It seems counterintuitive that achieving high pregnancy rates could lead to less profit. But that’s exactly the case if high rates of reproductive efficiency are not part of a well-thought out herd management strategy.

Albert De Vries, a University of Florida dairy specialist, set out to determine whether there is an optimal pregnancy rate dairy farms should strive for. “A review of published literature shows that greater pregnancy rates have been associated with greater profitability, but profits are less when pregnancy rates are already high,” he says.

In other words, there is likely a rate of diminishing return as pregnancy rates and reproductive efficiency climbs to higher and higher levels. Plus, improving pregnancy rates usually involve more cost.

In a simulation De Vries ran, moving from a 23% pregnancy rate up to 26% would generate about $35 more profit per milking cow. So if it costs less than $35 to increase the pregnancy rate by three percentage points, the difference would be a net gain. But if it costs more than $35, there would be a net loss.

De Vries also looked at 7,032 herds which participate in DHIA programs with records processed by Dairy Records Management System in Raleigh, N.C. The average herd size was 239 cows, with an average pregnancy rate of 19% and a herd average of 23,239 lb. Eleven percent of the herds, representing 21% of the cows in the study, had a pregnancy rate between 28 and 39%. These farms averaged 425 cows and had herd averages of nearly 26,000 lb.  

“Herds with greater pregnancy rates also had shorter days in milk, longer voluntary wait periods, but shorter days to first service, greater service rates, fewer days open, shorter actual calving intervals and more calves per present cow,” says De Vries. The main factor that drives profitability in these herds is shorter days in milk, which in turn means greater feed efficiency and therefore greater income over feed cost, he says.

Culling rates were the same

But De Vries also noticed an anomaly. Culling rates, at about 37%, were the same between the average and high pregnancy rate herds. So the average pregnancy rate herds weren’t culling fewer cows because they had reproductive failures and fewer heifers and the high pregnancy rates weren’t culling more because they had more heifers.

In the high pregnancy rate herds, this high rate of culling likely increases the genetic merit of the herd. But more first lactation cows with lower milk yield also has a dampening effect on total milk production for the herd.

“With improved reproductive performance, there is a greater potential to generate more dairy heifer calves,” says De Vries. “The benefits of increasing pregnancy rates probably depend on what is being done with the heifer calves.” he says.

A farm could raise all the heifers and increase culling, actually delay breeding or sell surplus heifers. Genomic testing may help in deciding which heifers to sell. Use of sexed semen also might not be profitable when all the heifer calves are raised and brought into the herd because the genetic gain might not offset the higher costs of the semen and increases in cow culling, says De Vries.  

In the end, there might not be one optimal pregnancy rate to strive for, and it likely varies by herd and the decisions each herd makes regarding surplus heifer calves, he says. 

Note: This story appears in the February 2017 issue of Dairy Herd Management.