Get ready for more open cows

By Les Anderson

Show, it’s been a tough summer. Along with high fuel costs, current inflation and high input costs, beef producers have had to contend with drought and extreme heat. Heat stress is normal for cattle in Kentucky because most of our cattle graze endophyte-infected fescue, but an early start this summer can cause some serious problems with pregnancy rates and calving rates.

Heat stress has profound effects on many biological processes that can lead to reduced fertility. Pre-estrus heat stress reduces follicle growth, hormone production and oocyte or egg viability. Together, this reduces fertilization rates. After fertilization, heat stress also reduces the growth of the newly formed embryo. This reduction in embryo growth is likely the result of increased cell death or a smaller corpus luteum producing less progesterone. This reduced growth rate and increased embryonic cell death result in more embryos being lost during the first week of pregnancy. Unfortunately, heat stress continues to affect embryo growth during the first 21 days, increasing the loss of these early pregnancies.

Heat stress problems persist throughout pregnancy. Heat stress in early pregnancies reduces fetal growth and may result in the loss of up to 20% of these pregnancies. Heat stress reduces placental efficiency, meaning the placenta’s ability to deliver nutrients to the developing fetus. Extreme heat stress towards the end of pregnancy can affect placental hormone production, which can cause not only premature birth, but also a sharp decrease in mammary gland development, affecting lactation. Thus, heat stress affects beef females from the beginning to the end of pregnancy. ugh.

What does this mean for beef producers right now? First of all, pregnancy must be diagnosed in your herd. Contact your herd veterinarian to schedule a palpation or ultrasound. Pregnancy can also be diagnosed by taking a blood sample or sending the samples to a diagnostic laboratory or using a new blood test kit from IDEXX called Alertys (they are available at most veterinary supply companies). Blood tests are accurate, but a consultation with your herd veterinarian is always recommended.

Pregnancy rates can drop to 50-60% when prolonged heat stress occurs during the breeding season. What options does a grower have if a breeding disaster occurs? If you have calving season or year-round calves, the decision to keep or cull females is a little easier. Simply move cows under 5 to the next breeding season. If cows only calve in the spring, the decision is more difficult. Heifer prices are high right now, and many market analysts suggest that heifer prices could remain high this fall. If the cost of replacing breeding stock remains reasonable, the optimal decision would be to cull and replace for this year.

The decision to cull cows that have been open for many years is not an easy one. Some would argue to cull all females that cannot conceive in their environment because their genetics do not match the environment or level of management. But the genetics for reproduction are less heritable, so genetics contributes little to reproductive failure. Also, if you only experience drought and extreme heat stress once every 5-10 years, should you penalize a cow whose genetics fit the environment most of the time? To further complicate the decision, cull cows are often replaced with two-year-old bred cows, which are inherently reproductively inefficient, will require additional feed inputs, and may take two years to reach optimal performance. In the long run, what really costs more? It’s an interesting problem to think about, and certainly not a one-size-fits-all answer for all manufacturers.

Markets and where we are in the cattle marketing cycle should influence the decision. Cow numbers are extremely low in the US right now, which usually results in high prices. A few years ago I received some incredible advice from an experienced beef producer. He had managed more than 1,000 cows over the decades and his strategy was when prices were high, own as many cows as you could and sell as many calves as you could. Extend the calving season if necessary because every calf sold was profitable. This producer didn’t really care about keeping women open. But when prices were low, he strictly controlled the calving season and culled cows that did not produce calves. This producer’s philosophy was to be efficient when times were lean and productive when times were good. Good advice. We seem to be in great shape in the cow season with low numbers and expected higher feeder calf prices. It may be time to store as many as you can afford to prepare you to take advantage of higher cattle prices on the horizon.

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