Volume 45 Number 4 Winter 1998
Ultrasonic Equipment Helping Produce Leaner Pork
Daryl Kuhlers, Nada
K. Nadarajah, Steve Jungst, Elisabeth Huff-Lonergan,
Consumers are demanding leaner red
meat with less fat, and the meat industry is striving to meet
that demand. A few meat packing plants already are paying a premium
price to market hog producers on the basis of percent lean in
individual carcasses. In general, a relationship exists between
total percentage of lean meat in pork carcasses with reduced
backfat thickness on the tenth rib and larger loin eye muscle
area. Hence, selective breeding for a combination of low fat
and more muscled pigs should play a major role in future pork
production and market success. An AAES breeding program has helped
define ways to correlate ultrasound measurements of live animals
and carcasses to sound breeding decisions.
Correlating ultrasound measurements of backfat and loin muscle depths on live pigs to selection of superior breeding animals for improvement of carcass yield and quality has been the focus of an on-going AAES research project. The study involving almost five generations of selective breeding has resulted in a population of pigs superior for lean meat production.
The study was initiated at the Auburn University Swine Breeding Unit in 1993 to select a line of Landrace pigs for larger loin muscle area using ultrasound techniques to measure the backfat thickness and loin eye muscle area of live pigs. The breeding experiment data were analyzed using the latest genetic evaluation methods to select superior breeding animals as parents on the basis of their genetic values (breeding value) estimates to produce the next generation of pigs. So far, four generations of selection have been completed and the fifth generation is underway. In order to evaluate the selection response and to compare the differences with an unselected base population of Landrace pigs, a control line was also maintained under similar feeding and management conditions throughout this study.
An Aloka 500V real-time ultrasound machine was used to measure fat thickness and loin eye muscle area on live pigs at about 168 days of age. Based on those measurements and subsequent analyses of the breeding data, a line of pigs was selected solely for increased real-time ultrasound loin eye area for the past four generations along with an unselected control line. Scanned data for loin eye muscle area and backfat thickness at the tenth rib on 1,142 pigs, sired by 78 boars and out of 187 sows over four generations, were available for the current analyses. Additional data from the fifth generation will be incorporated into the final analyses of this investigation.
In each generation, measurements were recorded for carcass length, tenth rib backfat thickness, loin eye muscle area, and percentage trimmed lean cuts from one barrow (a castrated boar) per litter. Additional measures of carcass quality were recorded on loin muscle, including meat color (1 = pale, 5 = dark) and marbling (1 = practically devoid, 5 = moderately abundant). In generations 3 and 4, firmness (1 = very soft, 5 = very firm) scores on pork chops cut from the tenth rib also were obtained. A total of 155 carcasses was evaluated.
The differences between
select and control lines for the subjective meat quality traits
of color were -0.27, -0.11, -0.59, and -0.54, and for marbling,
the line differences were 0.27, 0.34, -0.48, and -0.55, in generations
1, 2, 3, and 4, respectively. For firmness, the differences between
select and control lines were -0.91 and -0.95 in generations
3 and 4, respectively.
These results suggest that selection for loin eye area using real-time ultrasound will result in desirable changes in carcass loin muscle area, percent lean muscle cuts, and backfat thickness at tenth rib. However, undesirable changes in carcass length, color, marbling, and firmness may also occur.
and Anderson is Manager of the AAES Swine Breeding Unit..