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Ultrasound Measurements For Body Composition:RIBEYE AREA: Ribeye area is measured in square inches. Ribeye area is positively and highly correlated with retail product. The heritability of this trait is moderately high meaning that the trait will be passed on to progeny. FAT THICKNESS: Fat thickness is measured in inches. Fat thickness is a good indicator of percent retail product. The higher the fat thickness, the lower the percent retail product. Fat thickness is slightly lower in heritablity than ribeye area. PROCEDURE: Body composition measurements are taken with a PIR Medical 200 that has been designed specifically for animal use. Scan measurements for fat thickness and ribeye area are taken at the 12-13th ribs on each bull during the off-test weight date. Scan measurements for intra-muscular fat (marbling) are also taken at the 12-13th ribs. ADJUSTMENTS: Ribeye are is adjusted to 365 days using a linear area per day of age adjustment. MARBLING:
Marbling is measured as
percent fat. Heritability for marbling is in the moderate range.
Beef carcasses are traded on the amount of intramuscular fat
(marbling) they contain at the 12-13th ribs. However; marbling is
a very subjective score. Real-time ultrasound has the capability
to predict the actual percent fat in the ribeye muscle which is
what the USDA grader is primarily trying to visually evaluate. A
table is shown below that relates percent fat to amounts of
marbling in the USDA Quality Grading System. Several research
studies have indicated that the genetic correlation between
marbling and fat thickness are very low, meaning that producers
can select for increased marbling and not have to be concerned
about having animals put on additional external fat. Minnesota Hereford Breeders.
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