The use of genetic selection tools by cattle breeders has resulted in significant changes within many major breeds over the last 30 years. With a few exceptions, the genetic trend has been for more milk, higher weaning weight, and bigger mature weight. Without question, the use of Expected Progeny Differences (EPDs) has enabled this change. While we have achieved our goals of more, have we achieved our goals of better? The late Dr. Bob Taylor from Colorado State University said it well, “Profitable cattle are usually productive, but productive cattle are not always profitable.”
Weaning weight questions
Four benchmark data sets for commercial cow-calf producers from the states of Minnesota, North Dakota, Kansas, as well as Texas, New Mexico, and Oklahoma, have shown little to no change in average weaning weights or calf weaning rates in terms of the percentage of calves weaned per cow exposed over the last 15 years. How can it be that there has been such significant genetic change in several breeds that should increase weaning weights, but records from several commercial cow-calf data sets would indicate that there has been relatively no change?
In 2014, Dr. David Lalman from Oklahoma State University made a presentation at the Applied Reproductive Strategies in Beef Cattle meeting titled “Matching Cows to Forage Resources in a World of Mixed Messages.” Dr. Lalman made the case that the genetic potential of many cattle today is not supported by the forage resources available, so the animals never fully express their genetic potential. He presented data that shows the cost of maintaining larger cows with higher milk potential exceeds the value produced by small increases in calf weaning weights.
In 1988, Dr. Rick Bourdon, wrote a paper titled “Bovine Nirvana – From the Perspective of a Modeler and Purebred Breeder” where he presented the case that genetic selection should be toward the optimum for what a set of resources or environment could support. Dr. Bourdon stated, “To breed for optimum means to have a target insight beyond which you don’t want to go. If your goal is to maintain an optimum level for any trait, the evidence of your accomplishment is not visible change, but lack of it.”
Replacement heifer considerations
Cow-calf producers have EPDs and index tools to make genetic selection decisions related to traits that impact levels of productivity and longevity. Producers selecting sires from which to develop replacement heifers should evaluate where their cow herd is compared to what they believe optimum to be. Success in selecting for optimum means that many producers they will be selecting sires whose EPDs for milk production and mature weight will decrease the average in their herd. Simultaneously, they should be using EPDs to select for traits that will maintain or improve fertility and longevity. Genetic selection and breeding programs should focus on increased profit, and in many cases, this may mean selection for decreased mature weight and milk production to move future replacements for the cowherd towards optimum.
