6 May 2025

5 minute read

By: Penn State University

North America

It is well known that a dry period is necessary to ensure success in the subsequent lactation, but what is the ideal dry period length? Should it be 30, 45, or 60 days? What we do know is that if there is no dry period, milk production is reduced by 20% to 25% in the next lactation (Grummer and Rastani, 2004). Shortening dry periods is often discussed, as a shortened dry period could help improve energy balance during the transition period and could help with transition period diseases (Kok et al., 2017). 

Research has also shown that dry periods can be too long. A dry period that is very long, like 90 days or more, decreases lifetime milk production by about 8800 pounds (Kuhn et al., 2006). Often, cows that are dry for this long are hard to breed cows and/or low producers. Getting cows bred by 100 days in milk helps ensure they will be set up for a standard dry period length and success in their next lactation.

Historically, many farmers have aimed to have a 60-day dry period, allowing time to feed a far-off and close-up dry cow diet. Some new research has shown that it may be feasible to shorten this time period.

Does dry period length affect milk production?

There is conflicting information in the literature regarding the effect of dry period length on milk production. One study shows that cows with a shortened dry period of 35 days compared to 60 days produced 7% less milk during their first 100 days of lactation. A shorter dry period did not affect colostrum or body condition score. 

Another study showed no decrease in milk yield when shortening the dry period (Gulay et al., 2003). It is important to note that cows with shortened dry periods were fed differently than those with longer dry periods in that study. Cows who were assigned to the 60-day dry period group in this study were fed a far-off diet and then a close-up diet, while the 30-day dry period group only received a close-up diet.

Older cows seem to tolerate a shortened dry period more so than first-lactation animals. A study by Kuhn et al. (2006) looked at dry periods for the first three lactations to determine what length maximizes lifetime milk production. They found that first lactation animals needed a 40- to 50-day dry period while older animals only needed a 30- to 40-day dry period to maximize milk production.

Does dry period length affect milk composition?

In a time when components are a large portion of the milk price, it is essential to evaluate how management decisions affect milk composition. One study of around 780 cows on a commercial dairy found higher milk protein in cows with a shorter dry period (35 days) than a longer dry period (55 days). No difference was seen in milk fat (Watters et al., 2008). A study that analyzed DHIA records across the country looked specifically at Jersey cow records and found that a short dry period (30 days) increased fat and protein percentages but lowered milk yield, so it did not increase fat and protein pounds overall (Huhn et al., 2007).

Does dry period length affect reproduction?

There is also conflicting information regarding dry period length and reproduction in the literature. One study showed that a dry period of 40 to 60 days leads to better conception rates than shorter or longer dry periods (Guadagnini et al., 2023). Another study showed that dry period length does not affect the first insemination conception rate (O’Hara et al., 2020). Different repro protocols can influence the farmer's target dry period length. Depending on the goal, voluntary waiting period, dry periods could be longer or shorter.

Does dry period length impact disease incidence in the fresh period?

During the fresh period, cows often have a negative energy balance. For many years, cows have been thought to be immunosuppressed during the fresh period. New research out of the Baumgard lab at Iowa State has shown that cows may have a very active immune system during the fresh period, but the pathogen load increases, causing more disease incidences (Opgenorth et al., 2024). A meta-analysis by van Knegsel et al. summarized some studies showing improved energy balance through the fresh period because of a shortened dry period. van Knegsel et al. (2013) thought this was probably because, with a shorter dry period, cows produce less milk during the fresh period, creating less of a negative energy balance. This same meta-analysis looked at disease incidence. A short dry period reduced ketosis but didn’t affect other diseases. Another study showed that cows were twice as likely to have a retained placenta if they had a shortened dry period versus a 60-69 day dry period (O’Hara et al., 2020).

Does the dry period length of the dam affect the calf?

The van Knegsel et al. (2013) meta-analysis showed that cows without a dry period had fewer IgGs in their colostrum, but cows with just a shortened dry period saw no difference. A study that collected records from over 40,000 cows in Iran showed that dry period length does not affect dystocia incidence. This study also showed that bigger calves were born to animals with a dry period longer than 60 days (Atashi et al., 2013).

Conclusion

Dairy farmers must consider many factors when deciding on a dry period length for their farm. While science does play a part, other practical factors sometimes take precedence. How much room do they have in the dry cow pen? How much milk is currently in the bulk tank? Are they going through a quota period from their co-op? Does the farm have enough labor available right now? There isn’t any one-size-fits-all answer for every farm or every cow. If deciding to shorten the dry period, cows must be managed differently than those with a typical 60-day dry period. There are pros and cons to every dry period length.