Trial illustrates accuracy of genomic predictions

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In 2012, Certified Angus Beef (CAB) and Angus Genetics Inc. introduced the GeneMax test for Angus cattle, which is a simplified DNA test focusing on two traits – marbling and post-weaning gain. The idea is to provide producers with an economical test, at a cost of $17 per sample.

The test provides a GMX Score, from one to 100, which combines the animal’s genetic potential for marbling and gain, along with a separate percentile-based value of one to five for each of the two traits.

Producers can use the test to select replacement heifers based on their potential to produce high-value calves that gain and well, or to test feeder calves to provide genomic-based scores to use as a marketing tool. In the long run, CAB sees the test and resulting selection as a means to increase supplies of cattle qualifying for the premium-beef program.

After the genomic test GeneMax™ (GMX) was introduced in early 2012, Angus producers set about using it. Many saw a marketing advantage for sorting and selling cattle with a genomic profile for gain and grade potential. Others set about using the technology to top up female quality in their own herds, while selling the steer half of progeny based those average GMX scores.

Recently, CAB conducted a field trial in Kansas to evaluate how well the GMX scores correlated with actual feedyard performance and carcass value in Angus steers. Gary Fike, a beef cattle specialist for CAB, presented results of the trial at the Midwest Section of Animal Society of Animal Science in Des Moines, Iowa.

The trial used 173 Angus steers from one Kansas ranch fed in two pens at Pratt Feeders in Kansas, and harvested when they had a visually estimated half-inch of external fat on two sorting dates at a Dodge City, Kan., packing plant.

The researchers recorded average daily gains and marbling scores on the cattle, all of which had been DNA tested and rated for GMX scores of high, mid-high, mid-low or low. As shown in the tables below, actual marbling scores and actual average daily gains matched up well with the levels predicted by the GMX scores for each trait. The cattle with high GMX marbling ratings produced actual marbling scores averaging 538, well above the 500 cutoff for middle Choice  Quality grade and qualification for CAB. Cattle with mid-high GMX marbling scores produced actual marbling scores of 518, while those rated mid-low or low produced actual marbling scores of 479 and 466 respectively.

As for average daily gains, those with the high or mid-high GMX scores averaged 4.33 pounds and 4.35 pounds respectively, while those with the mid-low and low GMX scores gained 4.27 and 4.22 pounds per day respectively.

Among steers with the high GMX scores, CAB acceptance rate was 69.9 percent, while acceptance among those with low GMX scores was just 28.6 percent. Average carcass value for those with the high GMX scores was $1,924, compared with $1,894 for those with low GMX scores.

Read a more detailed summary of the field trial.

Table 1 - Marbling Score and Average Daily Gain by GMX Score Groups

GMX Score Group

No. head

Feedlot In-Weight, lb.

Days on Feed

Avg. GMX Score

Avg. GMX Marbling

Marbling Score*

Avg. GMX Gain Score

Average Daily Gain**

High

83

811.5a

142.0

90

4.52a

538a

4.64a

4.33

Mid-High

32

827.5ab

142.0

70

3.19b

518ab

4.06b

4.36

Mid-Low

30

854.1b

143.9

52

2.63b

479b

3.53b

4.27

Low

28

838.9ab

143.2

25

1.61c

466b

2.86c

4.22

abMeans within a column with unlike superscripts differ (P<0.05). Outcomes adjusted for varying in-weights. *400 = Low Choice; 500 = Middle Choice, minimum for Certified Angus Beef ® acceptance.  **ADG calculated based on 63.5% dress yield.

 Table 2 - Carcass measurements, CAB acceptance and dollar values by GMX Score Groups

GMX Score Group

HCW,

 lb.

Rib Fat,

 inches

REA, sq. inches

Calc. YG

% CAB Acceptance

Odds Ratioa

 Carcass Value

 (per head)

High

915.1

0.52

14.44a

3.41

69.88

4.96

$ 1923.94

Mid-High

915.4

0.52

14.63ab

3.55

65.63

4.62

$ 1926.42

Mid-Low

910.8

0.48

15.21b

3.22

43.33

2.35

$ 1893.21

Low

908.8

0.47

14.90ab

3.23

28.57

1.00

$ 1894.07

abMeans within a column with unlike superscripts differ (P<0.05). aOdds of qualifying for CAB in each treatment group comparing calves with GMX scores of 4 to 39;  95% confidence intervals.

 


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Gerald Poppy, DVM, MBA    
Park City KY  |  November, 12, 2013 at 10:08 AM

It is interesting that the change in carcass value from the high to the low barely covers the cost of the test, and it is noted the researchers didn't provide confidence intervals around the carcass value amounts. I would say from a financial standpoint this research shows the test doesn't provide value for someone selling on carcass value. They should also have provide actual ADG gain for the groups with confidence intervals. They biased the results by standardizing them to 63.5% yield.

Dave    
NE  |  November, 15, 2013 at 06:07 AM

The ADG certainly does not correlate with the Genomic Predictions. The companies who are providing the Genomic evaluations have made a significant investment in research and are compelled to try to recover it thru marketing a product that may not be quite ready at this time. Predicting ADG requires evaluation of the genetics for growth, appetite, behavior, e,g., aggressive or timid at the bunk, metabolic efficiency in the use of feed, healthfulness of the individual etc. At this point, the genomic evaluation of a trait that requires as a prerequisite the evaluation of the complex interaction of many other traits" is just not "Ready for Prime Time" in spite of the hype.

avatar    
November, 15, 2013 at 01:32 PM

Exactly. Not ready for prime time. And remember this is useful, to the extent it is, for straight Angus cattle only. Also, if you assume equal carcass weight it just about wipes out the slim advantage above cost of test.


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