Achieving a 100 percent calf crop is very difficult, unless a farmer has only one cow. But a 100 percent calf crop is a great goal according to Eldon Cole, livestock specialist with University of Missouri Extension.
"The percent calf crop weaned or weaning percentage is not always calculated the same way. That's the reason some boast of a 100 percent calf crop," said Cole.
The number of cows exposed is divided into the actual number of calves weaned at 7 months of age to figure the true weaning percentage. That is about a 16-month separation from breeding to weaning and a lot can happen in that span of time according to Cole.
"A calf crop weaning percentage traces back to the breeding season's number of cows and heifers artificially inseminated or exposed to a bull during the well-defined season," said Cole.
The season may be as short as 45, but more often approaches 90 days or somewhere in between. Cow owners that never pull the bull from the breeding pasture cannot accurately figure their calf crop percentage according to Cole.
Factors that may influence a drop in the weaning percentage are open cows at the end of the season, death loss of calves and cows due to weather as well as bull problems that caused the open cows.
"Researchers tell us that it's likely that over 90 percent of the females exposed to AI and/or bulls actually conceive but several will lose that pregnancy by 40 days and return to heat," said Cole. "This loss may be due to genetics, disease, nutrition, stress and toxins. This loss may also reduce the percent of calf crop weaned."
According to Cole, one way to improve the percentage is to have a pre-breeding exam done on all virgin heifers before exposing them to breeding. The veterinarian will discover heifers that have potential breeding problems and by eliminating them the percent calf crop will improve.
"This practice is a key item on the standards for the Missouri Show-Me-Select program," said Cole.
MU Extension often uses 90 percent as an acceptable goal for a "true" calf crop percentage.
"Ninety percent is likely the average in southwest Missouri, if figured to encompass that 16 month period from breeding to weaning, may be closer to the 80 percent figure," said Cole.