Lee, S. A., G. A. Casas, and H. H. Stein. 2018. The level of feed intake does not influence digestibility of calcium and phosphorus in diets fed to gestating sows, but gestating sows have reduced digestibility of calcium and phosphorus compared with growing gilts. Can. J. Anim. Sci. 98:591-594. Link to abstract

Until recently, rye has been less suitable for livestock feed than other cereal grains due to the risk of ergot contamination. However, recently developed hybrids are less susceptible to ergot contamination. There is limited information about the nutritional value of hybrid rye when fed to pigs.

In cereal grains, most of the phosphorus is bound to phytic acid, and is not available to pigs unless phytase is present. This is usually achieved by adding supplemental phytase, derived from microbes, to the diets. However, rye contains more intrinsic phytase than other cereal grains, so the phosphorus in rye may be more digestible. The addition of microbial phytase might also have less of an effect on phosphorus digestibility in rye than in other grains because of the high concentrations of intrinsic phytase in rye, but limited information about digestibility of phosphorus in rye has been reported.

Casas, G. A. and H. H. Stein. 2018. Young Scholar Presentation: Nutritional value of rice coproducts fed to pigs. J. Anim. Sci. 96(Suppl. 2):143 (Abstr.) Link to abstract (.pdf)

Most of the phosphorus in corn and other plant-based feed ingredients fed to pigs is bound to phytate. Pigs do not secrete phytase in adequate quantities to liberate significant amounts of phytate-bound phosphorus, meaning that most of the phosphorus in these ingredients is not biologically available. Calcium digestibility is also negatively affected by the presence of phytate in feed ingredients. One way for producers to ensure that pigs' requirements are met is to add supplementary phosphorus to diets. However, this adds to the cost of diets. The excretion of phytate-bound phosphorus also may contribute to algae overgrowth in waterways.

Another approach is to add supplemental phytase to the diets, to allow pigs to better utilize the phosphorus present in the ingredients. Phytases can be obtained from plants, animals, or microorganisms (bacteria, yeasts, and fungi).

GraINzyme is a source of phytase produced by genetically modified corn plants with genes derived from E. coli. In this experiment, the effect on growth performance, apparent total tract digestibility (ATTD) of calcium and phosphorus, and bone mineralization of adding GraINzyme to weanling pig diets was tested.

She, Y., Y. Liu, J. C. González-Vega, and H. H. Stein. 2017. Effects of graded levels of an Escherichia coli phytase on growth performance, apparent total tract digestibility of phosphorus, and on bone parameters of weanling pigs fed phosphorus-deficient corn-soybean meal based diets. Anim. Feed Sci. Technol. 232:102-109. Link to abstract

She, Y., Y. Liu, and H. H. Stein. 2017. Effects of graded levels of microbial phytase on apparent total tract digestibility of calcium and phosphorus and standardized total tract digestibility of phosphorus in four sources of canola meal and in soybean meal fed to growing pigs. J. Anim. Sci. 95:2061-2070. Link to full text (.pdf)

Blavi, L., D. Sola-Oriol, J. F. Pérez, and H. H. Stein. 2017. Effects of zinc oxide and microbial phytase on digestibility of calcium and phosphorus in maize-based diets fed to growing pigs. J. Anim. Sci. 95:847-854. Link to full text (.pdf)

Oliveira, M. S. and H. H. Stein. 2016. Digestibility of energy, amino acids, and phosphorus in a novel source of soy protein concentrate and in soybean meal fed to growing pigs. J. Anim. Sci. 94:3343-3352. Link to full text (.pdf)

Sotak-Peper, K. M., J. C. González-Vega, and H. H. Stein. 2016. Effects of production area and microbial phytase on the apparent and standardized total tract digestibility of phosphorus in soybean meal fed to growing pigs. J. Anim. Sci. 94:2397-2402. Link to full text (.pdf)