Hot temperatures are a reminder of the need to prepare cattle for heat stress events this summer. Some cows still hadn’t slicked off their haircoat in June before they were turned out to graze on grass due to the cool spring and may take a little longer to adapt to heat. Also, keep in mind that fertility can be affected in cows and bulls during heat events, so a little prevention can help ensure a successful breeding season.
Grant Dewell, Iowa State University Extension beef veterinarian, provides the following recommendations and precautions for cattle producers. “Grazing cattle should have access to cool clean drinking water and shade during the summer,” he notes. “Automatic waterers used in winter that are designed not to freeze may have a hard time supplying the quantity of water needed when it gets really hot.”
Surface water such as ponds can become stagnant and contaminated with feces if cows are allowed to stand in the water to cool off, says Dewell. Although cows can survive drinking this water and will not become dehydrated, they will not want to consume adequate amounts to deal with heat stress and maintain high reproductive performance.
Shade is critical to keep cows cool
Trees, shade structures or a building can provide adequate shade during the heat of the day. “Be careful of old buildings that do not have adequate ventilation,” he cautions.
High temperatures can affect grazing behavior and rotational grazing systems may need to be adjusted. It is also important to institute a good fly control program. Fly tags generally provide good control but consider some supplemental oilers, dusters or spraying to keep cows from congregating from excessive fly pressure.
Feedlot cattle are generally more susceptible to heat stress because of fat cover. “With the recent disruption in marketing finished cattle, many feedlots may be feeding calves longer and to heavier weights than typical,” says Dewell. “These cattle will need some extra precautions to minimize the risk of heat stress.”
Adjusting the feed ration can help
Also, remember that these heavy cattle are more susceptible to AIP (acute interstitial pneumonia) and fatigued cattle syndrome. Increasing the roughage and feeding 60% to 75% of the ration in the afternoon feeding can spread the heat load from rumen fermentation into the evening cooler temperatures. In extreme heat events sprinklers can be used to help cool the ground surface and the cattle to prevent death loss.
To reduce damage caused by heat stress, feedlots need to monitor environmental temperatures throughout the summer. When the heat index is above 90° F, cattle will be under heat stress. In addition, hot weather following a rain can dramatically increase the potential for a heat event. If overnight temperatures are above 70° F cattle will have increased heat stress because of a retained heat load. During times of increased heat stress, cattle should be observed closely to identify if additional strategies need to be used. For best results, feedlot managers need to monitor for heat stress and implement strategies to minimize impact on cattle to prevent death from heat stress.
More detailed information is available at https://store.extension.iastate.edu/Product/Heat-Stress-in-Beef-Cattle.