Relationship between blood lipid indicators and fat content and composition in Duroc pigs

The relationship between blood lipid indicators and subcutaneous and intramuscular fat (IMF) content and composition was investigated with the purpose to search for biomarkers specifically associated to one of them. The experiment was conducted on 111 purebred Duroc barrows, in which serum concentration of iron, glucose, total protein (TP), total cholesterol, HDL-Cholesterol (HDL-C), LDL-Cholesterol and total triglycerides, the percentage of lipoproteins (α-lipoprotein, β-lipoprotein, pre-β-lipoprotein and chylomicrons), and plasma insulin-like growth factor I (IGF-I) were determined at 120, 160, and 185 days of age. Carcass backfat (BT) and loin thickness were measured at 215 days, as well as IMF content in gluteus medius (GM) and longissimus dorsi (LM) muscles. Fatty acid composition in GM, LM and in subcutaneous fat was analysed by gas chromatography. Blood lipid indicators displayed an age-related pattern and a low correlation structure with commercial traits. Circulating TP was the best biomarker for early estimation of fatness (with a correlation of 0.49 and 0.32 with BT and IMF in GM, respectively, P<0.05), although HDL-C was the most consistent throughout age. Circulating IGF-I at later stages of growth may help for specifically biomarking BT against IMF. Thus, whereas HDL-C at 185 days correlated similarly with BT (0.28, P<0.05) and IMF (0.22, in GM, and 0.20, in LM, P<0.05), IGF-I at this age was more specifically correlated to BT (0.33, P<0.05) than to IMF (0.01, P>0.05). However, none of the studied blood lipid indicators has been revealed as an effective potential biomarker for differential fat deposition in pigs.