One southwest Missouri beef cow producer called University of Missouri Extension this spring when he had a serious problem on his farm. That producer had lost seven of nine calves born to fist-calf heifers due to dystocia (fancy name for calving difficulty).
Eldon Cole, a University of Missouri Extension livestock specialist with over 40 years of experience, got the farmer's call and agreed to make a farm visit to help determine the problem.
During the initial phone call, Cole said most things sounded normal. The owner said the heifer's body condition score was in the six range, which should be adequate. The producer thought the hay he was feeding might be the culprit causing his heifers delivery to be delayed.
"I also asked about the bull that bred the heifers. The owner assured me he was a calving ease bull he had purchased from a neighbor. These were the first calves out of him," said Cole. "The owner gave me the registration number of the bull. I looked him up on the breed's web site."
What Cole discovered was that the bull had a calving ease value that put him in the 85 to 90 percentile rank for his breed.
"That was a red flag," said Cole. "It's possible the seller thought anything ranking near 90% had to be good. Unfortunately, he was wrong. A 90% means 90% of the bulls in the breed are easier calving."
During the farm visit, Cole confirmed that the first-calf heifers were in good shape. There were no visible signs of other problems that caused him to change his concern over the likely cause of birthing problems.
"The bull's poor calving ease seemed to be the smoking gun," said Cole. "It is also a reminder of what a great tool EPDs are for genetic evaluation. We just need to be aware that some folks can get their numbers upside down."
Progressive cattle breeders are adopting the EPD and percentile rank system as they educate prospective buyers about genetic differences.
Calving ease direct EPDs predicts the average difference in ease that the bull's calves will be delivered when mated to virgin heifers. In this case, a large number indicates more unassisted births.
"EPDs do work very effectively over time, just be sure that you fully understand the percentile table and do not accidentally select for an extreme the wrong way," said Cole.
Source: University of Missouri Extension