Molecular markers associated with the study of molecular genetics, in addition to traditional genetic improvement, are tools that can be used to aid the selection of animals that have a characteristic of economic interest, through the study of polymorphisms in genes that determine this characteristic (GALLEGOS et al. , 2006), which has been studied to detect markers that are useful for association studies (MARRERO et al., 2016).Research has also focused on single nucleotide polymorphisms (SNPs) that are common throughout the genome and can predict an important step for studies of association with the characteristics of milk production in cattle and buffaloes (ANAND et al. , 2008).In order to identify milk markers associated with milk components in buffaloes (REN et al., 2009; COSENZA et al., 2009), as well as the association of molecular markers with milk production in cattle and buffaloes (LARA, 2011; ZETOUNI et al., 2013). Although buffaloes and cattle have strong genotypic and phenotypic similarities and belong to the subfamily Bovinae (SCHERF, 2000; BONDOC, 2013), few studies with molecular markers have been carried out with buffaloes.

Leptin is a non-glycosylated peptide hormone (16 kDa) product from ob gene, has an initial polypeptide chain of 167 amino acids, of which the first 21 amino acids represent a signal peptide that is discarded before the mature protein is secreted into the circulation, and it is produced almost exclusively in adipose tissue (ZHANG, 1995; TERMAN, 2005).

This protein is involved with the mechanisms that regulate both, energy intake and metabolism, preventing the excessive deposition of body fat, homeostatic regulation of food intake, immune function, energy distribution, milk production and fertility (ARGAWAL et al. 2010; GIBLIN et al., 2010; CLEMPSON et al., 2011; ORRÙ et al., 2012). The genetic polymorphism LEP-1620 (A / G), located in intron 2 of the leptin gene, was positively associated with the percentage of fat and protein (ZETOUNI et al., 2013). This polymorphism was also correlated with weaning weight in Nellore cattle (SOUZA et al., 2009). Cattle and buffalo have great contributions to the world agricultural economy with their products. According to MAPA (2016), the Brazilian herd of buffalo is estimated at about 1.15 million buffaloes, the North region being the largest producer in the country, with 720 thousand animals, the Northeast region with 135 thousand heads and the Southeast region, with 104 thousand heads.

In relation to milk production, cattle are the most studied animals in genetic research. However, studies that relate LEP-1620 SNP to milk production in buffaloes are rare in the literature. Based on these data, the objective of the present study was to identify the LEP-1620 (A / G) polymorphism in the gene coding for leptin hormone in buffaloes and to predict their association with milk production.