Application of Ultrasound for Genetic Improvement in Beef Cattle
Real-time ultrasound offers beef producers a means to make genetic improvement in body composition traits. Ultrasound data is useful in identifying animals that are superior or inferior for a particular trait of interest. Breed averages can be useful for characterizing a specific breed for body composition traits and how those traits may be incorporated into a crossbreeding program to compliment each other. Collecting ultrasound data is also a much cheaper and more efficient means of evaluating carcass traits on breeding animals relative to progeny testing and carcass data collection. Current research at ISU is investigating the potential for using a combination of ultrasound and carcass data to be used in carcass EPD calculation.
Typical ultrasound systems used for measuring
beef composition and quality.
The use of real-time ultrasound to measure fat thickness and ribeye area in live beef cattle has become widely accepted. Ribeye area and fat thickness are two traits that are highly related to retail product of a beef carcass and these two traits can be measured with a high degree of accuracy using ultrasound. Additionally, fat thickness and ribeye area are moderately to highly heritable, suggesting that differences found between animals would be expected to be passed on to their offspring.
The technician is collecting the image shown below
between the 12-13th rib of a beef animal.
Real-time ultrasound image collected for measurement of
ribeye area and 12-13th rib fat thickness.
Real-time ultrasound can be used to objectively measure marbling in live beef cattle. Marbling, however, is a very subjective score. Therefore, real-time ultrasound is used to predict the actual percent fat in the ribeye muscle. The percent fat is what carcass graders try to visually evaluate. Research studies at Iowa State University (ISU) have found a relatively high correlation (0.75) between ultrasound-predicted percent fat in the live animal and the actual percent fat in the carcass ribeye. The heritability for marbling is in the moderate range. In addition, the genetic correlation between marbling and fat thickness has been shown to be very low, suggesting that selection for improved marbling can be obtained without an increase in external fat.
The technician is collecting the image shown below for
calculation of percent intramuscular fat.
Real-time ultrasound image collected between
the 12-13th rib of a beef animal
.
This graph relates percent fat to marbling in the
USDA Quality Grading system.
(Graph taken from 1998 Beef Research Report - Iowa State University)
Relationships among various methods of categorizing amounts
of marbling in young beef cattle
(Table taken from 1998 Beef Research Report - Iowa State University)
Rump fat measurements can also be taken using real-time ultrasound. Rump fat is negatively related to percent retail product and is thought to be an additional indicator of carcass fat. Rump fat measures may be most useful for predicting percent retail product in leaner cattle which have less 12th rib fat.
Ultrasonic image used for measuring rump fat.