Seven Percent

Mark Z. Johnson, Oklahoma State University Extension Beef Cattle Breeding Specialist

The body condition scoring system (BCS) is used to assess body energy reserves in beef cows.  The BCS system used for beef cattle ranges from 1 to 9.  A score of 1 indicates cows that are thin and emaciated, cows of BCS 9 are fat and obese.  Pictures and definitions of the BCS system can be found in Chapter 20 of the 8th edition of the OSU Beef Cattle Manual.

When condition scoring cows, producers should look beyond age, frame size, depth, length pregnancy status and hair coat.  The condition scoring system is intended to provide a consistent system to quantify relative fatness regardless of these other factors that create difference in cows'appearance.  There is a strong relationship between weight and BCS.  For each unit change in BCS, cows should gain or lose approximately 7% of their BCS 5 weight.  For example, a cow that weighs 1,200 lbs. at a BCS 5 should reach a BCS of 6 at 1,284 lbs. or drop to a BCS 4 at 1,116 lbs.

Best time to Evaluate BCS?

Typically, late summer/early fall when cows are slicked off and in 2nd trimester of pregnancy is the most accurate and easiest time of the management cycle to evaluate BCS on cows. Weaning time or at time of fall pregnancy checks is realistically the most convenient time of the annual management cycle to capture a weight on cows. If cows need to be fed and managed to have adequate BCS by the start of calving season, managing for a target weight gain can be effective.

Why is BCS Important?

One of the major constraints in the improvement of reproductive efficiency in cows is the length of post-partum anestrous.  If cows are to maintain a calving interval of one year, they must bred back within 80 - 85 days after calving.  In both old and young cows, it is well established that BCS at calving time determines the rebreeding performance of beef cows in the subsequent breeding season.  Cows maintaining body weight, therefore having 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 by use of BCS is more useful in quantifying the energy reserves of beef cows.  The process 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 often faced by spring calving cows 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 adequate BCS at calving is so critical to reproductive performance.

The Goal

Producers should manage their calving season, genetics, grazing system, supplementation program and herd health to achieve an average BCS of 5 to 6 (target 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 the breed back of two-year old females raising their first calf, lactating for the first time and still growing themselves, accordingly the higher BCS of 6 is recommended.

References

Beef Cattle Manual. Eight Edition. E-913. Oklahoma Cooperative Extension. Chapter 20.