Hot Takes on Feeding Calves in Warm Weather
Heat stress is a unique challenge for preweaned calves. Their small size and greater body surface area make them more susceptible to fluid loss than adult animals. Calves lose water in times of heat stress by panting or sweating.
In warm weather, baby calves often lose more fluid than they consume. Until about 3 weeks of age, young calves consume very little “free” water because they do not know how to drink out of a pail yet. So, they must rely on the water they consume via bottle from milk or milk replacer.
At temperatures below 68°F, water losses are minimal and can be accommodated by feeding 4 quarts of milk or milk replacer daily. But if the mercury climbs into the mid 80’s, this moderate heat stress can increase water loss by more than 50%. And at temperatures in the mid 90’s, water loss increases to approximately 7 quarts daily, far outstripping the intake of 4 quarts of milk or milk replacer that kept up just fine at 68°F.
And if diarrhea is also present, water loss is even greater, and dehydration becomes a critical concern. Most calves that die of scours actually die from dehydration versus bacterial or viral pathogens.
In addition to water, sodium also escapes calves when they pant and sweat. Replacing lost sodium is necessary to ensure normal cardiac functions, maintain good water absorption in the intestine, and prevent metabolic acidosis.
So, how can we feed calves to best support them in periods of heat stress?
The primary methods include:
(1) Add an electrolyte feeding – Many successful operations add a midday feeding of oral electrolytes to calves up to 3 weeks of age in hot weather. In warmer parts of the country, they may do it all year long. This replaces the water and sodium that calves lose due to heat stress, at a time when they are not yet equipped to seek free-choice water.
There are many choices for commercial electrolyte products. The main distinction is that their buffering agents usually fall into one of two categories – sodium bicarbonate or sodium citrate. Either type of product can work well when fed proactively.
(2) Choosing milk replacer over milk – Commercial milk replacers are manufactured using milk co-products, including some from cheese production, like whey or whey protein concentrate. Compared to whole milk, these ingredients naturally raise the sodium in the liquid ration, which can help compensate for the sodium lost due to heat stress. For example, 4 quarts of fresh milk deliver 1.5 grams of sodium. Comparatively, 4 quarts with 1.1 pounds of milk replacer containing 0.7% sodium deliver 3.5 total grams of sodium, and 6 quarts with 1.6 pounds of milk replacer containing 0.7% sodium delivers 5.1 total grams of sodium.
(3) Feed a milk replacer with fatty acid balance – Proper fatty acid balance of the liquid diet has been reported to lower calf body temperature approximately as much as using fans to cool calves in a nursery. In the same studies, fatty acid balance also increased growth. At Strauss Feeds, we manufacture milk replacers with this in mind. We use ingredients high in milk fat and other sources of medium-chain-length fatty acids proven to help lower the body temperature of calves and be highly digestible.
(4) Offer free-choice water sooner versus later – Calves can’t learn to drink water on their own if they don’t have it available to them. Begin offering pails of fresh drinking water at a few days of age. Even if they don’t drink much initially, it will help them figure it out sooner. And in hot conditions, add a second pail for calves 6 weeks of age and older if space is available. Older calves will drink more water when it’s hot. Also, refill pails in the afternoon if needed for the oldest calves to ensure enough water is available as they need it.
Your Strauss Feeds representative can provide advice on hot-weather milk replacer formulations; electrolyte selection and feeding strategies; and other management steps to help calves navigate heat stress successfully.
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Heat stress is a unique challenge for preweaned calves. Their small size and greater body surface area make them more susceptible to fluid loss than adult animals.