
A numbers game
Research has borne out that a dry period does need to be part of the cycle — without it, production dips as much as 25% during the subsequent lactation. However, cutting down from the traditional 60 days could help reduce instances of transition period diseases and contribute to improved energy balance during that same phase. Researchers have looked at the variables over the years, including parity and length of dry period, with metrics hinging on production, components, reproduction, and calf health.
In a 2014 study, dropping the dry period to 35 days yielded a 7% reduction in milk during the first 100 days of lactation when the control group cows were kept at 60 days dry — a result that flew in the face of earlier, similar research with similar parameters but no loss in production. However, Fread pointed out that in the latter study, which compared 60- and 30-day dry periods, the cows in the latter 30-day group were not fed a far-off diet, only a close-up. This is a variable that should be taken into consideration when studying the data.
Parity is another inconsistency in herd demographics; a 2006 dry period study foregrounded it and found that older animals with more lactations under their belts tolerated a 30- to 40-day dry period while still able to max out lifetime production. On the other hand, first-lactation cows only met this metric at 40 to 50 days dry — any shorter and they came up short.
Of course, production is only part of the picture — components are increasingly being used as the ultimate measuring tool for herd economics. Researchers have looked at records and conducted their own studies, with mixed results: In one study, a shorter dry period was associated with higher milk protein and no difference in milkfat. An examination of Dairy Herd Improvement Association Jersey records revealed that a shortened dry period boosted both protein and fat percentages, but the drop in milk yield negated any overall gains.
The negative energy balance nearly synonymous with the fresh period also has been studied in relation to a shorter dry period, with some researchers suggesting that a shorter dry duration might simply lower production, which in turn means less energy is needed. And while a shortened dry period reduced ketosis in one study, another revealed a two-fold uptick in retained placenta for cows who experience a shorter-than-60-day dry period.
Regarding reproduction
Again, the record shows that shorter dry periods yield a mixed bag of results when it comes to reproduction. Fread noted that different reproduction protocols might dictate an ideal dry period duration, but producers can look to some studies for guidance. One, done in 2023, shows a clear advantage to dry periods between 40 and 60 days for conception rates; in another there appeared to be no difference in conception rates among different dry period lengths. When calves are birthed by a dam with a dry period of longer than 60 days, this offspring might be bigger than average, one analysis showed.
Fread said that ultimately, producers should not just take in the literature on dry period length — they should also evaluate their own operations. Space, labor, quotas, and other considerations should be factored in, she said, noting that shortened dry periods dictate different management methods.