Acta Vet. Brno 2012, 81: 353-358
Diagnosis of the bovine leukaemia virus infection in Polish Holstein-Friesian cows and comparison of their milk productivity
Economic losses due to the bovine leukaemia virus infection can come from reduced milk production. The aim of this study was to evaluate molecular multiplex Polymerase Chain Reaction (multiplex PCR) test as an alternative for serologic Enzyme-linked Immunosorbent Assay (ELISA) method in diagnosing bovine leukaemia virus infections and found possible differences in milk yield in seronegative and seropositive cows. The study involved two groups of Polish Holstein-Friesian var. black and white cows (a total of 147 individuals). Animals were grouped according to their serological response to the bovine leukaemia virus antigen: control group of 71 healthy cows and second group of 76 naturally infected animals. Both multiplex PCR and ELISA proved to be very sensitive methods with sensitivity up to 100% and 97.4%, respectively. Negative effect of bovine leukaemia virus on milk yield was observed. Leucosis-free cows achieved higher milk yield (+ 322.9 kg; P ≤ 0.01), protein yield (+ 5.2 kg, P ≤ 0.05), and better milk yield after calculation into daily milk yield corrected for fat (+ 106.6 kg, P ≤ 0.05) in comparison to seropositive cows. In infected cows a significantly higher (P ≤ 0.01) fat content (4.1%) was recorded. Because ELISA test does not provide information of the infection at an early stage and is not sensitive enough to detect every infected animal, a two-step protocol allows for elimination of seropositive animals and restriction of their introduction into herds in Europe.
Keywords
Enzootic bovine leucosis, multiplex PCR, dairy cows, milk traits.
