Milk feeding and the effect of temperature on young calf performance

The colostrum 1,2,3 rule is considered best practice for the newborn calf, Teagasc Dairy Specialist George Ramsbottom discusses the important factors to consider with calf rearing this spring.

Transition milk is milkings 2-6 from freshly-calved cows. Where there are no underlying cow health issues, such as Johne's Disease prevalent on farm, calves can safely be fed transition milk. While the concentration of antibodies in transition milk declines with each milking, it is still a better feed source than whole milk or good quality milk replacer for calves who have received their colostrum feed. Although no additional antibodies can be absorbed across the gut wall after 24 hours of age, there is a local protective intestinal effect and feeding at least four feeds of transition milk, after the initial colostrum feed, has been shown to reduce the incidence of illness in calves and results in less ‘runny’ noses and droopy ears.

After the calf has received all feeds of transition milk, it should be offered whole milk or good quality milk replacer. If feeding whole milk, no waste milk, milk with antibiotic residue or high SCC milk should be fed. Information on choosing a good quality milk replacer is available on the AHI website in the leaflet 'Early Nutrition and Weaning of the Dairy Calf'.

As a guide, the quantity of milk fed to calves should be gradually increased over the first week of life to ensure that calves are drinking 6 litres per day by the time that they are six days old. When feeding milk replacer, ensure a good quality concentrated whey protein or skim milk replacer is fed and follow the Animal Health Ireland guidelines. In summary, the following specifications included in the guidelines suggest the following:

• Protein content: 23-26% (predominantly dairy protein sources);
• Fat content: 16-20%;
• Ash content: 7-8%;
• Fibre content: maximum of 0.1%.

Table 1: General guidelines for the feed required to successfully rear calves 

 ¹3 litres when fed twice daily or if feeding once a day build up to 6 litres over a few days.

The following diagram shows the partitioning of the ‘typical feeding rate’ of milk replacer for maintenance and growth at 15°C.

The typical dairy breed calf (birth weight of approximately 35 kg) requires 380g of powder per day to maintain itself at 15°C. The remaining 370g of milk powder can be used for growth – as a rough rule of thumb, the daily gain supported by the ‘surplus’ powder is half of the surplus quantity. In other words a surplus of 370g of milk powder will support an average daily gain of 185g. Normally we’d expect the calf to grow at a rate of approximately 500-700g per day, so get the calves eating meals as quickly as possible to help it to achieve the target daily growth rate.

The lower critical temperature of a calf is the temperature below which it needs to use more energy just to maintain its core body temperature.  Young calves become cold stressed at temperatures <10°C – temperatures that are typical in February.  For every 5°C drop in temperature below 15°C the young calf (under 3 weeks of age) should receive 50g extra milk powder.  If the house is cold and it doesn’t receive extra feed, then growth rates are reduced.  Feeding calves at an enhanced level will provide enough energy to support maintenance, growth and the immune system. If nutrition falls below basic requirements the calf’s health system will be compromised.

As the calf grows older it becomes less sensitive to lower temperatures – particularly as the rumen starts to develop – see the following table.

Table 2: Lower critical temperature of calves at differing ages

The bedding material of choice to keep young calves warm is straw.  A dry bed of straw has a lower critical temperature of 8°C so it is sufficient to maintain the young calf without increasing the energy requirement for maintenance during the typical February; for damp straw this increases to over 10°C; and for calves lying on a dry concrete floor this increases further to 17°C. Concrete is one of the coldest surfaces that a calf can lie on. Therefore it is imperative that calves have a good thick bed of clean dry straw underneath them and that they lie at least 3 inches above the floor. Nesting scores are used to determine how well bedded your calves are in the house. And don’t forget that the young calf will spend 80% of its time lying down so a dry comfortable bed of straw is critically important to its growth. Other alternatives to help the calves to stay warm include using infra-red lamps in the pens with young calves or the use of jackets.

Read more: Watch: 'Back to basics' on calf care