Effect of phytate degradation using phytase and soaking and resistant starch in barley on phosphorus utilization, gut health, and growth in pigs
Final Report Abstract
Feed formulation is based mainly on ingredient digestibility data, whereas these data do not account for interactions among nutrients. Further research is required to define kinetics of nutrient digestion and fermentation such as P across different feedstuffs to optimize feed formulation. Fermentable fiber may increase endogenous losses of P and amino acids, thereby reducing apparent nutrient digestibility. Increasing inclusion of fermentable, low viscous acacia gum decreased diet digestibility of DM and energy, but ileal digestibility of crude protein and amino acids was not affected. However, increasing inclusion of acacia gum tended to increase dietspecific endogenous P losses and thus reduce standardized total tract digestibility of P. As an implication, feeding ingredients high in low-viscous, fermentable fiber, apparent total tract digestibility of P should be corrected for total endogenous P losses (basal plus specific) to calculate true total tract digestibility of P to avoid underestimation of dietary P digestibility. In pigs’ diets, barley grain is used as the main energy source providing starch. However, barley grain can vary greatly in nutrient composition depending on cultivar and agronomic conditions. Increased fermentable carbohydrates in cereal grains due to more amylose in starch or β-glucan in fiber may increase endogenous losses including for P, and thereby reduce apparent total tract digestibility of P. The results of the present study confirmed that whole grains high in fermentable fiber, e.g. β-glucans, in specific hull-less and hulled barley cultivars decreased diet digestibility of P and calcium. In plants, P is either presented as non-phytate- or phytate-P, known as any salt of myo-inositol 1,2,3,4,5,6-hexakis dihydrogen phosphate (InsP6). Plant based feedstuffs in pigs’ diets contain total P mainly in the form of InsP6. Depending on phytase activity, InsP6 is hydrolyzed down to less phosphorylated inositol phosphates and available P. However, in pigs, the hydrolysis of InsP6 is incomplete due to a lack of sufficient endogenous enzymes in the proximal gastro-intestinal tract. Grain fermentation can increase nutrient availability and can activate a variety of intrinsic cereal enzymes degrading fiber and antinutritional factors, especially InsP6. Furthermore, feeding fermented grain can lower the gastric pH, thus protect against coliforms and promote protein denaturation. In vitro, bacterial fermentation of barley grain using Lactobacillus reuteri and Weisella cibaria increased InsP6 hydrolysis by improving intrinsic plant phytase activity. Based on these results, grain fermentation can be considered as promising processing strategy to increase P digestibility and to reduce P excretion with manure leading to environmental pollution.
Publications
- 2019. Whole-grain fiber composition modifies phosphorus digestibility in grower pigs. Midwest Meeting, Omaha, USA, J. Anim. Sci. 97:99
Heyer, C. M. E., J. M. Fouhse, T. Vasanthan, and R. T. Zijlstra
(See online at https://doi.org/10.1093/jas/skz122.177) - 2020. Increasing inclusion of fermentable fiber decreases nutrient digestibility in grower pigs. Midwest Meeting, Omaha, USA
Heyer, C. M. E., L. F. Wang, and R. T. Zijlstra
