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Boost herd fertility with high fertility cycle practices

Bev Berens for Progressive Dairy Published on 08 December 2020

Is the modern dairy cow less fertile than 20, 30 and 40 years ago? Some would say, yes.

However, reproductive specialists Dr. Richard Pursley, Michigan State University, Dr. Paul Fricke and Dr. Milo Wiltbank, University of Wisconsin – Madison, have conducted research showing that fertility hasn’t been lost but rather modern dairy production with demands for high milk output places the cow at a reproductive disadvantage. Regaining a powerful fertility rate on the farm is achievable when a set of complex relationships between milk production, hormone metabolization and insemination timing are well tuned.

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Like most relationships, it’s complicated, but when the system comes together into harmonious rhythm, the result can be a profit boost. In fact, according to Pursley, increasing first service conception rates by 20 percentage points can increase profits by $65,000 per year on a 500-cow Michigan dairy.

The ever-evolving science of reproduction continuously uncovers new information that requires both a change of mindset and plan of attack on the farm. In this case, the trio urge producers to rethink three concepts to help move a herd into the high fertility cycle: Body condition score (BCS), combining timed A.I. with heat detection devices and reducing the number of twins born on the farm.

1. Maintain body condition score at 2.8

End of lactation and dry period are traditionally a time of increasing BCS to a calving time score of 3 or better, with the understanding that extra condition will be milked off during the first 30-60 days in milk (DIM).

However, research done by Dr. Jack Britt, and replicated by both Fricke and Pursley, leads to a paradigm shift that maintaining a lower BCS throughout lactation and the dry period benefits embryo quality, reproductive outcomes and overall cow health. Cows that maintained or gained BCS after calving had greater conception rates, less pregnancy loss and were healthier than cows losing BCS postpartum.

In the studies, conception rate at first service was 25% for cows that lost BCS and 62% for those that maintained. Percentages for all services was 42% for the losers and 61% for the maintainers. Cows that maintained BCS lost a pregnancy at a rate of 7.1%, while both groups of BCS gainers and losers lost pregnancies at 14.3%. Metritis, mastitis, ketosis and pneumonia incidents were all down significantly in groups that maintained or gained BCS. More than 60% of BCS gainers experienced less than one health event post-calving.

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Surprisingly, milk production during early lactation was not affected by BCS change during the first three weeks postpartum; however, peak milk measured near 60 DIM was less in both heifers and cows that either gained or maintained compared to cows that lost body condition during the first 30 DIM. The 305-day record shows 18,198 pounds of milk yield for those that lost BCS in early lactation, and 17,941 pounds for the BCS early gainers.

The studies show a clear relationship of increased fertility between getting cows pregnant quickly after the voluntary waiting period and calving at a lower BCS. A change in late lactation and dry cow nutrition may be necessary to prevent too much weight gain leading into parturition and lactation. BCS should be closely monitored in transition cows at three weeks pre-calving, at calving and at three weeks post-calving.

2. Combine fertility programs with observed heat detection

There is a myth that natural breeding leads to the highest fertility. In reality, the high-producing dairy cow is metabolizing hormones quickly. Her body is diluting them to a level that alters her ability to become pregnant and maintain the pregnancy and has little to do with service delivery.

Fifteen to 20% of cows ovulate but show no signs of heat; others may have a standing time as short as one or two hours. Estradiol is being metabolized but not in enough concentration to trigger the hypothalamus to produce standing heat.

The introduction of fertility management programs brought about technology to adjust hormone levels in the high-producing cow to the degree that can bring a cow into heat and ready her body for pregnancy.

Twenty years ago, the 21-day pregnancy rate in the average U.S. dairy herd hovered at 14%. Most herds were barely able to achieve a 20% goal and rarely exceeded 40%. The onset of fertility programs such as Double-Ovsynch or G6G used for timed A.I. increased both A.I. service rates and pregnancies per A.I. The current average 21-day pregnancy rate in the U.S. is above 20%. More than 60% of Dairy Records Management Systems Holstein herds exceed 50% conception rates, thanks to breeding synchronization and fertility management programs.

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There is no doubt that complex programs requiring multiple treatments over several days can present issues in labor, cost, protocol management and extra documentation. But, there are many fertility programs to fit a variety of needs and circumstances. Heat detection devices like tail markers should be included as part of a complete system.

Fricke advises to establish and keep a hard rule regarding the number of breeding opportunities any cow in the herd receives, culling after hitting the magic number of failed opportunities.

3. Reduce number of twinnings

A second myth is that fertility programs are at fault for an increase in twinnings. However, the high-producing cow, generally milking 90-100 pounds per day, will naturally have a low progesterone level, as does an older cow. Because progesterone is so low, a second follicle often matures, resulting in two fertilizations from a breeding and a set of fraternal twins.

Hormonal manipulation of cows to increase progesterone during development of the ovulatory follicle results in fewer double ovulations. The Double Ovsynch program presynchronizes cows to maximize progesterone while the ovulatory follicle grows, decreasing double ovulation rates and subsequent twinning.

No fertility management program is perfect, but even without considering an altered BCS, the results are an average 52% conception rate.

Based on research, there is a defined connection in BCS, fertility and twinning. Every farm strives to achieve cow pregnancy as quickly as possible after the voluntary waiting period.

Getting and keeping cows in a cycle of high fertility is achievable. Cows that maintain or gain BCS after calving have greater fertility than cows that lose BCS, a paradigm shift worth consideration. An increase in reproductive performance and a decreased number of maternal twin births is achievable using fertility programs. Managed together, reproductive goals can be achieved and results multiplied over time.  end mark

Bev Berens is a freelance writer in Holland, Michigan. 

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