Do an Internet search for “early weaning of beef calves” and a lot of information will pop up. Rick Rasby at University of Nebraska – Lincoln provides a good summary:

I’m working on a spreadsheet to look at the cost of weaning early vs feeding the lactating cow and calf. I should have it reviewed and out by tomorrow.

Advantages of Early Weaning

1. Dams of early weaned calves are in better condition at calving and that carries over to breeding season.
2. Calves can be fed to grow to their genetic potential when forage conditions are not optimal for the dam.
3. It may be the key to more efficient feed use during times of drought or other periods of feed shortage.
4. Early weaned calves are very efficient of converting feed to gain.
5. A high percentage of early weaned calves fed a growing ration for a short period of time then stepped-up on a high concentrate diet can achieve a USDA Quality Grade of average choice or better.
6. Early weaning permits more cows to be carried on a limited forage supply.
7. Calves weaned before or very early in the breeding season, pregnancy rates will be greater for thin cows.

Disadvantages of Early Weaning

1. Excellent calf nutrition and management is required.
2. More labor is necessary.
3. The facilities and feed must be available for small calves.
4. Calves spend a lot of time in a dry lot prior to slaughter.
5. If you have developed a cow herd that has above average milk output, the potential increase in weaning weights through milk production is not realized.
6. Information on dam performance from production records will be of limited use.

Dr. Rick Rasby, Professor of Animal Science
Animal Science, University of Nebraska – Lincoln, Lincoln, NE