The William H. Miner

Agricultural Research Institute

Miner Institute
Farm Report

FACTORS AFFECTING FERTILITY IN DAIRY HEIFERS

Last fall, I was speaking to a dairy group in Oneida County about dairy reproduction and reproductive issues on their farms. One attendee asked me about issues he was having with poor conception rates (CR) in his heifers. He recognized that of all the animals on his farm, his breeding age heifers should be the most fertile. He indicated that he didn’t want a lecture about heat detection because he didn’t feel that was the problem. He wondered what his expectations should be in terms of their fertility. While little research has been done to establish benchmarks for heifer fertility, the Animal Improvement Programs Laboratory at USDA in Beltsville, MD, summarized records from 537,938 breedings of 362,512 heifers in 2,668 herds from 41 states between 2003 and 2005 and found the overall mean CR for US Holstein heifers was 57% (Kuhn et al., 2006). Approximately 88% of US herds had heifer CR ranging from 40 to 70%.

Ten years ago, Dr. Phil Senger gave a presentation at the 2003 Western Dairy Management Conference, entitled, Fertility Factors - Which ones are really important? He organized Fertility Factors, as they pertain primarily to mature cows, in three categories:
1. Controlled by man
2. Controlled by the reproductive system of the cow
3. Natural to any herd or cow
The point he made was to focus our efforts on those factors we can control through our actions and decision-making. I think he provides a great footprint for evaluating the Fertility Factors that impact reproductive performance of dairy heifers. Below, I have summarized and modified the Fertility Factors controlled by man outlined by Dr. Senger, and estimated some of the expected ranges for dairy heifers.

Heat Detection Efficiency
This factor is defined as the percentage of cows displaying estrus that are identified as being in heat. We can assume that all post-pubertal heifers should be cycling normally and our heat detection efficiency should be at least 10% higher than for the cows in our herds. Often times, the location of the heifers, away from hubbub of the main farm operation, results in limited time spent watching for heat activity. When someone only passes through once a day for feeding and cleaning, there may not be much opportunity to see heifers actually exhibiting signs of estrus unless someone is dedicated to watching for heat activity on a daily basis. For most herds, improvement in heat detection efficiency will impact overall reproductive performance of their heifers. However, in the situation of the Oneida County producer, he indicated that heat detection was not the issue…strong heats were observed and heifers often did not conceive when bred.

Heat Detection Errors
Estrus detection errors are defined as the proportion of the cows that are inseminated that are not in estrus. Studies have shown that between 5-30% of all inseminations take place in cows that are not in heat and I assume the same errors apply to inseminations in heifers. Poor heifer identification because of overcrowding and dim lighting in a rambunctious pen of heifers can contribute to this error. Also, financial incentives for workers to submit heifers for insemination may promote errors.

Skill of the Inseminator
Many evaluators of reproductive programs assume that anyone trained in AI can do so with a high degree of success. Research conducted years ago by Ed Graham at the University of Minnesota found the skill of the artificial inseminator is a significant factor in influencing fertility in dairy cows. Even trained AI technicians have varying degrees of accuracy when it comes to semen placement in the reproductive tract. It only makes sense that heifers require even more skill to carefully thread the breeding pipette through a much narrower cervix and deposit it in the body of the uterus. Research conducted by Senger’s group found that conception rates in cows were reduced if semen is deposited in the cervix rather than the uterus, with no difference in conception rates between deposition of semen in the uterine body vs. uterine horns. With little research on heifers, we can assume conception rates in heifers is impacted similarly if not more than cows.

An important factor that can influence the skill of the inseminator that should not be overlooked is the environment we expect heifers to be bred. Many times, AI technicians are left on their own to venture into overcrowded heifer pens, with no system to restrain animals, and expect the heifers to be run into a stall to be bred. Any of you who have been put into this situation know that accuracy of semen placement is the last thing on your mind. I have had some professional inseminators admit that sometimes when a situation is too dangerous, they cut their losses and deposit semen as quickly as possible (intravaginally…on the floor even) being concerned about getting hurt. While I don’t condone this action, I can understand it when their livelihood depends on them being mobile with two functioning arms. Communication between the AI technician and the producer is warranted to ensure the safety of the breeder and subsequently improve the fertility of the heifers.

While there are other Fertility Factors listed we can consider when breeding heifers, the Oneida County producer seemed to pause when the skill of the inseminator was discussed. I explained that I’ve known quite a few inseminators that get great CR when breeding cows but fall short when it comes to breeding heifers. Whether it’s lack of accuracy or the breeding environment we put them in, I think the skill of the inseminator probably has one of the biggest impacts on heifer fertility. While it is something that is difficult to measure, it should be considered when trying to improve fertility of heifers.

— Katie Ballard

* References available upon request.

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The Miner Institute Farm Report is written primarily for farmers and other agricultural professionals in the Northeastern U.S. and Eastern Canada. Most articles deal with dairy and crops topics, but also included are articles dealing with environmental issues and global agriculture as well as editorial commentary.

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