title: The effect of genetic selection for Johne's disease resistance in dairy cattle: Results of a genetic-epidemiological model.
abstract: The objective of this study was to model genetic selection for Johne's disease resistance and to study the effect of different selection strategies on the prevalence in the dairy cattle population. In the Netherlands, a certification-and-surveillance program is in use to reduce prevalence and presence of sources of infection in milk by culling ELISA-positive dairy cows in infected herds. To investigate the additional genetic effect of this program, a genetic-epidemiological model was developed to assess the effect of selection of cows that test negative for Johne's disease (dam selection). The genetic effect of selection at the sire level was also considered (sire selection), assuming selection of 80% of sires producing the most resistant offspring based on their breeding values, as well as the combined effect. Parameters assumed to be affected by genetic selection were the length of the latent period, susceptibility (i.e., the number of infectious doses needed to become infected), or the length of susceptible period as a calf. The effect of selection was measured by the time in years required to eliminate infection. Sensitivity analysis was performed for heritability, accuracy of selection, and intensity of selection. For dam selection, responses to selection were small, requiring 379 to 702 yr for elimination. For sire selection, responses were much larger, although elimination still required 147 to 223 yr. The response to selection was largest if genetic selection affected the length of the susceptible period, followed by the susceptibility, and finally the length of the latent period. Genetic selection for Johne's disease resistance by certification and surveillance is too slow for practical purpose, but that selection on the sire level is able to contribute to the control of Johne's disease in the long run.
authors.affiliation: Department of Farm Animal Health, Utrecht University, PO Box 80.151, 3508 TD Utrecht, the Netherlands; Department of Human Genetics, Radboud University Medical Center, PO Box 9101, 6500 HB Nijmegen, the Netherlands. Electronic address: kimmvanhulzen@gmail.com.
authors.forename: K J E
authors.initials: KJ
authors.lastname: van Hulzen
authors.affiliation: Department of Farm Animal Health, Utrecht University, PO Box 80.151, 3508 TD Utrecht, the Netherlands.
authors.forename: A P
authors.initials: AP
authors.lastname: Koets
authors.affiliation: Department of Farm Animal Health, Utrecht University, PO Box 80.151, 3508 TD Utrecht, the Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Nielen
authors.affiliation: Clinical Sciences of Companion Animals, Utrecht University, PO Box 80.163, 3508 TD Utrecht, the Netherlands.
authors.forename: H C M
authors.initials: HC
authors.lastname: Heuven
authors.affiliation: Animal Breeding and Genomics Centre, Wageningen University, PO Box 338, 6700 AH Wageningen, the Netherlands.
authors.forename: J A M
authors.initials: JA
authors.lastname: van Arendonk
authors.affiliation: Department of Farm Animal Health, Utrecht University, PO Box 80.151, 3508 TD Utrecht, the Netherlands.
authors.forename: D
authors.initials: D
authors.lastname: Klinkenberg
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology / Q000235:genetics* / Q000382:microbiology; D003612:Dairying / Q000379:methods*; D060467:Disease Resistance / Q000235:genetics*; D005260:Female; D008297:Male; D008957:Models, Genetic; D016927:Mycobacterium avium subsp. paratuberculosis / Q000502:physiology; D009426:Netherlands / Q000453:epidemiology; D010283:Paratuberculosis / Q000453:epidemiology / Q000235:genetics* / Q000382:microbiology; D012641:Selection, Genetic
keywords: Johne’s disease; dairy cow; genetic-epidemiological model; selection response