Each dairy operation has its own set of unique challenges, but most dairy producers have a common concern: reproduction. When cows don’t maintain healthy pregnancies, money spent on animal health products, veterinarian visits and artificial insemination (A.I.) is wasted.

In fact, the U.S. dairy industry as a whole is struggling with the issue of reproduction. In the last 50 years, pregnancy rates in the United States have steadily declined. The causes of poor fertility and poor conception rates are complex, making them difficult to identify and solve.

Why aren’t cows getting pregnant?
There are several reasons dairy cows experience reproductive problems, including:

Fetal loss – Dairy producers are seeing a trend of increased levels of fetal losses between the first pregnancy check conducted between 28 and 40 days of gestation and the second pregnancy check, conducted between 60 and 100 days of gestation. Factors leading to fetal loss include:

•transition cow issues (i.e., retained placenta, DAs, ketosis, acute metritis)
•subclinical endometritis
•poor body condition or extreme loss of body condition
•heat stress
•clinical and subclinical mastitis

Poor or inefficient heat detection – Dairy cattle are traditionally inseminated after the first estrus detection. However, the U.S. average rate of heat detection is only 40 to 50 percent. Thus, in many cases, inseminations may not be timed properly.

Environmental challenges – There are also unmistakable environmental reasons that cows don’t get pregnant. For example, animals suffering heat stress often produce poor quality embryos, making it difficult for that animal to conceive and resulting in less-viable pregnancies. Other factors impacting fertility and pregnancy include poor nutrition, body condition score (BCS) and the age of the cow.

Cow health events – Events that compromise the overall health of the cow, such as mastitis and retained placenta, can also impact fertility. Cows with clinical mastitis during the first 45 days of gestation are 2.7 times more likely to abort pregnancies in the first 90 days after insemination. Cows that experience retained placenta typically experience conception rates one-half that of normal cows, also making subsequent breedings less likely to result in a pregnancy. Clearly, healthy cows have healthy fertility and conception rates, resulting in robust pregnancies.

Anovular cows – Approximately 25 percent of U.S. dairy cows are anovular at the end of the voluntary waiting period (50 to 70 days in milk). Anovular cows can have a significant impact on heat detection rates, conception rates and timed insemination programs. Research has evaluated the value of progesterone supplementation during programs like Ovsynch™. In those studies, progesterone seemed to provide a beneficial boost to pregnancy rates of anovular cows submitted to a timed insemination program.

It is important, nonetheless, to reduce the incidence of anovular cows as much as possible. A well-managed transition cow period, coupled with a well-balanced ration, is the best way to avoid anovular cows.

What can producers do?
With such a varied list of factors impacting fertility, what can producers do to manage the reproductive health of their herd? There are several measures that producers can take that will improve reproduction in healthy cows.

By working with a veterinarian to incorporate the best management practices that ensure the overall health of fresh cows – including a comprehensive vaccination program, fresh cow management and sound nutrition – producers can best prepare their cows for favorable reproductive outcomes and improve conception rates. Synchronization and resynchronization programs can also improve conception rates.

Synchronization
In the case of undetected or poorly detected estrus, producers benefit greatly from using a timed insemination program. Current research clearly indicates that well-managed, presynchronized Ovsynch yields the best results. However, the key to a successful reproductive management program is compliance to that protocol. Dairy producers are encouraged to work with veterinarians to develop a program that best fits the dairy’s management capabilities.

Resynchronization
The longer a cow is open, the less milk she is likely to produce. The goal is to have cows conceive as quickly as possible after the end of the voluntary waiting period. That will shorten the number of days she’s open and not contributing optimally to the milk supply. The vast majority of cows bred in a dairy are cows that failed to conceive after first service. Thus, it becomes imperative to conduct regular pregnancy diagnostics so that open cows can be identified as soon as possible and be re-synchronized. The same rule applies to re-checking cows found pregnant at the first pregnancy diagnosis. As discussed above, a significant percentage of cows can suffer embryonic loss or abortion, especially before 40 days of gestation.

Because heat detection is a challenge on most dairies, more producers are choosing to enroll open cows into a timed insemination program. This way, producers can assure that open cows will be re-inseminated nine to 10 days after the pregnancy check.

Conclusion
Reproduction problems on the dairy farm are challenging because the causes can be so varied and complex. But through good management of a cow’s environment and health, compliance with your reproductive program, more accurate timing of insemination and by working with your veterinarian to monitor pregnancy status, producers can minimize the negative effects of reproductive inefficiency. PD

References omitted but are available upon request at editor@progressivedairy.com

—Excerpts from Pfizer Animal Health Dairy Wellness Journal, Vol. 2, No. 1