The Angus Terminal Sire index (ATS) is designed for situations where Angus bulls are being used as a terminal sire over mature breeding females and all progeny, both male and female, are slaughtered.
The Angus Terminal Sire Index focusses on increasing growth, carcase yield and eating quality.
Daughters are not retained for breeding and therefore no emphasis is given to female fertility or maternal traits.
Figure 1 shows the traits that are considered in the ATS index, and how much they contribute to the overall balance of the selection index. The larger the segment, the greater the impact on the selection index.
Figure 2 shows the selection advantage if animals are selected using the ATS index.
The selection advantage is calculated by ranking well used sires within the Angus breed on the ATS index, and comparing the average EBVs of the sires in the highest 10% with the average EBVs of all sires from which they were selected. For example, the sires ranked in the highest 10% based on the ATS index had 20 kg higher 400 Day Weight EBVs and 0.4 kg lower Birth Weight EBVs than the average EBVs of the sires from which they were selected.
The selection advantage is indicative of the relativity of response that will occur in individual traits if selection is based on the ATS index. The actual response that is observed will vary depending on the features of the individual breeding program.