Bovine leukemia virus antibodies in dairy cattle farms and milk cooling tanks

Background: Bovine leukemia virus (BLV) is a retrovirus. It is common infectious viruses of cattle with worldwide distribution. Milk from infected cows often contains BLV-infected cells are a common cause of infection. Eradication and control of BLV is based on early diagnostic. Both serum and milk samples can be tested by ELISA and it is possible to test either individual samples or, at a herd level, milk cooling tanks (MCT) samples. The aim of this study is to determine BLV antibodies (Abs) in the MCT, milk cans, and individual blood and milk samples of dairy cows in dairy cattle managements located in Burdur center and its districts and to follow and study the infection on the milk production chain. Materials, Methods & Results: Milk samples were collected from 50 main MCT. Studies were carried out in the managements that seven BLV Ab (+) and seven Ab (-) in their main MCT were located. For this purpose, milk samples were collected from mixed milk cans that were collected from managements providing milk for main MCT. Blood and milk samples were collected from dairy cows, housed in managements where BLV Ab (+) and Ab (-) was detected. Highest and lowest percent BLV (+) management, percent BLV (+) can numbers and percent milk amount were in 1 ton and 2 ton MCT, respectively. Moreover, these parameters were paralleled in all MCT. Percent BLV (+) and milk amounts were highest in 3 ton MCT and lowest in 2 ton MCT. In addition, these parameters were paralleled in all MCT. Distributions in BLV (+) managements ranged from 15 to 75%. It was detected at the individual animal levels, BLV (+) milk sample distributions ranged between 7.4 and 38.4%. Age range of the BLV (+) cows was between 3 and 11 years. Individual BLV tests between milk and serum samples were correlated positively in 5 managements (71.4%). On the other hand, the correlation was not detected in 2 of the managements (28.6%) that the individual milk and serum samples were collected. BLV (+) managements (%), BLV (+) cans (%) and milk volumes (%) were highest in 1 ton MCT and lowest in 3 ton MCT as BLV Ab (-). In addition, these 3 parameters were correlated in all MCT. BLV (+) cow numbers (%) and milk yields of the cows (%) were also correlated in all MCT. Although the MCT were found to be BLV (-), 3.9-37.5 % of the managements that provided milk to BLV (-) MCT were BLV (+). Furthermore, only 7.2-9.2 % of individual milk tests for the cows in managements that provided milk into BLV (+) MCT was BLV (+). Age of the BLV (+) animals was ranged between 3 and 11 in all MCT. The individual BLV tests between milk and serum samples were correlated positively in two managements (28.6 %). On the other hand, the correlation was not detected in 5 of the managements (71.4 %) that the individual milk and serum samples were collected. Discussion: The current study concluded that sampling milk cans is more appropriate than sampling MCT for BLV program. There was a correlation among the number of BLV (+) managements providing milk to milk tanks, number of cans and amount of milk in the cans. Furthermore, there was a correlation between the number of BLV (+) animals and milk volume of BLV (+) animals. Stage of a lactation period could be important for BLV screening since this appeared to affect the BLV test outcomes. There were also no effects of BLV infection on the milk yield and were no correlations between the individual blood and milk sample tests from the same animals. Moreover, blood samples of the cows with Ab (-) milk samples should be tested individually for BLV infection.