FACTORS AFFECTING SUBCUTANEOUS FAT DEPTH AT 2 SITES ON BEEF CARCASSES

Over a 12-month period, fat depths at the P8 rump and 12-13th rib site s were measured on 10968 beef carcasses at 4 Tasmanian abattoirs. All cattle were assigned to 1 of 5 breed types: British beef, dairy, dairy -beef cross, beef cross, and European and European cross. Dairy-beef c ross and European breeds were excluded from the analysis because of sm all numbers. Sex and age (dentition) were recorded. As the data set wa s unbalanced and no single relationship between P8 rump and 12-13th ri b sites applied, models describing the relationship between fat depths at the 2 sites were developed for subsets of the data. These showed t hat breed type, sex, age, season, and carcass weight all affected the relationship between fat depths at the 2 sites. In general, British be ef and beef cross cattle could be considered as 1 group, but dairy cat tle were different. In the former group, for the no-teeth age class a seasonal and sex effect was evident, giving rise to 4 models, 1 for ea ch of the steer and heifer groups in winter-spring and summer-autumn. For the no-teeth dairy cattle there was no sex effect and all seasons were pooled to form an overall model. For older cattle (2, 4, and 8 te eth) there was significant monthly variation, and few overall models c ould be developed. In addition, the relationship between fat depths at the 2 sites was generally independent of carcass weight in older catt le. The analysis revealed that within the subcutaneous fat depot the r elationship between sites for fat depth can be influenced by a range o f variables.