Last week’s article posed the question: Which bull transmits more profit potential to this operation? Before the answer, here’s a brief recap of the example.
A herd using bulls as rotational sires, selecting the best 20 percent of heifers to develop as replacements and selling all other calves at weaning has the following performance levels:
• 1,400 pound average mature cow size (4-7-year-old cows).
• 85 percent pregnancy rate.
• 82 percent calf crop weaned.
• Average weaning weight: 500 lbs.
• Pounds of calf weaned per exposed female: 410 lbs.
This data indicates that improving the pounds of calf weaned per exposed female on a whole-herd basis results in more profit potential for this operation.
The average genetic values of the five bulls that sired the existing cow herd were the following:
• Weaning weight (WW): 71.
• Heifer pregnancy (HP): 9.
• Milk: 20.
• Mature weight (MW): 88.
Now we consider the genetic values of two new potential herd bulls.:
• New herd bull No. 1: 71 WW, 15 HP, 20 Milk and 68 MW.
• New herd bull No. 2: 101 WW, 9 HP, 20 Milk and 122 MW.
What should we expect if we fast forward five to six years?
If we select bull No. 1:
• 1,380 lb. average mature cow size.
• 91 percent pregnancy rate.
• 88 percent calf crop weaned.
• Average weaning weight: 500 lbs.
• Pounds of calf weaned per exposed female: 440 lbs.
If we select bull No. 2:
• 1,434 lb. average mature cow size.
• 85 percent pregnancy rate.
• 82 percent calf crop weaned.
• Average weaning weight: 530 lbs.
• Pounds of calf weaned per exposed female = 434.6 lbs.
So if this was a 100 cow operation, by the next generation:
If we select bull No. 1, we would be selling 79 weaned calves (44 steers and 35 heifers) at 500 lbs. = 39,500 lbs. of weaning pay weight.
If we used bull No. 2, we would be selling 74 weaned calves (41 steers and 33 heifers) at 530 lbs. = 39,220 lbs. of weaning pay weight.
Furthermore, the lighter calves would be worth more dollars per pound, and the 1,380 lb. cows would cost less in feed and maintenance than 1,434 lb. cows.
The best answer would be to choose bull No. 1 because of the genetic potential to improve fertility, reduce mature cow size and maintain the current level of weaning growth, adding more profit potential to the operation. — Mark Z. Johnson, Oklahoma State University Extension beef cattle breeding specialist
