Over the past few years, dry cow management has been re-examined with respect to nutrition housing and health. This [article] focuses on new ideas in lighting for dry cows and altering the length of the dry period as methods to improve overall productivity and health during the transition and subsequent lactation.

Dry period length reduction

A dry period length of 60 days has been an industry standard for more than 60 years. The original recommendation was based on retrospective studies of large DHIA datasets that indicated cows dry for less than 40 days, or more than 70 days, had lower yield in the subsequent lactation relative to contemporaries. In addition, results from a small number of designed studies that compared different dry period lengths directly supported the concept that less than 60 days dry was detrimental to subsequent yield.

Yet the need for a 60-day dry period has been revisited in recent years because of changes in production, management and nutrition that resulted in many cows drying off at relatively high milk yields.

With regard to designed comparisons, work from Wisconsin and Arizona directly tested the necessity of a 60-day dry period versus 30 days dry. Annen et al. found that while primiparous cows required a 60-day dry period for optimal production in the next lactation, multiparous cows were not adversely affected by a 30-day dry period.

Rastani et al. drew similar conclusions regarding multiparous cows’ dry period length and observed feed management of dry cows could be simplified by reducing dry period length. Thus, direct comparisons indicate no significant loss of yield occurs when the dry period is reduced from 60 to 30 days in mature cows.

Retrospective analytical approaches to determine optimal dry period length have also been revisited recently. Workers at the USDA-Beltsville examined more recent records from large numbers of cows on DHIA and concluded a 60-day dry period remains optimal. However, models developed from that same dataset indicate minimal loss of milk occurs between 40 and 60 days dry, and so other management advantages, such as fewer diet changes, may mean a shorter dry period is optimal overall.

Photoperiod recommendations for dry cows

Previous evidence indicates the best management approach to light exposure for dry cows is a reduction in the length of light exposure to eight hours per day, (i.e., a short-day photoperiod [SDPP]). Indeed, we have shown that limiting light exposure to eight hours per day increases milk yield in the next lactation, improves dry matter intake (DMI) during the dry period and limits the immunosuppression cows experience around parturition.

Two recent experiments extend our understanding of the response and how to best manage implementation of short days with dry cows. The purpose of the first study was to determine if the effects of SDPP during the dry period could be observed with a 21-day treatment that could be implemented at the beginning of the transition period and reduce the amount of time animals are housed in an enclosed facility.

At dry-off cows were assigned randomly to one of four dry period treatments:

•long-day photoperiod (LDPP)

•short-day photoperiod (SDPP)

•natural lighting schedule during dry period (AMB)

•SD21 (AMB until 21 days prepartum followed by SDPP)

After parturition, animals were exposed to natural lighting during lactation. There were three cohorts of cows for each treatment, with cohorts being dried off in October, January and April.

In confirmation of previous studies, exposure to SDPP for a 60-day dry period caused higher yield in the subsequent lactation relative to LDPP. Cows on SDPP also had greater yield than those on ambient photoperiod or SDPP for only the final 21 days of the dry period. These results suggest that if SDPP treatment is limited to only the final 21 days of the dry period, the production response is not observed.

A second study was designed to examine the impact of combining a reduced length of the dry period with exposure to SDPP. Forty cows were dried off approximately 42 days before expected calving and housed under SDPP or LDPP from dry-off to calving. We also made extensive behavioral observations of the cows during the dry period to assess the impact of photoperiod manipulation on animal well-being. Although the milk yield data is incomplete as of this date, a number of observations made about the behavior of dry cows lead to recommendations about housing of those cows during this critical phase of the production cycle.

Similar to lactating cows, dry cows spend the majority of their time lying down, although dry cows average more than 15 hours per day lying, which far exceeds the 11 to 12 hours lactating cows typically lie down. Part of the difference in lying activity during lactation relative to the dry period likely results from the other demands on the time of lactating cows (i.e., milking, holding pen time).

However, it is important to consider that dry cows will lay down for longer periods if stall space is available, and so the recommendation of clean, comfortable stalls they don’t have to compete for (i.e., stocking density of 100 percent or less) is as critical to dry cows as it is during lactation.  PD

References are available upon request. This e-mail address is being protected from spambots. You need JavaScript enabled to view it

—From University of Illinois 2006 Dairy Days Proceedings