After weaning and prior to winter can be one of the most economical times to improve the body condition score (BCS) of a spring-calving cow.
If you have cows that are thinner than normal, consider weaning earlier to give those cows a chance to gain body condition, and hold it through the winter. This is especially true for younger females.
Data from the Gudmundsen Sandhills Laboratory Practicum teaching herd illustrates how the time of weaning affects the cow Body Condition Score (BCS) over the winter and into the next summer. (See the graph below.) By weaning in September, cows maintained almost an entire BCS greater than weaning in October. This can be especially important if we have a wet and cold winter like 2018-2019. If it gets cold enough, there may be times producers cannot feed enough to give cows the energy needed to withstand the cold. In periods like this, cows lose body condition to offset an energy-deficient diet. Body condition scoring is an effective management tool to estimate the energy reserves of a cow, and in essence, cows with a BCS of 5 or greater going into the winter are an insurance policy or risk management tool.
via Wean Early to Prep Thin Cows for Winter Weather — On Pasture