All Purpose Index (API)
API is a bio-economic selection index that utilized CattleFax market projections, USDA beef production simulators and the International Cattle Evaluation with over 16 million cattle records to evaluate overall genetic profitability taking into account every economic facet of cattle production.
Expected Progeny Differences (EPDs)
EPDs are the most accurate and effective tool available for comparing genetic levels. In using EPDs, the difference between two sires’ EPDs represents the unit difference expected in the performance of their progeny. For example, if sires A and B have EPDs of +10 and – 5, a 15-unit difference would be expected in their progeny (moving from -5 to +10 yields 15 units). Key to using EPDs is knowing in what units they are expressed. For example, if the above case referred to weaning weight EPDs, sire A would be expected to sire 15 pounds more weaning weight than sire B. If calving ease was the trait, sire A would be expected to sire 15 percent more unassisted births in first-calf heifers; in other words, if sire B sired 30 assists in a group of 100 heifers, we would expect sire A to require 15 assists. A percentile-ranking chart is required to determine where a bull’s EPDs rank him relative to other bulls in the breed. For more detailed information about EPDs and $ indexes, visit www.simmental.org. Listed below are the units in which ASA EPDs are expressed.
All bulls offered on TBeef have genomically-enhanced EPDs. Genomic data is extremely valuable but is still of the utmost value when included with all other information in the EPDs. Therefore, to make the most powerful, most accurate genetic selection decisions with the use of genomic data, that genomic data must be included in the EPDs in the form of genomically-enhanced EPDs.
All-Purpose Index (API)
Dollars per cow exposed under an all-purpose-sire scenario. (See $ Indexes for more details.)
Back Fat (BF)
Inches of carcass backfat at 475 days.
Birth Weight (BW)
Pounds of birth weight.
Calving Ease (CE)
Percentage of unassisted births when used on heifers.
Carcass Weight (CW)
Pounds of carcass weight at 475 days.
Using API and TI
First, determine which index to use; if you are keeping replacements use API, if not, use TI. Then, just as with EPDs, zero in on the unit difference between bulls. (As described above, index units are in dollars per cow exposed.) The difference can be used to determine how much a bull is worth compared to another. Put another way, how much you can pay for one bull compared to another. For example, when buying an all-purpose-type sire, you can quickly figure a bull scoring +100 for API is worth an extra $6,000 over a +50 bull if both are exposed to 30 cows over 4 years ($50 diff. x 30 hd. x 4 yr.=$6,000). A percentile-ranking chart is required to determine where a bull’s index value ranks him relative to other bulls in the breed. For more detailed information about EPDs and $ indexes, visit www.simmental.org.