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Abstract

Objective—To use magnetic resonance (MR) imaging to describe and compare the anatomic distribution of a lipid contrast medium injected via the retrobulbar and Peterson nerve block techniques in heads of bovine cadavers.

Design—Original study.

Sample—5 grossly normal heads obtained from cattle at necropsy.

Procedure—Standardized techniques for the modified retrobulbar and Peterson nerve blocks were established. Each cadaver had 1 treatment performed on a randomly selected side of the head; the second treatment was performed on the alternate side of the head. Injections were performed with canola oil, which is an MR-positive contrast medium. Images of heads in the transverse and dorsal planes were obtained with a 3.0 Tesla short-bore MR system.

Results—The retrobulbar technique was characterized by widespread distribution of the contrast medium around the periorbital structures; further distribution of the medium was detected along the optic nerve and in the ethmoid turbinates and nasopharynx. After the Peterson nerve block technique, contrast medium was repeatedly located in the pterygopalatine fossa, but distribution to surrounding structures was minimal.

Conclusions and Clinical Relevance—Results indicate that the retrobulbar injection technique results in a greater distribution of contrast medium to the target nerves and surrounding structures, compared with that achieved via the Peterson nerve block technique. This may explain the previously reported clinical impression that the retrobulbar block is more reliable than the Peterson nerve block but is associated with a greater risk of complications. (J Am Vet Med Assoc 2003;223:852–855)

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine the effects of serologic status for Neospora caninumon short-term weight gain, feed intake, and feed efficiency (feed intake/gain).

Design—Longitudinal observational study.

Animals—34 weaned mixed-breed beef steers.

Procedure—Serologic status for N caninum was determined for each steer on days 0 (weaning), 88, 116, 144, 172, and 200, using an agglutination test. Individual steer body weight was measured on days 0, 88, 116, 144, 172, 200, and 242 (slaughter). Daily feed intake was monitored from days 116 through 242. Serologic status was matched to animal performance for the period immediately following serum sample collection. A mixed mode, using repeatedmeasures with an unstructured covariance matrix, was used in the analysis. Breed, age, and pen effects were controlled for in the analysis.

Results—A reduction in average daily gain for the period following a positive serologic result was detected for the entire trial (6 measurements/steer). This may have been attributed to a significant impairment in feed efficiency rather than to an impairment in feed intake. Changes in serologic status in individual steers over time were common; additionally, the effects of serologic status on steer performance were also transitory.

Conclusions and Clinical Relevance—Significant reductions in short-term weight gain and feed efficiency were associated with the presence of antibodies against N caninumin postweaning beef steers. (J Am Vet Med Assoc 2001;219:1259–1262)

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine the seroprevalence for Neospora caninum in a population of beef calves in a feedlot and the association of serologic status with postweaning weight gain and carcass measurements.

Design—Longitudinal observational study.

Animals—1,009 weaned beef steers from 92 herds.

Procedure—Samples were obtained from all steers at time of arrival at a feedlot. Serologic status for Neospora spp was determined, using an agglutination test. Results of serologic testing were compared with calf growth and carcass data, using multivariate regression with generalized estimating equations.

Results—Of 1,009 calves, 131 (12.98%) were seropositive, and 54 of 92 (58.7%) consignments had ≥ 1 seropositive calf. Median within-consignment prevalence for consignments in which there was ≥ 1 seropositive calf was 20%. Seropositive status was associated with significant reductions in average daily gain, live body weight at slaughter, and hot carcass weight and an increase in ribeye area-to-hot carcass weight ratio. Seropositive status also was associated with significant increases in cost of treatment and significant reductions in income. Sick seropositive calves had the highest cost of treatment. An economic loss of $15.62/calf was projected for seropositive calves.

Conclusions and Clinical Relevance—Significant reductions in postweaning weight gain, carcass weight, and economic return were associated with detection of antibodies to N caninum in beef calves in a feedlot. (J Am Vet Med Assoc 2000;217: 1356–1360)

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine the epidemiologic plausibility of a sylvatic transmission cycle for Neospora caninum between wild canids and beef cattle.

Design—Spatial analysis study.

Animals—1,009 weaned beef steers from 94 beef herds in Texas.

Procedure—Calves were grouped on the basis of seroprevalence for N caninum and ecologic region in Texas. The Morans I test was used to evaluate spatial interdependence for adjusted seroprevalence by ecologic region. Cattle density (Number of cattle/259 km2 [Number of cattle/100 mile2] of each ecologic region) and abundance indices for gray foxes and coyotes (Number of animals/161 spotlight-transect [census] km [Number of animals/100 census miles] of each ecologic region) were used as covariates in spatial regression models, with adjusted seroprevalence as the outcome variable. A geographic information system (GIS) that used similar covariate information for each county was used to validate spatial regression models.

Results—Spatial interdependence was not detected for ecologic regions. Three spatial regression models were tested. Each model contained a variable for cattle density for the ecologic regions. Results for the 3 models revealed that seroprevalence was associated with cattle density and abundances of gray foxes, coyotes, or both. Abundances of gray foxes and coyotes were collinear. Results of a GIS-generated model validated these spatial models.

Conclusions and Clinical Relevance—In Texas, beef cattle are at increased risk of exposure to N caninum as a result of the abundance of wild canids and the density of beef cattle. It is plausible that a sylvatic transmission cycle for neosporosis exists. (J Am Vet Med Assoc 2000;217:1361–1365)

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To estimate the prevalence of paratuberculosis in purebred beef cattle in Texas and identify risk factors for seropositivity.

Design—Epidemiologic survey.

Animals—4,579 purebred cattle from 115 beef ranches in Texas.

Procedure—Blood was collected, and serum was analyzed for antibodies with a commercial ELISA. Fecal samples were collected and frozen at −80°C until results of the ELISA were obtained, and feces from seropositive cattle were submitted for mycobacterial culture. Herd owners completed a survey form on management factors.

Results—Results of the ELISA were positive for 137 of the 4,579 (3.0%) cattle, and 50 of the 115 (43.8%) herds had at least 1 seropositive animal. Results of mycobacterial culture were positive for 10 of the 137 (7.3%) seropositive cattle, and 9 of the 50 (18%) seropositive herds had at least 1 animal for which results of mycobacterial culture were positive. Risk factors for seropositivity included water source, use of dairy-type nurse cows, previous clinical signs of paratuberculosis, species of cattle (Bos taurus vs Bos indicus), and location.

Conclusions and Clinical Relevance—Results suggested that seroprevalence of paratuberculosis among purebred beef cattle in Texas may be greater than seroprevalence among beef cattle in the United States as a whole; however, this difference could be attributable to breed or regional differences in infection rates or interference by cross-reacting organisms. Veterinarians should be aware of risk factors for paratuberculosis as well as the possibility that unexpected serologic results may be found in some herds. (J Am Vet Med Assoc 2005;226:773–778)

Full access
in Journal of the American Veterinary Medical Association