Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/30/2004
Publication Date: 10/1/2004
Citation: Hume, M.E., Edrington, T.S., Looper, M.L., Callaway, T.R., Genovese, K.J., Nisbet, D.J. 2004. Salmonella genotype diversity in non-lactating and lactating dairy cows. Journal of Food Protection. 67:2280-2283.
Interpretive Summary: Some dairy cows may carry Salmonella in their gastrointestinal tract without getting sick. The potential for this increases with herd size and the detection of Salmonella in feces (shedding) may be triggered by stresses placed on the animals. The scope of the current study was to determine the effects that milk production (lactation) and time of day may have on shedding of different Salmonella types. A genetic typing method called pulsed field gel electrophoresis was used to analyze Salmonella obtained from lactating and non-lactating Holstein dairy cows on two different sampling dates. Twenty-three gene types were detected on the first date and twenty-seven on the second date. The presence of multiple Salmonella gene types in the herd suggests multiple contamination sources. However, there was no conclusive effect of lactation status or time of day on shedding status for dairy cows.
Technical Abstract: Dairy cows may serve as asymptomatic carriers of Salmonella. The potential for herd carrier status increases with herd size and Salmonella shedding may be triggered by stresses placed on the animals. The scope of the current study is to determine the effects lactation and time of day may have on Salmonella genotypic diversity among detected serotypes. Fecal samples were collected on two sampling dates from sixty non-lactating and sixty lactating Holstein cows. Samples were collected during the morning and afternoon. No serotype was predominant over the two collection dates, although S. Albany, S. Anatum, S. Newport, S. Senftenberg were detected in relatively high numbers. Twenty-three genotypes were detected on the first date and twenty-seven on the second date. The greatest genotypic diversity was seen among S. Newport, and S. Senftenberg with five and nine genotypes, respectively. The presence of multiple serotypes and genotypes in the herd suggest multiple contamination sources. However, there was no conclusive effect of time of day on genotype shedding status for non-lactating and lactating cows.