4 Precautions to follow after drought and heat

The heat and drought conditions may be waning across parts of the country, but it doesn't mean the impacts won't last.

September 12, 2022

2 Min Read
7-18-22 cows and calves in drought_1.jpg

Although Iowa has had some recent rains and cooler temperatures, producers need to be mindful of the aftermath of heat and drought.

1. Monitor the cow herd for open females.

Heat stress can reduce both semen quality and potential fertility in bulls. Research indicates there is an 8-week lag from the end of heat stress to the return of normal semen production in bulls, and in females heat stress 42 days prior up to 40 days after breeding can affect pregnancy rates. 


2. Analyze the nutritional value of hay to be fed this winter.

As the temperature of the growing environment increases, it has the following overall effects on forage quality: accelerated rate of maturity, increased lignification, decreased leaf:stem ratio, and decreased digestibility. Drought-stressed hay may be deficient in energy, available crude protein and Vitamins A & E. Diets including heat- and drought-stressed hay will require reformulation and supplementation to meet the nutritional requirements of the animal.


3. Test the nitrate level in green-chopped corn and corn silage before feeding.

Because the lower 1/3 of the corn stem is higher in nitrates than the upper stem, raising the cutter bar will reduce the nitrate level in the forage. Research reports that 4-5 weeks of ensiling can reduce the nitrate concentration by ~40 percent. If the nitrate levels are high, dilute the feedstuff with low nitrate feeds and slowly adapt the cattle to the feed. Heavier feedlot cattle, stocker cattle over 700 lb, and open replacement heifers over 700 lb. are usually more tolerant to nitrates.

4. Manage sorghum forages to reduce the potential for prussic acid poisoning.

Death is most common when livestock have eaten sorghum-family plants that are very young, stunted by drought, or frosted. Drought-stricken plants are hazardous because they are mostly leaves which contain higher levels of prussic acid than other plant parts. New shoots are especially poisonous and may appear after drought-stressed plants receive rain. Prussic acid poisoning is greatest in grazed > green-chopped > silage. However, do not feed new silage for at least 8 weeks after harvesting and storage. Graze or green-chop sudangrass only after it is 18 inches tall. Sorghum-sudangrass should be 24-30 inches tall before grazing.

Source: Iowa State University, who is solely responsible for the information provided and is wholly owned by the source. Informa Business Media and all its subsidiaries are not responsible for any of the content contained in this information asset. 


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