delays gastric emptying, which prolongs the action of phytase in the stomach at its optimum pH. When Na phytate was added to the diets, total P ATTD was enhanced, possibly reflecting efficient phytate hydrolysis by intrinsic phytase.

Digestibility of nutrients in growing-finishing pigs is affected by Aspergillus niger phytase, phytate and lactic acid levels. 1. Apparent ileal digestibility of amino acids

In growing–finishing pigs, the effects of microbial phytase, lactic acid and phytate levels in a maize-soybean meal diet on the apparent ileal digestibility (AID) of N and amino acids were studied. The experimental design was a 2×2×2 factorial arrangement plus a positive control treatment. Six crossbred castrates of 37 kg initial BW, fitted with steered ileo-caecal valve cannulas, were used during six collection periods. The dietary treatments consisted of Aspergillus niger phytase (Natuphos®; 0 or 900 FTU kg−1), Na phytate (0 or 1.5 g P kg−1) and lactic acid (0 or 30 g kg−1). The positive control diet was supplemented with 1.0 g P kg−1 from monocalcium phosphate monohydrate (MCP). Ileal digestible amino acids were supplied at 80% of the Dutch recommended allowances for a 60-kg growing pig. The feeding level was 2.3 times the maintenance requirement for energy (418 kJ ME BW−0.75). Estimates of AID were calculated using Cr2O3 as a marker. Results showed that for almost all amino acids there was a significant interaction between Na phytate and phytase. Supplementing Na phytate to the diets without phytase increased the AID of N and amino acids. In general, phytase alone stimulated the AID of N and amino acids in the diets without Na phytate. Supplementing both Na phytate and phytase slightly decreased AID compared with the diets with only one supplement. Lactic acid stimulated the AID of N and amino acids, but a synergistic effect between phytase and lactic acid was not detected. Adding MCP had no effect on the AID of N and amino acids. It was concluded that when diets are supplemented with either phytase or lactic acid, AID of amino acids is improved. However, supplementing both did not result in a further increase in AID.

Diurnal variation in degradation of phytic acid by plant phytase in the pig stomach

The effects of plant phytase on the gastric degradation of phytic acid and digestibilities of DM and P, and their diurnal variation were evaluated in pigs from 90 to 115 kg BW fitted with simple duodenal T-cannulas. Three diets were fed to three pigs in four collection periods according to a cross-over design. The diets were a wheat–barley-based diet (phytase activity 1005 phytase units [FTU] kg−1), a maize-based diet (91 FTU kg−1) and this maize-based diet mixed with 30% wheat (342 FTU kg−1). Digestibility of DM in the duodenal samples was zero in all treatments. Digestibility of P was high (17%) and equal for all treatments. The diurnal disappearance ratios of DM and P were similar for all diets. Their levels were dependent on gastric retention time. The lowest ratios were found 3 h post-feeding; maximal ratios were observed prior to feeding. The gastric degradability of phytic acid was 3% in the maize-based, 31% in the wheat–maize-based and 47% in the wheat–barley-based diets. The diurnal disappearance ratio of phytic acid degradation was similar for all treatments, and dependent on gastric retention time. Marked differences in degradability levels were observed among the diets.