The second important result is the illustration of the need for EPDs for the economically relevant trait of heifer pregnancy, and not EPDs for the indicator trait of scrotal circumference. Having an EPD for scrotal circumference instead of heifer pregnancy would not provide the appropriate selection tool to improve female first calf fertility. This point is made especially clear when the genetic trend for heifer pregnancy in Figure 1 is compared to the genetic trend for scrotal circumference in Figure 6. Clearly it would be misleading to assume heifer fertility was improving because scrotal circumference was improving. The scrotal circumference had a positive genetic trend, not because of increased fertility, but because it is positively related to growth.
Growth is generally unfavorably related to the genetic potential for heifer pregnancy.
The results of this study clearly show that larger scrotal circumference size does not necessarily mean the bull's daughters will be more fertile as heifers. It is important for Red Angus breeders to realize that bulls with high growth EPDs will not necessary have daughters that are less fertile as first calf heifers. The results of this study show that a heifer pregnancy EPD should be included in the RAAA sire summary. Heifer pregnancy is an economically relevant trait. It also will help to ensure that shorter breeding seasons can be used to get heifers pregnant.