Longissimus Muscle Histological Characteristics of Simmental × Angus, Hereford × Angus and Limousin × Angus Crossbred Steers as Related to Carcass Composition and Meat Palatability Traits

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Abstract
Twelve Simmental × Angus (SXA), 12 Hereford × Angus (HXA) and 12 Limousin × Angus (LXA) crossbred steers fed the same finishing ration were slaughtered in three equal groups (four from each breed) after 200, 242 and 284 days on feed after weaning. After obtaining U.S.D.A. quality and yield grade data from the chilled carcass, 3.18 cm thick steaks were removed from the 10-ll-12th rib locations from the right wholesale rib for taste panel, Warner-Bratzler shear and histological evaluation. The lean plus fat portion of the 9-10-1 lth rib section from the left wholesale rib was analyzed for moisture, chemical fat and protein. The right side of each carcass was fabricated into retail product, fat trim and bone. Histological samples from the medial and lateral positions of the longissimus muscle were cryogenically frozen and stored on dry ice. Samples were later sectioned on a cryostat and stained by using myosin ATPase and DPNH diaphorase procedures. Photomicrographs were made from the stained muscle sections and fibers were classified as ±R, ±W or ²R, and the number of each in a given area was counted. The size of each fiber type in selected areas was also measured. LXA crosses had more (P<.05) ±W fibers and slightly fewer ±R fibers than other breed crosses. Fiber diameters were not different (P>.05) between breeds. The LXA crosses had more (P<.05) retail product and lower (P<.05) yield grades than either SXA or HXA crosses. HXA crosses had more (P<.05) total fat trim (kg) and less (P<.05) total bone (kg) than either SXA or LXA crosses. The longissimus muscle medial position contained slightly more ²R fibers and the lateral position had more (P<.05) ±W fibers in all breed crosses. ²R and ±R fiber diameters were smaller (P<.05) in the lateral position than in the medial position. Palatability traits were not different (P>.05) between breeds except for taste panel juiciness scores which were lower for LXA crosses. Correlations between muscle histological characteristics, composition and palatability traits were not significant (P>.05). Copyright © 1977. American Society of Animal Science . Copyright 1977 by American Society of Animal Science.