Research Summary

We are evaluating peripartum calcium metabolism in dairy cows. Lactating cows often are unable to meet the sudden demand of the udder for calcium immediately postpartum. Hence, plasma calcium pools are depleted, resulting in clinical symptoms associated with parturient paresis (milk fever). A study conducted by our group indicates that intramammary infusion of calcium helps moderate variability in plasma calcium concentration during the first few days postpartum. In practice, this response could eliminate the negative effects of low plasma calcium on subsequent feed intake and milk production.

We also are evaluating the influence of feeding anionic salts to prepartum dairy cows on the ability of their calves to absorb antibodies from colostrum. In our initial study, calves born to cows consuming anionic salts had lower serum antibody content at 12 and 24 h of age than did calves from cows not receiving the salts. Apparent efficiency of absorption of antibodies also was reduced by these salts. This suppression was evident regardless of whether calves received colostrum from cows that had consumed anionic salts, or from cows that had not. Hence, the interference with acquisition of passive immunity was caused in utero, and could not be attributed to changes in the characteristics of the colostrum. We are seeking funding to determine the mechanism behind the suppression of passive immunity acquisition accompanying the feeding of anionic salts prepartum.

Another focus of our group is to evaluate the economic viability of raising dairy calves in a greenhouse barn versus traditional calf hutches. We are completing the winter phase of this project, and will conduct a separate study to evaluate the degree of heat stress for calves housed in this barn during the summer in Mississippi.

Finally, low-input dairying is being evaluated by our group. Beginning March 1, 1998, we placed 20 mid- to late lactation cows on ryegrass paddocks with no supplementation other than loose mineral. Production of these cows will be compared with that of 20 control cows housed in a free stall barn and receiving a total mixed ration. In addition to milk yield, we are monitoring milk composition and body condition scores, and are estimating ryegrass intake until the project ends on May 23, 1998.