Weaning calves successfully and target weights

During the first weeks of life, the calf is entirely dependent on milk as a source of nutrition, with the digestion of milk occurring in the abomasum.

Young calves have little to no rumen capacity in early life. Careful nutritional management before weaning ensures that the rumen develops to allow the transition to an entirely solid diet. Successful weaning is a balancing act between achieving an adequate growth rate and promoting rumen development.

Tips to develop the rumen in advance of weaning:

• Calves must have access to clean, palatable starter concentrates as soon as possible, even though they will only eat small amounts in the first three weeks of life;
• Providing a small amount fresh every day reduces wastage, encourages calves to eat and allows you to monitor intakes;
• Calves fed coarse starter mixes initially eat more and have greater weight gain than calves fed pelleted starters – the coarseness is also of benefit for the growth of the muscle layers in the rumen wall;
• In addition to ration, calves need to drink water to help ensure bacterial growth. A calf requires four to five litres of water for every 1kg of concentrates, so provide calves with clean, fresh water at all times.

Weaning should begin only in a healthy calf that is consuming at least 1kg concentrate feed per day. Don’t water down milk replacer or whole milk prior to weaning. Instead, reduce the volume fed. If calves are being fed manually more than once a day, the first move is to change to once-a-day feeding. This is best to do approximately one month prior to weaning to allow calves time to adjust to the new regime and further develop their rumen prior to reducing total liquid feed amount.

Once they are accustomed to one feed daily and consuming 1kg of concentrates consistently, the reduction in milk feeding can begin. In automatic feeding systems, calves can be weaned more gradually. The weaning protocol again starts about a month before weaning and the amount fed is reduced gradually until they are weaned.

Target weaning weights for replacement heifers are based on their mature weights (Table 1). Weaning can safely take place when the heifer has reached approximately 15% of her target mature weight.

Table 1: Predicted mature weight and target weaning weight of replacement heifers of different maintenance sub-indexes

This article was first published in the March Teagasc Dairy Advisory Newsletter, to access the full newsletter, click here.