Summer heat can be just as challenging for calves as winter cold. This article explores how rising temperatures affect calf feeding behavior, nutrition, and facility conditions—and offers practical solutions to help you maintain intake, ensure diet quality, and support both calves and caretakers during hot weather.
By
on June 5, 2025 Feeding Calves Through the Heat: Practical Strategies to Manage Summer Stress and Nutrition
We often think about the most stressful time for our calves as winter, but summer creates challenges for both calves and our personnel feeding calves. What constitutes summer heat varies globally. What is heat stress on one farm might not be as severe as on others. For countries in more temperate areas of the world, the variation in temperature maybe greater within a day or from day to day than more prolonged high temperatures in warmer climes. These conditions may have a significant impact on intake and calf feeding behavior than in locations where they may adjust to higher temperatures.
Research and experience tell us that there is a thermoneutral zone and at the extreme’s energy requirements increase. Unfortunately, we know less about the impact of higher environmental temperatures. During these times, calves require more energy to get rid of body heat. Unlike colder temperatures, smaller calves have more surface area/unit of body weight and are more efficient in cooling than larger birthweight calves.
Summer heat also has an impact on quality of the liquid and dry diets. Whole milk is more susceptible to bacterial growth than most milk replacers. Similarly, calf starter quality can decline more rapidly.
Finally, excessive heat makes working conditions less than optimal for workers particularly during the afternoon feeding. Provide plenty of opportunities to keep them hydrated.
Managing heat stress
Facilities. Elevated calf housing is used in both outside and inside facilities. Outside facilities are typically made of wood. Airflow is poor and the roof is frequently close to the calf which is not optimal. Where nighttime cooling occurs calves may be exposed to both extremes of cold and heat stress.
Most plastic hutches have openings which can be opened during hot weather. Some farms elevate the rear of the hutch, but ventilation is still problematic.
Indoor individual pens with solid walls may limit calf to calf contact but are difficult to provide fresh air at the level of calf.
Group pens as used in acidified free choice or autofeeder facilities can provide the best ventilation. Roofs should be insulated and accommodation made for a significant increase in airflow during the summer.
Nutrition. It’s important to maintain dietary nutrient consumption as higher temperatures tend to discourage intake. Unfortunately, there’s few options when calves are fed using buckets or bottles. First, keep temperatures close to 100F or 38 C when the liquid diet is delivered. Some milk replacers require higher mixing temperature which must be modified by adding cold water after mixing. Autofeeders maintain feeding temperatures within a narrow optimal range.
Unfortunately, there are labor limitations in most calf feeding systems to allow feeding calves during the cooler hours of the day. If possible, the morning feeding should be as early as possible.
It’s common to reduce fat content of milk replacers to reduce cost and to encourage intake. However, this also limits energy consumption, which is particularly important for the calves less than a month old.
Diet quality. With higher environmental temperatures, sanitation of all milk contact surfaces becomes much more important as this accelerates growth of bacteria. Implement aggressive sanitation protocols and monitor effectiveness using ATP meters or periodically measure bacterial growth of the diet prior to feeding the calves. Bacteria counts should be less than 20,000 cfu/ml.
Milk replacers will typically support lower bacterial growth initially than whole milk or waste milk. It’s especially important to monitor effectiveness of the pasteurizers during the summer. Post pasteurizer counts should be less than 20,000 and lower levels (<2,500) are achievable with well managed systems.
Feeding calves their milk with buckets is especially challenging to maintain low bacteria counts, particularly if water is fed in the same bucket after milk feeding. Bacteria count exceeding 500,000 cfu/ml are common.
Autofeeder systems and heat stress. These systems enable calves to postpone intake of the liquid diet to the cooler hours of the day thereby potentially enhancing intake during the summer season.
Autofeeder systems utilize group housing systems which have the greatest opportunity to maintain diet quality. Schedules can be implemented where the equipment is cleaned automatically at frequent intervals. Proper amounts of detergent and an acid rinse are utilized consistently to achieve a high level of sanitation. Milk replacer powder is mixed with water just prior to feeding the calf thereby minimizing bacterial growth. Nipples impregnated with an antibacterial substance further limit growth.
When milk is utilized, the challenge continues in immediately cooling milk after harvest and maintain this until delivered to the autofeeder.
The hygiene box is a recommended accessory as it enables the feeder to automatically clean all milk contact surfaces within the feeder as well as the milk lines from the feeder to the nipple. Nipples are rinsed with water between calf feeding visits to the feeder.
Other measures to accommodate heat stress. It’s customary practice on many calf facilities located in warmer climates to provide a feeding of an electrolyte solution which provides essential minerals and water.
Sometimes we forget that calves are influenced by the same factors as we are. A final evaluation of the suitability of the dietary management provided to the calves would be…… Would we drink it? If the quality is not there, don’t expect the calf to achieve success in growth or health!
