Submitted to: Journal of Animal Science
Publication Type: Proceedings
Publication Acceptance Date: 8/2/2002
Publication Date: N/A
Technical Abstract: Fecal samples were obtained in replicate from lactating (LAC; n = 60) and non-lactating (NLAC; n = 60) Holstein cows to determine the influence of time of day (AM vs PM), parity, and lactation phase [< 60 or > 60 d in milk (DIM)] on shedding of Escherichia coli O157:H7 (EHEC), Escherichia coli (EC), and Salmonella spp. (SM). Samples were collected at 0700 (AM) and 1700 (PM), placed on ice and shipped to our laboratory for microbiological analyses. Mean ambient temperatures at time of collection were 24.9 and 31.8°C for AM and PM, respectively. Mean relative humidity was 50 and 24% for AM and PM, respectively, on the day(s) of collection. Temperature-humidity index was 72 for AM and 76 for PM. Incidence of EHEC, EC, and SM shedding was 56, 100, and 53%, respectively, in all cows. In LAC cows, SM shedding was increased (P < 0.05) in AM (60%) compared to PM (40%). Shedding of EHEC was increased (P < 0.05) in the AM, and SM shedding was increased (P < 0.05) in the PM in NLAC cows. Shedding of EHEC was more (P < 0.0001) prevalent in LAC (66%) than NLAC (34%) cows with no differences for EC and SM. More (P = 0.06) multiparous (67%) LAC cows shed SM than primiparous (33%) LAC cows. Parity did not influence (P > 0.10) shedding of pathogens in NLAC cows. Cows in early lactation (less than or equal to 60 DIM) shed more (P < 0.05) SM and had a tendency (P = 0.10) to shed more EC than cows > 60 DIM. The most common Salmonella serotypes were Senftenberg (18%), Newport (17%) and Anatum (15%) of a total of 17 different serotypes and several animals were shedding more than one Salmonella serotype within a day. Time of day that fecal samples are collected may influence shedding of bacterium. In the current study, lactating cows shed more E.coli O157:H7 than non-lactating cows. Cows in early lactation (less than or equal to 60 DIM) shed more Salmonella and E. coli compared to cows in later lactation.