The High Fertility Cycle

Posted: 10月 24, 2023

Podcast Topic

Dr. Fricke starts this episode by describing the long-term negative trend for reproductive performance in dairy cows that took place from the mid-1950s to around 2000.

Guests:

Dr. Paul Fricke and PhD Candidate Megan Lauber, the University of Wisconsin-Madison

Episode 88: The High Fertility Cycle

Timestamps:

The reversal of this trend is due to the use of genomics to select for fertility and the use of synchronization and fertility programs in dairy cows. (6:07)

Dr. Fricke explains the high fertility cycle starts with a change in body condition. Observations from the late 1980s and early 1990s showed that cows who calved at a higher body condition and lost condition after calving had worse reproductive performance than cows who calved at a lower body condition and did not lose as much condition after calving. This is known as the Britt Hypothesis. (13:27)

Paul describes studies aimed at finding the mechanism of action for differences in fertility. One study split cows into groups based on performance in a superovulation and embryo flushing protocol. Cows who gained body condition after calving had the best quality embryos, while cows who rapidly lost condition and didn’t gain it back had very poor-quality embryos. (18:50)

In another experiment, cows were body condition scored at calving and 21 days later to measure postpartum condition change. All cows were on a double ovsynch fertility protocol. About 40% of cows lost condition over that time period, 35% maintained condition, and 25% lost condition, but milk production was the same for all. This implies that cows gaining or maintaining condition were eating more feed than those losing condition. Cows who lost condition after calving had a 25% conception rate. Cows who maintained condition had around a 40% conception rate, and cows who gained condition after calving had over 80% conception. These differences were not dependent on the synchronization protocol. (21:18)

Megan said many large farms are starting to body condition score cows at calving and 21-30 days after calving to measure and manage this. She also said cows who lose are less fertile and have a higher pregnancy loss than cows who maintain or gain condition post-calving. In a study where cows who lost three-quarters of a condition score or more from dry off to 30 days in milk had a 25% conception rate, while cows who maintained or gained body condition over that same time period had over 50% conception. (26:24)

One of Megan’s studies found cows bred with sexed semen who were submitted to a double ovsynch fixed-time protocol showed a 6-7% advantage compared to cows submitted to AI after estrus detection. The entire treatment effect was observed in cows who lost the most condition after calving. (33:18)

Paul and Megan encourage dairy producers to body condition score cows at dry off, at freshening, and 21-30 days after that. If cows are losing a large amount of condition, that could be playing a critical role in reproductive performance. In addition, the first test, fat-to-protein ratios, also tells a story about fat mobilization. A cutoff of over 40% might indicate that cows are mobilizing body fat and losing condition rather than going up to the bunk to eat to drive milk production. (40:03)

Megan and Paul said that taking a herd from a low fertility cycle to a high fertility cycle includes an aggressive reproductive management program, evaluating somatic cell count and mastitis to ensure those aren’t impacting fertility, and taking a critical look at the nutrition program, including grouping cows with different rations. (46:54)

Megan’s final thought for the audience is that having cows in the high fertility cycle with aggressive reproductive management to increase our reproductive performance really gives us a lot of power. Managing cow body condition score drives profitability and allows a lot of opportunities. (1:01:05)

Paul concludes that over his 25 years on faculty at Wisconsin, he’s lived through the whole reproduction revolution in the dairy industry. Right now, the high fertility cycle is the big barrier to the performance on dairies, but this is very doable. If you get herds into the high fertility cycle, everything is easier. Cows are healthier. Milk production is great. Reproduction’s good. (1:01:55).

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