Evaluation of a subjective fat scoring system for lamb carcasses

Abstract

Two surveys were conducted, the first to examine the ability of subjective fat scores to sort carcasses independently of variation in carcass weight, and the second to objectively describe fat scores in terms of an easily recorded carcass measurement. Survey 1 examined the distribution of subjective fat scores (1-very lean to 5-very fat) within carcass weight ranges for 60 262 carcasses. There was little variation in fat scores within carcass weight ranges and therefore fat scores provided little additional information for sorting carcasses over that of carcass weight alone. This was particularly so in the two most common carcass weight ranges (14.0- 16.5, and 17.0- 19.5 kg) in which over 95% of carcasses were given fat score 3. This highlighted the need to establish an objective basis for fat scores. The second survey related fat scores to tissue depth, measured 1 10 mm from the midline of the 12th- 13th rib junction (GR) for a range of carcass weights. GR measurements for fat scores 3,4 and 5 were positively related to carcass weight. Nevertheless, individual fat scores reflected carcasses of similar percentage subcutaneous fat over a range of carcass weights, although the range of GR within fat score-carcass weight category was large, with considerable overlap between scores. Objective boundaries for fat scores in terms of GR measurements are proposed for a range of carcass weights.