Wednesday, July 18, 2018

Weaning Weight Data and Project Update


The LiveWiRED project is nearly two and a half years into action. Forty-two calves have been weaned and are being backgrounded in Missouri with plans for shipment to a Kansas feedlot in early August. With newly collected weaning weight data, the project is one step closer to unveiling the power of EPDs for the genetic improvement of the Red Angus breed as well as the beef industry as a whole.

About the Project
The initial design of the LiveWiRED project was to evaluate the actual performance of sires compared to what their EPDs predict. In order to obtain an accurate assessment of the sires, a Gelbvieh cow named Penny was used as the sole donor cow for the entirety of the project. By utilizing a single donor cow as the dam of all the LiveWiRED calves, we can isolate sire-side genetics and obtain results that accurately portray the performance of multiple Red Angus sires compared to what their EPDs predicted.

Penny was flushed to five different bulls to produce calves for this project. Three of these Red Angus bulls rank high in the breed for growth and carcass traits and are referred to here as “high-growth sires.” The other two bulls rank poorly in the breed for growth and carcass traits and are referred to as “low-growth sires.” Throughout the duration of the project, the two sire groups will be compared in various ways, and, in some cases, calves by individual sires will also be compared to determine if observed performance differences match those predicted by the sires’ EPDs.

Project Update—Weaning Weights
Taking a look at the entire calf crop, the heaviest weaned calf stepped on the scale at 486 pounds while the lightest calf came in at 351 pounds. The average weaning weight was only 421 pounds after the 205-day adjustment. With weaning weights being significantly lighter than expected for all progeny, there is little doubt that non-genetic factors caused reduced growth rates. Sub-par nutrition took a toll on the calves and they were also affected by drought, which has been a problem in the area where the calves were raised.

When evaluating bulls and heifer calves in the Red Angus breed overall, the average weight difference among fall-born calves is 42 pounds, with bulls being heavier. The LiveWiRED calves showed only a 19-pound difference in 205-day weights between the sexes (less than half the normal weight difference). Nutritional/environmental limitations undoubtedly created the lack of spread between the heifers and bulls across all calves in the project, and also limited the growth expression of the high-growth versus low-growth sired calves. Weight differences between the bulls and heifers were ‘compressed’ by environmental factors, so it is understandable that the sires’ Weaning Weight EPDs were not fully expressed either.

For the purpose of this discussion and analysis, all calves were adjusted to a 205-day weaning weight and all heifers were adjusted up 19 pounds to account for observed sex differences. Sire EPDs are the main factor being evaluated in the project, since all calves have the same dam. One sire in the high-growth group, Sire A, sired 16 calves. Six of these calves ranked in the top 10 for heaviest weaning weight among all project calves. The adjusted 205-day weights for high-growth Sire A were then compared with the weights from low-growth Sire B, who sired 11 calves in a simple statistical test.  Sire A and Sire B were the top two sires in progeny count, so it made sense to directly compare their progeny.

The data showed that high-growth sire A calves weighed, on average, 22.6 pounds more than low-growth sire B’s calves. The actual difference in Weaning Weight EPD between these two sires is 40 pounds, so only a little over half of this genetic difference was actually expressed due to the aforementioned non-genetic limitations. Even so, our p-value was 0.04 (p<0.05) in this analysis, therefore, we can be more than 95 percent confident that a statistically significant difference in weaning weight occurred between the two sire groups. The graph below provides a good visual of this data, illustrating the cause-effect result between Weaning Weight EPDs and actual weaning weights.


The weaning weight data is giving us a great start in comparing Red Angus sire performance. As these calves continue to grow and perform, as well as change environments during their transition to the feedlot, a greater spread in weights between high- and low-growth sires is expected. Even with the smaller weaning weight spread, we can still clearly see a positive correlation between higher weaning weight EPDs and heavier actual weaning weights, which is the ultimate goal of the LiveWiRED project.

Thank you to the Red Angus Foundation Inc. for sponsoring the LiveWiRED project!



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