MEASURABLE INDICATORS can help cow-calf producers select replacement heifers at weaning that are most likely to produce calves, based on University of Arkansas Division of Agriculture research.

“Selecting replacement heifers is an economically important consideration for the cow-calf beef producer,” said Charles Rosenkrans, animal physiologist for the Arkansas Agricultural Experiment Station. “It's relatively easy to assess growth rate of a developing heifer, but identifying the reproductive capacity of a heifer prior to puberty is difficult.”

Rosenkrans and other UA animal scientists set up a study that allowed them to model the ability of a replacement beef heifer to produce calves as a 2-year old.

Using cattle at the UA livestock research facility at Savoy, Ark., they collected the body weight, hip width and height of calves at weaning. They also measured activity of lactate dehydrogenase (LDH), a metabolic enzyme that serves as a physiological marker. Rosenkrans developed an index based on those measurements that was compared against the calving performance of the mature cows.

“We found these measurements were useful predictors of calving for 2-year-old cows,” Rosenkrans said. “The index allowed us to differentiate between heifers in our study with a 72 percent chance of calving and heifers with a 44 percent chance.”

“Our results indicate that these combinations of physical measures and metabolic indicators, taken at weaning, can be used to select replacement heifers that have a greater likelihood of calving as 2-year-olds,” he said. “Early determination of calving potential will allow producers to cull potential replacements that have a low likelihood of calving and save them the cost of raising non-productive heifers.”

Rosenkrans can be contacted by phone at 479-575-4376 or by e-mail at crosenkr@comp.uark.edu.