There’s been a significant increase in the number of new dairy traits developed industrywide over the past couple years, and new traits will continue to be developed. With all this change and progress, it may be difficult to determine which traits hold the most value for your dairy and how you can best utilize the information that is available. It may even become information overload. For this reason, you might consider using genetic sub‑indexes.
One benefit of the Ideal Commercial Cow™ (ICC$™) indexes for Holsteins and Jerseys is that they are comprised of sub-indexes, enabling you to narrow genetic emphasis to better achieve your breeding goals. Said another way, it is easier to select genetics through a sub‑index than to individually select for all traits that contribute to a specific breeding objective.
The table below lists the top 25% of the GENEX Jersey lineup (April 2018 data) ranked by the ICC$™ index. You have decided to choose the top five bulls from this group that meet your breeding program goals. If production is your main emphasis, you would choose the top bulls for the Cheese Maximizer (ChMAX$) sub-index. See the values highlighted in yellow.
If you choose to concentrate on Sustainability (SUST$) or Fertility (FERT$), the same logic would apply. The top five SUST$ sub-index values are highlighted in teal and the top FERT$ values are highlighted in dark blue. Note the top five bulls for each sub‑index varies. This demonstrates how sires typically perform better in certain sub-indexes compared to others.
The table’s bottom row shows the ICC$™ index average of the top five bulls for each sub-index. As you can see, the averages for the top five ChMAX$ and SUST$ sub-index bulls are very similar (+775 and +767 respectively). The ICC$™ index average for the FERT$ sub‑index list, however, is slightly lower (+733). In this instance, you may decide the decline in overall ICC$™ index values does not meet your overall needs when selecting for ideal commercial cows, and you may instead choose to exclude bulls that do not meet a minimum threshold for the FERT$ sub-index.
The second FERT$ column shows which sires may be the best option when choosing high ICC$™ index sires with positive FERT$ values; these values are highlighted in purple. The overall ICC$™ index average of these five bulls (+771) is comparable to those selected based on ChMAX$ or SUST$. This demonstrates the relative ease in which sub-indexes may be used for achieving specific breeding goals.
In the future, sub-indexes are likely to become even more prevalent. Even now, the Dairy Wellness Profit (DWP$) index published by Zoetis includes two economic-based sub-indexes in Calf Wellness dollars (CW$) and Wellness Trait dollars (WT$). One could speculate that Net Merit $ and Cheese Merit $ indexes published by the Council on Dairy Cattle Breeding (CDCB) may transition to economic-based sub-indexes eventually as well.
As more and more genetic traits are developed, sub-indexes become a logical way to eliminate the oversaturation of traits and to focus on specific breeding objectives. It is much easier to select on a single sub-index that emphasizes the desired area of farm management than to select on the many traits that may be associated with it.
For more information on using the ICC$™ index and its sub-indexes to achieve your breeding objectives, contact your local GENEX representative or contact customer service.
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