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

Lee, S. A., C. L. Walk, and H. H. Stein. 2018. Comparative digestibility and retention of calcium and phosphorus by gestating sows and growing pigs fed low- and high-phytate diets without or with microbial phytase. J. Anim. Sci. 96(Suppl. 2):83 (Abstr.) Link to abstract (.pdf)

Stein, H. H. 2017. Procedures for determining digestibility of amino acids, lipids, starch, fibre, phosphorus, and calcium in feed ingredients fed to pigs. Anim. Prod. Sci. 57:2317-2324. Link to abstract

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)

Stein, H. H., L. A. Merriman, and J. C. González-Vega. 2016. Establishing a digestible calcium requirement for pigs. Pages 207-216 in Phytate destruction—consequences for precision animal nutrition. Walk, C. L., ed. Wageningen Academic Publishers, Wageningen, Netherlands. Link to full text 

Merriman, L. A., C. L. Walk, C. M. Parsons, and H. H. Stein. 2016. Effects of tallow, choice white grease, palm oil, corn oil, or soybean oil on apparent total tract digestibility of minerals in diets fed to growing pigs. J. Anim. Sci. 94:4231-4238. Link to full text (.pdf)

Zinc oxide, when added to weanling pig diets in pharmacological quantities of up to 2,500 mg/kg, can help prevent diarrhea during the post-weaning period. However, adding large quantities of zinc to diets has drawbacks. Zinc can interfere with calcium digestibility because it competes for the same transport pathway in cells lining the small intestine. Zinc may also reduce calcium digestibility by forming complexes with calcium and phytate.

The standardized total tract digestibility (STTD) of calcium in various ingredients has only recently been determined, and possible interactions between zinc and phytase on the STTD of calcium have not yet been reported. Therefore, an experiment was conducted to determine the effects of addition of zinc oxide and microbial phytase on STTD of calcium in diets fed to weanling pigs.

Milk co-products are used in pig diets to provide lactose and, in some cases, high quality protein. In addition, milk co-products also provide calcium to the diets. However, this calcium can potentially bind to the phytate contained in the plant ingredients in the diets, which would reduce its digestibility.

Merriman, L. A., C. L. Walk, and H. H. Stein. 2016. The effect of microbial phytase on the apparent and standardized total tract digestibility of calcium in feed ingredients of animal origin. J. Anim. Sci. 94(Suppl. 2):110 (Abstr.) Link to abstract (.pdf)