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The physiological state of the sow is known to affect the standardized total tract digestibility (STTD) of Ca, the retention of Ca and P and the efficacy of phytase to release Ca and P. However, variations of these parameters along the gestation have not been explored. The objective was to test the hypothesis that STTD of Ca, retention of Ca and P and the response to microbial phytase on STTD of Ca and apparent total tract digestibility (ATTD) of P in diets fed to gestating sows are constant throughout gestation. Thirty-six gestating sows (parity = 3.3 ± 1.5; d of gestation = 7 d) were allotted to 4 diets in a factorial design (2x2) containing either 0 or 500 units of microbial phytase per kilogram and containing calcium carbonate or not (Ca-free diet). Sows were offered the experimental diets and were housed in metabolism crates only from days 7 to 20 (early gestation), days 49 to 62 (mid-gestation), and again from days 91 to 104 (late gestation).
Results indicated that outcomes were not influenced by the interaction between period of gestation and dietary phytase. The basal endogenous loss of Ca was greater by sows in early gestation than by sows in mid- or late-gestation, but supplementation of microbial phytase to the Ca-free diet decreased the basal endogenous loss of Ca and tended to increase ATTD of P. Supplementation of microbial phytase did not affect ATTD of DM, STTD of Ca, Ca retention, ATTD of P, or P retention in sows fed the calcium carbonate-containing diet. The ATTD of DM was not affected by period of gestation, but the ATTD of Ca, the ATTD of P, and the retention of Ca were least in mid-gestation, followed by early and late gestation, respectively, and the STTD of Ca in mid-gestation was also reduced compared with sows in early or late gestation. Phosphorus retention was greater in late gestation than in the earlier periods.
It was concluded that Ca retention was less negative and ATTD of P tended to increase with supplementation of microbial phytase to the Ca-free diet regardless of gestation period. The basal endogenous loss, STTD of Ca, ATTD of P, and retention of Ca and P in gestating sows change during gestation with the greatest digestibility values observed in late gestation.
Lee SA, Lagos LV, Walk CL, Stein HH. Basal endogenous loss, standardized total tract digestibility of calcium in calcium carbonate, and retention of calcium in gestating sows change during gestation, but microbial phytase reduces basal endogenous loss of calcium. Journal of Animal Science. 2019; 97(4): 1712-1721. https://doi.org/10.1093/jas/skz048