During the normal production cycle, a cow should be in her best body condition at the time of calving. After calving, the nutritional stress of lactation will cause most cows to lose weight and body condition up to the point of weaning.
Bottom line: It is easier to feed cows for optimum body condition score (BCS) when they are dry. The BCS system is intended to provide a consistent way to quantify the relative fatness of cows to serve as a management tool for producers. If cows are to maintain a calving interval of one year, they must be bred back within 80-85 days after calving. In cows of all ages, it is well established that BCS at calving time determines the rebreeding performance of beef cows in the subsequent breeding season. The BCS system used to assess a cow’s body energy reserves ranges from 1 to 9. A score of 1 indicates cows are thin and emaciated, and cows with a BCS of 9 are obese.
There is a strong relationship between weight and BCS. For each unit change in BCS, cows should gain or lose approximately 7% of their weight at a BCS of 5. For example, a cow that weighs 1,300 pounds at a BCS of 5 should reach a BCS of 6 at 1,391 lbs. or drop to a BCS of 4 at 1,209 lbs.
Cows that maintain body weight and therefore have ample energy reserves before parturition exhibit estrus sooner than cows losing weight. Body weight change during pregnancy is confounded with fetus and placenta growth. Therefore, the estimation of body fat using BCS is more useful in quantifying the energy reserves of beef cows. The processes of fetal development, delivering a calf, milk production and repair of the reproductive tract are all physiological stresses. These stresses require the availability and utilization of large quantities of energy to enable cows to rebreed in the required 85 days. Cold and/or wet weather that spring-calving cows often face adds additional environmental stress, resulting in energy intake that is below body maintenance needs. The cow compensates by mobilizing stored energy or adipose tissue, which is why an adequate BCS at calving is critical to reproductive performance.
Producers should manage their calving season, genetic potential for growth and milk levels, grazing system, supplementation program and herd health to achieve an average BCS of 5 to 6 (ideally 5.5) in the mature cow herd at calving time. The goal for first-calf heifers is a BCS of 6. Typically, the greatest reproductive challenge in beef cattle is breeding back 2-year-old females raising their first calf, lactating for the first time and still growing themselves. Accordingly, a higher BCS of 6 is recommended. This fall, as you wean, assess the BCS of cows and manage your feeding and supplementation program accordingly. It will pay dividends in the reproductive performance of your cow herd next spring. — Mark Z. Johnson, Oklahoma State University Extension beef cattle breeding specialist
