Lagos, Vanessa, Mike R. Bedford, Hans H. Stein. 2020. Effect of formulating diets based on a ratio between STTD Ca and STTD P and the inclusion of phytase on growth performance, plasma Ca and P, and bone ash of pigs from 11 to 130 kg. J. Anim. Sci. 98(Suppl. 3): 104-405.  doi.org/10.1093/jas/skaa054.178. (Abstr.). Link to abstract.

Calcium requirements by pigs are expressed as total Ca because of a lack of data for the digestibility of Ca in feed ingredients, but it is believed that a ratio between standardized total tract digestible (STTD) Ca and STTD P is a more appropriate way to express requirements for Ca by pigs. Values for Ca digestibility in different Ca-containing feed ingredients were recently generated using diets without or with microbial phytase, which allowed for the formulation of diets based on STTD Ca values. A number of experiments were also conducted to determine STTD Ca to STTD P requirements to optimize growth performance and bone mineralization of pigs from 11 to 25 kg, 25 to 50 kg, 50 to 85 kg, and 100 to 130 kg. However, these experiments were performed independently and in experiments lasting only 3 to 5 weeks. Therefore, a follow-up experiment was conducted to test the hypothesis that the requirement for Ca expressed as a ratio between STTD Ca and STTD P obtained in short-term experiments may be applied to pigs fed diets without or with microbial phytase from 11 to 130 kg.

Lagos L. Vanessa, Su A. Lee, Guillermo Fondevila, Carrie L. Walk, Michael R. Murphy, Juan J. Loor and Hans H. Stein. 2019. Influence of the concentration of dietary digestible calcium on growth performance, bone mineralization, plasma calcium, and abundance of genes involved in intestinal absorption of calcium in pigs from 11 to 22 kg fed diets with different concentrations of digestible phosphorus. Journal of Animal Science and Biotechnology. 2019. 10:47.