Ask the Vet

Dr. Ken McMillan, Contributing Columnist

READER: We are looking for a bull, and the sale we are looking at has both EPDs and indexes for all the bulls. They are very different for the various breeds. I am confused with all this data.

DR. McMILLAN: Let's start with EPDs (expected progeny differences). The numbers predict the expected performance of an animal on a single production trait compared to other animals within the same breed. EPDs can't be compared across breeds without applying across-breed EPD (ABEPD) adjustment factors.

EPDs start by assuming a 50% contribution from the dam and sire. In most breeds, genomic testing can increase the accuracy and reliability of an animal's EPDs. Depending on the trait, genomically enhanced EPDs (GE-EPDs) can increase the accuracy equal to having the data on eight to 35 calves. EPDs also change and become more accurate as producers report data to the breed associations on the animal's performance, the performance of progeny and the performance of other relatives.

The trait names and numbers can be confusing, and different breeds express things a little differently. Calving-ease direct EPD is expressed as a percentage of unassisted births, with a higher value indicating greater calving ease in first-calf heifers. The EPDs for birthweight, weaning weight and yearling weight are expressed in pounds and are a predictor of a sire's ability to transmit each of these to his progeny. The milk EPD is a predictor of a sire's genetic merit for milk and mothering ability as expressed in his daughters compared to daughters of other sires. Rib eye area is expressed in square inches, and scrotal circumference is expressed in centimeters. This only scratches the surface of the EPDs offered by many breed associations.

EPDs can be a powerful tool to improve your herd. Several years ago, we looked at the hard data from calves we sent to the feedlot and visual assessment of the cows, and determined we needed to increase rib eye area, marbling and udder quality while decreasing our mature cow weights. We looked for bulls -- both to purchase and for artificial insemination (AI) -- that had very good EPDs in these areas. These four areas were our focus, but we made sure the rest of the EPDs also fit with our goals. We feel we have made great progress using EPDs in this manner.

EPD INDEXES

If you are still confused at this point, here come the EPD Indexes. Breed associations realized this confusion and created indexes based on specific goals to hopefully simplify the process, especially for commercial producers. They combine various EPDs and economic factors in a special formula to reflect the value of an animal compared to other animals within that breed relative to these goals. Indexes are expressed in dollars per head, so comparing them is a little easier.

The American Angus Association created the Angus $Values with several multitrait selection indexes. Here are some examples. Weaned Calf Value ($W) focuses on preweaning value. Feedlot Value ($F) focuses on postweaning value. Grid Value ($G) focuses on carcass grid merit. Beef Value ($B) looks at the future progeny performance for postweaning and carcass value compared to progeny of other sires, and combines the contributions of $F and $G.

Each breed has a little bit of a different twist. The American Hereford Association has two indexes that focus on crossbreeding, the Baldy Maternal Index (BMI$), which looks at maximizing profit for commercial cow/calf producers who use Hereford bulls in rotational crossbreeding programs on Angus-based cows. The Brahman Influence Index (BII$) does the same thing for Hereford bulls used on Brahman cows. The Certified Hereford Beef Index (CHB$) is a terminal sire index, where Hereford bulls are used on British-cross cows, and all offspring are sold as fed cattle on a CHB pricing grid.

If you are still confused, talk to your veterinarian, Extension agent or other producers, or visit some of the farms with bulls consigned to the sale. Most seedstock producers would welcome a visit and a chance to show off their cattle and operation.

**

-- Please contact your veterinarian with questions pertaining to the health of your herd. Every operation is unique, and the information in this column does not pertain to all situations. This is not intended as medical advice but is purely for informational purposes.

-- These are only my thoughts and general guidelines. Please get with your veterinarian and together develop the best program for your herd.

-- Email Dr. Ken McMillan at vet@dtn.com

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