FEATURE ARTICLE
THE IMPLICATIONS OF A BREED’S MATURE WEIGHT by Dr. Bob Hough Table 1. Breed effects for mature weight adjusted for selection for 16 breeds evaluated in the Germ Plasm Evaluation program at the USMARC, Clay Center, NE. Units are expressed in pounds deviated from a Brangus base. Breed Angus Red Angus Beefmaster Brahman Brangus Braunvieh Charolais Chiangus Gelbvieh Hereford Limousin Maine-Anjou Salers Santa Gertrudis Shorthorn Simmental
Direct breed effect for Mature Weight 108.2 9.6 -43.2 61.1 0.0 -192.5 88.6 11.7 -37.2 69.7 12.9 27.0 53.6 41.5 -24.2 34.5
If a producer wants to get a good conversation going, all he or she needs to bring up is cow size, and varying opinions of what is the right size cow will come fast and with conviction. Using selected facts, which expert they listened to last, what direction the sands of social media are blowing, or just what they are used to raising, will generally arm a person with just enough information to justify whatever their preconceived notion is. In reality, whether you are considering biological or economic efficiency, efficient cows come in all sizes. However, to be considered an efficient cow there are two initial standards that must be met. First, they have to match the environment in which the cow herd is going to be asked to perform. Second, they have to produce a calf every year that will meet a carcass window with the pounds and quality to be profitable. Above all in the second criteria, their progeny’s carcasses must avoid the large discounts for noncompliant carcasses that are too heavy and especially too light. The matrix of variables that determine the genetic needs for a cow herd include management, feed resources and market, and in what environment they will be expected to perform. This results in continuum of biological types that includes the most appropriate genetic potential for mature weights and production traits that are right for each 36
March 2022
individual operation. There are also many well-known “truths” that might have been correct 35 years ago, but don’t hold up to scientific scrutiny today. One of these is the mature size of different breeds in relationship to each other. Luckily, we have the U.S. Meat Animal Research Center (USMARC) in Clay City, NE where some of the most talented geneticists in the world have been running a Germ Plasm Evaluation (GPE) program for the past 52 years, which describes the biological properties of the various breeds. In 2021, the USMARC and University of Nebraska scientists released the long-awaited mature weight comparisons for the 16 breeds involved in the USMARC’s GPE project. The results are shown in Table 1 and for the purposes of this article are expressed as deviation in pounds off of the average mature weight of Brangus. These results came from the analysis of 108,957 weights taken at different stages of production within a year as repeated measures on 5,156 cows measured over a series of years. First, the average weight of this population was a hefty 1,430 pounds. Because different breeds are represented in the population at different frequencies, this average weight doesn’t equate to a particular breed but instead the whole population. Rather than an average weight, these results are represented as comparisons, which USMARC typically does with Angus as the base, but for the purpose of this article, Brangus was used as the base. Also, the heritability of mature weight in this study was high at 0.56, meaning it is a trait that will respond readily to selection. When one just looks at where Brangus ranks among the breeds, they definitely come across today as a moderate breed, with most breeds’ cow size being larger than Brangus. This is an interesting breed position, as those whose memories stretch back to the frame race in the 1980s know that Brangus was a full participant, which gave them a reputation as having some big cattle during that era. Next some general observations. Gone are the days when one could make blanket statements that Continental breeds made the biggest cows and the British breeds the most moderate. If anything, the relationship tends to be the opposite now, with by far the largest mature cows being Angus and the third largest are Herefords. On the other end, Braunviehs had by far the smallest cow size and other breeds like Gelbvieh, Limousin and even Simmental have moderated considerably. There are considerations when deciding what is the most appropriate cow size, and one of the most important is feed resources. In population genetics, as growth increases mature
(continued on page 38)
