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Virginia BCIA Update

Livestock Update, November 2000

Scott Greiner, Extension Animal Scientist, Beef, Virginia Tech

Culpeper Senior Bull Sale
The 43rd Annual Culpeper Senior Bull Sale will be held Saturday, December 9, 2000 at noon at Culpeper Agricultural Enterprises just outside Culpeper, Va. Scheduled to sell will be approximately 60 head of Angus, Hereford, and Gelbvieh bulls. The bulls are currently being evaluated on a 119-day gain test at Glenmary Farm near Rapidan, Va. At the conclusion of the test, all bulls will be evaluated for reproductive soundness. Bulls will sell with complete performance information; including test information, EPDs, and ultrasound measurements for carcass traits. All consignors to the test and sale are members of the Virginia Beef Cattle Improvement Association. For more information or a sale catalog, contact the Virginia BCIA office at (540) 231-9163.

Wytheville Senior and Junior Bull Tests & Sale
81 Senior bulls (50 Angus, 21 Simmental, and 10 Charolais) and 116 Junior bulls (91 Angus, 10 Charolais, 9 Simmental, 5 Gelbvieh, and 1 Limousin) were delivered to the Southwest Bull Test Station on October 3, 2000. These bulls were weighed and vaccinated for IBR, PI3, BVD, BRSV, 7-way Clostridial, Haemophilus Somnus, and were dewormed. Senior bulls were allocated to three pens, and junior bulls to three pens. After a two-week adjustment period, bulls will be weighed on test. They will be weighed and measured for frame size according to the following schedule:

On TestOct. 16 & 17Oct. 16 & 17
56-day WeightDec. 12Dec. 12
84-day WeightJan. 9Jan. 9
112-day Weight---Feb. 6
Off TestFeb. 5 & 6Feb. 26 & 27

Senior bulls will be subjected to a 112-day gain test, and junior bulls to a 133-day test. At the completion of the test, bulls will be evaluated for reproductive and structural soundness. Ultrasound evaluation of carcass traits will be conducted at or near the end of the test. Eligible bulls will be sold on March 24, 2001.

Understanding EPDs: Part 3

Note: This article is Part 3 in a three part series dealing with EPDs.
The first two EPD articles have dealt with the basic definitions and applications of Expected Progeny Differences (EPDs) as well as specifics related to the effective utilization of EPDs for growth and maternal traits. This month's article will focus on the use of EPDs to improve carcass traits.

Carcass Traits:
Due to the increasing emphasis on end product by the beef industry, breed associations have placed considerable emphasis on providing carcass trait EPDs. These EPDs may be used to make desired directional change for carcass traits. Carcass trait EPDs are expressed at a constant slaughter age endpoint, usually around 480 days of age. Carcass trait EPDs are not available for all breeds, and not on all bulls within a breed. As emphasis on carcass traits continues to increase, more data will become available for carcass trait EPD calculation. The adoption of carcass trait measures estimated from ultrasound scans on yearling bulls and replacement heifers has added significantly to the carcass trait database of several breeds.

 Carcass Weight EPDMarbling EPDRibeye Area EPDFat Thickness EPD% Retail Product EPD
Bull A+20+.20+.50-.04+.5
Bull B+10+.00+.25+.00-.3

Carcass Weight:
Carcass weight EPDs predict the difference in carcass weight (pounds) between bulls of interest. In the above example, Bull A should produce calves that have carcasses that are 10 pounds heavier than calves sired by Bull B. Carcass weight is an indicator of the total amount of retail product in a carcass, but a poor indicator of carcass composition (quality and cutability).

Marbling EPDs reflect genetic differences in marbling potential passed from a sire to his offspring. These values are expressed in a numerical marbling score. The following table relates quality grade and numerical marbling score:

Quality GradeNumerical Score

This table indicates that a 1.0 change in numerical marbling score is equal to a change of a full quality grade (4.5 = Select vs. 5.5 = Choice-). In the example above, Bull A would sire slaughter progeny with superior marbling scores compared to Bull B (marbling EPD +.20 vs. +.00). Higher marbling EPDs increase the likelihood of a bull's progeny attaining higher quality grades.

Ribeye Area:
Ribeye area EPD is expressed in square inches. Again using the above example, calves sired by Bull A would be expected to have ribeyes that are .25 square inches larger than calves sired by Bull B. Ribeye area is an objective assessment of muscling, and an indicator of total muscle in the carcass or live animal. Ribeye area has been shown to have a positive influence on percentage of carcass retail product. Therefore, bulls with larger ribeye area EPDs will sire calves with more muscle and a higher percentage of carcass retail product.

Fat thickness:
Fat thickness EPDs are expressed in inches, and predict differences in carcass 12-13th rib fat thickness. Using the two bulls above, Bull A should sire calves that have .04 inches less carcass fat cover (at a constant slaughter age) compared to calves sired by Bull B. Fat thickness is the primary factor that determines percentage of saleable product in the carcass, and is also the primary factor affecting USDA beef carcass yield grades (increased fat thickness is associated with less desirable yield grades). As fat thickness increases, the percentage of carcass retail product declines.

Percent Retail Product:
Percent retail product EPDs predict differences in the yield of closely trimmed retail cuts from the carcass and are expressed on a percentage basis. Percent retail cuts is calculated from the same traits used in the USDA yield grade equation (carcass weight, ribeye area, fat thickness, and % kidney, pelvic, and heart fat). Sires with higher % retail product EPDs are expected to produce progeny with increased cutability and more desirable yield grades. In the above example, Bull A should sire slaughter progeny whose carcasses will have .8% more retail product than progeny of Bull B (+.5 vs. -.3 % retail product EPD).

Carcass EPDs are the most effective tool to improve end product merit. Attention to these traits is warranted in the commercial cow-calf sector. Carcass traits need to be considered along with the many other economically important traits (reproduction, growth, maternal ability) in a balanced trait selection scheme. Currently, for many cow-calf producers carcass traits carry significantly less importance economically compared to reproduction and growth. As the beef industry progresses, and changes are made in marketing systems and animal identification, genetic merit for carcass merit will become increasingly important. This is likely to occur for all producers- even those who do not retain ownership. Consequently, carcass traits need attention in today's selection programs so that producers may position themselves for the future- and be able to capture the economic rewards for superior end product that meets consumer expectations.

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