"Most areas have gotten a reprieve from the 2011 drought, but others are still feeling the lingering effects of low rainfall and high feed costs," said Kansas State University animal scientist, Chris Reinhardt.

"Early weaning is an effective way to save on summer pasture and preserve cow body condition going into the winter. In fact, weaning earlier may be worth considering every year regardless of summer pasture conditions."

Reinhardt, who is a beef specialist with K-State Research and Extension, said a calf's rumen begins to develop at the first opportunity to consume solid food. Although calves rely on milk as their primary nutrient source as long as the supply is abundant, they also will begin to graze alongside their dam at a few weeks of age. This is when their mother teaches them what to eat and what to avoid.

The grass that is consumed early in life enters the rumen and begins to be fermented by bacteria which the calf picks up from its mother and the world around it, he said.

As this fermentation progresses, and the calf consumes greater quantities of grass, the rumen grows in size and develops papillae, or finger-like projections, which aid in nutrient uptake from the rumen. So the suckling calf is actually a fully functioning ruminant by 90 days of age.

In addition, the six- to seven-month weaning age window may have disadvantages compared to weaning at a younger age, Reinhardt said.

The passive immunity provided by colostrum remains active for three to four months but then wanes, after which time the calf must rely completely on its own immune system.

But in many cases its system is not fully competent to battle all antigens that attack the newly-weaned calf, such as viruses, bacteria, dust and internal parasites. So it is possible that the 90-day-old calf may have an immunological advantage to the 205-day-old calf in battling pathogens.

"Weather also plays a large factor in weaned calf health," he said.

"If we could guarantee sunshine and moderate temperatures throughout the fall weaning season, calf health would not be an issue. But, cold temperatures, precipitation, wind and mud in the fall further suppresses an already incompetent immune system---a perfect recipe for respiratory disease."

Finally, the elimination of milk production after weaning allows the nutrients consumed by the cow to go back into rebuilding body condition.

This could result in substantial reductions in winter feed requirements because nutrients harvested by the cow are nearly always lower cost than feeds harvested and transported to the cow, and forage quality in late summer and fall is nearly always greater than during the winter.