title: Experimentally induced Staphylococcus aureus mastitis in selenium-deficient and selenium-supplemented dairy cows.
abstract: Ten Holstein cows were fed a selenium-deficient (SeD) diet containing 0.04 mg of Se/kg of dry matter for 3 months before and throughout their first lactation. A selenium-supplemented (SeS) group of 10 cows was fed an additional 2 mg of Se/head/d to increase dietary Se concentration of the dry matter to approximately 0.14 mg/kg of body weight. An intracisternal challenge exposure of 40 to 60 colony-forming units (CFU) of Staphylococcus aureus was administered into 1 or 2 quarters of the udder of each trial cow at about the twenty-second week of lactation. Blood Se concentration (micrograms/ml +/- SEM) at the time of challenge exposure was 0.035 +/- 0.002 in SeD and 0.139 +/- 0.006 in SeS cows. Infections were established in 14/16 of the challenge-exposed quarters in SeD and 16/19 of the challenge-exposed quarters in SeS cows. The infection in 1 quarter of each Se group cleared without treatment by the end of the 8-week trial period. Log10 peak bacterial concentrations in milk from infected SeD quarters (5.04 +/- 0.25 CFU/ml) were higher (P less than 0.05) than those of infected SeS quarters (4.40 +/- 0.12 CFU/ml). Log10 peak somatic cell count (SCC) in milk from infected SeD quarters (7.18 +/- 0.08 cells/ml) did not differ from that of SeS quarters (7.17 +/- 0.05 cells/ml). Peak bacterial concentrations were attained sooner (P less than 0.05) in SeD quarters (9.5 +/- 4.0 days) than in SeS quarters (20.7 +/- 3.1 days). Similarly, peak SCC were reached earlier (P less than 0.05) in SeD (4.3 +/- 1.1 days) than in SeS quarters (13.3 +/- 3.8 days).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Veterinary Science, Pennsylvania State University, University Park 16802.
authors.forename: R J
authors.initials: RJ
authors.lastname: Erskine
authors.forename: R J
authors.initials: RJ
authors.lastname: Eberhart
authors.forename: R W
authors.initials: RW
authors.lastname: Scholz
mesh_terms: D000818:Animals; D002417:Cattle; D015169:Colony Count, Microbial / Q000662:veterinary; D005260:Female; D005979:Glutathione Peroxidase / Q000097:blood; D007113:Immunity, Innate; D008414:Mastitis, Bovine / Q000209:etiology* / Q000382:microbiology; D008892:Milk / Q000382:microbiology; D011247:Pregnancy; D012643:Selenium / Q000008:administration & dosage*; D013048:Specimen Handling / Q000662:veterinary; D013203:Staphylococcal Infections / Q000209:etiology / Q000382:microbiology / Q000662:veterinary*; D013211:Staphylococcus aureus / Q000187:drug effects / Q000472:pathogenicity; D013997:Time Factors
chemical_list: D005979:Glutathione Peroxidase; D012643:Selenium