Many farmers are finding that a diet based on medium to low quality long hay fed free choice and balanced with concentrate to meet the protein and mineral needs of the cow makes an excellent dry cow feeding program. The luxury consumption of protein as well as energy should be avoided during the dry period. The major concern in the mineral feeding of dry cows relates to the provision of optimum levels of calcium and phosphorus in order to limit the occurrence of milk fever. Numerous studies have been conducted using widely varying ratios but no one ratio is regarded as clearly superior. While calcium to phosphorus ratio is important, the actual quantities of each mineral fed are at least equally important.
Recent reviews support limiting the intakes of calcium and phosphorus during the dry period.
In general, recommendations are to limit calcium intake to less than 100 grams per day and feed phosphorus at the rate of 30-50 grams per day. Large amounts of high quality legume forages should be avoided due to their high calcium content. In addition to a relationship between calcium and phosphorus nutrition and milk fever, a calcium phosphorus imbalance may also increase retained placenta and metritis. Supplementation with high levels of vitamin D or one of its metabolites beginning about l week prepartum has been shown to reduce the incidence of milk fever in cows with a history of this disorder. However, timing is critical and the difficulty in accurately predicting the calving date makes this approach impractical.