Relationship Between Breed, GH and CAST Genotypes, and FA Composition in the Ovine Intramuscular Fat of Musculus Semimembranosus

The aim of the study to evaluate relationship between breed, <i>GH</i> and <i>CAST</i> genotypes, and FA composition in the ovine intramuscular fat of <i>musculus</i><i>Semimembranosus</i>. To fulfil this aim, 175 blood samples were drawn by jugular vein puncture from Lithuanian Black-Headed (N43), Lithuanian Black-Headed *Ile de France (N43), Lithuanian Black-Headed *Suffolk (N44), and Lithuanian Black-Headed *Texel (N45) lambs. The lambs were weighed weekly, and the growth rate was calculated using birth weight and month weight values. Genomic DNA was extracted from blood samples taken into EDTA containing tubes, using a "GeneJET Genomic DNA Purification Kit" (Thermo Scientific, Waltham, MA, USA). The method of polymerase chain reaction and restriction length polymorphism were used to genotype growth hormone (<i>GH</i>) and (<i>CAST</i>) gene polymorphisms. Meat samples of four lamb breeds were taken for analysis (200-250 g from <i>musculus</i><i>Semimembranosus</i> were taken 48 h after carcass meat cooling). The fatty acid methyl esters (FAMEs) were analyzed using a gas chromatography mass spectrometry (GC/MS) instrumental technique. All data were evaluated statistically. Studies have shown that purebred Lithuanian Black-Headed lambs are born with a higher weight, so it is not advisable to mix them with Ile de France, Suffolk, or Texel breeds. Also, our research shows that the most beneficial breed are lambs that have the BB genotype of the <i>GH</i> gene and the MN genotype of the <i>CAST</i> gene, as these lambs are born with the greatest weight and gain. The meat of Lithuanian Black-Headed lambs showed the lowest content of SFA and the largest content of PUFA. The ratio ω-6/ω-3 FA varied from 2.71 (Lithuanian Black-Headed * Suffolk) to 4.52 (Lithuanian Black-Headed). Based on the research, it can be concluded that the purebred Lithuanian Black-Headed lambs had higher birth weight, therefore it is not appropriate to mix them with Ile de France, Suffolk, or Texel breeds.