Productive and reproductive performance in cattle infected with bovine leukosis virus

Abstract

Economic losses caused by enzootic bovine leukosis (EBL) have been of interest since World War II, when the neoplastic form of EBL increased dramatically in Europe. Olson (1974) and House et al. (1975) showed that animals with lymphosarcoma caused by the bovine leukosis virus (BLV) had reduced milk yields, a less efficient reproductive performance and high veterinary costs and mortality rates, while many carcasses were rejected at slaughter. However, the actual impact of BLV infection in cattle without lymphosarcoma is not clear. The purpose of the study reported here was to compare some productive and reproductive responses of cattle that were antibody-positive (BLVj) or negative (BLVk) for BLV.Holstein dairy cows in commercial dairy farms were used in this study. Blood samples were collected and subjected to BLV serological examination by the agar gel immunodiffusion test of Miller & van der Maaten (1976). Animals were then grouped as BLVj or BLVk according to their serological response to the BLV antigen. Productive and reproductive histories were obtained from individual animal records and the following factors were considered : milk production, calving interval and birth rate. For milk production, we had the daily milk yields of 547 animals, and for calving interval the time between two successive parturitions for 444 cows. These values were examined by ANOVA and when this was significant a Student's t test was carried out for each age group. Birth rates, the percentage of animals that calved in 1 year, were available for 557 animals and were examined with the Z-two proportion test. For all analyses, P 0n05 was considered significant.   Mean daily milk yield was lower by 11 % in BLVj than in BLVk cattle (19n4 v. 21n8 kg ; Table 1) and this was significant or approached significance for some age groups. This agrees with the findings of Reinhardt et al. (1988) and Brenner et al. (1989), who found decreases in milk yield of 3 and 3n5 % respectively. However, Langston et al. (1978), Huber et al. (1981) and Burridge et al. (1982) found no differences in the milk production of BLVj and BLVk cattle.No differences were found in the reproductive characteristics investigated (calving interval and birth rate ; see Tables 2 and 3). These results agree with the observations of previous workers (Langston et al. 1978 ; Huber et al. 1981 ; Brenner

Bovine leukemia virus infection in cattle of China: Association with reduced milk production and increased somatic cell score

“…Studies in the United States (Ott et al, 2003) and Canada (Sargeant et al, 1997) have demonstrated a negative effect of BLV infection on milk production at the herd level. Similarly, Olson (1974), Da et al (1993), andD'Angelino et al (1998) showed that animals with persistent lymphocytosis and lymphosarcoma caused by BLV infection had reduced milk yields. However, no association has been found between BLV infection and milk production in several studies in individual animals (Jacobs et al, 1991;Kale et al, 2007;Tiwari et al, 2007).…”

Soroepidemiologia da leucemia bovina (LB) em bovinos curraleiros dos estados de Goiás e Tocantins, Brasil

“…Garcia et al 7 e Birgel Jr. et al 8 não encontraram interferência na imunidade humoral e celular, enquanto Azedo et al 9 identificaram alterações funcionais em fagócitos mononucleares de animais sororreagentes. D'Angelino et al 10 ressaltaram a possibilidade de quedas na produção leiteira em animais sororreagentes, porém não foram observadas diferenças nos índices reprodutivos. Em rebanhos leiteiros dos Estados Unidos, foi estimada queda de 3% na produção, significando perda de US$ 59 por fêmea nos rebanhos sororreagentes 11 .…”

A new nanostructured Silicon biosensor for diagnostics of bovine leucosis

“…At any age animals can be infected with bovine leukaemia virus (BLV), but tumour (lymphosarcomas) is seen typically in the animals over 3 years old. Infections are usually sub clinical; only 30-70% of the infected cattle develop the persistent lymphocytes and only 0.1-10% -develop the tumours [3].…”