Noel Mues, Extension Educator Furnas County

 

Body condition at calving for spring-calving cows has a major impact on reproductive performance during the next breeding season. Cows and first-calf-females in good body condition at calving will resume estrous cycles and breed early in the breeding season. How cows are managed late in the grazing season will have a major impact on their body condition as they enter winter.

 

A production activity that has a major drag on how nutrients are partitioned in the beef cow is lactation. Cows have a nutrient need for lactation. Until the diet meets, and then exceeds that requirement, nutrients will not be partitioned off to other activities, such as replenishing body energy reserves.

 

The balance between nutrient resources available to the cow and level of milk production is critical. Too much milk matched with medium to low quality feed resources results in a cow herd that must play catch-up in regard to body condition.

 

Weaning time can be the best time for feed resources and milk-producing ability for mature cows to be matched in an ideal production system. Cows would be a little thin, but once the calves are weaned and that nutrient demand for lactation is removed, after about 45 days post-weaning cows begin to gain back body condition.

 

Also in this production system, cows would be in BCS 5 going into the winter without any supplementation. However, if weaning occurs late in the grazing season for spring-calving cows and the grass resources are decreasing rapidly such that quality is low, then gaining back body condition will be a challenge without some supplementation.

 

The challenge is spring-calving first-calf-cows and managing body condition of this group without a lot of supplementation. These females are the ones that are likely to be thin in the fall at weaning. Body condition is critical for this group of females and it impacts their ability to stay in the cow herd. Because they have not reached maturity, a smaller rumen is available compared to mature cows. This is the major reason the quality of the diet is so important. Warm-season pasture quality decreases as the season changes from summer into fall. From a young-cow management perspective, this is a critical time of the year to manage condition.

 

The Gudmundsen Sandhills Laboratory conducted an experiment to look at the effect of weaning date of March-born calves on cow body condition score change. The primary grass resource at this location is warm-season native pasture where the nutrient quality peaks in late May and early June and begins to decline rapidly in August. They began weaning the March-born calves in mid-August and weaned every two weeks until the end of November. The study showed that for every two weeks that weaning is delayed beyond Aug. 18, there is 0.1 of a unit decrease in BCS.

 

In addition to the effect of weaning date on cow body condition, the data in this same experiment suggest that calf weight increased up until Oct. 13 at the same time that cow BCS decreased. After Oct. 13, calf gain was minimal as cow BCS continued to decrease. Knowing this information can allow management of BCS of young, lactating females and more closely predict the impact of delaying weaning. In some management systems, it may be time in the grazing season that gets condition back on them using the grass resource instead of waiting later in the grazing season when supplementation is likely to be needed.

 

One management technique theorizes that to put condition back on young females and reduce the stress on the calf, one should wean the calf for a period of time to "dry up" the dam then reintroduce the calf to its dam. This technique, if successful, would reduce the stress on the calf, because it is back with its non-lactating dam, and allows the cow to gain back body condition as she is no longer lactating.

 

To use this management technique, calves would need to be weaned from their dam for at least 30 days for the dam "dry up" before dam and calf can be co-mingled.

 

SOURCE: Rick Rasby, UNL Extension Beef Specialist