In vitro susceptibility of Yersinia enterocolitica isolated from the oral cavity of swine.

Antimicrobial susceptibility of 181 (107 ail-harboring isolates and 74 non-ail-harboring) Yersinia enterocolitica isolates obtained from the oral cavity of swine was determined against 24 antimicrobial agents. All Y. enterocolitica isolates were susceptible to sulfamethoxazole/trimethoprim, enrofloxacin, aminoglycosides, and nitrofurantoin. Susceptibility to tetracycline appeared to vary by lot of origin. Isolates were resistant to sulfonamides (other than sulfamethoxazole/trimethoprim), penicillin, ampicillin, ticarcillin, cephalothin, macrolides, and tiamulin.

Prevalence of pathogenic Yersinia enterocolitica in groups of swine at slaughter.

In order to estimate the prevalence of swine herds infected with pathogenic Yersinia enterocolitica, 103 lots of market swine were randomly selected at slaughter during six 1-month intervals. Pigs within each lot were sampled by swabbing the oral-pharyngeal surface, poststunning and postexsanguination but prescalding. Ninety-five lots (92.2%) contained at least one pig infected with Y. enterocolitica. Pathogenic strains were defined as those harboring the ail gene which has been identified in Y. enterocolitica that causes human clinical disease. Identification of those strains harboring the ail gene was accomplished using a polymerase chain reaction technique. Twenty-nine lots (28.2%) contained at least one pig from which ail-containing (pathogenic) Y. enterocolitica were isolated. Of the 107 pathogenic Y. enterocolitica isolates identified, 89.7% were serotype O:5 and 3.7% were serotype O:3. The results from this study will aid in the design of future epidemiological investigations concerning on-farm prevalence and associated risk factors for pathogenic Y. enterocolitica. Additionally, the results support the hypothesis that swine are a significant potential reservoir for human infections by Y. enterocolitica.

Effects of hypocalcaemia on abomasal motility.

Abomasal mechanical and myoelectric activity were measured in two adult Holstein cows. Hypocalcaemia was induced using a constant infusion of disodium EDTA and serum total and diffusible calcium concentrations were measured. Abomasal motility remained normal in the face of declining calcium concentrations until a threshold value was reached (1.2 +/- 0.2 mmol litre-1) below which all mechanical and electrical activity was absent. A similar threshold effect was observed when calcium concentrations were allowed to rise. These data do not support hypocalcaemia as being a clinically important cause of abomasal atony.

Bovine ketosis and somatotrophin: risk factors for ketosis and effects of ketosis on health and production.

Aspects of the metabolism and health of 63 cows which had been treated with different amounts of bovine somatotrophin (BST) daily in the preceding lactation and 25 control cows were studied. The aims of the study were first, to identify cows with ketotic conditions, either by measurements of blood metabolite concentrations or by clinical observations, secondly, to evaluate the risk of such conditions in cows treated with BST in the preceding lactation, and thirdly, to examine the metabolic and production consequences of the ketotic conditions in an environment in which the cows' health, body condition and nutrition were closely observed. The cows were categorised objectively by the use of cluster analysis into non-ketotic cows and ketonaemic cows, on the basis of their plasma metabolite concentrations. Twelve of the control cows and none of the cows previously treated with BST were classified as ketonaemic. Similarly, nine of the control cows but only two of the cows previously treated with BST had clinical ketosis. Some, but not all, of the decrease in the risk of clinical ketosis was attributable to the lower body condition score of the cows previously treated with BST. The clinically ketotic cows had a greater risk of other illness in the first 10 days post partum than their herdmates, but the ketonaemic cows had a significantly lower risk of other disease in the first 10 days post partum. The ketonaemic control cows were significantly heavier than the non-ketotic control cows, but they maintained a higher dry matter intake than the latter cows, probably a key factor in reducing the risk of clinical ketosis.

Meat from dairy cows: possible microbiological hazards and risks.

The authors provide an overview of the circumstances associated with culling of dairy cattle in the United States of America (USA) and focus on the possible significant microbiological hazards associated with meat from cull dairy cows. Cull dairy cows are an important source of food in the USA, accounting for at least approximately 17% of ground beef. The potential microbiological hazards for foodborne illness from cull dairy cows discussed here include Salmonella (with special attention to S. Typhimurium DT104), Escherichia coli O157:H7, Campylobacter jejuni, Listeria monocytogenes, Clostridium perfringens and Staphylococcus aureus. Possible sources and means of contamination are pointed out, as are the potential foodborne risks from Bacillus cereus and Aeromonas spp. In conclusion, widespread microbiological studies are needed to determine the prevalence and risk of foodborne pathogens in cull dairy cattle.

Lymph drainage of the conjunctiva: topographic anatomic study in calves.

The topographic pattern of lymph drainage from the conjuctiva was ascertained in 1- to 2-week-old calves. Multiple, small lymph vessels within and on the surface of the orbicularis oculi muscle converged to form fewer vessels which followed the course of the superficial temporal artery and vein or crossed the zygomatic arch in a more rostral position to reach the primary site of lymph collection, the parotid lymph node. Marker dye, injected into the subconjunctiva, was collected in the midrostral and rostroventral parts of the node. Drainage from the parotid node passed via multiple lymph vessels into the lateral retropharyngeal node, where marker dye concentrated in the rostrodorsal aspect of the node. Single or multiple lymph vessels carried drainage from the lateral retropharyngeal node indirectly by way of the cranial deep cervical lymph node or directly into the tracheal lymph trunk.

Enzyme-linked immunosorbent assay for measurement of anti-Moraxella bovis antibodies.

Antibodies of the immunoglobulin (Ig) G and IgA classes specific for Moraxella bovis in serum or lacrimal secretions of cattle were detected with an enzyme-linked immunosorbent assay, using soluble extracts of M bovis or whole organisms. The amount of detectable antibodies was influenced by the type of antigenic preparation used in the enzyme-linked immunosorbent assay. The test indicated that 2 subcutaneous inoculations of M bovis cells induce significantly (P less than 0.0001) increased anti-M bovis serum antibodies. The infection of calves with M bovis induced specific IgG antibodies in serum and predominantly IgA antibodies in lacrimal secretions.

Pulmonary clearance of Serratia marcescens in calves.

The pulmonary clearance rate of Serratia marcescens was determined in 17 calves exposed to an aerosol from a modified Hendersen apparatus. The mean bovine pulmonary clearance was 50.2 +/- 4.1% at postaerosolization hour (PAH) 1, 72.5 +/- 7.0% at 2 hours, 88.6 +/- 5.2% at 4 hours, 97.3 +/- 2.8% at 8 hours, and 99.9% at PAH 24 and 48. Regional pulmonary mean percent retention (MPR) of S marcescens in 10 calves was determined in dorsal or ventral and in cranial or caudal regions. Dorsal MPR was less than ventral MPR for PAH 1, 2, and 4, whereas cranial MPR was greater than caudal MPR for PAH 1, 2, 4, and 8. Difference in regional airway oxygen tensions was suggested as the most probable reason for differing regional MPR values.

Genotypic, phenotypic, and biological characteristics of Moraxella bovis.

Several isolates of Moraxella bovis obtained from cattle with infectious bovine keratoconjunctivitis killed monocytes and macrophages in vitro and carried 3 to 5 plasmids. Cloned and noncloned M bovis isolates readily induced the disease, killed the phagocytes in vitro, and carried 3 plasmids. Moraxella bovis isolates of low in vivo virulence carried 5 plasmids and did not kill phagocytes to the extent that isolates with 3 plasmids did. The possible implications of these findings in the pathogenesis of infectious bovine keratoconjunctivitis are discussed. Also, a classification of M bovis colonies into rough or smooth varieties according to their staining characteristics with crystal violet is suggested.

Impact of bovine somatotropin administration beginning at day 70 of lactation on serum metabolites, milk constituents, and production in cows previously exposed to exogenous somatotropin.

Metabolic and production responses are reported for 72 cows treated with bovine somatotropin (BST) for 30 days starting at day 70 of lactation. Of these 72 cows, 48 had been exposed in the preceding lactation to long-term treatment with BST at 3 dosages and 24 (controls) had not been given BST. Approximately half of the cows in each group were parity-2 cows, the rest were older. Comparisons between groups were made separately for parity-2, and older cows. Analyses, using pretreatment values of each variable as a covariate, indicated that older cows, but not parity-2 cows, significantly (P less than 0.05) increased milk production during treatment. Parity-2 cows, however, had a significantly higher milk fat percentage than controls following treatment. Cows treated with 51.6 or 86 mg BST/d in both parity groups had significantly higher serum-free fatty acids than controls. Estimated net energy balances were significantly lower for older treated cows, but did not significantly differ from controls for parity-2 treated cows. Older cows in the 86 mg of BST/d group tended to have higher concentrations of blood glucose than did older control-group cows. Treatment with BST did not significantly increase serum ketone concentrations in any group of animals, and none of the cows developed clinical ketosis during this period. Estimated net energy balance (ENEB) during treatment was a significant (P less than 0.05) covariate for free fatty acid concentrations in older cows and for milk fat percentage in parity-2 cows. Covariate adjusted analyses, using ENEB during treatment as a covariate, indicated that lipolytic stimuli already acting may be enhanced by treatment with BST, but a negative energy balance was not a necessary precondition for free fatty acid concentrations to increase following somatotropin treatment. Similarly, milk fat percentages for parity-2 treated cows were significantly (P less than 0.05) higher during treatment than controls when ENEB during treatment was used as a covariate. Increased milk fat concentrations in parity-2 treated cows were not associated with significant increases in the ratio of C18:C4-10 milk fatty acids, indicating that increased milk fat resulted from either an increase in incorporation of C18 fatty acids into milk fat coupled with an increase in de novo mammary synthesis of C4-10 milk fatty acids or an increase in C12-16 fatty acids that may arise either from increased tissue mobilization, from diet, or from de novo mammary synthesis.

Iatrogenic lidocaine toxicosis in ewes.

Lidocaine intoxication developed inadvertently in a group of ewes. Six ewes used in a student laboratory session on laparotomy procedures were anesthetized locally with lidocaine hydrochloride (20 mg/kg) prior to simultaneous bilateral laparotomy. Shortly after the administration of lidocaine hydrochloride, the ewes developed muscle tremors and became recumbent, with a variety of neurologic signs including dullness, opisthotonos, odontoprisis, mydriasis, blindness, extensor rigidity, and convulsions. The ewes were given intravenous fluid therapy, and 90 minutes after the onset of signs, the ewes were standing, dull, and appetent. The laboratory session was rescheduled 2 weeks later, using the same ewes and a reduced dosage of lidocaine hydrochloride (10 mg/kg). There were no adverse effects and the simultaneous bilateral laparotomy procedure was completed without complications. The authors recommend the use of lidocaine hydrochloride at a dosage not exceeding 10 mg/kg for ewes requiring extensive local anesthesia.

Expanding food-animal veterinary services through nutritional consultation.

Practitioners can increase their value to their clients as well as increase the gross veterinary product by developing supplemental expertise in nontraditional disciplines. This can be accomplished through continuing education and the utilization of technical support services such as the professional nutritionist. In addition, contemporary technology such as the electronic moisture tester and the pH meter can be implemented in the acquisition of nutritional diagnostic data. A comprehensive herd health program is precisely the delivery system into which such complimentary expertise can be integrated successfully.

Acute diarrhea in horses of the Potomac River area: examination for clostridial toxins.

Fecal specimens from horses in Montgomery County, Md, and in Fairfax and Loudoun counties, Va, were examined for Clostridium perfringens type A enterotoxin and for C difficile cytotoxin (92 and 108 specimens, respectively). The toxins were found in feces from horses that had experienced an acute diarrhea syndrome and from clinically normal horses. The toxins did not appear to be primary determinants of the diarrhea syndrome, although they may have contributed to the spectrum of clinical entities observed.

Diversity of Salmonella serotypes in cull (market) dairy cows at slaughter.

OBJECTIVE: To determine the diversity of Salmonella serotypes isolated from a large population of cull (market) dairy cows at slaughter. DESIGN: Cross-sectional study. SAMPLE POPULATION: Salmonella organisms isolated from the cecal-colon contents of 5,087 market dairy cows. PROCEDURE: During winter and summer 1996, cecal-colon contents of cull dairy cows at slaughter were obtained from 5 US slaughter establishments. Specimens were subjected to microbiologic culturing for Salmonella spp at 1 laboratory. Identified isolates were compared with Salmonella isolation lists published by the Centers for Disease Control and Prevention (CDC) and the National Veterinary Services Laboratory (NVSL) for approximately the same period. The Simpson diversity index was used to calculate the likelihood that Salmonella isolates selected randomly by establishment were different. RESULTS: Of 58 Salmonella serotypes identified, Salmonella ser. Montevideo was the most prevalent. Two of the top 10 CDC serotypes identified from in 1996, Salmonella ser. Typhimurium and S Montevideo, appeared on our top 10 list; 8 of the top 10 were found on NVSL listings. Thirty-one of 59 S. Typhimurium isolates were identified as DT104 and found at a west slaughter establishment, 30 during the winter and 1 during the summer. The greatest diversity of serotypes was at a southeast establishment during the summer; the least diversity was at a central establishment in the winter. CONCLUSIONS AND CLINICAL RELEVANCE: 58 Salmonella serotypes were isolated from market dairy cows at slaughter and could pose a threat for food-borne illness. Salmonella Montevideo was the most frequently isolated serotype and may contribute substantially to salmonellosis in dairy cattle.

Prevalence of Salmonella spp in cull (market) dairy cows at slaughter.

OBJECTIVE: To determine the prevalence of Salmonella spp in the cecal-colon contents of cull (market) dairy cows at slaughter because of potential public health ramifications. DESIGN: Survey study. SAMPLE POPULATION: Cecal-colon contents collected from 5,087 cull (market) dairy cows at slaughter at 5 slaughter establishments across the United States. PROCEDURE: During 2 periods of the year, winter (January and February) and summer (July through September), 5 cull (market) cow slaughter establishments in the United States--west (WE), southeast (SEE), central (CE), north central (NCE), and south central (SCE)--establishments were visited, and cecal-colon contents of cull dairy cows were obtained at the time of slaughter. Samples were examined by microbiologic culture at a single laboratory for Salmonella spp. RESULTS: Salmonella spp were detected in 23.1% of cecal-colon content samples from cull dairy cows across the 5 slaughter establishments. The highest site prevalence (54.5%) was detected at the WE during the summer period, whereas the lowest was found at the CE during the summer (4.3%) and at the NCE during the winter (4.5%). Considerable variation in the daily prevalence of Salmonella spp was found, particularly at the WE and the SCE. Salmonella spp were isolated from 93% of cecal-colon contents collected on a summer day at the WE. CONCLUSIONS AND CLINICAL RELEVANCE: Results strongly suggest that there is a high prevalence of Salmonella spp in cull dairy cows at slaughter, which could burden Hazard Analysis Critical Control Point programs implemented in slaughter establishments. Procedures to reduce Salmonella load at the dairy farm and during transport to slaughter could reduce the risk of spread during the slaughter process.

Bovine somatotropin.

Bovine somatotropin has the potential to alter profoundly the way that dairy herds are managed and to change the ways in which veterinarians provide services to those herds. This article describes the structure, function, and action of somatotropin. The metabolic effects of somatotropin on dairy cattle are discussed.