Arie K Kies | PubMed Health

PubMed2006

Interaction between protein, phytate, and microbial phytase. In vitro studies.

The interaction between protein and phytate was investigated in vitro using proteins extracted from five common feedstuffs and from casein. The appearance of naturally present soluble protein-phytate complexes in the feedstuffs, the formation of complexes at different pHs, and the degradation of these complexes by pepsin and/or phytase were studied. Complexes of soluble proteins and phytate in the extracts appeared in small amounts only, with the possible exception of rice pollards. Most proteins dissolved almost completely at pH 2, but not after addition of phytate. Phytase prevented precipitation of protein with phytate. Pepsin could release protein from a precipitate, but the rate of release was increased by phytase. Protein was released faster from a protein-phytate complex when phytase was added, but phytase did not hydrolyze protein. Protein was released from the complex and degraded when both pepsin and phytase were added. It appears that protein-phytate complexes are mainly formed at low pH, as occurs in the stomach of animals. Phytase prevented the formation of the complexes and aided in dissolving them at a faster rate. This might positively affect protein digestibility in animals.

6-Phytase↗

PubMed2005

Mineral absorption and excretion as affected by microbial phytase, and their effect on energy metabolism in young piglets.

Positive effects of dietary phytase supplementation on pig performance are observed not only when phosphorus is limiting. Improved energy utilization might be one explanation. Using indirect calorimetry, phytase-induced changes in energy metabolism were evaluated in young piglets with adequate phosphorus intake. Eight replicates of 8 group-housed barrows each were assigned to either a control or a phytase-supplemented diet [1500 phytase units (FTU)/kg feed]. Piglets were fed a restricted amount of the control or phytase diet. The diets were made limiting in energy content by formulating them to a high digestible lysine:DE ratio. Fecal nutrient digestibility, portal blood variables, organ weights, and apparent absorption and urinary excretion of ash, Ca, P, Na, K, Mg, Cu, and Fe, were also measured. A model was developed to estimate energy required for absorption and excretion, which are partly active processes. Phytase tended to improve energy digestibility (P = 0.10), but not its metabolizability. Energy retention and heat production were not affected. At the end of the 3-wk period, pancreas weight (P < 0.05) and blood pH were lower (P < 0.01), and CO(2) pressure was higher (P < 0.01) due to phytase. This suggests that phytase reduced energy expenditure of the digestive tract, and increased metabolic activity in visceral organs. The potential increases in energy retention due to phytase were counterbalanced by increased energy expenditures for processes such as increased mineral absorption (for most P < 0.05), and their subsequent urinary excretion. Energy costs of increased absorption of nutrients, and deposition and excretion of minerals was estimated as 4.6 kJ/(kg(0.75) . d), which is 1% of the energy required for maintenance. The simultaneous existence of both increases and decreases in heat production processes resulted in the absence of a net effect on energy retention.

6-Phytase↗