Detection of Staphylococcus aureus in bulk tank milk using modified Baird-Parker culture media.

The purpose of this project was to evaluate the use of 2 selective/differential culture media for detecting Staphylococcus aureus in bulk tank milk. One medium was Baird-Parker agar base supplemented with egg york tellurite emulsion and acriflavine. The other medium was Baird-Parker agar base supplemented with rabbit plasma/bovine fibrinogen and acriflavine. An increased inoculum of bulk tank milk (0.3 mL) was used to enhance the detection of S. aureus in samples containing low numbers of organisms. The sensitivity and specificity for detecting S. aureus in bulk tank milk were 94.8% and 100%, respectively, using Baird-Parker agar base supplemented with egg yolk tellurite emulsion and acriflavine, and 89.7% and 100%, respectively, using Baird-Parker agar base supplemented with rabbit plasma/bovine fibrinogen and acriflavine. Both media are practical for detecting S. aureus in bulk tank milk and monitoring its spread in lactating dairy herds in Alberta.

Persistent shedding of Salmonella enteritidis from the udder of a cow.

Salmonella enteritidis phagetype 8 was isolated from ill humans, milk-line filters, milk from a bulk tank, and milk from the right hind quarter of a five-year-old Holstein cow on a dairy farm in southern Alberta. The affected animal was removed from the herd and continued to shed S. enteritidis from this quarter during a seven-month interval in an isolation facility. Milk from the affected quarter was visually normal, and no other pathogen was isolated from the udder during the investigation. After removal of the infected cow from the herd, milk from the bulk tank was culturally negative for Salmonella sp. during the succeeding 15 months.

An investigation of risk factors for nocardial mastitis in central Alberta dairy herds.

A case-control study was undertaken during the summer of 1989 in central Alberta dairy herds to identify independent predictors of nocardial mastitis. Thirty-seven herds with nocardial mastitis were matched with control herds based on herd size, milk production, and enrolment in Alberta Dairy Herd Improvement Services. Control herds were considered free of nocardial mastitis based on negative cultures of four weekly bulk tank milk samples and one composite milk sample collected during the same period from each lactating cow in the herd. A detailed questionnaire on herd management was completed during farm visits. The use of blanket dry cow therapy was not found to be a risk factor for nocardial mastitis. Dry cow therapy with intramammary products containing neomycin and the use of multidose vials of dry cow medications were the only predisposing factors identified as being significantly associated with nocardial mastitis in central Alberta dairy herds. Use of neomycin as a dry cow therapy increased the odds of nocardial mastitis occurring in these dairy herds by 169 times.

Detection and quantitation of pea and soy-derived proteins in calf milk replacers.

Preruminant calves on several farms had diarrhea nonresponsive to treatment and were doing poorly, despite being fed a high quality calf milk replacer. Because these reconstituted milk replacers always had a sediment, they were suspected of containing insoluble nonmilk-derived proteins. Microscopic examination of the milk replacer, however, did not show any evidence of starch granules. We therefore analyzed the samples by SDS PAGE. We were able to identify and quantitate pea protein in calf milk replacers in which all the protein was supposedly milk-derived. We were also able to differentiate polypeptides derived from pea and soy. We concluded that PAGE is a sensitive technique for detecting nonmilk-derived proteins in calf milk replacers.

Colitis in calves: natural and experimental infection with a verotoxin-producing strain of Escherichia coli O111:NM.

Verotoxin-producing Escherichia coli O111:NM were isolated from two five week old Holstein calves with dysentery. On necropsy both calves had pseudomembranous ileitis, mucohemorrhagic colitis and proctitis. Large numbers of E. coli O111:NM were isolated from the colon and lesions typical of attaching-and-effacing E. coli were evident. The isolates from both calves had identical biochemical reactions and antimicrobial resistance patterns. Oral inoculation of a four day old colostrum deprived calf with 1 x 10(10) organisms of E. coli O111:NM produced a mild, focal colitis with typical attachment and effacement lesions. We conclude that the strain of E. coli O111:NM isolated from the clinical cases has the ability to produce colitis characterized by attachment and effacement of the colonic mucosa.

Dwarfism in a swine herd: suspected vitamin A toxicosis.

Dwarfism was observed in a group of 30 crossbred pigs. Affected pigs had short limbs and retarded growth. Reduced long-bone length as well as flattening and caudal rotation of the humeral head and the distal femoral condyles were seen at necropsy. Metaphyseal growth plates in vertebrae were narrow and, in long bones, were closed prematurely. There was a sparing of growth plates in traction epiphyses. Vitamin A toxicosis was considered as a possible cause.

Ontogeny of the immune response: effect of protein energy malnutrition in neonatal calves.

Immunocompetence of neonatal, Holstein bull calves fed for maximal growth (Control; n = 4) or protein energy malnutrition feeding (PEM; n = 4) for four weeks was assayed in vitro and in vivo. All calves exhibited elevated cortisol levels for ten days postnatally. At this time calves also were neutrophilic and lymphopenic. In addition lymphocyte function, as measured by lymphocyte proliferation and interleukin-2 activity, was reduced at this time as compared to older calves. After two weeks of protein energy malnutrition feeding, calves had significantly lower body weight, lymphocyte interleukin-2 activity and lymphocyte proliferation when compared with age-matched controls. Two weeks after protein energy malnutrition ration reversal, interleukin-2 activity and lymphocyte proliferation was comparable for both groups. There was no significant difference in serum cortisol concentration between control and protein energy malnutrition calves. The kinetics of the protein energy malnutrition group's primary humoral immune response was retarded, thus significantly lower antibody levels to K99 antigen were observed 8 to 12 days postimmunization. There was no significant difference between groups when comparing secondary response to K99 antigen.

A case study of respiratory disease in a veal calf operation.

An outbreak of respiratory disease occurred in a central Alberta veal operation, after production capacity had been increased fourfold. Mortality rate reached 24.6% despite agressive antibiotic therapy. A review of the records revealed a cyclical disease pattern in each room. Weekly cleaning of occupied calf rooms was correlated with the disease pattern. Aerosols generated by a high pressure sprayer appeared to trigger transmission of respiratory pathogens in malnourished neonatal calves.DISEASE OCCURRENCE DECREASED AND PROFITABILITY INCREASED SIXFOLD AFTER THE INTRODUCTION OF THE FOLLOWING MEASURES: 1) discontinuing the use of the high pressure washer in the occupied calf rooms, 2) feeding calves a better quality milk replacer with supplemental milk for the poorest calves, 3) sale-yard calf purchases were abandoned in favor of direct buying.

Protein energy malnutrition and fat mobilization in neonatal calves.

Fat stores and organ weights were assessed in calves at birth (n=5) and after seven days of milk (n=5) or electrolyte (n=5) feeding.Compared to newborn calves, milk-fed calves had a significant (p < 0.05) redistribution of fat from perirenal area to bone marrow. The thymus also involuted during milk feeding.In electrolyte-fed calves there was a significant loss of perirenal and bone marrow fat. The visible omental, mesenteric and subcutaneous fat stores were depleted. Epicardial fat stores were not visibly affected.There was a high correlation between bone marrow crude fat and bone marrow dry matter (R=0.92). This suggests that dry matter estimations can be used to assess bone marrow fat stores. Perirenal fat may be intermediate in type between brown and white adipose tissue because it is mobilized in response to fasting, and formalin fixed perirenal fat did not contain detectable levels of thermogenin.