Vet’s perspective: Managing cattle through heat and drought

Aug 12, 2011
by WLJ

Managing cattle through heat and drought

This summer’s heat and dry weather throughout the western states has presented an added challenge to producers in the region. According to the National Weather Service, more than 1,000 heat records have been set or tied during the month of July throughout the nation. Cattle sales have been primarily drought-driven this year; with commercial cow slaughter suspected to be higher than last year’s top numbers. The reduction in forage supply and pasture growth has significantly increased auction sales as well.

First and foremost, cattle daily water requirements are increased during warm weather and dry forage seasons. According to Glenn Selk, Extension animal scientist with Oklahoma State University, typical requirements for beef animals that are not lactating are between 0.75 to 1.5 gallons of water per 100 pounds of body weight. This number usually equates to approximately 10 percent of the animal’s body weight. Cows in lactation have significantly higher needs, at approximately 18 percent of their body weight.

If possible, shades and sprinkler systems should be in place to aid animal cooling. Efforts should be made to feed supplemental forage and grain during the cooler times of day, such as early morning or evening. This allows cattle to metabolize additional feed without generating an excess of heat during the natural intestinal fermentation process. It is important to remember that cows can’t pant to release heat as many other species are capable of!

Another concern for cattle living on pasture lands is the growth of weeds that are typically more drought-resistant due to their ability to compete and proliferate amongst the desirable forage grasses. Toxic plants tend to be unpalatable and, thus, animals will not ingest them when pasture growth is adequate. When cattle are faced with the option of eating these normally inedible varieties, toxic insult—or death—can be a probable result. Managers should become familiar with toxic plant species in their region, and recognize the need for pasture rotation or supplementation as needed.

Supplementing cattle during drought involves providing additional feed to ensure adequate energy, protein, vitamins, and minerals. Energy supplements should be highly digestible to cattle; grain can be added at a rate of 0.2 percent of an animal’s body weight. Avoid grains that are very finely ground as they create dusty conditions and decrease palat ability,as well as increase risk of acidosis and founder in the herd.

Dormant pastures are often especially lacking in vitamin A, protein and phosphorus content. During periods of drought, it is not uncommon to see producers selling more cattle to reduce the amount of mouths to feed, or to rent additional land for grazing. Reducing the stocking rate in pastures will allow plants to re-grow with less stress placed on them by overgrazing.

Vitamin A deficiencies are seen often during fall and winter after cattle have grazed drought-stricken pastures during the warm season. A multivitamin injection is a good preventative measure for cows 30 days before calving; boosters of vitamins A and D may be given to calves at birth as well.

Mineral and salt supplements are critical during warm months; phosphorus content is very important during drought seasons. This can usually be fulfilled by feeding a 50 percent combination of trace salt and 50 percent dicalcium phosphate free choice to the herd. Always have water available and close to mineral feed stations. Cattle will often consume up to 0.1 percent of their body weight in salt, and this intake should encourage cattle to drink more water as well.

Protein deficiencies may arise due to dormant pasture, resulting in poor body condition and decreased reproductive parameters such as conception rates. Cows in lactation should be supplemented with 1 to 1.2 pounds of additional crude protein as soybean meal, alfalfa hay, or various other protein meal formulations such as grain processing by-products like beet pulp, soyhulls or corn gluten feed.

Managers can help get cattle eating and reduce performance losses by ensuring enough water space per head is in place on farms (approximately 2 inches per head according to a study by Great Plains Livestock Consulting, Inc.), as well as keeping water sources clean and free of stagnant water. Drinking water sources should be checked for growth of blue-green algae—a potential toxin when consumed in varying amounts.

Daily monitoring of herds is critical to success in preventing a deadly heatstroke.

Look for weak and dehydrated animals when making rounds during feeding time. Any acute reduction in weight gain or production should raise a red flag of heat stress. — Dr. Genevieve Grammer [Dr. Genevieve Grammer is a mixed-species veterinarian practicing in eastern Colorado. Please direct correspondence to drgigi19@].