Use of oral boluses comprised of readily absorbed calcium salts and Solanum glaucophyllum leaf administered a single time after calving to reduce hypocalcemia in dairy cows

Abstract

Hypocalcemia is commonly observed in periparturient cows. If persistent beyond the first day of lactation, it contributes to poor milk production and other health problems (Neves et al., 2017). Oral Ca boluses can provide Ca for rapid absorption of Ca to support blood Ca concentration. Because their actions are short-lived (3-6 hrs), they are often administered at calving and again 12-24 hrs later. 1,25-dihydroxyvitamin D (1,25 VD) and its analogs have been utilized to prevent milk fever, but must be given 1-3 days prior to parturition to be effective as 12-24 hrs are required to stimulate intestinal Ca absorption (Hove and Kris­tiansen, 1982). A major obstacle to the use of 1,25 VD to prevent hypocalcemia is administration within the effective window. Given too early, the dose must be repeated. Given too late, the cow can still suffer severe hypocalcemia. Solanum glaucophyl­lum (SG) is a plant whose leaves contain an inactive glycoside form of 1,25 VD. Within the rumen the glycoside is cleaved by rumen bacteria, liberating 1,25 VD which is rapidly absorbed into the blood. Our hypothesis is that administering a bolus with readily absorbable Ca and SG leaf will improve plasma Ca in periparturient cows when administered at the time of calv­ing. The Ca will sustain improved blood Ca concentrations for up to 12 hrs after calving and the SG leaf will stimulate intesti­nal Ca absorption from 12 hrs until 72 hrs after calving.