Research Helps Producers and Heifers
By Kathryn Barry
July 23, 2001
Calving difficulty, or dystocia, costs
the U.S. beef and dairy cattle industries more than $400 million annually.
Females giving birth to their first calf are most likely to have difficulty.
But producers have dramatically reduced dystocia and resulting deaths of calves
and their mothers, thanks to several decades of research by scientists at the
ARS Fort Keogh Livestock and Range Research Laboratory, in Miles City, Mont.
Previously, retired ARS physiologist Robert Bellows and colleagues
pinpointed calf birth weight as the most important cause of calving difficulty:
Large calves mean more problems. They also found that feeding heifers to
maximize growth from weaning to breeding increases the size of their skeleton
and pelvis, which helps reduce dystocia. The scientists further showed that
large, high-gaining sires produce calves with large birth weights.
Based on this information, geneticists developed selection tools to improve
calving ease. Additionally, breeders stopped selecting primarily for weaning
weight and looked closely at keeping birth weight under control.
Now laboratory scientists are focusing on hormonal and genetic influences.
Theyve discovered that cows with difficulty calving have different
estrogen and progesterone levels than cows that don't need assistance. They
also have evidence that a gene on chromosome 2 may influence birth weight
without influencing subsequent growth. Eventually, this information may yield
more tools to help cows deliver calves easily.
An article describing this research appears in the July issue of Agricultural Research, ARS'
ARS is the chief scientific research agency of the
U.S. Department of Agriculture.