Learn about Carcase Traits in
Angus GROUP BREEDPLAN

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Carcase EBVs
60 - How are carcase EBVs estimated
61 - Do carcase EBVs of bulls reflect carcase traits in steer progeny
62 – How well does the EBV for IMF% reflect marbling in progeny
63 - Why do scans often differ from carcase measurements
64 - Doesn't feeding and maturity differences influence muscling in bulls

60 : How are Carcase EBVs estimated

Carcase EBVs are estimated from eye muscle area, subcutaneous and intramuscular fat measurements made by an ultrasound scanner, similar to that used in medical practice. These measurements are taken by an accredited Breedplan scanner when the calves are between 300 and 800 days of age.

The scan records are analysed in a similar way to other EBVs, adjusting for age and management variation, heritability factors etc.

Actual carcase measurements can also be used to estimate carcase EBVs, but as few Breedplan recorded animals are slaughtered as contemporary comparison groups, Breedplan carcase EBVs are mainly derived from scan data.

As for growth EBVs, carcase EBVs shown as +/- from the zero herd or breed baseline (0), and are expressed in sq cm for eye muscle, mm fat depth and % for IMF and Yield.

61 : Do carcase EBVs reflect actual performance in steer progeny. . . . . . . . . . . . . . . . . Go to Top

Yes, the results from progeny groups of steers from sires with carcase EBVs show that the ranking of the sires is reflected on the hook. Thus carcase EBVs can be used to select sires to increase muscling, marbling, or to alter the fatness levels of steer progeny. Carcase EBVs are reported as 300kg (carcase) steer equivalents.

62 : How well does the EBV for Intramuscular Fat (IMF%) reflect marbling in progeny. . . . . . . . . . . . . . . . . Go to Top

Variation exists within breeds for marbling and if we can identify those animals with superior marbling then it is possible for seedstock herds to change marbling within a herd or breed.

Research in Australia and overseas shows that it is possible to measure marbling using real-time ultrasound scanning of yearling bulls and heifers. This research has also shown that IMF measurement by scanning in seedstock is positively and genetically related to intramuscular fat expressed in finished steers.

Breedplan now produces an EBV for Intramuscular Fat (IMF%) which is estimated using records from live animal ultrasound scans of intramuscular fat and abattoir carcase data .

Note - The relationship between visual marble score and intramuscular fat is not absolute – about 70%. Both traits are moderately heritable (between 20 and 40%). Factors other than genetics influence marbling including pre and post slaughter management, age, weight and nutrition.

63 : Why do scans from the live animal often differ from the measurement taken on the carcase. . . . . . . . . . . . . . . . . Go to Top

• the two measurements are made by different people, at different times & using different equipment
• the carcase measurement is not necessarily taken at the same site as the scan
• when the hide is removed, the fat expands - this is why the hot fat measure is generally 1 mm or so higher than the scan measurement. Also, when a hot carcase is hung, the fat can slump giving an incorrect measurement at the selected site
• if the carcase is quartered at an angle, the measured eye muscle area is exaggerated
• the carcase measure may be wrong - in fact experience has shown that often the scan is more right than the carcase measurement
• all measurements have small errors attached to them and the errors don't always go in the same direction. For example, if both measurements are overstated by 1mm, no error is observed, whereas if one measurement is over by 1mm and the other is under by 1mm, then a 2mm error is observed, even though the accuracy of both measurements are the same

64 : Doesn't feeding and the stage of maturity influence muscling in bulls. . . . . . . . . . . . . . . . . Go to Top

Yes, that is why scan results are analysed within management (feed) groups and adjusted to a standard end-point carcase weight of 300 kg. To be analysed scans must be taken within the range of 300 to 800 days of age.