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1 Department of Veterinary Preventive Medicine, The Ohio State University, Columbus 43210
2 Department of Animal Sciences, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster 44691
Corresponding author: P. J. Rajala-Schultz; e-mail: rajala-schultz.1{at}osu.edu.
The association between milk yield at dry-off and intramammary infections at calving was evaluated from 116 lactations in one herd. Duplicate quarter samples were collected within 3 d after calving to estimate prevalence of intramammary infection at calving; information on cows parity, daily milk yields, weekly somatic cell counts, and dry-off and calving dates were available for the data analyses. Generalized linear models with logit link were used to model the probability of a cow or a quarter being infected at calving, accounting for the clustered data. Increasing milk production at dry-off was a significant risk factor for both a cow and a quarter being infected with environmental pathogens at calving, but infections caused by coagulase-negative staphylococci at calving were not associated with milk yield at dry-off. For every 5-kg increase in milk yield at dry-off above 12.5 kg, the odds of a cow having an environmental intramammary infection at calving increased at least by 77%.
Key Words: milk yield dry-off intramammary infection
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