Preventing And Treating Heat Stress In Cattle

How do you keep your animals comfortable when there is high humidity and high temperature? Above 80 degrees and as humidity increases, we all get feeling more uncomfortable. Animal in production will drop in milk production and feed intake. While grazing well managed pastures with fresh vegetation may have a cooling effect on the digestive tract of herbivores, direct exposure to an unrelenting sun while out on pasture can have negative impact. The same goes for animals housed with poor ventilation.

Obviously we all feel the heat but there are some things that can keep animals feeling comfortable. The number one best way is tunnel ventilation, if you have it. This also keeps flies from being a problem as they cannot fight the air current. However, most graziers I know don’t have tunnel ventilation because the idea is to have the animals outside of the barn. Even if you don’t have tunnel ventilation, it may be better for your animals to be taken off pasture during those blazing midday hours – keeping them around the barn yard out of direct sunlight if possible. Most people have a large box fan or over head fans to help animals keep cool.

Keeping the animals in for the least amount of time is many graziers’ goal. However, keeping animals relatively cooler by keeping them in during the day with whatever fans and practicing night time grazing may be better to keep animals comfortable during the hottest stretches. Portable shades in pasture are helpful as long as there are enough square feet of shade provided for the amount of animals.  And remember that water availability is incredibly important – both in quality and quantity. Cows can drink anywhere from 10-30 gallons per day depending on season and stage of lactation. Do NOT short your animals on water.

What about if one of your animals is experiencing heat stress or heat stroke? Symptoms include open mouth breathing, rapid respiration, not moving, a distant look to their eyes, and general discomfort. At some point, they may weaken to the point of only laying down with rapid, shallow respiration. Temperatures will be about 106 to 109 with heat stroke.  Unfortunately, once the temperature gets much above 108, cows will not recover, even if they show temporary improvement. Check the temperature of the worst affected animal to know where she is on the temperature spectrum.

On the worst days, normal cows will have elevated temperatures in the range of 103+/- when they are coming in from pasture or when in the barnyard congregated together. Heat stroke will usually affect animals which have had pneumonia at some point in the past (remember when she was a calf?) or just-fresh older cows with low blood calcium levels. The older fresh cows sometimes get “caught” in the sun and can’t get out of the area since they are too weak to get up due to the milk fever. Effectively treat the milk fever first.

Treating heat stress or heat stroke is rather straight forward – cool the animal down as rapidly as possible. This means cold or cool water for a good 20 – 30 minutes with a hose being best. If standing, they will stay there and enjoy it. If she is outside but near the barn, stretch a hose and use it. The entire animal’s body must be repeatedly soaked, nose to tail, and especially behind the head at the neck since the heat thermostat in the brain is near there. After about 20 – 30 minutes of hosing down the cow, tube feeding 5 gallons of cold water will further cool off the internal aspects of the animal.

Do NOT drench a cow that is breathing hard – it is way too easy to have the fluid end up in the lungs. Generally speaking, the temperature will drop to about 103 by the time the cow is more comfortable looking – breathing less rapidly and a little more deeply, looking more bright and alert, maybe even eating a little grass in front of her. It is OK – and good – to give flunixin (Banamine®) but certainly an injection of flunixin by itself will do virtually nothing for the animal that is experiencing true heat stress or heat stroke. Massive water quantities are the absolute best solution and will work by itself.

A handy hint for calves in hutches is to raise the back of the hutch off the ground by placing a cinder block there to prop up the back. This will give nice ground flow of air circulation, which will greatly help keeping the animal cool. Simply prop up the back for the rest of the season until it cools down in September sometime.

Other heat related problems usually are associated with exploding populations of parasites thriving in the form of stomach worm larvae out on pasture and flies around your cows and you. While various forms of prevention are necessary, I am getting more and more convinced that having chickens running out onto the paddocks help to reduce both flies and stomach worm larvae, simply because they destroy the medium (cow paddies) that sustain these parasitic life forms.

Try to have the chickens out there about a day or two after the animals have gone through the paddock. Hogs will also root around in cow manure paddies, probably instinctively seeking nutrients that have passed through the cow that the pigs need. Chickens peck more for the insects and grubs and destroy the paddies in that way. 

Clipping pastures can splatter out the manure paddies while also cutting down rank weed growth as well as giving even re-growth. Simple dragging of pastures with a set of chains to destroy the manure paddies will also work. Flies around the barn can be reduced by sticky tape and fly traps that attract them by pheromones. Hanging a solar paneled sprayer barrel can be very helpful for those yearling heifers out in pasture that cannot be manually sprayed like adult cows in the barn.

Strategically placing predator wasps will also help. It is only when employing all these methods that the botanical fly sprays will work best. Good pasture management will provide meaningful cooling vegetation for your cows’ nutritional needs, keep the ground cooler, and keep down parasite problems. It takes labor, time and management – but your cows will be less likely to experience the stresses that come with hot summer days.

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