Dr. Grant Dwell, DVM
Associate Professor
Vet Diagnostic & Production Animal Medicine
gdewell@iastate.edu
Recent hot temperatures brings the reminder to prepare for some heat stress events this summer. Some cows still hadn’t slicked off before grass turn out due to the cool spring and may take a little longer to adapt to heat. Fertility can be affected in cows and bulls during heat events so a little prevention can help ensure a successful breeding season. During heat events bulls can become less active breeding and cows may not have as strong of heats. Younger calves can become dehydrated quickly during excessive heat conditions.
Grazing cattle should have access to cool clean drinking water and shade during the summer. Automatic waterers used in winter that are designed not to freeze may have a hard time supplying quantity of water needed when it gets really hot. Surface water can become stagnant and contaminated with feces if cows are allowed to stand in the water to cool off. 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. Congregating cows during heat events can damage stream banks or other riparian areas and may need to be fenced off.
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. High temperatures can affect grazing behavior and rotational grazing systems my 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 since cows can’t dissipate heat as well when tightly grouped.
More detailed information is available at https://store.extension.iastate.edu/Product/Heat-Stress-in-Beef-Cattle