Mother Nature dictates how we farm. The problem, of course, is that we can’t predict the fickle nuances of rain events or droughts. As such, we play the odds and hope to roll sevens instead of snake eyes.

The toxicity of Kentucky 31 tall fescue has been well documented. We know that the levels of ergovaline are somewhat cyclical throughout the growing season, being highest around seedhead emergence in May and June. The toxicity declines, but doesn’t disappear, as pastures become vegetative during summer and fall.

Thanks to Mother Nature, we are learning that fescue toxicity levels can be altered by changing weather conditions. One example of this was highlighted in a recent article written by the University of Kentucky’s Ray Smith and Krista Lea.

“We normally aren’t concerned about toxicity in tall fescue during the fall, and this is part of the reason that fall calving has been encouraged in the region,” the extension specialists explain. “The lower ergovaline levels in the fall result in good milk production for fall calves and fewer rebreeding issues than with spring-calving herds, which are being bred during the very toxic late spring period.”

Not always safe

In recent years, late summers and early falls have been characterized by dry conditions in Kentucky and some other Fescue Belt states, which made fall stockpiling difficult because pastures were moisture stressed.

Once more frequent rain events resumed, tall fescue began to grow. Unfortunately, the new growth after these periods of drought stress was documented as having abnormally high levels of ergovaline, and this was causing significant reproductive problems on some farms. These were documented in the article as follows:

• One producer was breeding his herd in late October to early November and had zero conception rate on cows with a long history of great conception. He also had 30% of his herd get tender feet during this period, and he treated for foot rot, even though it did not appear to be foot rot.

• A producer had a few abortions during the late-fall period on his January-calving cows. His cows’ feet were also tender.

• In Virginia, there was a major drought. About mid-August, it started to rain, and the stockpiled tall fescue was abundant. Later that fall, many cows exhibited fescue-related issues, including little or no milk and thickened placentas. The problems were the worst on farms that were practicing good grazing management and had good soil fertility. They were creating an environment in which fescue thrived.

• One farm had less than 15% success with embryo transfers on a herd of over 20 cows. Bulls accomplished a better conception during the next cycle, but there were still some cows that conceived late.

• A producer had a herd of 35 cows, which were bred artificially with timed insemination. He had eight out of the 35 cows conceive. The clean-up bull did get pregnancies, but still with disappointing results.

• Two other herds that do a lot of embryo work also reported poor reproductive results. On the flip side, a herd on novel-endophyte fescue had three out of three embryo recipients conceive and carry the pregnancy, and eight out of 11 cows conceived using timed A.I.

The common denominator in all these cases was drought followed by rain. Apparently, the stress of drought raised the plant’s ergovaline levels beyond what is “normal.”

What can be done to counter this effect?

The Kentucky specialists suggest that if you are currently seeing issues or have in the past few years, you can take cows off predominantly tall fescue pastures in the fall. Animals can return to these pastures once a couple of hard freeze periods have occurred.

Legumes, especially red clover, help alleviate fescue toxicity, so feeding hay containing red clover can be beneficial. An alternative is feeding soybeans at a rate of 2 pounds per head per day or soy hulls at 5 pounds per head per day.

If a novel-endophyte tall fescue field is available, let cows graze these fields before, during, and just after the breeding season. You can also test for ergovaline levels by submitting fall fescue samples to a testing lab.