Sel’skokhozyaistvennaya Biologiya [Agricultural Biology], 2012, № 6, p. 49-55 UDK 636.2.034:636.08.003:578.82/.83:577.2.08 PREVALENCE OF BOVINE LEUKEMIA VIRUS IN BLACK AND WHITE COWS WITH THE DIFFERENT LEVEL OF MILK PRODUCTIVE TRAITS 1 All-Russia Research and Development Institute for Livestock Husbandry, RAAS, Dubrovitsy settlement 142132, Moscow province, Russia e-mail: n_zinovieva@mail.ru N.A. Zinovieva1, E.A. Gladyr’1, I.V. Vinogradova1, M.E. Mikhailova2, L.A. Molofeeva3, L.K. Ernst 1 3 Moscow State University of Medicine and Dentistry named after A.I. Evdokimov, Moscow 127473, Russia e-mail: lyda19-80@mail.ru 2 Institute of Genetics and Cytology, NAS of Belarus, Minsk 220072, Belarus e-mail: m.mikhailova@igc.bas-net.by Received August 13, 2012 S umma r y The association study of BLV status (carrier, non-carrier) with the level of milk productive traits in Black and White cows of different lactation periods was performed. <...> The blood samples were derived from the whole herd including 382 cows of fist lactation period, 253 cows of second lactation period and 197 cows of third lactation period. <...> The presence of provirus form of BLV in blood leuco-cytes was detected by nested PCR using developed system. <...> Based on results of PCR analysis the cows received BLV+ or BLV- status. <...> The significantly higher BLV prevalence (+9.0…+ 21.7 per cent) in fist lactation period cows with the «mean» (within Xaverage±σ) and «high» (more than Xaverage+σ) levels of milk productive traits (milk yield, fat content, milk fat and protein yield) comparing to «low» productive cows (less than Xaverage-σ) was observed. <...> The increase of the level of most milk productive traits (milk yield, fat content, milk fat and protein yield) in cows of different genealogical lines with BLV+ status comparing to BLV- status was observed. <...> Such metabolic load is peculiar to high yielding cows as specific type of metabolism associated with increased synthesis and secretion of milk; in most cases it results in metabolic stress – violation of some energetic processes related to, in particular, reproduction and health (2). <...> Metabolic stress during lactation affects the nature of immune response, which <...>