|Van Vleck, Lloyd|
Submitted to: Midwestern Section of the American Society of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: 2/6/2006
Publication Date: 3/20/2006
Citation: Snowder, G.D., Van Vleck, L.D., Cundiff, L.V., Bennett, G.L. 2006. Genetic factors influencing bovine respiratory disease in feedlot cattle [abstract]. Journal of Animal Science. 84(Suppl. 2):136. Abstract #331. Interpretive Summary: No interpretive summary is required.
Technical Abstract: Bovine respiratory disease (BRD) is the most common and costly disease of feedlot cattle in the US yet the genetic components for resistance to this disease have not been examined. Therefore, this study's objective was to characterize genetic factors influencing the incidence of BRD in feedlot beef calves. Growth and health records of 18,112 feedlot calves from 12 different breed types over a 15 yr period (1987 to 2001) at the USMARC, Clay Center, NE were analyzed. Breed types consisted of nine pure breeds (Angus, Braunvieh, Charolais, Gelbvieh, Hereford, Limousin, Pinzgauer, Red Poll, and Simmental) and three composite breeds (MARC I, MARC II, and MARC III). Five breeds (Braunvieh, Pinzgauer, Red Poll, Simmental, and Limousin) were present only from 1987 to 1991. Hereford calves were fed from 1987 to 1999. Incidence of BRD varied across years with the highest incidences observed between 1987 and 1992 (18 to 44%) followed by a period (1992 to 2001) of lower incidences (5 to 14%). Morbidity was highest in Limousin (32%), Pinzgauer (35%), and Simmental (33%); and lowest in Angus (10%). Mortality related to BRD was highest in Red Poll (9%) and lowest in Angus (2%). The epidemiological pattern showed that incidence increased dramatically after 5 d, peaked within 14 d and remained high until approximately 80 d in the feed lot. After 110 d on feed the numbers of morbid calves observed per day were negligible. Components of variance for animal genetic effects and for breed by year interaction as an uncorrelated random effect were estimated using MTDFREML. The heritability estimate for resistance to BRD in the feedlot was low, 0.08 ± 0.01. However, because BRD incidence is a dichotomous threshold trait, adjusted heritability for resistance to BRD on an underlying continuous scale was estimated to be 0.18. Development of an accurate and humane challenge for resistance to BRD would likely be a useful tool to use with selection to reduce BRD in the feedlot.