Performance of cross and purebred corriedale lambs slaughtered at 5 month of age

2. Measurements of the Longissimus dorsi and subcutaneous fat depth in the live animals, and its relations with fat score and meat conformation in the carcass

Abstract

The subcutaneous fat depth (SFD) and the area ofthe muscle Longissimus dorsi ( eye muscle area: EMA) were ultrasonically determined on 520 female and male lambs (32.04 ±5.4 kg and 141.5 ±30.9 days old) resulting from the crossbreeding of Corriedale sheep with 21 rams of Corriedale (C), Texel (TX), Hampshire Down (HD), Southdown (SD), lle de France (IF), and Milchschaf (MF) breeds. The IF-cross lambs showed the highest values for SFD, and the MF lambs the lowest (7.1 vs 4.8 mm, P≤0.01, respectively). The measurements ofEMA were superior for the crossbreds (P≤0.01 ), particularly when sired by rams from meat breeds (1303, 1289, 1281, 1266 mm² vs 1225 mm², P≤0.01, TX, SD, IF, HD and C, respectively). A positive association (P≤0.0001) was found among SFD, body condition (BC), tissue thickness at the GR point (GR) and the scale used for carcass typification based on fat coverage (TFC). The correlations ranked from medium to high among SFD, BC and GR, and low in the case ofTFC. The correlation between EMA estimated by ultrasonography and determined on the carcass was medium positive (r=0.5; P=0.0001). Intermediate correlations were found between this last value and the proportion of valuable cuts (r =0.66; P≤0.0001) or the scale used to typify carcasses based on meat conformation (r=0.55; P≤0.0001).