University of Washington dairy scientists found no difference in the incidence of mastitis following shortened dry periods in herds they studied. What they did find, however, is that cows with 30-day to 45-day dry periods produced 2,500 lb./cow less milk in the next lactation.
The study involved four herds comprising a total of 156 cows. Cows in two herds were assigned to either 30-day or 60-day dry periods. Cows in the other two herds were assigned to 30-day or 45-day dry periods.
Reports of new intramammary infections ranged from 6% to 9% but were not found to be statistically different. Nor were linear somatic cell counts during the first six to seven months of the subsequent lactations.
However, mature equivalent (ME) milk production was greater in cows with 60-day dry periods. These cows averaged 26,300 lb. of ME milk. Cows with 30-day dry periods averaged 23,650 lb. of ME milk. And cows with 45-day dry periods produced no more than cows with 30-day dry periods.