Field trial to determine the efficacy of two doses of 1 alpha-hydroxycholecalciferol in the prevention of milk fever.

The efficacy of 1 alpha-hydroxycholecalciferol (1 alpha-HCC) for the prevention of milk fever has been tested in a controlled field trial using a total of 601 cows on 18 farms with a history of a high incidence of milk fever. The trial protocol proposed two doses of 1 alpha-HCC with the first injection seven days before the predicted calving date and a second injection five to seven days later if the cow had not calved. Of 301 cows receiving either one or two injections of 1 alpha-HCC, 70 had milk fever, and of 300 cows that received a placebo, 102 had milk fever. The difference in incidence between the two groups was statistically significant (P = 0.005) and indicated an overall efficacy of 32 per cent for treatment with 1 alpha-HCC. An improved efficacy was demonstrated in 67 cows that received two injections of 1 alpha-HCC with the second injection administered either on the day of calving or one day previously (60 per cent efficacy). For 42 cows that received a single injection of 1 alpha-HCC between two and five days before calving an efficacy of 79 per cent was achieved.