Influence of management technology and parturition on antibody levels in cows with bovine leukosis.
Sera from 97 Holstein-Friesian cows kept in isolation (herd I) were tested on 9 occasions with an interval of 90 days. The cows had previously given a positive reaction with bovine leukaemia virus antigen in the agar gel immunodiffusion (AGID) test. During the period of loose housing (at tests 1-3) 0-3 cows per test (0-3.1%) gave a negative reaction. When the same animals were kept in the tie-in system (at tests 4-7) the number of negative reactors varied between 9 and 26 (16.9-20.1%). Twenty-eight cows of herd II were tested serologically by the AGID test on a total of 9 occasions from day 60 before term up to postpartum day 90. The lowest antibody level was obtained at calving, when 7 cows gave a negative result in the AGID test. In three cows the decline of antibody level was so pronounced that their serum was negative even after postpartum day 60. One cow was negative even at the end of the test period (on postpartum day 90). The variation in serum antibody level was demonstrable also by ELISA; however, by that test none of the animals gave a negative result. The antibody level demonstrable in the milk reached its peak at calving and then it underwent a gradual decline; however, it did not drop below the detectability limit by the end of the test period. It is concluded that in bovine leukosis infected herds the performance of the AGID test is extremely impaired by the use of the tie-in housing system, as well as by a combined effect of tying in and parturition. Therefore, during the leukosis eradication and qualification of herds kept in a tie-in system, ELISA is the method that can be used, instead of AGID, with satisfactory efficacy even for the testing of sera.
Tekes
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Central Veterinary Institute, Budapest, Hungary.
D000818:Animals; D000914:Antibodies, Viral / Q000032:analysis* / Q000097:blood; D002417:Cattle; D016583:Enzootic Bovine Leukosis / Q000097:blood / Q000276:immunology*; D005260:Female; D006799:Housing, Animal; D007743:Labor, Obstetric; D001909:Leukemia Virus, Bovine / Q000276:immunology*; D008892:Milk / Q000276:immunology; D011247:Pregnancy
D000914:Antibodies, Viral