On farms where calving begins in mid-January, there will now be calves between nine and 10-weeks-of-age, and it may be time to start preparing for weaning.
Weaning should be done based on weight, not just age, and ideally during the rearing period you want calves to have doubled their birth weight.
The weaning process is important, as this is when a calf moves from a monogastric to a ruminant animal.
This is where the calf goes from getting most of their nutrients from milk to solid food, such as grass/silage/hay or concentrates.
Weaning
As they are monogastric, calves are entirely dependent on whole milk or milk replacer as a source of nutrition with digestion occurring in the abomasum.
Calves have little to no rumen capacity in early life, but careful nutritional management during the rearing stage allows the rumen to develop and allows calves to transition to an entirely solids diet.
During the milk feeding or rearing period, you are aiming to strike a balance between achieving adequate growth rates in your calves – while promoting rumen development.
Rumen development is achieved by calves eating a source of fibre in hay or straw, starter ration and water. All three are need for rumen development to occur in calves.
Method
Calves are generating weaned when they are eating around 1kg of concentrates or starter ration/day.
In most cases, this is achieved when calves are around 12-weeks-of-age, but it can be achieved sooner.
As calves get older and their concentrate intake increases, they should be transitioned onto a once-a-day (OAD) feeding regiment.
You should not water-down milk replacer or whole milk prior to weaning. Instead, reduce the volume calves are being fed to encourage increased consumption of concentrates.
The aim is to move calves onto OAD feeding approximately one month prior to weaning to allow calves time to adjust to the new regime and to further develop their rumen prior to reducing total liquid feed amount.
Once they are accustomed to OAD feeding 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 or maintenance figure within their economic breeding index (EBI).
Weaning can safely take place when the heifer has reached approximately 15% of her target mature weight.