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Nutrition, Feeding & WaterFeeding Cows in Heat Stress
Hot, humid weather makes cows eat less and breathe harder, and milk production follows. Smart feeding changes, good water and cooling work together to keep intake up.
Key points
- Heat lowers intake, so concentrate nutrition and keep feed fresh.
- Move feeding toward cooler hours and push feed up often.
- Water access and cleanliness matter as much as the ration.
- Cooling at the bunk helps cows keep eating.
- Plan with your nutritionist before hot weather, not during it.
What heat does to a cow
A lactating cow makes a lot of body heat just from digesting feed and making milk. When the air is hot and damp, she cannot shed that heat easily. She responds by eating less, drinking more, breathing fast and standing instead of lying down.
Because she eats less, she takes in fewer nutrients just when she needs them. Fertility, milk yield and milk components can all suffer. Managing heat stress is partly a cooling job and partly a feeding job.
Signs to watch in the herd
Do not wait for a thermometer reading to tell you the herd is struggling. The cows will show you.
Walk the pens in the afternoon and look for the following.
- Fast, open-mouth or panting breathing.
- More cows standing in the alley or crowding the water.
- Slobbering and drooling.
- Leftover feed at the bunk, especially from the daytime feeding.
- Slower milk letdown and lower yields.
Shift feeding to the cooler parts of the day
Cows eat more when it is cooler. Many herds move more of the feed delivery to the evening and early morning so that fresh feed is available when the cows want it. Talk with your nutritionist about timing that fits your milking schedule.
Push feed up often, and keep the bunk clean. Hot, wet feed spoils fast, and cows quickly turn away from anything that smells off. Remove leftovers before they heat and ferment.
Walk the bunk at the end of each shift and note how much feed is left and when. If most of the refusals sit there after the afternoon heat, that tells you cows are skipping the hot hours, and the delivery schedule can shift to match. Keep the same routine each day so cows learn when fresh feed arrives and come to eat. Check the mixer and the mix itself. Wet byproducts and silage can heat quickly in summer, so clean out the mixer and the bunk often and keep the mix consistent from the first cow to the last. Cows that sort or avoid a warm, sour mix lose even more intake.
Ask about ration density and fiber
When intake drops, the ration needs to deliver more nutrition in each bite. Your nutritionist may adjust energy, protein, minerals and fiber for hot weather. Do not do this on your own by adding grain, because too much grain with too little effective fiber raises the risk of rumen upset.
Mineral needs also shift in the heat because cows lose more through sweat and saliva. Ask what changes make sense for your herd, and do not guess at amounts.
Water is the most important feed
Hot cows drink a great deal. Make sure there is plenty of trough space, that the flow rate keeps up with demand, and that troughs are cleaned often. Algae and feed buildup turn cows away.
Place water where cows leave the parlor and in the pens so no cow has to walk far. Check for leaks, broken floats and low pressure every day in hot weather.
Combine feeding with cooling
Feeding changes work best alongside shade, airflow and sprinklers or misters at the feed line. Cows that are cooled at the bunk tend to stay and eat. Follow manufacturer guidance for fans and electrical equipment, and keep wiring and water safely separated.
Reduce crowding and avoid unnecessary moving or handling during the hottest part of the day.
Cows just before and just after calving carry the most risk in hot weather because their intake is already tight. Give them the best shade, the most airflow and easy access to water and feed. Ask your vet and nutritionist what extra monitoring makes sense, since heat can also raise the chance of metabolic trouble around calving. Record which cows struggle each summer. The same animals and groups often show up year after year, and those notes help you plan cooling and feeding earlier next season.
Common mistakes and what to ask
The most frequent errors are feeding all the ration at one time, letting water troughs get dirty, and boosting grain in a panic. Plan for summer before it arrives.
Ask your nutritionist and extension specialist these questions before the heat builds.
- What ration changes should we make once the weather turns hot?
- When should we shift feeding times?
- How should we protect close-up and fresh cows, who are most at risk?
- Do our water and cooling systems match our herd size?
Sources and further reading
Organization homepages are linked so you can search them for current guidance on this topic.