BeefTalk: Revising the bull pen
December 23, 2014
Each year, the Dickinson Research Extension Center reviews the bulls from the previous year to cut back on what bulls need to be overwintered. Because the bulls are bought based on their ability to transmit the right genes into the cow herd, their expected progeny difference (EPD) values already have stood the evaluation tests of when they were purchased.
Throughout the fall season, the primary reason for culling a bull is his general thriftiness, condition and well-being. Bulls do wear out, so there is no reason to feed older bulls that will not make another breeding season.
Younger bulls sometimes have a difficult time staying where they are supposed to, so those bulls also are asked to leave.
The final point is temperament. As bulls age, some settle down and behave while others do not. Those that become more defiant, belligerent and seek the top of the pecking order on a regular basis are asked to leave.
That leaves those bulls that will be used in the breeding pastures next year, so the process begins of evaluating the genetics of the "keeper bulls" prior to bidding on new bulls to determine what needs to be purchased.
The center maintains several breeds of bulls, but let's just look at Angus, Red Angus and Simmental bulls.
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As a reminder, I like to start with the basic growth traits that are "touchy, feely" traits that connect what I see in the cattle to what the data is trying to tell me. For simplicity, the baseline EPD growth traits I look at are birth weight, weaning weight and yearling weight.
Last year, the center's Angus bulls had average EPD values for birth weight of 0.93 pound, weaning weight 53 pounds and yearling weight 92 pounds. After culling the bulls, the "keeper" Angus bulls averaged minus .9 pound for birth weight, 52 pounds for weaning weight and 92 pounds for yearling weight.
After culling, the center's keeper Angus bulls have less birth weight but similar weaning and yearling weight as the previous year. As noted, the 50 percentile of the Angus breed shows EPD values of 1.7 pounds for birth weight, 50 pounds for weaning weight and 88 pounds for yearling weight.
In addition, the keeper Angus bulls have an average rib-eye area EPD of 1.09 and a marbling EPD of .51. Both scores were well above the 50 percentile of the Angus breed. Those values are rib-eye area EPD of .43 and marbling EPD of .39 unit of marbling score.
I hope those of you reading this column are hanging in there with the numbers because numbers can overwhelm the mind and even make one look cross-eyed. However, numbers tell a very important story.
Embedding the right EPD values for the chosen traits into the herd is critical for long-term genetic success. These numbers set the lower thresholds for the selection of the replacement bulls. The goal is to be constantly updating the bull averages to reflect the current genetic desires and to steer the genes that are going into the herd.
Before I present the Red Angus and Simmental EPD values, let's revisit a fundamental point. The EPD values for a given bull represent our best estimate of the bull's ability to transmit the right genes into the cow herd for the next calf crop. The average EPD values for the bulls that are in the breeding line up need to be calculated and averaged to better understand what genes are available.
The assumption is that these bulls will all breed a similar number of cows, so the average EPD values are what will be transmitted to the next calf crop. Realizing that some bulls will breed more cows than other bulls, we need to except that fact as being a limitation we have no control over.
Data, particularly averages, hold true through the years. If one bull breeds less cows, the bull has less genetic influence in next year's calf crop. However, through time, similar bulls will breed a similar number of cows and the genetic trends will move in the direction of the desired outcomes. For those who struggle with numbers, accept the fact that the trends will work for individual traits.
Rather than move on to the Red Angus and Simmental bull EPDs, perhaps a good point to end with is on the use of an index. An index is a great tool for focusing on the selection of a desired genetic outcome without bogging down on too many numbers. An index for a defined trait works and will guide the genes within the population toward the end objective.
However, the first thing one needs to do is set goals that are kept. EPD values impact the performance of the herd, so we always want to improve on the numbers using EPDs as the tool. More later.
May you find all your ear tags.