Detection of polymorphisms in the ovine leptin (LEP) gene:: Association of a single nucleotide polymorphism with muscle growth and meat quality traits

Leptin, the expression product of the obese gene produced primarily in the adipose tissue, is related to feed intake, growth and lipid metabolism. In beef and swine, polymorphisms of the leptin gene (LEP) are associated with body composition and fat deposition traits. The objective of this study was to identify polymorphisms in the ovine LEP gene and to test for their possible association with growth (average daily gain), carcass composition (% bone, fat and lean, loin eye area, fat and muscle depth), longissimus (L) structural and metabolic characteristics [fiber types, citrate synthase (CS) and lactate deshydrogenase (LDH) activity] and meat quality traits (color, pH, shear forces and chemical composition) in sheep. A population set of Dorset (n = 70) and Suffolk (n = 69) lambs was screened for polymorphisms of the ovine LEP gene. Three single nucleotide polymorphisms (SNP) were identified (A103G, C154T and C617G). In the Suffolk breed, the A103G SNP is associated with reduced muscle thickness (-1.36 mm) and loin eye area (-137.58 mm(2)) and with increased shear forces (+1.091 kg), pH (+0.168) and cross-sectional area (CSA) of the slow-twitch oxidative (SO) fibers (+818 mu m(2)) of the L muscle. In the Dorset breed, the A103G variant is also associated with an increased CS activity in the L muscle (+3.19 IU g(-1)) and in subcutaneous fat (+0.36 IU g(-1)).