Prevalence of Bovine Leukemia Virus in Black and White Cows With the Different Level of Milk Productive Traits

Abstract

S u m m a r yThe 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 increase of the number of cows with BLV + status from 28.5 per cent of fist lactation period cows to 36.1 per cent of third lactation period cows was observed. 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 data analysis in aspect of different milk productive traits indicated the higher differences between the groups differed in milk fat yield (18.3-21.7 per cent, p < 0.999). The tendencies described above in the most of cases were observed in the second and third period lactations' cows. 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.Keywords: Keywords: bovine leukemia virus, DNA diagnostics, milk productive traits.Breeding cattle for high milk production contributes to changes in animals' health (1). Higher output of milk extends the share of available energy utilized in the synthesis of milk, and thereby promotes a negative energy balance that can be restored for the expense of body reserves, which in turn, causes a partial decline of condition. 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 stressviolation of some energetic processes related to, in particular, reproduction and health (2). Metabolic stress during lactation affects the nature of immune response, which was confirmed by K. Kimura et al. (3) who revealed differences in leukocyte patterns of Holstein cows after mastectomy and normally lactating ones. The changed immune profile of high yielding cows is seen as the cause of their susceptibility to diseases (4-9). For example, milk yield and susceptibility to mastitis are linked by the positive genetic correlation varying from 0,24 to 0,55 (5). K.L. Ingvartsen et al. (9) have detected undesirable genetic correlations between milk yield and the incidence of ketosis (0,26-0,65), ovarian cysts (0,23-0,42), mastitis (0,15-0,68), and lameness (0,24-0,48). Increased milk production is also associated with widespread occurrence of bovine leukemia virus (BLV) in dairy cattle. It was shown that Holstein cows of Cana...

Molecular Characterization of Bovine Leukemia Virus with the Evidence of a New Genotype Circulating in Cattle from Kazakhstan

“…showing a similar distribution of BLV seroreactivity between particular regions. BLV infection was also found in the neighboring countries and includes 28.5-36.1% in Russia [32], 3.9% in Mongolia [33] and 49.1% in China [34].…”