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United States Department of Agriculture

Agricultural Research Service

Title: Genetic and Environmental Factors Associated with Incidence of Infectious Bovine Keratoconjunctivitis in Preweaned Beef Calves

Authors
item Snowder, Gary
item Van Vleck, Lloyd
item Cundiff, Larry
item Bennett, Gary

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 2, 2004
Publication Date: March 1, 2005
Citation: Snowder, G.D., Van Vleck, L.D., Cundiff, L.V., Bennett, G.L. 2005. Genetic and environmental factors associated with incidence of infectious bovine keratoconjunctivitis in preweaned beef calves. Journal of Animal Science 83:507-518.

Interpretive Summary: Infectious bovine keratoconjunctivitis (IBK), most commonly known as pinkeye is one of the most economically important diseases in preweaned calves. The heritability of this disease was previously not reported. Breed differences in susceptibility to pinkeye have not been clearly evaluated. Therefore, this study examined health records of 45,497 calves over a 20 yr period to determine environmental and genetic factors influencing the incidence of pinkeye in preweaned calves. Three studies were conducted. The first study evaluated environmental factors and genetic differences among 9 purebred (Angus, Braunvieh, Charolais, Gelbvieh, Hereford, Limousin, Pinzgauer, Red Poll, and Simmental) and three composite breeds (MARC I, MARC II, and MARC III). Pinkeye infection decreased calf weaning weight by 8.9 kg. Incidence of pinkeye was related to age of the calf and the seasonal life cycle of the face fly. Incidence of pinkeye increased in the spring (June), peaked during the summer months (July to September) and then decreased in the fall. The Hereford breed was the most susceptible breed compared to all other purebreds and composites. Estimates of heritability for pinkeye resistance were generally low and ranged from 0.00 to 0.28. The second study determined if the effects of crossbreeding purebreds (Hereford and Angus) improves resistance to pinkeye. No significant evidence was found to suggest crossbreeding improves resistance to pinkeye infection. In the third study, susceptibility to pinkeye of crossbred calves sired by tropically adapted breeds (Brahma, Boran, Tuli) compared to purebred and crossbred British and Continental types was investigated. Calves sired by tropically adapted breeds were less susceptible to pinkeye than most breed types but did not differ from Herefords and Angus crossbred and purebred Angus calves. Response to genetic selection to reduce the incidence of pinkeye in beef herds will likely be slow. Significant breed differences in susceptibility to pinkeye may be important to some producers and management systems.

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

Last Modified: 11/21/2014
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