A cow's greatest nutritional requirements (quantity and quality) are during lactation. If she is shortchanged during that time she will (a) lose body condition and not return to heat very quickly after calving--either calving later the next year or coming up open, and/or (b) not milk as well as she might otherwise, producing a calf that does not grow as well as it could.

When pastures are dry, it is often better to wean calves early. If calves are left on the cows in these conditions, feed must be supplemented with adequate amounts of energy and protein to keep the cows from losing weight.

It's best to schedule calving and weaning to take advantage of climate and feed availability--so cows' peak needs coincide with green grass (providing quality and quantity, with least expense).

The optimum time for calving and weaning can vary with pasture and weather. Some producers have tried summer calving (May-June) and found heat stress during breeding season (August-September) results in lower conception rates. But in general, for a spring calving herd, traditional weaning time is often later than what's best for the cows. Early weaning gives cows a chance to regain lost body condition (especially young cows) before going into winter.

Early Weaning Benefits
Fall is the most economical time to improve cow condition for spring calvers, according to Ron Bolze (Kansas State University extension livestock specialist), while grass is still available and cold stress is not a factor in cows' nutritional needs. Weaning decreases nutritional demands on the cow, enabling her to regain the desired weight before calving. Cows still milking on mature grass pastures, with forage quality declining, lose weight in late summer and fall, since lactation requires 50 percent more feed, 70 percent more energy, and twice as much protein as pregnancy.

One extension research project showed cows (on unsupplemented pasture) that continue nursing calves until December lose about 150 pounds and 1.5 points in body condition score by the next calving. If calves are left on cows this late, feed must be supplemented with adequate amounts of energy and protein to keep the cows from losing weight--and this is money out of the rancher's pocket.

Extension livestock specialists at Kansas State University did an economic analysis of weaning dates, looking at body condition scores at calving, calf prices and calf weaning weights. Keeping the calves on the cows may seem to look best for weaning weights, but the economic toll comes later. When cows are pulled down to calve at a body condition score of 4 or less, the next year's calf crop percentage is lowered (more weak and sick calves, and greater chance for calf losses) and replacement costs increase--with higher rates of open and culled cows the next year.

Whether to wean early is a decision best made on a year-to-year basis depending on quantity and quality of feeds available, and weather conditions. Early weaning can be a way to save feed costs (saving best pastures for weaned calves and putting the cows on rougher pastures) and keep the cows in better body condition.

Nutrition in late gestation affects health of the cow and calf at calving time, and how well the cow will milk again. It's never wise to leave a calf on a cow too long; she needs a chance to recover again before her next calving. The final 1/3 of gestation (especially the last 60 days) is most crucial for the developing fetus, nutrition-wise. The first two-thirds of the pregnancy makes very little demand on the cow's body. The fetus makes 70 to 75 percent of its demands during the last two months, since this is the time it is growing fastest. If a cow is in good condition she can rob a little of her own body fat to supply the need, if necessary, but if she's thin (and if weather is cold), she'll need extra feed.

Leaving a calf on too long and pulling her down in body condition is counterproductive for next year's calf. The pregnant cow needs proper nutrition for the growing fetus--and to make good response to vaccinations (to pass immunities to her calf via good quality colostrum). Leaving calves on cows after pasture quality declines or weather turns cold takes a toll on cows' body condition and ability to do justice to the next calf and breedback.

Young cows tend to lose the most weight during their first lactation; they need extra nutrition for growth as well as for lactation and reproduction. The two year old, especially, is at a difficult age. She's growing, milking, and hopefully pregnant again, and also shedding the last of her baby teeth, which may make eating more difficult for awhile. If you can wean her calf early, it gives her a better chance to do justice to her next calf and be in adequate body condition to rebreed. Weaning calves off two and three year old cows early is often the most effective management tool to ensure these young cows stay in the herd and don't come up open.

By contrast, mature cows can nurse their calves longer without detriment to themselves. They can get by on plainer feed or fall pasture after weaning, and actually lose a little weight during winter with no adverse effect on productivity, as long as they have good feed and adequate nutrition after calving.

Feed costs generally make up more than half a cow's total expense, but you can save on costs by proper timing of weaning, to take advantage of natural feeds early enough in the season to put weight back on cows before winter. Then cows can "coast" through winter on lesser amounts of expensive feeds (hay, supplements) than it would take if you were having to feed the weight back on.

You can use supplemental protein on rough feeds to increase digestibility and intake, but this gets expensive if you are trying to meet requirements of a lactating cow. Dry pregnant cows, with calves already weaned, won't need supplemental protein, unless they are on very low-quality forage. The post-weaning period, if you time it right for your calving season and climate conditions, is the best time to cut feed costs, since the cow at that time has the lowest nutritional requirements of her production year. She can utilize poorer-quality roughages, crop residues and by-products, and you can find numerous ways to reduce her feed bill. ©