Why do we feed calves the way we do? The traditional recommendation for feeding dairy calves is to offer them 8 to 10% of body weight in whole milk or milk replacer per day. Since calves are usually not weighed at birth and the average weight of a newborn Holstein calf is about 40 kg, this is generally further simplified into the feeding of 2 litres of liquid feed twice daily. This amount of liquid feed basically covers the maintenance requirements for a calf of average weight until they start to eat concentrates. Under perfect conditions (little or no stress or disease, low infectious pressure and housing that is neither too cold nor too hot) a 40 kg calf could gain about 200g weight per day with that volume of milk (4L/day).
Under this regime, calves will be hungry and will start to eat concentrates early, allowing them to be weaned from liquid feed as soon as possible.
What are the limitations of this system?
There are several reasons why feeding 2 litres twice daily is no longer considered adequate: • not all calves are average weight. If all calves are fed the same amount of milk, then heavier calves will not get enough to even maintain their weight • there are many situations in which calves need more energy, e.g. temperatures below 15°C, heat stress, disease, or after vaccination. Under these circumstances calves may be severely underfed • it has been shown in studies that calves that get more than 4L/day of milk grow faster, and are healthier • heifers that grow faster before weaning calve earlier and have higher milk producing potential.
Newborn calves are totally dependent on milk as a source of nutrition. The abomasum (the fourth stomach) is the only stomach working at this stage. For the milk to enter the abomasum, the oesophageal groove has to close by reflex, so that milk does not spill into the rumen. This works best if calves suckle from a teat or nipple. It works also in many, but not all, calves that are trained to drink from a bucket. If the reflex doesn't work, the calves will get sick and will not thrive.
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