by Sarah Morrison, Ph. D., Miner Institute
The thermoneutral zone of a calf under three weeks of age is between 59 and 77℉ (15 and 25°C). Below the thermoneutral zone the heat that a calf normally produces is equal to, or less than, the amount of heat lost and the calf experiences cold stress. Therefore, to maintain body temperature, the calf must either consume more energy to generate more metabolic heat or else the calf will be forced to use what limited body reserves it has for this purpose. This prioritization of nutrients will always go first to maintenance (thermal regulation, immune and stress responses) and then toward growth. With this in mind there are several feeding strategy considerations that can support calves through winter.
The youngest calves rely heavily on milk or milk replacer for the nutrients they need to support maintenance and growth but we must not forget about water and calf starter. Although calves less than three or four weeks of age are probably not consuming enough starter to appreciably contribute to their requirements, early starter intake is beneficial for initiating the rumen development process. Starter and water should be offered during this time as these two things are very important for hydration, rumen development, and eventual weaning.
Fuel the fire. Offer starter from birth as calves will increase, and often double, the starter they consume each week. Depending on the milk or milk replacer feeding program, you may not see large amounts of starter intake initially. Still, the cumulation of starter intake before weaning is very important for weaning success and preventing postweaning slumps. Initiation of starter intake stimulates fermentation of that feedstuff in the rumen. Fermentation generates metabolic heat which helps calves consuming starter tolerate a wider range of environmental conditions (i.e. they can tolerate a colder environment).
The 4:1 rule. Calf feeders often fight with frozen water pails in colder temperatures, which can be pretty frustrating! However, water is THE most essential nutrient for animals and, as a result, should not be abandoned in winter. Water is not only the number one requirement for animals; it is crucial for starter intake and rumen development. A good rule of thumb for calf water consumption is the 4:1 rule as calves will consume four parts water for every 1-part starter they consume.
Calves may also increase the amount of water they drink in response to the solid concentration in milk or milk replacer. Increasing milk solids is often a method used in cold temperatures to support increased nutrient requirements. As solids increase above 14% in milk replacer, expect calves to drink more water. In the first weeks of life, calves drink 1.5 to 3 quarts/liters of water a day, whereas by a month of age, calves will consume around 4-8 quarts/liters of water per day. It is important to note that water provided in milk or milk replacer is not sufficient on its own to meet the needs of the calf. Free choice water should be provided on its own so that calves may regulate their intake in response to what they require based on solids percentage in the liquid diet or based on their starter intake.
Timing. Calves should have free access to water throughout the day and from birth. However, when temperatures get consistently below freezing, it can be challenging to battle frozen water in buckets. Therefore, offering smaller amounts of warm water to the youngest calves (less than three weeks of age) multiple times throughout the day will help promote water intake. Provide 2 quarts of water to the youngest calves after milk or milk replacer feeding. An additional water feeding in the middle of the day would provide an opportunity for the calves to consume more water. For older calves eating more starter, increasing the amount of water offered after milk or milk replacer feeding is vital. As calves wean, providing water during regular milk or milk replacer feeding times will encourage starter intake in these calves.
Temperature matters. Milk and water consumed by calves can impact the amount of energy needed to maintain normal body temperature (101-102⁰F). If calves consume milk or water that is below their normal body temperature, they must expend additional energy to warm their drink to normal body temperature, which increases maintenance requirements.
Therefore, the temperature of milk or milk replacer provided to calves is important to monitor so that it is provided at the appropriate temperature to minimize the effect of cold temperatures for young calves. Regardless of the nutritional value, make sure every liquid meal a calf gets is at or above body temperature (target 105⁰F) when the calf is consuming that meal. Usually, milk replacer tags have recommended mixing temperatures. However, it is important to ensure that when that milk replacer finally makes it to the calf it is not below 105⁰F.
Furthermore, calves prefer to drink warm water. Ideally, offer water at 100°F or just above. By providing warm water compared to cold water, the amount of energy expended by the calf to warm water up to the calf’s body temperature is minimized. Cold water will also reduce the temperature of the rumen. Work in the 1960s measured the change in rumen temperature in response to different water temperatures. Calves were fed 46-81°F water, and it dropped the temperature of the rumen for approximately 1-2 hours by as much as 15°. Whereas 99°F water only minimally changed rumen temperature for a shorter period. If the temperature of the rumen drops, this may reduce the efficiency of the rumen and also reduce the amount of metabolic heat produced from fermentation.
Things to Remember. Overall, providing water and starter from a young age can help support calves during winter. Starter is important for rumen development and can provide some metabolic heat for that calf. Do not forget about water for young calves! It is essential from a hydration standpoint and essential for rumen development and efficiency. Strategically plan when and how much water you offer to calves depending on their age and the amount of starter they are eating. Can you find a way to provide warm water throughout the day to help encourage calves to drink and find ways to increase starter intake?
Sarah Morrison, Ph.D. is a Research Scientist at the William H. Miner Agricultural Research Institute in Chazy, NY.Sarah grew up on her family’s dairy farm in Addison County, Vermont. She has a Bachelor’s of Science degree in Animal Science from the University of Vermont and a Master’s of Science and a Ph.D. from the University of Illinois. Her research at Miner focuses on dairy cattle nutrition and management, with a focus on calves and heifers. She can be contacted with questions at morrison@whminer.com.
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