Dairy farmers invest a considerable amount of money and effort in fans, sprinklers, shade, and other animal-cooling methods in order to avoid the reduced productivity and well-being that comes from heat stress. However, if we stress animals out during times of hot weather with poor handling, those heat abatement investments will be less effective.

It is generally believed that cattle begin to experience heat stress in the form of reduced milk production when the temperature-humidity index (THI) reaches 68. However, different animals can respond to heat in various ways even when they experience the same environment. “So, even though THI is a very helpful metric to help you plan ahead and anticipate conditions that lead to heat stress, it’s also important to look for the signs that cows themselves show that they’re experiencing heat stress,” said University of Wisconsin-Madison animal welfare specialist Jennifer Van Os.

Panting is a clear sign of heat stress, but if you wait to see panting, the effects the cow will experience are already going to be extreme, continued University of Wisconsin county extension educator Sarah Grotjan. A cow’s normal respiration rate is 25 to 50 breaths per minute, she said. Panting cows are reaching 100 breaths per minute. She advised monitoring respiration rate and watching for cows bunching in the barn or standing more to be more proactive.

Moving creates heat

We cannot completely avoid moving cattle just because it is hot out, but when temperatures rise, we should take efforts to limit how much we handle them and use best practices to avoid having cows reach the point of panting or sacrificing lying time to dissipate body heat.

It is best to move cattle during cooler parts of the day if at all possible, noted county extension educator Aerica Bjurstrom. An animal’s internal temperature will peak approximately two hours after the environmental temperature does, and it will take four to six hours for them to cool down to a normal body temperature, the group described in a fact sheet.

Use shade and fans where possible and move animals in smaller groups to help facilitate airflow around them. Holding pens can be particularly stressful — consider how many bovine “space heaters” are bunched together in one area. Bjurstrom advised making smaller holding pen groups if it is possible. Similarly, aim to limit the amount of time cattle are in headlocks or restrained in any way because their physical stress can worsen heat stress.

If cattle must be moved with a trailer, again try to avoid the hottest part of the day. Additionally, reduce the number of animals being moved together.

Vaccination also requires special care, the extension team said. A normal reaction to a vaccine can include a mild fever, and if this is combined with a high THI, heat stroke may be induced. They advised vaccinating early in the morning or late in the evening during times of high temperatures.

The bottom line is that an animal’s body temperature will naturally rise when they become nervous or stressed, which can occur during handling. While we can’t control the environmental temperature and the stress that can come with it, we can limit how much animals become stressed from how they are handled. Don’t exacerbate heat stress with poorly planned, chaotic handling. Calm cattle handling is always important but especially when the mercury is high.

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(c) Hoard's Dairyman Intel 2024
June 27, 2024
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