Abstract
This study compared the carcass characteristics of ram and ewe lambs from South African wool, dual-purpose, meat, and fat-tailed sheep types, reared to produce premium lamb carcasses. The lambs were reared on a feedlot diet (10.41 MJ ME/kg feed and 19.06% crude protein) from weaning (30 kg live weight) until they attained a back-fat depth of ~4 mm, measured using ultrasound. After slaughter, the carcasses were assessed for retail cut yields, composition, and physical meat quality. Later, maturing lambs attained heavier carcass weights than early maturing breeds (~20.7 kg vs. 16.9 kg, respectively; p ≤ 0.05), and differences in carcass composition and retail cut yields were ascribed to differences in the frame size and pattern of fat deposition of the respective breeds. Small differences in physical meat quality were observed, with meat from Dormer and Namaqua lambs having notably higher shear-force values (~46 N) than that from Meatmaster carcasses (~34 N). These differences though are expected to have little influence on the perceived quality of the meat.
Highlights
Lamb consumers are generally concerned with the fattiness, tenderness, colour, and freshness of the purchased product, which is expected to be consistent [1]
No significant interactions between the main effects of sex and breed were noted for the majority of the carcass and quality characteristics measured; only the main effects are presented in the tables with any interactions being described in the text
This was expected as a fat thickness of 5.2 mm at the rump region was taken as the indication for the lambs being ready for slaughter, with no differences observed for fat depth at this site (p > 0.05)
Summary
Lamb consumers are generally concerned with the fattiness, tenderness, colour, and freshness of the purchased product, which is expected to be consistent [1]. In order to assist the consumer, carcass descriptors have been set by the South African carcass classification system [2] based on the age, fat cover, and conformation of the lamb carcass to provide information on the composition of the carcass as well as the expected quality characteristics with the fat cover being the main price determinant. Previous studies have shown how subcutaneous fat cover can be used as a predictor for carcass composition, measurements taken on the longissimus lumborum muscle between the third and fourth lumbar vertebrae [3]. This specific measurement is used to classify carcasses in terms of tissue composition from no fat (fat score 0) to excessively fat (fat score 6). While not being graded as premium lamb, there is a great demand for carcasses with these classifications (A2), Foods 2020, 9, 648; doi:10.3390/foods9050648 www.mdpi.com/journal/foods
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