Calf milk feeding – volume, milk solids, and adjusting for cold weather

Anna Welboren, Amanda Fischer-Tlustos, and Dr. Michael Steele

Department of Animal Biosciences, University of Guelph

It is becoming abundantly clear that calf growth and health during the preweaning stage can have a profound influence on future productivity. It is essential that we implement preweaning milk feeding strategies that promote, rather than hinder, calf health and development.

One of the most controversial topics around milk feeding is what volume to feed. However, additional factors, including consistently and precisely feeding an adequate concentration of milk solids and adjusting your milk feeding regimen when cold weather hits, are also essential components of a well-developed milk feeding program.

Milk volume

When reared with the dam, the dairy calf would typically suckle seven to 10 times daily, consuming more than 10 L of milk per day.

Over the past decade, there has been a shift away from “conventional” milk feeding programs (with milk feeding rate at approximately 10 per cent of body weight) to “elevated” programs offering up to 20 per cent of body weight or more than eight L of milk per day. The reason for this shift is two-fold:

1. Improved welfare: Feeding elevated levels of milk reduces hunger-associated behaviours.
2. Enhanced productivity: Calves offered an elevated milk feeding program can double their average daily gain during the preweaning period, especially during the first weeks of life when starter intake is low, and display improved mammary development, reduced age at first calving, and greater milk production during lactation.

Producers often believe it is only possible to reap the benefits of feeding elevated levels of milk with the use of automated feeding systems. However, research from Norway has shown that two-week-old calves voluntarily consume between five to nine L of milk per meal without any overflow to the rumen. Our research has also shown that calves offered four L of milk per meal twice a day are able to slow the rate at which milk is emptied to the small intestine. This serves to regulate the delivery of milk nutrients to their absorption site to ensure proper nutrient digestion, absorption, and utilization. This research shows that we have largely underestimated the capability of calves to consume large meals and that it is possible to offer four L of milk per meal twice daily to maximize preweaning calf productivity and welfare.

Milk solids

A feeding solution that does not involve milk volume is to increase the percentage of solids in milk replacer. The percentage of solids in milk replacer ranges from 12.0 to 18.0 per cent (120 to 180 grams per litre), whereas whole milk contains around 12.5 per cent. However, research from Clemson University in the United States has shown that increasing the percentage of solids in milk replacer to greater than 15 per cent results in loose feces. Furthermore, care should be taken with increasing the percentage of solids as it increases osmolality—the number of particles dissolved in one kilogram of fluid.  

Milk replacer osmolality is up to two-fold higher than that of whole milk depending on its lactose and mineral content and the percentage of solids (400 to 600 vs. 300 mOsm/kg). A higher osmolality reduces water absorption in the gut, eventually causing osmotic diarrhea. Furthermore, increasing milk replacer osmolality makes the gut more permeable to pathogens, which could cause infection and inflammation. Therefore, when feeding a milk replacer containing around seven per cent ash and 45 per cent lactose, it is recommended to not exceed a solids percentage of 15 per cent (150 g/L). 

Apart from solids per litre, precision and consistency are key factors to minimize intestinal upset. When using automated feeders, consider calibrating the feeders to improve precision. When feeding manually or with automated feeders, a practical and easy tool that can be used to measure precision and consistency is a Brix refractometer. Test the Brix value of the milk replacer during feeding and add a value of 1.5 to the Brix reading to estimate total solid percentage (a Brix reading of 12 indicates a total solid percentage of 13.5 per cent). For whole milk, add a value of 2.0 to the Brix reading. Ultimately, aim for a Brix value between 11 and 13.  

Feeding considerations during winter

It is important to note that maintenance requirements alone equal approximately three L of milk per day during the first weeks of life. Environmental temperatures of -10°C (average temperature in Ontario in January/February) increase energy requirements for maintenance (e.g. heat production) by up to 100 per cent in calves 21 days of age or younger. Moreover, housing calves outdoors might be more challenging due to lower temperatures and exposure to wind and precipitation. The increased energy requirements for maintenance can be attenuated by bedding calves deeply in straw, providing a shelter or housing calves together in pairs. Furthermore, feeding more to meet increased energy requirements can be achieved by increasing milk volume per meal, implementing an extra meal per day, feeding milk replacer with a higher fat content or a combination of these strategies (Figure 1). As previously mentioned, increasing the percentage of solids in milk replacer or adding milk replacer powder to whole milk is not recommended as a compensatory strategy.

milk-feeding-chart

Figure 1. Feeding considerations to meet increased energy requirements for maintenance during the winter months of January and February (average temperature of -10°C in Ontario) for milk-fed calves weighing 40 to 60 kg (Source: National Research Council. 2001. Nutrient Requirements of Dairy Cattle: Seventh Revised Edition, 2001. Washington, DC).

Take home message

Milk provides the calf with the energy it needs to not only maintain basic physiological functions, but also to grow. It is important that we feed milk at a volume that ensures calf welfare and growth, and that we adjust this volume as needed during the winter months. Feeding milk or milk replacer at an ideal solids concentration—a value that can easily be measured with a Brix refractometer—is also a key factor influencing the efficacy of your milk feeding program. Taking all of these factors into consideration when designing your milk feeding program will ensure that you raise healthy calves that increase the efficiency and profitability of your operation.

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