By: Warren Rusche, Cow/Calf Field Specialist, SDSU Extension
Why is it that nearly every article on beef cow nutrition in the winter seems to focus on body condition? Surely with all the advanced knowledge and research that has been done over the years we have something better to go on than a visual estimation of body fat on a cow to evaluate the success or failure of nutritional status?
The short answer to that question is that we focus on body condition because it works. The best indicator that we have for the nutritional status of a beef cow is her body condition. Right now most spring calving herds are either in or are approaching the last trimester. Managing body condition in the last three months ahead of calving is important for two very big reasons:
- Thin cows tend to produce poorer quality colostrum with lower levels of immunoglobulins. They also tend to have calves that take longer to stand and are less able to produce enough body heat to maintain their temperature under cold conditions.
- Cows that are thin at calving are less likely to breed back in the first 21 days of the breeding season and are more likely to be open in the fall.
Between those two factors, body condition influences the size of the next two calf checks. That’s the reason for the focus, because body condition can have such a sizeable impact on a rancher’s bottom line.
There are a number of checklists and visual guides that have been developed to condition score cows. The process doesn’t have to be complicated. If you can see more than one or two ribs and the outline of the spine is visible, then that cow is below the optimum body condition score. In a group of cows the key factor is how many cows in the group are below that optimum line. If there’s only a small number (perhaps 5 to 10 percent), there is little reason to be concerned. These cows may simply be cattle that don’t fit their environment and spending a lot of extra money on the entire group to pick up the handful at the bottom isn’t likely to be profitable. It would be more feasible to sort this group and manage them separately. Larger percentages of thin cows indicate that additional inputs will be required or that changes to the production system need to be made, or both.
If additional feed energy needs to be supplied, the sooner that process begins the easier it will be to put on the necessary weight. To change a cow one body condition score (approximately 70 lbs. to 90 lbs. of body weight) in 90 days requires about 20 percent more energy; 30 percent more energy is required if that change needs to happen in 60 days. To put it another way, feeding a cow in late gestation an alfalfa-grass mixed hay diet should add about one body condition score in 90 days. A sixty day period would require something similar to straight alfalfa as far as energy content; adding that much weight in 30 days would require a diet similar to corn silage.
Influence of Body Condition on Reproductive Performance of Beef Cows by SDSU Extension