Calving distributions of individual bulls in multiple-sire pastures.

The objective of this project was to quantify patterns in the calving rate of sires in multiple-sire pastures over seven years at a large-scale cow-calf operation. Data consisted of reproductive and genomic records from multiple-sire breeding pastures (n = 33) at the United States Meat Animal Research Center (USMARC) from 2007 to 2013. Calving intervals were analyzed in 21-day periods. A ranking system for each bull was developed based on the calving rate per pasture over the breeding season, with Rank 1 = the bull with greatest calving rate, Rank 3 = the bull with the least calving rate, and Rank 2 = all other bulls. A total of 179 bulls and 3703 calves were successfully genotyped over seven years. A uniform distribution described the expected percentage of calves sired per rank within pasture. Rank 1 bulls sired 113% greater calves than the expected pasture-average, Rank 2 bulls sired 6% less than expected, and Rank 3 bulls sired 81% less than expected. A rank by calving interval interaction effect was identified (P < 0.05). A Rank 1 bull in calving interval 1 produced a greater average percent of the total calf crop over the entire season, compared to a Rank 2 and Rank 3 bull. The calving rate for individual sires is not homogeneous and there is a large difference between bulls siring the greatest and least number of calves. More research is needed to determine how rank changes over multiple breeding years and its association with dominance, libido, and fertility.

Economic considerations for diagnostic and control options for Neospora caninum-induced abortions in endemically infected herds of beef cattle.

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.)

Repeatability and accuracy of reproductive tract scoring to determine pubertal status in beef heifers.

The objective of this study was to compare the repeatability and accuracy of palpation per rectum to transrectal ultrasonography and serum progesterone concentrations for determining pubertal status in beef heifers. One hundred and seventy-four rectal examinations were performed on 29 predominantly Angus heifers by two veterinarians (A and B) and assigned individual reproductive tract scores (RTS) during monthly examinations over a 3-month period. Heifers were examined in the morning by both veterinarians, randomized, and re-examined in the afternoon. The size and location of ovarian structures of each heifer were determined by ultrasonography. Heifers with follicles >10mm in diameter or corpora lutea were classified as pubertal. Serum progesterone concentrations at the time of the examination and 10 days later were determined by radioimmunoassay and used to classify heifers as prepubertal (<1 ng/ml in both samples) or pubertal (at least one sample >or=1 ng/ml). Kappa, which describes degree of agreement beyond chance, was used to determine repeatability of the RTS system. Multicategory Kappa for agreement was 0.64 within veterinarian, 0.46 between veterinarian, and 0.35 between palpation per rectum and transrectal ultrasonography. Sensitivity and specificity of palpation per rectum for diagnosis of pubertal status compared to serum progesterone levels were higher (82 and 69%, respectively) than sensitivity and specificity of ultrasonography (79 and 59%, respectively). This study validates the RTS system as a repeatable and accurate screening test to evaluate pubertal status in groups of heifers prior to the onset of the breeding season.

Factors related to in-house agricultural animal caseloads in US veterinary teaching hospitals.

A retrospective observational study was conducted to determine whether agricultural animal caseloads at veterinary teaching hospitals declined between 1995 and 1998. Thereafter, the effect of organizational and demographic factors on 1998 in-house agricultural animal caseloads was examined. Caseload data were obtained from the American Association of Veterinary Medical Colleges. Demographic and organizational data were obtained by surveys, telephone interviews, and web-based resources. Complete data were available from 25 veterinary colleges, and data from these schools were used in subsequent analyses. In 1998, in-house food animal caseload decreased relative to 1995 in 17 schools and increased relative to 1995 in 8 schools. This trend was not significant (P = .053); however, the power of the test was limited (.50). Mean 1998 caseload was 886 +/- 504. Among schools with a discipline-based organizational structure, annual mean caseload was 464 +/- 220. Among schools with a species-based organizational structure, mean caseload was 1,167 +/- 463. The regression model that best predicted caseload was a forward-stepping model that included only organizational structure as an independent variable. No additional independent variable was significantly associated with caseload.