Relationship between blood physiological attributes and carcass characteristics in Iranian fat-tailed sheep

The relationship between blood physiological attributes and carcass characteristics was studied in 40 randomly selected 8-month-old ram lambs of Ghezel and Mehraban (20 rams per breed) sheep. One day before slaughter, blood samples were obtained after a 24 hr fast. Serum samples were assayed for glucose, cholesterol, serum urea nitrogen (SUN), total protein, albumin, triglycerides, creatinine, and calcium and magnesium ion concentrations. Dry matter, crude protein, crude fat (ether extract) and ash were determined in carcass soft tissues (carcass without bone and tail fat). Overall, serum cholesterol (r=-0.70; P<0.01) and creatinine (r=-0.48; P<0.05) concentrations were negatively correlated with the crude protein percentage of soft tissues dry matter (CPDM) in these sheep. Serum cholesterol concentration was positively correlated with the total dissected fat in both Ghezel (r=0.83; P<0.01) and Mehraban sheep (r=0.60; P<0.01). CPDM was negatively (P<0.01) correlated with a serum glucose concentration in Ghezel (r=-0.60), and with a SUN concentration in Mehraban (r=-0.60). A positive correlation was also found between the serum cholesterol concentration and crude fat (ether extract) as a percentage of the soft tissues dry matter in Ghezel (r=0.66; P<0.01). In general, fewer carcass traits in Mehraban were significantly correlated with cholesterol, and the coefficients were generally smaller than those for the Ghezel breed. The regression equations showed that blood cholesterol, glucose, triglyceride and SUN could be regarded as good predictors of carcass characteristics in Ghezel sheep. Serum cholesterol concentration was the only blood attribute that was retained in equations for Mehraban sheep. The coefficients of determination for Mehraban sheep were much smaller than those for Ghezel. More research with a larger number of animals is needed before they find application in carcass evaluation.