THE IMPLICATIONS OF A BREED’S

from March 2022 Brangus Journal

by International Brangus Breeders Association

Gene-Editing, Is it a Reality?

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.

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 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

Breed

Direct breed effect for Mature Weight

Angus 108.2 Red Angus 9.6 Beefmaster -43.2 Brahman 61.1 Brangus 0.0 Braunvieh -192.5 Charolais 88.6 Chiangus 11.7 Gelbvieh -37.2 Hereford 69.7 Limousin 12.9 Maine-Anjou 27.0 Salers 53.6 Santa Gertrudis 41.5 Shorthorn -24.2 Simmental 34.5

(continued from page 36) size tends to increase in a correlated manner. There is also the relationship between mature cow size and carcass weight to contemplate. The industry has experienced the trend to increase carcass size. This increased weight is due to genetics for larger carcasses, as well as a change in carcass composition as we are making these cattle fatter than we were 10 to 15 years ago. Now let’s break this down to what it means at a commercial cow calf operation.

In four major Western commercial databases including SPA out of the Southwest and CHAPS in the Northern Plains, commercial weaning weights have been flat for the last 10 to 20 years. Despite this, the seedstock industry continues to linearly increase preweaning growth potential and cow size. This is mostly due to the high influence of Angus on the nation’s commercial cow herd population, which now tops all breeds for growth and mature weight. This results in some commercial operations buying bulls that overshoot the mark for preweaning growth potential past what an environment will allow to be expressed. So, the end result is the same feeder cattle payweight, but from a cow herd that is significantly bigger and more expensive to feed. Not a scenario for profitability.

Be cautious when reviewing actual performance data. Just because a seedstock operation’s weaning weights are continuing to rise maybe explained by virtue of them running their herd in a better environment than their commercial customers. Therefore, weaning weight genetic predictions should be looked on as a threshold trait, which each operation should select for the correct amount of growth potential to fit their operation. Too much growth potential will result in expensive cows to feed and decreased reproduction and longevity. Too little growth potential, and a producer will not gross enough income to make it work. Objectively, Brangus appear in a good place and it is important to keep the breed there.

How the cattle are marketed also impacts ideal cow size. If all progeny from a commercial operation are going to be calf fed, then a larger cow is called for as there is a fairly close relationship between cow size and slaughter weight of fed progeny. However, if the calves are going to go through a backgrounding phase, cow size can moderate some and still result in the same heavy carcass weights. If the cattle are to be extensively stockered, like grazing wheat pasture, then cow size can be further moderated to produce the desired heavy carcasses. Best not hit the guard rails where cattle are extreme large or small that they only have one route to be marketed. Over the long run, having flexibility built into herd in terms of how you can market your calves will generally pay.

Another consideration is whether a cow herd is being managed in an environment where heat retention or dissipating heat is higher priority. In most environments in the U.S., retaining heat is the major consideration, which is related to metabolic body weight. Metabolic body weight is body weight raised to the .75 power and is representative of body surface and maintenance costs. When body weight is adjusted to metabolic bodyweight, the amount of body surface per pound is fractionally less the bigger the animal is. That means in most environments, it is energetically more efficient for a cow to maintain its body temperature and to meet maintenance requirements per hundred weight on a larger rather than smaller cow, all other things being equal.

However, in some regions of the U.S., many of which are target markets for Brangus, dissipating heat is the major concern, so the larger amount of body surface per pound associated with a comparatively smaller cows is more efficient. Having the extra hide associated Bos-indicus cattle also provides more surface area per pound to dissipate heat. IBBA EVP Dr. Darrell Wilkes might have put it best to think about the proportion of body surface in relation to body weight as being analogous to the size of the animal’s radiator that can remove heat.

The old judging team axiom to evaluate animals as they compare to a universal ideal just no longer makes sense in our multifaceted industry. The bottom line is there are no right or wrong answers when it comes to mature weight; there are only scenarios in which the cattle must work. Each of those scenarios is a matrix of environmental, management, feed resources and market that will determine the correct production for various traits, including mature size, for an individual operation. It is also important as an industry to recognize how we continue to benefit from the work of USMARC scientists who keep us informed about the current state of germ plasm that each breed represents.