|Martinez, C - NM STATE UNIVERSITY|
|Ross, T - NM STATE UNIVERSITY|
Submitted to: Journal of Animal Science
Publication Type: Proceedings
Publication Acceptance Date: April 30, 2005
Publication Date: June 20, 2005
Citation: Edrington, T.S., Martinez, C.H., Ross, T.T., Callaway, T.R., Genovese, K.J., Anderson, R.C., Nisbet, D.J. 2005. Salmonella persistence on a southwestern United States dairy. Proceedings of Western Section of the American Society of Animal Science. 56:230-233. Interpretive Summary: Dairy cattle may contain the bacteria Salmonella that can make people sick, but normally the cattle are not affected by them. However, in a specific region of the United States, several dairy farms experience problems because Salmonella makes their cows sick at a certain time of the year. The purpose of the present study was to determine why these bacteria are in the animals all year long, but only cause sickness in the late summer. Time of the year affects Salmonella populations to some degree with more Salmonella typically found in the summer months. The cow’s response to long term heat stress and the high incidence of Salmonella on this farm are likely contributing factors. Results showed that there are several places on a farm that Salmonella can live and possibly infect cattle and that Salmonella control on the farm is a challenging problem.
Technical Abstract: Dairy cattle are reservoirs for Salmonella and mature cattle typically appear asymptomatic while shedding this pathogen into the environment. However, in specific geographic regions, Salmonella outbreaks have been reported in lactating animals resulting in lost milk production and cow mortality. Dairy cattle on a single farm (2000 hd dairy; southwestern U.S.), were identified and sampled upon entering the milking string immediately following freshening. Thirty head were randomly selected from a group scheduled to calve within a 14 day period. Fecal samples were collected from the same cows, via rectal palpation, and cultured for Salmonella monthly from January to October 2004. Due to culling, only 26 of the original group remained by October. Individual feed ingredients, TMR, water, and soil were also sampled monthly. Salmonella was isolated from dairy cattle each month with prevalence ranging from 19 to 96%, and averaged 53% over the 10 month period. Although the cattle did not break with Salmonella as in previous years, the highest prevalence (96%) was observed in August when Salmonella is typically a problem for this area’s dairy producers. Individual feed ingredients were positive on four occasions. A portion of the water samples collected each month tested positive, with all samples negative in May and August. Although not all TMR samples were positive for Salmonella, at least one positive sample was collected each month and generally, most samples tested positive throughout the 10-month period. However, a positive TMR sample did not always correlate to a feed ingredient or water sample testing positive. Numerous soil samples collected tested positive for Salmonella with the greatest incidence observed in August through October. Results indicate that control of foodborne pathogens on the farm is a complex task with numerous routes of infection and environments for persistence.