In the course of crossbreeding, you set goals, select concepts and choose breeds. You then wait a year or two to evaluate weaning weights and carcass factors. Is there a better way?
I prepared for this column by creating a computer spreadsheet that permits a look into the future through the use of hypothetical animals. If you were to use this spreadsheet, you would begin by estimating the breed composition of your cow herd. You would divide your cows into groups of 10 and estimate the breed percentages of each group, always making sure the percentages totaled 100. After completing your year-one profile, you would calculate profiles for future years, replacing cows with home-raised bred heifers at the annual rate of 20 percent. Thus, you would begin changing the makeup of your cow herd in year four and complete it in year eight.
The next step would be to estimate the potential of your cows to contribute to your goals for their calves — high weaning weight with high values for quality grade, yield grade and retail yield. This requires multiplying percentage-of-breed figures for each breed of cows in your herd by breed values for these qualities from association records or other records or assumptions. For example, if your cows are 48 percent Breed A and that breed’s average for Choice and Prime carcasses is 70 percent, that cow breed will contribute a value of 34 percent to your calves.
Now select breeds for your bull battery using the principle of complementarity. Match the strengths of bulls with weaknesses of cows. Rotational and terminal crossbreeding schemes were more complex than I wanted for this project, so I focused on 50/50 hybrid bulls — Balancers (Gelbvieh/Angus) and Durham Red (emerging Shorthorn/Angus).
You are now ready to calculate the breed composition of the calves you’ll produce. This is done by multiplying the percentage-of-breed contribution of your hybrid bull by the same figure for your cows, once for each breed.
The semi-final step is to translate the breed makeup of your calves into carcass values and weights. This step is accomplished in the same manner as described above for the transmitting potential of cows. Finally, you calculate a probable weaning weight for your calves by multiplying the percentage for each breed in their composition by an estimated breed-based weaning weight. For example, if a calf is 49 percent Angus and the weaning weight for Angus calves is 475 pounds, this breed’s contribution to weaning weight is 233 pounds.
The accompanying table provides snapshots of what happens over a 10-year period to the breed makeup of the cow herd plus the breed makeup and performance of their calves. I must confess that I don’t yet know to what degree my weaning weights include the effects of heterosis. Heterosis is easy to figure the first time you put a bull of Breed A on a cow of Breed B, or when you mate a Breed A bull to a crossbred cow of Breeds C and D. But I’m assuming that you’re beginning with crossbred cows for which the heterosis effect is already in the history of their calves.
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