Weaning - How Much Starter is She Eating?
The volume of calf starter grain being consumed by a calf has often been suggested as a workable guide to when we could stop feeding milk.
Some years ago we often used the threshold of 2 pounds per day. More recently the threshold has been moved up to between 4 and 5 pounds. This upper value has some good science behind it - and, it agrees with the threshold I used with my calves as well.
A recently published review of work on how calves utilize the nutrients in calf starter grains suggests that it could make sense to use an additional threshold. That is, "What is the total volume of calf starter grain consumed by the calf?"
This is not entirely new. We have been recommending that before taking calves completely off milk they should have been regularly eating calf starter grain for three weeks. That length of time implies a significant volume of grain consumed.
Quigley's work suggests that a minimum volume of starter should be consumed before rumen development will have progressed to the point where calves can be expected to be able to replace energy from milk with energy from grain.
Because calf starter grains vary widely in their composition I was not able to come up with a volume that fits all starters. However, this idea should make us think about the need to track starter intake on our "ready-to-wean calves." It's not just how much grain did she eat today - over time, has the total volume been enough to support the development of a functional rumen?
My current recommendation is calf starter grain consumption of at least one large handful daily for a minimum of three weeks and current grain intake of at least 4.5 - 5 pounds daily at full weaning.
Quigley, J.D., "Symposium Review: Re-evaluation of National Research Council energy estimates in calf starters" Journal of Dairy Science 102:3674-3683 December 2019