Dr. Julio Giordano at Cornell University led a project to determine the days in milk at which first breeding offers the best chance for profitability. The two-part study coupled on-farm research with economic analysis, comparing a 60-day VWP versus 88-day VWP using 100 percent timed artificial insemination (A.I.).
From the standpoint of fertility and reproductive health, increasing the days from calving to first service offered advantages for some cows, but not for others. Giordano shared that extending the VWP from 60 to 88 days resulted in more cyclic cows before synchronization, along with less uterine disease and more cows with body condition scores at or greater than 2.75 at the time of insemination.
The group most positively impacted by the change was first-lactation cows, which tended to show a greater rate of pregnancies per A.I. at the first service in response to the additional days in milk before breeding. According to Giordano, conception rates were 9 percentage points higher for the first-lactation cows given 88 days versus their herdmates with a 60-day VWP. However, a less significant response was observed in second-lactation and greater cows (a difference of only about 3.5 percentage points).
Impact of VWP on cash flow
An economic analysis conducted in Giordano’s lab put a dollar figure to the difference that 28 days can make. The cash flow prediction at 18 months after calving accounted for six factors: income over feed cost (IOFC), reproductive-related cost, calf value, replacement cost, operating cost and rbST (which was more widely used at the time of data collection).
For 2-year-old cows, the 88-day VWP yielded $68 more than the 60-day VWP. “The main difference was the replacement cost,” Giordano explains. “Mostly because of greater replacement costs in the subsequent lactation. We have a few more of these first-lactation cows that left early in the subsequent lactation, and we’re still trying to figure out the reasons why.”
For those older cows, economics backed up the advantages of a 60-day VWP, with a benefit of $85 per 18 months. Two main factors strongly influenced these results. “There is an effect on IOFC [$39], and there was also a difference in replacement costs [$49]. In this case, it was mostly because more cows were leaving during the lactation in which we extended the VWP,” he adds.
In many herds, older, open cows 150 to 200 days in milk are more likely to be culled, particularly when heifer inventories are high. “That has a cost,” Giordano reinforces. “Any time the cash cost for replacing an animal is negative – it’s more expensive to bring in a new animal than to keep the one you have – you have that effect.”
The analysis also considered various changes in economic conditions, yet results did not waver. “First-lactation cows always benefited by extending the VWP; lactation two and greater always benefited by keeping the VWP at 60 days,” Giordano says. “And replacement costs explain more than 90 percent of the total variation. That’s why it’s so important to account for the replacement costs.”
Further, when the economic value of pregnancy was compared only for cows that became pregnant after the first breeding, the value of settling from an 88-day first service was $138 greater than at 60 days for first-lactation heifers, and the older cows profited $114 more when they became pregnant from the first breeding 60 days after calving rather than 88 days. However, Giordano notes substantial variation in profitability based on days in milk to pregnancy.
On-farm application
These findings provide the basis for making adjustments to the VWP at the farm level.
“I think we have enough evidence to say we can think about starting to split VWP based on lactation, with a slight extension for first-lactation cows,” Giordano concludes. 
Dr. Julio Giordano presented during the 2018 Vita Plus Dairy Summit, Dec. 4-6, in Red Wing, Minnesota.
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Peggy Coffeen
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