High Performance Females May Experience Longer Calving Intervals

Cow-calf profits depend less on achieving maximum production than on maintaining optimal output within a given set of ranch resources.  CowTek’s recent analysis of calving intervals makes this point clear.  Longer intervals between calves were consistently observed in young cows with high genetic ability for milk and growth compared to same-age females with lower growth and milk genetics.  This finding is significant, because calving intervals are an important measure of reproductive efficiency.  And among factors that affect the cow-calf producers’ bottom line, nothing is more important than reproduction.

The research involved seven major U.S. beef breeds (including Angus).  In each participating breed, females ranking in the top 40% for Milk EPD and the top 40% for Yearling Weight EPD were grouped together and compared to females in the bottom 40% for both traits.  The high milk/high growth and low milk/low growth groups were then aggregated across breeds to produce a breed-neutral comparison.

Longer calving intervals among high milk/high growth females suggest that reproduction can become compromised in order to accommodate the dam’s own growth and her higher milk output.  Failure to re-breed during a fixed-length breeding season could be a problem as a result.  High performance females may be especially vulnerable to reproductive delays and/or reproductive failure during periods of restricted feed supplies, such as during a drought.

---CowTek, Inc. Research Study Conducted in 2000