Studies of Milk Fever in Dairy Cows. VI. Effect of Three Prepartal Dosage Levels of Vitamin D on Milk Fever Incidence

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Abstract
A field study involving 164 parturitions in Jersey cows, all with previous milk fever histories, in 26 Ohio herds was conducted to obtain further information on how much vitamin D must be fed prepartal to provide maximum protection against milk fever. The assigned vitamin D dosage, 15, 20, or 30 million units/day, was fed on a twice-a-day basis beginning approximately 5 days before the expected calving date and for one feed after parturition. If 7 days feeding were completed before parturition, vitamin D feeding was terminated. On-schedule cows were those that received at least 3 days of vitamin D feeding and calved within one day after termination of vitamin D feeding. In all, there were 113 in the on-schedule group. In the off-schedule group 10 cows calved too early and 41 calved too late. Three vitamin D concentrates were used: viosterol (capsules), type 142F irradiated dry yeast, and super drex 3000. Average per cent protection for the 3 dosages, based on 64% milk fever expectancy in Jersey cows with previous milk fever histories, was 67.1% for the 15 million unit level, 82.0% at the 20 million unit level, and 79.2% at the 30 million unit level. No statistically significant differences were found in milk fever incidence or per cent protection among the 3 vitamin D dosage levels. Vitamin D was fed for an average of 5.6 days (11.2 feedings) prepartal, including the day of parturition in the on-schedule group. Because the 15 million unit/day dosage level resulted in a lower average protection than the 2 other dosages, it was considered unwise to recommend less than 20 million units per day, until more numbers can be studied. There was no evidence, however, that 30 million units per day would be more effective than 20 million units per day. All 3 vitamin D concentrates used appeared to be equally effective when consumed. Certain cows did not accept irradiated yeast readily. The viosterol capsules had the advantages gained from forced feeding and super drex 3000 offered no palatability problem. Evidence obtained indicated that protection increased for the first 3 days of vitamin D feeding, remaining at a high level after the 3d through the 7th day, and dropped precipitously after one day had elapsed following cessation of vitamin D feeding.