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Evaluation of growth and performance characteristics prior to entering the feedlot as an indicator for contracting Bovine Respiratory Disease
The objective of the current study was to evaluate growth and performance traits prior to entering the feedlot as potential indicator of bovine respiratory disease (BRD) susceptibility. A population of 560 spring born crossbred steers (2009-2011) from the Central Research Station and the Hill farm Research Station in Louisiana were evaluated for growth and performance prior to being shipped (2010-2012) to a commercial feedlot in Guymon, OK. The growth and performance traits evaluated consisted of birth weight, weaning weight and hip height. Bovine respiratory disease status was recorded by the feedlot, and consisted of animals treated for BRD or animals that subsequently perished due to BRD infection. A total of 24 steers over the two year evaluation period contracted BRD and were subsequently treated or perished in the feedlot. The Mixed model procedure of SAS was utilized to determine if associations between growth and performance traits and BRD status in the feedlot were linked. Fixed variables in the model included year of entrance into the feedlot, farm of origin and BRD status while in the feedlot. Growth and performance traits were fit in the model as random variables. Analyses revealed that no one trait had a significant effect (P < 0.05) on BRD status in the feedlot. However, birth weight did exhibit a genetic trend (P < 0.09) in which animals with larger average birth weights (39.84 kg) had a higher degree of BRD incidence in the feedlot than animals with smaller birth weights (37.63 kg) in the utilized population. While no one growth and performance trait was statistically significant (P < 0.05), the fixed variable of year was highly significant (P < 0.0001) in the statistical model thus necessitating further evaluation of other environmental and management variables that could be influencing susceptibility of contracting BRD during the feedlot stage of production.
Keywords: Bovine Respiratory Disease, Feedlot, Growth and Performance