Back in the day the gold standard of cow breeding called for getting cows pregnant by 60 days so they could calve again in 365 days, given a 60-day dry period. That’s when 20,000-lb. herd averages were exceptional.
Today, genetics have advanced so cows are capable of producing much more milk then previous generations. It seems a shame to cut off lactations early when cows are producing at levels far above breakeven. So why do we need to get cows bred back so fast?
Breeding later into lactation by extending the voluntary waiting period (VWP), has risks and rewards. A Cornell University study led by Julio Giordano evaluated reproductive performance, herd exit dynamics and lactation performance for cows with a VWP at either day 60 or day 88. About 2,700 cows on three commercial New York dairies were part of the study. All cows were on double ovsynch protocol on first service. Here’s what researchers found:
- Extending days to first service increased pregnancies per service from 41% at 60 days to 47% at 88 days
- First lactation cows saw the largest benefit (46% vs. 55%)
- Second and later lactation cows saw minimal advantage (36% vs. 40%)
- Cows at 88 days in milk were more physically ready to be pregnant, gauged by better uterine health and body condition score, among other factors.
- Cows with longer VWP had delayed time to pregnancy and greater risk of leaving the herd, especially older cows.
- Later VWP extended lactations by an average of 13 days, resulting in greater total lactation milk yield.
Researchers say the data “highlights the importance of considering the complex interactions between reproductive performance, herd exit dynamics and lactation performance” in addition to the effects of age on defining VWP.
Extending the VWP does allow high producing cows more time to complete the lactation. But reproductive management has to be top notch so cows don’t go too long. Timed AI helps reduce this risk, as does activity monitoring.
Monitoring cow movements and activity brings a tremendous amount of data to the dairy. “With more data there is greater confidence in creating pregnancies,” says Steve Pavelski, field training and customer support manager with SCR. “That enables producers to breed cows when it is most profitable to do so, not necessarily based on where she is in her lactation cycle.”
In today’s economy, where every drop of milk means more cash flow, extending the VWP might be a viable option.
“Getting high producing cows pregnant early creates too early of a cut off at the end of lactation,” Pavelski says. “This has an impact on productive life for these cows and this, combined with the loss of profit at the end of lactation are why getting all cows pregnant early can cost dairies money”
Note: This story appeared in the November issue of Dairy Herd Management.
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