Repeatability of calving difficulty in young heifers an often-repeated question over the years

Thursday, December 21, 2017

Questions about the repeatability of calving difficulty in young heifers seems to crop up annually, not unsurprisingly given the money invested in growing the heifer into a two-year-old cow.

The question was posed like clockwork throughout the 30-plus-year career of Glenn Selk, Oklahoma State University Cooperative Extension emeritus animal scientist who still serves as editor of the popular OSU Cow-Calf Corner newsletter.

“Should the young heifer be culled next fall because of calving difficulty this spring?” he asked rhetorically. “A look back through scientific literature sheds some light on this subject.”

Research conducted by Colorado State University and published in the Journal of Animal Science in 1973 looked at parturition records of 2,733 Hereford calves sired by 123 bulls and born to 778 cows or heifers. A repeatability estimate was obtained from heifers calving both as 2 year-old and 3-year-old animals.

“The estimate was 4.5 percent,” Selk said. “Of 195 heifers that had no difficulty in calving at two years of age, 7.2 percent had difficulty at three years of age. Of the 77 two-year old heifers that experienced calving difficulty, 11.7 percent had difficulty again at three years of age.”

Heifers that experienced calving difficulty at two years of age weaned 59 percent of calves born, whereas those having no difficulty weaned 70 percent of calves born. Calving difficulty in heifers at two years of age affected the number of calves weaned when the animal was three years of age, as well as the weaning weight of those calves. Heifers that experienced calving difficulty at two years of age weaned a 63 percent calf crop a year later. Heifers having no difficulty at two years of age weaned a 77 percent calf crop a year later.

“This research indicated calving difficulty as a two-year-old had a profound effect on productivity,” Selk said. “The likelihood that calving difficulty will happen again next year is only slightly greater than in heifer counterparts that calved unassisted.”

Selk added proper heifer development to a body condition score of 5.5 or 6 at calving, along with breeding heifers to low birth weight expected progeny difference bulls, should help reduce calving difficulty in two-year old animals.

Oklahoma ranks second nationally in terms of beef cow inventory, according to USDA National Agricultural Statistics Service data.