Transcript abundance of the pig stearoyl-CoA desaturase gene has no effect on fatty acid composition in muscle and fat tissues, but its polymorphism within the putative microRNA target site is associated with daily body weight gain and feed conversion ratio1

Fatty acid composition in porcine intramuscular fat affects the dietetic value and technological properties of meat. The stearoyl-CoA desaturase (SCD) gene is a strong positional and functional candidate for fatty acid composition. Our sequence analysis in 4 breeds (Duroc, Pietrain, Polish Landrace, and Polish Large White) revealed a novel SNP in the 5′-fl anking sequence and 9 novel SNP and 2 novel indels in the 3′ untranslated region (UTR). Transcript level of the SCD in subcutaneous fat was signifi cantly greater than in muscle tissue (n = 83; P < 0.001) and the interbreed comparison revealed a greater transcript level in the fat tissue of Polish Landrace (P < 0.01). We found no association between the abundance of the SCD transcript and fatty acid composition in any of the tissues. We performed an association analysis between 4 SNP (c.353C > T, c.-233T > C, c.*164A > G, and c.*928G > C), 1 indel (c.*2574_2576delGTC), and production traits in Polish Large White (n = 185) and synthetic line 990 (n = 243). The most pronounced associations were observed for the c.*928G > C polymorphism, which occurs within a predicted target site for 2 microRNA (ssc-miR-185 and ssc-miR-491). In line 990, this polymorphism was signifi cantly associated with daily BW gain (P < 0.04 under the general model) and feed conversion ratio (P < 0.0004) but not with fatness traits. The same tendency, but not signifi cant, was observed in the Polish Large White breed. When both breeds were analyzed together, these associations were again highly signifi cant (daily BW gain P < 0.003; feed conversion ratio P < 0.0001). We conclude that c.*928G > C is a promising marker for both porcine traits.