STAT5A/AvaI polymorphism in Podolica bulls and its effect on growth performance traits

STATs are a group of transcription factors that mediate actions of a variety of peptide hormones and cytokines within target cells (for example prolactin and growth hormone). Therefore, STAT5A gene is a candidate marker for quantitative traits in farm animals. In this study the STAT5A/AvaI polymorphism was investigated with PCR-RFLP in a sample of 108 Podolica bulls. This polymorphism is localized in the coding region of the bovine STAT5A gene. It is a substitution C ? T at position 6853 within the exon 7. All the three possible genotypes for the C/T polymorphism were identified. The overall frequencies of alleles C and T were 0.44 and 0.56 respectively; the Hardy-Weinberg equilibrium was verified. In order to study relationship between STAT5A/AvaI polymorphism and growth performance traits the animals' body weights at 180 (BW180), 270 (BW270), 360 (BW360) and 450 (BW450) days were measured. Moreover average daily gains (ADG) in four intervals were calculated (ADG180-270; ADG270-360; ADG360-450; ADG180-450). The CC and CT bulls tended to show a higher live weight and a faster growth in comparison with TT animals. In fact in the CC and CT animals the live body weight at the age of 450 days was similar (444.50 and 444.64 kg respectively) and significantly higher than that of TT individuals (427.24 kg). Moreover CC bulls seem to show an initial faster growth which determined higher BW180 and BW270. On the contrary, CT bulls exhibit a faster growth in the last stages of the test namely in the period between 270 and 450 days. Growth of TT animals is steady but they achieved, at the age of 450 days, a lower live weight in comparison with other genotypes.