The tendency of purebred livestock producers is to focus intently on increasing growth traits, including weaning weights. Using EPDs and actual weights, weaning weight is a straight forward trait to select for and easily increased. According to the American Angus Association, the average weaning weight EPD across the breed has increased from -7 in 1972, to +18 in 1990, +31 in 2000, +45 in 2010, and +52 in 2014. Many purebred Angus producers are weaning calves that are 800 lbs, and some even over 1000 lbs (calculated to 205 days). These weights sound awfully impressive, but raise questions as well: What level of creep feeding occurred to obtain these weights? What would the calves weigh if they were not creep fed? How big are the cows? How much milk do the cows give? How much did it cost to achieve these weights?
Extremely high weaning weights are only achieved with unlimited high quality feed. Most often, commercial cattlemen in the western U.S. are not afforded the conveniences of improved pasture and unlimited feed. Therefore, when put in a commercial situation these high growth genetics over-tax available resources and the cattle cannot reach their genetic potential. This comes at a cost to both the cows and calves. For starters, as weaning weight increases, so does cow size and milking ability. According to the American Angus Association, the average Angus cow weighs over 1400 lbs and has an average milk EPD of +24 lbs. It is assumed a cow will consume about 2.2% of her body weight per day, so a 1415 lb cow will consume 31.1 lbs of forage per day compared to a 1200 lb cow that will consume 24.6 lbs of forage per day. Moreover, cows of equal body weight with low milk production consumed 2.2 lbs per day less than cows with high milk production (Montano-Bermudez and Nielson, 1990). Therefore, the typical Angus cow in the industry today needs more feed to maintain her body weight and milk production (nearly 7 lbs more feed per day) compared to a smaller, moderate milking cow. If the extra feed resources are not available to maintain the cow, she will drop weight and body condition and be more likely to come up open.
The calves with extremely high growth genetics are going to suffer also. Interestingly, we have bred cows to a popular AI sire with a weaning weight EPD over +60 lbs. Of the bulls in our sale the past two years, the adjusted weaning weights from that sire averaged 562 lbs. Compare this to bulls with more moderate weaning weight EPDs that we have used extensively: OCC Paxton (+46), Manzano 0176 (+44), and Manzano 1172 (+54). Sons of these bulls had average adjusted weaning weights over the last two years of 638 lbs, 624 lbs, and 647 lbs, respectively. In our environment, it seems the calves out of Paxton, 0176, and 1172, are reaching their genetic potential for growth while calves out of the higher weaning weight bull are not. It doesn’t make sense to select for extremely high growth genetics and get all the negatives (big, high maintenance cows) when the calves can’t meet their genetic potential for growth without artificially inflating the environment.
We believe the range for an ideal commercial cow is 1050-1250 lbs. She should wean 45-65 percent of her body weight while breeding back in a timely manner every year. This range takes into account year to year differences in feed availability, age of cow, and differences between ranches. This is the model we follow at Manzano Angus. More and more purebred Angus producers have heavy milking cows that weigh in excess of 1500 lbs. With unlimited feed resources these cows may raise big calves, however in our environment they just don’t work!