May 22, 2019

Interpretive Summary: Effects of microbial phytase on feed digestibility of growing pigs

Interpretive Summary: Effects of microbial phytase on mucin synthesis, gastric protein hydrolysis, and degradation of phytate along the gastrointestinal tract of growing pigs.

By: Anne Wallace

Phytates are plant storage sugars that are phosphate esters of the sugar inositol. They are present in many plant foods, including bran and cereal grains. Due to their affinity for minerals, phytates are considered an anti-nutrient and can detrimentally impact production by reducing feed digestibility.

In this paper published in the February 2019 Journal of Animal Science, researchers studied the effects microbial phytase—an enzyme that degrades phytate—had on feed digestibility in growing pigs. They hypothesized that feed supplemented with phytase would counter anti-nutrient properties, improving the digestibility of amino acids (AA) and the minerals calcium (Ca) and phosphorus (P).

Eight growing barrows were fed a basal diet that met nutrient needs, except for Ca and P. The experimental feeding period lasted 14 days (4 periods, 4 x 4 Latin square design). Pigs were fed: (1) control diet without microbial phytase, (2) microbial phytase added to feed at the concentration of 750 FTU/kg, (3) 1500 FTU/kg, or (4) 3000 FTU/kg. All pigs were fitted with T-cannula connecting to the small bowel.

Apparent ileal digestibility (AID) and apparent total tract digestibility (ATTP) of the minerals Ca and P increased with increasing concentrations of phytase. However, digestibility of AA was unchanged. Higher concentrations of phytase were found to be more effective than lower concentrations at breaking down phytates.

Dr. Stein emphasizes the importance of concentration: “…whereas IP 6 and IP 5 esters are mostly degraded if 750 FTU of phytase is used, it takes 3,000 FTU to degrade the lower ester phytates such as IP 4 and IP 3. This is an important observation because IP 4 and IP 3 may have detrimental effects in the intestinal tract, and we now know that it may take up to 3,000 FTU of phytase to completely eliminate these esters.”  He also points out “…a significant linear increase in plasma inositol as the concentration of phytase in the diets increased. This demonstrates that at least some of the phytase was completely destroyed in the intestinal tract by the phytase and the resulting liberated inositol was absorbed.”

The results of this study partially supported the authors’ hypothesis and emphasize the importance of phytase concentration in feed. Overall, this study supports supplementing pig feed with microbial phytase to improve mineral (P and Ca) digestibility, although larger studies to reconfirm findings and determine the effectivity of higher concentrations of microbial phytase are warranted.

To view the article, visit the Journal of Animal Science.