A field trial to evaluate the efficacy of a combined rotavirus-coronavirus/Escherichia coli vaccine in dairy cattle.

A field trial was designed to determine the efficacy of a combination rotavirus-coronavirus/Escherichia coli vaccine on dairy farms in southwestern Ontario. In Part A of the trial, 321 cows on 15 farms were randomly assigned to either vaccination or placebo groups. On eight farms, 50% of the dams were vaccinated, while on the other seven farms, 80% of the dams were vaccinated. In Part B of the trial, 26 farms were randomly assigned to either a total vaccination program or to no vaccination program. Mortality, disease occurrence and weight gains were recorded on all calves for the first two weeks of life. In Part A, 23.5% of all calves were treated in the first two weeks of life, 20.9% were treated specifically for scours and 3.6% of live-born calves died. Enteropathogenic E. coli was identified on 13 of the 15 farms, rotavirus on 11 and coronavirus on ten. At least one of the three potential pathogens was found on every farm. There were no significant differences between calves from placebo-treated and vaccine-treated dams with regard to the proportion treated for all diseases, or for scours, or the proportion which died. Neither were there differences in days to first treatment for all diseases (seven days on average), days to first scour (6.7 days), duration of treatments (3.9 days for all diseases, 3.7 days for scours), or estimated weight gains (0.5 kg/day to 14 days). These results were not altered when the presence or absence of enteropathogenic E. coli, rotavirus or coronavirus on the premises was accounted for.(ABSTRACT TRUNCATED AT 250 WORDS)