Miller Brangus 10-26-19

Fertility Traits/Indexes IBBA ARTICLE | JOHN GENHO 8/20/2018 IBBA’s release of selection indexes and maternal EPDs puts more tools into the hands of commer- cial producers in making bull selections. Most commercial producers are trying to find the bal- anced bull. They want a bull that can produce de- cent market steers that have high weaning weights, have high marbling scores leading to decent qual- ity grades, but at the same time don’t have calving ease problems or too much fat on the carcass. This balancing act is constantly managed by bull buyers as they look across the previously available EPDs. However, typical bull buyers also want this same bull to produce heifers that can go back into the herd as replacements. These heifers must be able to breed as yearlings, have the calf unassisted, then continue producing calves for several years with minimal inputs. They typically must have moder- ate sizes to fit the harsh environments that Bran- gus cattle are expected to perform in. While pro- ducing good market steers is important, the heifer side of the equation is roughly more than twice as important economically. Cows that fail their first year or two, or that require high inputs to perform, are very costly to an operation. To address the maternal side of this equation, IBBA has released three new EPDs. The Mature Cow Weight EPD is a prediction of how much an animal’s daughters will weigh as a five-year-old versus the average of the breed. The Stayability EPD predicts the likelihood an animal’s daughters will still be in the herd at six years old versus the average of the breed. The Heifer Pregnancy EPD predicts the probability that an animal’s offspring will breed and have a calf as a two-year-old. Heifer pregnancy and stayability have direct impacts on the economics of commercial cow/calf operations. Females that do not breed as yearlings and cannot remain as productive cows are costly to an opera- tion. While mature weight is not as directly related to returns, it is correlated to a cow’s ability to thrive in a commercial setting and continue producing calves. Larger cows have higher nutritional needs and often cannot produce in commercial settings without supplementation. This is especially true in harsh environments, a place where Brangus cattle thrive as a breed. Therefore, the goal with the ma- ture cow weight EPD should be selecting a moder- ate cow that is not too large. Balance is the key to any selection program. We of- ten want to maximize certain traits, such as weight or marbling, without realizing that there are con- sequences to this maximization. To help create this balance, selection indexes combine many traits into a single number. Weighing the costs and benefits in selecting for or against certain traits is done systematically by statistical modeling. This allows the bull buyer to not have to perform this complex weighting on the back of an envelope or in his head at a bull sale. This single number allows a buyer to confidently select the balanced bull for a particular set of traits. IBBA has released two selection indexes. The first is a fertility selection index that combines heif- er pregnancy, stayability, the age a cow will first calve, mature cow weight, and back fat EPDs into a single number. The second is a growth index that combines birth weight, weaning weight, milk production, post wean gain, ribeye area, marbling, and back fat EPDs into a single number. These in- dexes are expressed as standard deviations from the breed average, meaning that bulls with a +2 index are two standard deviations above the aver- age. For both indexes, higher numbers are superi- or. As a point of reference, 95% of the population will be between -2 and +2 standard deviations of the mean. This infers that only 2.5% of the animals will be worse than a -2 for an index, and only 2.5% of the animals will be greater than a +2 index. The bottom line is that animals with an index value above 2 are very good animals for the traits being considered. These additional tools of maternal EPDs and se- lection indexes give bull buyers the ability to more confidently make purchase decisions based on sound data. As buyers adopt these tools and use them in purchases, they will see the difference in the economics of their cow herds. 4 | MBRANGUS.COM