Milk fever in dairy cows. VIII. Effect of injected vitamin D3 and calcium and phosphorus intake on incidence.

In a field trial, effects of prepartal intermuscular injection of 10 million units of vitamin D3 on incidence of milk fever were examined both in relation to intake of calcium and phosphorous during the dry period and previous history of milk fever. Based upon intake of calcium and phosphorus cooperating herds were grouped as feeding: 1) greater than .53% of the total ration dry matter as calcium and greater than .28% as phosphorus: 2) less than .47% as calcium and greater than .28% as phosphorus; 3) greater than .47% to less than .53% as calcium and greater than .22% to less than .28% as phosphorus. Injections of vitamin D3 given approximately 1 wk prepartum reduced incidence of milk fever in cows with previous history of milk fever in all three groups but had no effect in cows with no previous milk fever. Incidence of milk fever was lower in group 3 than for cows of groups 1 and 2 with previous milk fever and than for cows of group 1 with no previous history. The results indicate that careful control of calcium and phosphorus intake during the dry period at .5% calcium and .25% phosphorus of the dry matter of the total ration will limit milk fever incidence to about 10%. Injections of vitamin D3 as described will reduce inicidence of milk fever further in cows with previous milk fever but not in cows with no previous milk fever.