The University of Laval in Canada recently compared the effects of two different dry period lengths on health and reproduction.
The study, published in the July Journal of Dairy Science, featured 850 Holstein cows from 13 commercial dairy herds that were assigned to either a 35-day (short) or a 60-day (conventional) dry period, based on milk yield, number of calves and estimated calving interval. Cows enrolled in the conventional dry period group were fed a dry cow ration from dry-off until 21 days pre-partum, at which time they were switched to a pre-calving ration. A pre-calving ration was fed to cows of the short dry period group throughout the entire shortened dry period. Results showed:
- Significantly higher cull rates for cows that had more than one calf (i.e. twins) in the short dry period group compared to those enrolled in a conventional dry period group.
- Lower incidence of metabolic disorders for second lactation, compared to third or later lactation cows in both groups.
- Cases of mild ketosis were lower for cows in the shortened dry period group.
- Occurrence of retained placenta was higher for second and later lactation cows in the short dry period. However, this did not lead to increased cases of metritis.
Researchers concluded that a short dry period can transition cows back to the milking herd sooner, without major effects on health and reproduction parameters.