Abstract
BackgroundHere, we jointly summarise scientific evidence for genetic variation in resistance to infection with Mycobacterium bovis, the primary agent of bovine tuberculosis (TB), provided by two recent and separate studies of Holstein-Friesian dairy cow populations in Great Britain (GB) and Ireland.MethodsThe studies quantified genetic variation within archived data from field and abattoir surveillance control programmes within each country. These data included results from the single intradermal comparative tuberculin test (SICTT), abattoir inspection for TB lesions and laboratory confirmation of disease status. Threshold animal models were used to estimate variance components for responsiveness to the SICTT and abattoir confirmed M. bovis infection. The link functions between the observed 0/1 scale and the liability scale were the complementary log-log in the GB, and logit link function in the Irish population.Results and discussionThe estimated heritability of susceptibility to TB, as judged by responsiveness to the SICTT, was 0.16 (0.012) and 0.14 (0.025) in the GB and Irish populations, respectively. For abattoir or laboratory confirmation of infection, estimates were 0.18 (0.044) and 0.18 (0.041) from the GB and the Irish populations, respectively.ConclusionsEstimates were all significantly different from zero and indicate that exploitable variation exists among GB and Irish Holstein Friesian dairy cows for resistance to TB. Epidemiological analysis suggests that factors such as variation in exposure or imperfect sensitivity and specificity would have resulted in underestimation of the true values.
Highlights
We jointly summarise scientific evidence for genetic variation in resistance to infection with Mycobacterium bovis, the primary agent of bovine tuberculosis (TB), provided by two recent and separate studies of Holstein-Friesian dairy cow populations in Great Britain (GB) and Ireland
Estimates were all significantly different from zero and indicate that exploitable variation exists among GB and Irish Holstein Friesian dairy cows for resistance to TB
This paper summarises the scientific evidence for genetic variation in resistance to infection with M. bovis provided by two recent and separate studies of Holstein-Friesian dairy cow populations in the GB and Ireland [3,4]
Summary
Ante mortem surveillance of TB The tuberculin test is the international standard for ante mortem diagnosis of bovine TB in cattle [5]. ≥0.29 of being culled as a reactor, whereas in the Irish dies as compared with clinical mastitis (0.094; 12); even study the equivalent group of cows had a somewhat with low heritabilities clinical mastitis is directly or higher estimated risk, ≥0.48, of exhibiting a standard indirectly (via reduced somatic cell count) incorporated reaction to the SICTT. This may be an indication that into breeding programmes in many countries. To be drawn regarding the level of exploitable genetic resistance to TB that exists in the GB and Irish Holstein-Friesian populations
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