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The reproduction and production traits are closely connected in cattle and therefore the genetic improvement of the reproduction traits is critical for the efficient course of lactogenesis and lactopoesis. The same physiological processes affect not only reproduction system but also lactation. Generally low numbers of genetic markers significantly influencing the reproduction traits were detected, because most of them are characterized by coefficients with small heritability. One of the promising possibilities is the analysis of different genetic variants of hormones and protein factors mediating their actions that have a key role in reproduction system (Kowalewska-Luczak, 2009; Szatkowska et al., 2011). In mammalian is reproduction regulated mainly by estrogens synthesized in the ovaries trough the androgens aromatization. Except other functions these hormones stimulate lactogenesis in many species with well-developed mammary glands. In lactation the estrogens provide the stimulation of prolactin secretion and possibly other hormones from the pituitary gland (Kowalewska-Luczak, 2010). For the biosynthesis of estrogens from androgen precursors are crucial the enzymatic complex of two proteins, nonspecific microsomal flavoprotein reductase and specific haemoglycoprotein, which is known as cytochrome P450 aromatase. The converting of androgen steroid precursors into estrogens has also indirect effect on mammary gland development and milk production (Simpson et al., 1994; Conley and Hinshelwood, 2001; Kowalewska-Łuczak et al., 2013). The gene encoding cytochrom P450 aromatase (CYP19) was mapped on bovine chromosome 10 to band q2.6 (Vanselow et al., 2001). The gene expression is regulated by tissue-specific alternative promotor regions which correspond to the 5’-UTR transcripts, but the coding region is identical for all tissues (Kalbe et al., 2000). Then the increase of number of prolactin and growth hormone receptors influence the mammary cells. The CYP19 gene is transcribed to six different promotor regions. The genomic sequence of CYP19 locus (125kbp) includes untranslated regions (exons and promotor) and nine encoding exons that have 89 and 36 kbp, respectively (Vanselow et al., 2008). In promotor regions of CYP19 gene was found only several single nucleotide polymorphisms (SNPs) (Vanselow et al., 2001) which were associated with milk production traits in cattle (Kowalewska-Luczak, 2010; Jędrzejczak et al., 2011; Kowalewska-Łuczak et al., 2013). In this work was analysed the polymorphic site (A/G transition) in the promotor 1.1 region that was recognized by restriction enzyme PvuII (Vanselow et al., 1999). The aim of this study was to determine the animal genotypes, evaluate the genetic structure of population based on polymorphism in CYP19 gene and estimate the effect of CYP19 genotype on long-life milk production traits in Slovak Simental cattle.

Analysis of cyp19 gene polymorphism as factor affecting milk production of cattle