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Title: Ileal and total tract digestibility of energy and nutrients in pig diets supplemented with a novel consensus bacterial 6-phytase variant.
Author: Espinosa CD, Torres LJ, Velayudhan DE, Dersjant-Li Y, Stein HH.
Journal: J Anim Sci; 2022 Dec 01; 100(12):. PubMed ID: 36331062.
Abstract:
An experiment was conducted to test the hypothesis that increasing levels of a novel phytase increases the apparent ileal digestibility (AID) and apparent total tract digestibility (ATTD) of nutrients in diets fed to young pigs. A negative control (NC) diet based on corn, soybean meal, and canola meal that contained approximately 0.83% phytate (i.e., 0.23% phytate-bound P) was formulated to be deficient in Ca, P, and standardized ileal digestible amino acids (AA). Five additional diets were formulated by adding 250, 500, 1,000, 2,000, or 4,000 phytase units/kg of the novel phytase to the NC diets. Eighteen ileal-cannulated pigs (17.81 ± 1.71 kg) were allotted to a 6 × 3 incomplete Latin square design with six diets and three 11-day periods. There were three pigs per diet in each period; therefore, there were nine replicate pigs per diet. The initial 5 d of each period was considered an adaptation period to the diet. For each period, fecal samples were collected via anal stimulation on days 6, 7, 8, and 9, whereas ileal digesta were collected on days 10 and 11 using standard procedures. Results indicated that the AID of crude protein, indispensable AA, and dispensable AA was increased (quadratic, P < 0.05) as the concentration of microbial phytase increased in the diets. Dietary inclusion of the novel phytase at 1,000 or 2,000 FTU/kg increased the AID of total AA from 73.7% to 79.8%. Increasing levels of microbial phytase increased (quadratic, P < 0.05) the AID of dry matter and minerals (i.e., Ca, P, K, Mg, Cu) in the diets. Likewise, a linear increase (P < 0.05) in the AID of ash and Na was observed as the inclusion level of phytase increased in the diets. Increasing levels of microbial phytase increased (linear, P < 0.01) the AID of gross energy (GE) and starch in the diets. A quadratic (P < 0.05) increase in the ATTD of ash, Ca, P, K, and Cu in experimental diets was observed as the concentration of microbial phytase increased in the diets. The ATTD of Mg and GE also increased (linear; P < 0.05) as concentration of dietary phytase increased. In conclusion, the novel microbial phytase used in this experiment was effective in increasing the AID of dry matter, GE, starch, minerals, and AA, as well as the ATTD of gross energy and minerals in diets formulated to be deficient in Ca, P, and AA. The effect of microbial phytase on amino acid (AA) digestibility has been inconsistent, but in many experiments, relatively low levels of phytase were used and it is not known if greater concentrations of phytase are needed to increase AA digestibility. A novel consensus bacterial 6-phytase variant has been recently developed, but it is not known if this phytase results in increased digestibility of AA and other nutrients. Therefore, an experiment was conducted to test the hypothesis that dietary inclusion of increasing levels of the novel phytase (i.e., 0, 250, 500, 1,000, 2,000, and 4,000 phytase units/kg) increases ileal digestibility of AA and total tract digestibility of energy and minerals in diets for growing pigs. In this experiment, it was demonstrated that increasing levels of phytase increased the apparent ileal digestibility of starch, gross energy, minerals, crude protein, and AA, as well as the apparent total tract digestibility of gross energy and minerals. The impact of phytase on AA digestibility is possibly dependent on diet composition, phytate and phytase sources and concentrations, and pig maturity; however, further research is needed to confirm this.

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