Short communication: Determination of Salmonella clustered regularly interspaced short palindromic repeats (CRISPR) diversity on dairy farms in Wisconsin and Minnesota.

Salmonella enterica ssp. enterica is a foodborne pathogen able to cause disease in both humans and animals. Diverse serovars of this pathogen exist, some of which are host specific, causing a range of clinical symptoms from asymptomatic infection through morbidity and mortality. According to a 2007 survey by the USDA National Animal Health Monitoring System, fecal shedding of Salmonella from healthy cows occurs on 39.7% of dairy farms in the United States. Certain serovars are frequently isolated from dairy farms and the majority of isolates from the National Animal Health Monitoring System study were represented by 5 serovars; however, genotypic diversity was not examined. The objective of this study was to determine the diversity of clustered regularly interspaced short palindromic repeats (CRISPR) loci in Salmonella collected from 8 dairy farms with a previous history of salmonellosis. None of the cows or calves sampled on 2 of the 8 dairy farms were shedding Salmonella, although Salmonella was detected in a cow bedding sample on 1 of these farms. Salmonella populations were discrete on each farm, according to CRISPR typing, with the exception of an Anatum var. 15+ type on farms 5 and 6 and the Montevideo type on farms 1 and 2. One to 4 distinct CRISPR genotypes were identified per farm. The CRISPR typing differed within serovars, as Montevideo, Anatum var. 15+, and Muenster serovars had no overlap of spacer content, even on the same farm, reflecting between- and within-serovar genetic diversity. The dynamic nature of Salmonella populations was shown in a farm that was sampled longitudinally over 13.5 mo. Changes in serovar from 3,19:-:z27 to Montevideo was observed between the first sampling time and 8 mo later, with concomitant change in CRISPR alleles. The results indicate that Salmonella strains present in smaller dairy herds (<500 head) are specific to that farm and new Salmonella strains may emerge over time.

Effect of supplementation with an electrolyte containing a Bacillus-based direct-fed microbial on immune development in dairy calves.

Immune characteristics in 65 calves were evaluated in response to a Bacillus-based direct-fed microbial (DFM) provided in electrolyte scour treatment. Blood samples were analyzed for cell surface markers and α(1)-acid glycoprotein (AGP) concentration. AGP increased in scouring calves given electrolyte containing Bacillus at day 7 post-placement compared to scouring calves administered electrolyte alone and non-scouring calves, enhancing the inflammatory response for pathogen clearance. The Bacillus promotes T cell subsets including greater proportions of activated, mature cells (CD8(-)CD25(+), CD8(-)CD45RO(+), CD8(-)TCR1(+)) in calves given electrolyte containing Bacillus than scouring calves administered electrolyte alone and non-scouring calves. Also, the Bacillus may be alleviating inflammation at day 3 post-placement as the proportion of monocytes and granulocytes lacking L-selectin (CD172a(+)CD62L(-)) was greater in scouring calves given electrolyte compared to the other groups. Electrolyte containing Bacillus administered at the onset of scours influences components of innate and adaptive immune development during and following the scouring event.

Benefits of Supplementation of an Electrolyte Scour Treatment with a Bacillus-Based Direct-Fed Microbial for Calves.

A Bacillus-based direct-fed microbial (DFM), Omni-BosCB™, added to an electrolyte was evaluated as a therapy for scours. Fecal shedding of presumptive Clostridium perfringens at day 7 was reduced in scouring calves treated with electrolyte plus DFM compared to scouring calves treated with electrolyte alone. Total therapeutic treatment costs during the first 2 weeks were significantly reduced by supplementing the electrolyte with the DFM: $18.69 and $21.57 for electrolyte plus DFM and electrolyte treated calves, respectively. Electrolyte treated calves experienced more severe scours than electrolyte plus DFM treated calves as additional therapy with Lactated Ringer's Solution was only necessary for electrolyte treated calves. The DFM may have other ancillary benefits after supplementation has ended, as evidenced by decreased recurrence of a second scouring event. This is the first report demonstrating efficacy of a DFM used therapeutically for mitigating calf scours. These findings have implications as alternatives to chemical interventions for disease control.