Genetic and environmental factors associated with incidence of infectious bovine keratoconjunctivitis in preweaned beef calves

摘要: Infectious bovine keratoconjunctivitis (IBK) is one of the most economically important diseases in preweaned calves. This study examined health records 45,497 calves over a 20-yr period to determine environmental and genetic factors influencing incidence IBK. Three data sets were analyzed with an animal model. The first set (n = 41,986) evaluated differences among nine purebred (Angus, Braunvieh, Charolais, Gelbvieh, Hereford, Limousin, Pinzgauer, Red Poll, Simmental) three composite breeds (MARC I, MARC II, III). Weaning weights diagnosed IBK 8.9 kg lighter (P < 0.05) than healthy Incidence was related age calf seasonal life cycle face fly (Musca autumnalis). increased spring (June), peaked during summer months (July September), then decreased fall. Herefords susceptible breed compared all other purebreds composites. Estimates direct heritability for generally low ranged from 0.00 0.28 by breed. maternal permanent effects dam on not significant breeds. second 9,606) used estimate heterosis Hereford Angus diallel design. effect reciprocal Hereford/Angus crossbred slightly negative 0.12) but large. higher x (13.3 vs. 8.9%) suggests sired tropically adapted (Brahma, Boran, Tuli) Bos taurus types investigated third 2,622). Crossbred had lower 0.05), they different either crosses or Response selection decreasing likely be slow because Significant may some producers management systems.