Dairy farmers could lower costs associated with heifer rearing by making improvements in their herd reproductive management, based on research being conducted by Ph.D. candidate Magdalena Masello and Cornell University’s Dairy Cattle Biology and Management Laboratory.

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Tamara Scully, a freelance writer based in northwestern New Jersey, specializes in agricultural a...

Julio Giordano, of Cornell’s Department of Animal Science, presented an overview of the research at the Summer Dairy Research Update session held across New York.

Various parameters are used to measure reproductive success on the dairy. Although the 21-day pregnancy rate “is the one that everyone talks about,” Giordano said, it’s actually service rate that has shown to be a primary concern on many farms.

The 21-day service rate is indicative of “how fast you are breeding heifers once eligible,” he said, and represents the percentage of eligible heifers that actually get bred in that time period. “If you don’t breed them, they won’t get pregnant.”

Common sense says breeding heifers should be more successful than breeding mature cows. Data indicates, however, the heifer pregnancy rate is only slightly higher than that of second- or higher-lactation cows – 23 percent versus 21 percent – on many dairy farms, indicating they simply aren’t paying close enough attention to the heifers.


From a biological perspective, “It doesn’t make any sense. It should be much better,” Giordano said. “[Heifers] show really great heats,” and they show heat longer than do cows. Most heifer herds will do very well with a lot of heat detection,” Giordano said. “But timed A.I. can help” to enhance breeding success among this group.

Reproductive studies

Giordano’s research team studied three commercial dairy farms in New York, employing three different reproduction management strategies on each of the farms in the study. Giordano shared results from this research, which was supported by a grant from the New York Farm Viability Institute.

For the study, all heifers at each farm were enrolled at 12 months old between November 2015 and February 2016. Heifers were kept in the same pen. In all instances, sexed semen was utilized for the first service and conventional semen for the second and subsequent inseminations.

A low-intensity strategy involved up to three prostaglandin F2-alpha injection (PGF-2) treatments every 14 days and estrus detection plus A.I. (EDAI) for the first service. This method relied primarily on the detection of estrus for first service.

The high-intensity program utilized 100 percent timed A.I. with the five-day Cosynch plus progesterone protocol, the most expensive and most labor-intensive approach. A mid-level strategy used Presynch (two PGF-2 treatments given 14 days apart with insemination only after the second PGF-2 treatment) and EDAI, plus the 5-day Cosynch protocol for heifers not detected in estrus within nine days of Presynch.

All three programs shared the same second-service approach that combined EDAI and five-day Cosynch for heifers not re-inseminated within 28 to 34 days after their previous A.I.

“We wanted to make sure we did something with the heifers that were open,” Giordano said, “as most studies do not do so.”

He shared data from three of the farms, comparing two farms with very effective heat detection programs and one with very poor heat detection. On Farm A and Farm B, both with good estrus detection, the low-intensity program resulted in 99 percent of the eligible heifers being bred.

On the farm with very poor detection, Farm C, that rate dropped to 53 percent. With good heat detection, 78 percent of the heifers were bred after the first PGF-2 treatment, compared to a mere 18 percent on Farm C.

“Can we breed heifers in heat only? Absolutely,” Giordano stated.

When the mid-level strategy was employed, the farms with good heat detection demonstrated 81 percent insemination, compared to a low of 21 percent for Farm C. Last, all farms employed the high-intensity timed-A.I. approach with all heifers being bred.

On Farm C, the days to pregnancy with the low-intensity PGF-2 and EDAI protocol averaged 45 days, while the high-intensity timed-A.I. approach had a 24-day average, and the mid-level strategy resulted in 23 days to pregnancy.

For the other farms, all three strategies resulted in more consistent days to pregnancy across all approaches, with the low-intensity program at 26 days, mid-level at 22 days and 100 percent timed A.I. at 21 days.

“One hundred percent timed A.I. got heifers pregnant faster,” Giordano said. But on Farm A and Farm B, there is only a slight statistical difference between the three reproductive strategies. On Farm C, however, “the differences are substantial. Farms like this truly benefit from a more proactive timed-A.I. program to reduce days to pregnancy.”

Economics and heifer reproduction

The economic data is still being tabulated, as some enrolled heifers have not finished the lactation part of the experiment. Researchers will be accounting for all feed costs, milk production, fixed costs, treatments, pregnancy checks and any calves born or animals sold for beef during the study. On all three farms in the project, the average age at calving was 21.9 months.

While Farm C’s data is still being tabulated, the economic data on Farm A and Farm B indicate the profitability for all heifers is highest when using the mid-level reproductive strategy of Presynch and timed A.I.

The high-intensity strategy of 100 percent timed A.I. increased the cost of reproduction on the farms with good heat detection slightly but was also economically superior to the least intensive strategy, which relied primarily on EDAI.

“There are many different ways to get you to successful reproduction. One of the critical aspects to consider is the possibility of running an effective heat detection program in combination with timed A.I.,” Giordano said. The key is “to implement a program that is consistent and proactive to reduce time to pregnancy while adapting to farm-specific conditions.”

The low-cost, low-intensity PGF-2 plus EDAI was very successful on farms with strong heat detection, but it did result in more heifer-rearing days and delayed initiation of lactation.

“Regardless of the treatment, there is tremendous difference between getting heifers pregnant immediately after they become eligible” or not, Giordano said. “More rearing days equals more fixed costs and fewer days in first lactation per unit of time. A heifer which joins the lactating herd earlier will generate a great amount of revenue that one calving later will not.”  end mark

PHOTO: Cattle at the feed bunk. Staff photo.

Tamara Scully, a freelance writer based in northwestern New Jersey, specializes in agricultural and food system topics.


  • Service rate – A measure of the proportion of eligible heifers serviced during a given 21-day period. Each individual, non-pregnant heifer should exhibit estrus during a 21-day period. In ideal conditions, producers should aim for more than 90 percent of heifers in estrus in a 45-day period.

  • Conception rate – In order to achieve a high conception rate, heifers will need to be at the proper bodyweight and adequate body condition at the time of breeding. Producers should expect a high conception rate with a natural, standing heat compared to a timed-A.I. program. Heifer raisers should aim toward a conception rate goal of 60 percent or greater.

  • Pregnancy rate – The rate at which heifers become pregnant after reaching puberty. Pregnancy rate = service rate x conception rate. Thus, maximizing the conception rate (as well as service rate) provides an opportunity for producers to take control of reproduction and overall profitability in their heifer reproduction program.

—Source: Dairy Cattle Reproduction Council