Absorption of Ca and P by active transport in the small intestine is regulated by calcitriol, which is the active form of vitamin D (1,25-dihydroxycholecalciferol) and the hormones calcitonin and PTH. One-alpha-hydroxycholecalciferol (1-α-OH-D3) is an active vitamin D3 analog that does not require the second hydroxylation step for vitamin D3 to be active. It is possible that supplementation of 1-α-OH-D3 may increase absorption of Ca and P.
The requirement for Ca and P by gestating sows increases in late gestation compared with early- and mid-gestation because of increased needs by the developing fetuses. It is also possible that dietary concentrations of Ca and P affect the rate of absorption of Ca and P in sows but data to demonstrate this have not been reported. Therefore, the objective of this experiment was to test the hypothesis that the Ca and P concentrations in diets fed to gestating sows in late gestation and supplementation of 1-α-OH-D3 affect apparent total tract digestibility (ATTD) and retention of Ca and P as well as the ATTD of GE and concentration of DE in diets. The second hypothesis was that there is an interaction between dietary Ca and P concentrations and supplementation of 1-α-OH-D3 in diets fed to gestating sows.
A total of 36 gestating sows, parity 2 to 6, were fed experimental diets from d 91 to 105 of gestation. Sows were housed individually in metabolism crates and randomly allotted to 4 diets. Two diets were formulated to contain 75 or 100% of the required Ca and P with a Ca to P ratio 1.3:1.0 in both diets. Two additional diets were formulated by adding 12.5 mg/kg of 1-α-OH-D3 to each of the initial diets (Alpha D3, Premex Inc., NC). Feed was provided daily in 2 meals and a feeding level equivalent to 1.5 × the daily maintenance ME requirement was used. Fecal and urine samples were quantitatively collected, and the ATTD and retention of Ca and P in experimental diets were calculated based on intake and fecal and urine output of Ca and P. The ATTD of GE and DE in diets were also calculated.
No interactions between Ca and P concentratrions and use of supplemental 1-α-OH-D3 were observed for the ATTD of DM and GE or Ca and P balance (Table 1). The ATTD of DM, DE in diets, the ATTD of Ca and P, and retention of Ca and P were not affected by the level of Ca and P in the diets.
Although feed intake was not different among treatments, fecal excretion was less (P < 0.05) from sows fed diets supplemented with 1-α-OH-D3 compared with sows fed diets with no 1-α-OH-D3, which resulted in greater ATTD of DM in sows fed diets supplemented with 1-α-OH-D3 compared with sow fed no supplemental 1-α-OH-D3. Concentrations of DE in diets, the ATTD of Ca and P, and retention of Ca and P by sows were greater (P < 0.05) in sows fed diets with supplemental 1-α-OH-D3 compared with sows fed no supplemental 1-α-OH-D3.
- Calcium and P balance by sows in late gestation were not affected by dietary Ca and P levels.
- Supplementation of 1-α-OH-D3 increased the ATTD and retention of Ca and P regardless of dietary Ca and P concentration.
- Supplementation of 1-α-OH-D3 increased the ATTD of GE and concentration of DE in diets fed to sows.
Table 1. Concentration of DE in diets and Ca and P balance for sows fed experimental diets