Source: Pennsylvania State University
The Voluntary Waiting Period (VWP) is the time between calving and when a farmer chooses to rebreed that cow. A VWP of 60 days is used to calculate daughter pregnancy rate and is a standard throughout the dairy industry (VanRaden et al., 2004). Delaying breeding allows for uterine involution to occur and time for cows to recover from a negative energy balance after they freshen.
Some farms have trouble reaching a VWP goal of 60 days; others consciously choose to extend the VWP. A study looking at Dairy Herd Improvement (DHI) records from across the country showed that the median days to first service was 90 days (Miller et al., 2007). VWP is a goal that farmers set on a farm, and days to first service reflects when cows are actually being bred for the first time. This makes days to first service an excellent check to see if the VWP is being met. Some farms may choose to have a longer VWP if they are trying to extend the lactation of high producers. Others may adjust the VWP seasonally, for example, raising it during the summer, as the likelihood of conception is lower. Some farms may consider lengthening the VWP if they do not have enough labor for increased calvings or want to decrease the number of calves coming onto the farm (Burgers et al., 2022). Another reason for extending the VWP is to allow the reproductive tract more time to return to normal after calving.
Many studies have examined the economic impact of different VWP lengths. The most profitable VWP has been found to be less than 70 days, but it is still profitable as long as it is greater than 42 days (Inchaisri, 2011). Some economic studies have examined primiparous vs. multiparous animals, as parity may play a role in an ideal VWP. One study showed that having a longer VWP for first lactation animals is better economically (Weller and Folman, 1990). Another study comparing the economic viability of extending the VWP for primiparous vs. multiparous cows showed it’s only financially viable for primiparous animals. This was because when multiparous cows VWP increased from 60 to 88 days, they were more likely to leave the herd (Stangaferro et al., 2018). Farmers may consider extending the VWP for primiparous cows because they often experience a more significant negative energy balance after calving than multiparous cows due to the energy they put towards growth (Fodor et al., 2019). Another study showed that a longer VWP for primiparous animals leads to a greater first-service conception rate and fewer inseminations per conception (Rasmussen, 2023).
There is not much evidence supporting shortening the VWP below 60 days. Uterine involution takes about 42 days in primiparous cows and 50 days in multiparous cows to occur (Buch et al., 1955). Breeding cows before this happens is bound to be unsuccessful. It is an industry standard to breed cows for the first time before 80 days in milk and have them bred by 120 days in milk. This helps maintain a consistent calving interval of 12 to 13 months. Depending on the goal VWP, days to first service may vary from farm to farm.
Troubleshooting should occur if a farm is not reaching its goal and its days to first service are very high. A farmer should start by assessing whether or not they are missing heats. If heats are being missed, additional labor may be required to spend more time checking animals. A synching protocol may be necessary if increased time checking heats doesn’t solve the problem. Technologies such as activity monitors can also help with heat detection. If heat detection is not the problem, it could be a scheduling issue with an A.I. technician. If a farm is not having trouble breeding cows for the first time before 80 days but is having a hard time with conception rates at this first service, they may need to assess the transition program and body condition scores of their cows. Cows that are too thin or fat will have conception issues, which can be a sign of a poor transition program.
When a farm decides on what VWP to set, it must first think about the long-term goals of the operation. A farm may be trying to increase conception rates, decrease transition problems, or extend milk production as long as possible. Depending on a farm’s goals, a 60-day VWP may be appropriate, or a longer one may be necessary. VWP is only one management factor that can affect reproductive and lactation performance. The VWP set can impact the calving interval and length of lactation. No matter what a farm’s VWP is, checking if they are meeting their goal regularly is essential. Looking at average days to first service can indicate how close they are to the target VWP.
References
Buch, N. C., W. J. Tyler, and L. E. Casida. 1955. Postpartum estrus and involution of the uterus in an experimental herd of Holstein-Friesian cows. J. Dairy Sci. 38:73-79.
Burgers, E. E. A., A. Kok, R. M. A. Goselink, H. Hogeveen, B. Kemp, and A. T. M. van Knegsel. 2022. Revenues and costs of dairy cows with different voluntary waiting periods based on data of a randomized control trial. J. Dairy Sci. 105:4171-4188.
Fodor, I., G. Gabor, Z. Lang, Z. Abonyi-Toth, and L. Ozsvari. 2019. Relationship between reproductive management practices and fertility in primiparious and multiparous dairy cows. Can. J. Vet Res. 83:218-227.
Inchaisri, C., R. Jorritsma, P. L. A. M. Vos, G. C. van der Weijden, and H. Hogeveen. 2011. Analysis of the economically optimal voluntary waiting period for first insemination. J. Dairy Sci. 94:3811-3823.
Miller, R. H., H. D. Norman, M. T. Kuhn, J. S. Clay, and J. L. Hutchison. 2007. Voluntary Waiting Period and Adoption of Synchronized Breeding in Dairy Herd Improvement Herds. J. Dairy Sci. 90:1594-1606.
Rasmussen, A. E., R. Bage, K. Holtenius, E. Strandberg, C. von Bromssen, M. Akerlind, and C. Krongvist. 2023. A randomized study on the effect of an extended voluntary waiting period in primiparious dairy cows on fertility, health, and culling during first and second lactation. J. Dairy Sci. 106:8897-8909.
Stangaferro, M. L., R. Wijma, M. Masello, M. J. Thomas, and J. O. Giordano. 2018. Economic performance of lactating dairy cows submitted for first service timed artificial insemination after a voluntary waiting period of 60 or 88 days. J. Dairy Sci. 101: 7500-7516
VanRaden, P. M., A. H. Sanders, M. E. Tooker, R. H. Miller, H. D. Norman, M. T. Kuhn, and G. R. Wiggans. 2004. Development of a national genetic evaluation for cow fertility. J. Dairy Sci. 87:2285-2292.
Weller, J. I., and Y. Folman. 1990. Effects of calf value and reproductive management on optimum days to first breeding. J. Dairy Sci. 73:1318-1326.
