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in Journal of the American Veterinary Medical Association

Abstract

Objective—To compare economic outcome for herds not exposed to Neospora caninum with that for herds with various seroprevalences of N caninum infection and evaluate 3 control strategies.

Design—Economic simulation model.

Sample Population—Beef herds with various seroprevalences of N caninum infection.

Procedure—A 5-year simulation model was used. Control strategies that were evaluated included culling females that fail to calve, selling seropositive females and purchasing seronegative replacements, and excluding the daughters of seropositive dams as potential replacements.

Results—For a 5-year period with low prices for feeder calves, endemic N caninum infection decreased mean return to fixed assets by 22.2% when true seroprevalence was 10% and by 29.9% when true seroprevalence was 70%. Percentage decrease in return to fixed assets was less dramatic when a 5-year period with high prices for feeder calves was evaluated. Analysis indicated that 2 control strategies (culling females that fail to give birth to a calf and selling seropositive female cattle and purchasing seronegative replacement female cattle) were not likely to be economically beneficial. The third control strategy (testing the entire herd for N caninum infection and excluding the female offspring of seropositive dams as replacements) appeared to be a reasonable control strategy.

Conclusions and Clinical Relevance—For the assumptions in the model, endemic N caninum infection decreases return to fixed assets for cow-calf herds. Of the potential control strategies evaluated, testing the entire herd for N caninum infection and excluding the daughters of seropositive dams as potential replacements provided the best economic return. (J Am Vet Med Assoc 2004;224:1597–1604)

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine whether somatic cell counts (SCCs) or California mastitis test (CMT) scores for individual quarter milk samples could be used to detect subclinical intramammary infection among dairy cattle in a herd with a high bulk tank SCC.

Design—Prospective clinical trial.

Animals—278 Holstein-Friesian dairy cattle from a single herd.

Procedure—Individual quarter milk samples were collected and submitted for bacterial culture, California mastitis testing, and determination of SCC. Additional milk samples were collected 34 days later and submitted for bacterial culture.

Results—During the initial visit to the herd, milk samples were collected from all 278 cows. However, because of blind mammary quarters or missing data, results for 1,057 quarter milk samples were included. Bacterial culture did not yield any growth for 622 (58.8%) of these samples. Regardless of the cutoff that was used, sensitivity of the CMT score was ≤ 0.50 and sensitivity of the SCC linear score (SCS) was ≤ 0.60. For 497 mammary quarters, results of bacterial culture of samples collected 34 days apart were concordant; bacterial culture did not yield any growth for 342 (68.8%) of these quarters. Regardless of the cutoff that was used, sensitivity of the CMT score was ≤ 0.61 and sensitivity of the SCS was ≤ 0.76 for mammary quarters with concordant bacterial culture results.

Conclusions and Clinical Relevance—Results suggest that neither CMT score nor SCC is sensitive enough to be useful as a screening test for identifying infected mammary quarters among dairy cattle in a herd with high bulk tank SCC. ( J Am Vet Med Assoc 2004;224:419–423)

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in Journal of the American Veterinary Medical Association