Predicting end-of-test semen quality in bulls prior to performance testing.

The first objective of this study was to determine if serum concentrations of specific hormones (testosterone, progesterone and androstenedione) in bulls at the start of performance testing could predict semen quality at the end-of-test when used in a multivariate model. The second objective was to evaluate other clinical measurements (breed, age, body weight, hip height and scrotal circumference) for predicting end-of-test semen quality. End-of-test semen quality was related to steroid concentrations and several pre-testing measurements, including age, body weight, hip height and scrotal circumference (SC). Combining the 3 steroid concentrations into a predictive test had a sensitivity of 0.6 and specificity of 0.5 at its most accurate point. The repeatability of the test result was extremely low (r(2) = 0.16; P < 0.05). In multivariate analyses, breed and start-of-test SC remained significant predictors of end-of-test semen quality (P < 0.05) while the other variables were nonsignificant (P > 0.1), suggesting that start-of-test SC was the most accurate predictor of end-of-test semen quality. Removing bulls at the start-of-test that had scrotal measurements of less than 20 cm, 24 cm, 28 cm or 32 cm resulted in sensitivities and specificities of 0.19, 0.94; 0.41, 0.81; 0.64, 0.56; and 0.94, 0.12, respectively. No cut-point had both adequate sensitivity and specificity. Because clinical tests were correlated, combining the tests to improve accuracy was not justified.

Distribution of bovine cysticercosis in Washington.

Data from slaughter plants (n = 3) and feedlots (n = 18) in eastern Washington were analyzed to characterize occurrence patterns of cysticercosis in Washington during 1984. Three concurrent peaks in cysticercosis rates (0.6/1,000 to 5/1,000 slaughtered cattle) were detected at 3 slaughter plants. Peaks were observed at 8 feedlots from December 1983 to March 1984, at 6 feedlots from April to July 1984, at 2 feedlots from August to October 1984, and at 3 feedlots from November 1984 to February 1985. Affected feedlots were not closely associated geographically and were feeding cattle from many, predominantly northwestern, origins. For 3 feedlots for which time in the feedlot was available for each slaughter shipment, an increase in cysticercosis rate with increasing time in the feedlot was noticed. Within these 3 feedlots, cases of cysticercosis were widely scattered spatially. The pattern of cysticercosis indicated human fecal contamination of a regionally available feed source. Of feedstuffs in use, potato waste, a byproduct of the processed potato industry, appeared to be the most likely source of Taenia saginata ova.

Arsenic toxicosis and suspected chromium toxicosis in a herd of cattle.

Arsenic toxicosis and suspected chromium toxicosis were diagnosed in a herd of cattle that ingested ashes from lumber treated with copper, chromium, and arsenic. Findings included peracute death, depression, ataxia, weakness, recumbency, and watery diarrhea. Chemical analyses of liver, kidney, abomasal contents, rumen contents, and ashes revealed high concentrations of arsenic and chromium. Histologically, specimens of abomasum and duodenum had diffuse mucosal degeneration and engorged capillaries. Epithelial cells of the proximal convoluted tubules and distal collecting tubules of the kidney were swollen and had mild granular cytoplasmic degeneration. Burning lumber treated with copper, chromium, and arsenic does not remove the heavy metals from them, and ingestion of the ashes from the wood constitutes a hazard to livestock health.

Vertebral fracture associated with trauma during movement and restraint of cattle.

Two female Limousin calves in a group of 68 calves suffered fractures of a lumbar vertebra subsequent to moving through a chute and being restrained to facilitate administration of vaccines. One calf collapsed as it exited the chute, whereas the second calf collapsed 10 minutes after it was released from the chute. Both heifers were euthanatized. The fractures, of the first lumbar and of the third lumbar vertebral bodies, respectively, were not associated with mineral imbalances. Fractures were determined to be the result of calves attempting to escape through a gap formed by erosion of the area beneath a gate in the holding pen of the corral system. By moving cattle in such a way as to bypass the gate, further injuries were avoided. The calves described here underscore the importance of the use of corral systems appropriate for cattle of various sizes and the necessity of maintaining properly repaired corral systems to prevent injuries to cattle.

Amebic meningoencephalitis in a sheep.

A 1.5-year-old Suffolk ewe with acute onset of incoordination and blindness unresponsive to antibiotic treatment was examined at necropsy. The meninges were congested, opaque, and thick. Microscopically, focal areas of hypercellularity in the left cortical gray matter and the meninges were observed. The inflammatory response consisted of gliosis and perivascular cuffing (lymphocytes, plasma cells, and variable numbers of eosinophils). An amebic organism in 2 life stages was found in the cerebral parenchyma. Numerous large (15 to 35 microns in diameter) organisms, interpreted as trophozoites, were characterized by vacuolated cytoplasm and small nuclei with a prominent eosinophilic nucleolus (karyosome). The smaller (10 to 17 microns in diameter) encysted stage was surrounded by a capsule-like membrane, and contained a large central body sometimes surrounded by a clear halo. Immunofluorescence studies for amebic antigens were strongly positive for an ameba recently isolated in human beings and baboons (Leptomyxid sp).

Enterprise analysis: a method to evaluate alternative production and management practices for cow/calf operations.

Food animal veterinarians recognize the need to economically justify their recommendations regarding whole-herd management programs. An enterprise analysis technique may be used by veterinarians to determine the actual cost of production on beef cattle operations. Enterprise analysis was used on 2 groups of cattle to demonstrate the financial impact of a recommendation to modify the winter-supplementation program of a large ranch. Pregnancy rates improved from 62 to 95% for group-1 cattle and from 75 to 94% for 2 groups of cattle in the 2-year study. Additionally, the calving cycle was shortened and the number of calves born earlier in the calving season was notably increased, which raised the total pounds of calves sold at weaning. These outcomes were realized without additional winter-supplementation expenses for either group. Veterinarians can use enterprise analysis to determine the value of their recommendations, thus allowing them to charge more appropriately for the services provided.

Use of performance ratios to calculate the economic impact of thin cows in a beef cattle herd.

OBJECTIVE: To determine gross income lost that was attributable to thin cows in a beef cattle herd, to estimate the cost of added nutrition necessary to prevent thin cows in the herd, and to determine the financial outcome of the improved nutritional practices. DESIGN: Prospective, observational study. ANIMALS: Four hundred and twenty-two Santa Gertrudis cows and their calves. PROCEDURE: At pregnancy examination in the fall of 1992, cows were assigned a body condition score (BCS), using a scale of 1 (emaciated) to 9 (obese), and the ratio of the productivity of BCS-3 and BCS-4 cow groups (thin cows), compared with the mean productivity of BCS-5 and BCS-6 cows (cows in good condition), was determined. Measures of productivity evaluated included pregnancy rates, weaning weights, and prices per hundredweight of calves. The performance ratios of BCS-3 and BCS-4 cows were multiplied by the mean gross income of BCS-5 and BCS-6 cows to calculate their gross income. This was then subtracted from the mean income of BCS-5 and BCS-6 cows to estimate the amount of lost gross income per thin cow. The cost of a nutritional program that would prevent thin cows in the herd was subtracted from the lost gross income of the thin cows to yield the amount of increased net income that could be generated from a nutritional program that would maintain cows in the herd at a BCS of 5 or 6. RESULTS: Cows with a BCS of 3 were 0.48 as productive, and cows with a BCS of 4 were 0.74 as productive as the average of the BCS-5 and BCS-6 cows combined. Each BCS-3 cow generated $215.06 less, and each BCS-4 cow generated $107.53 less gross income than the average gross income of BCS-5 and BCS-6 cows. The added cost of nutrition that would have reconditioned BCS-3 and BCS-4 cows to a BCS of 5.5 was $91.48/BCS-3 cow and $43.67/BCS-4 cow. Implementation of the reconditioning nutrition program the previous fall would have resulted in an extra net income of $123.58/BCS-3 cow and $63.86/BCS-4 cow, received over a 2-year period. The 262 thin cows in the herd accounted for a total net income loss of $19,897. CLINICAL IMPLICATIONS: The time of pregnancy examination is a strategic intervention point to estimate the past negative economic impact of thin cows and to implement a plan to prevent these losses in the future. Pregnancy examinations should be performed at least 100 days before the beginning of the calving season, and thin pregnant cows should be sorted into a special group and fed a reconditioning diet that will improve their body condition to an average BCS of 5.5 by the onset of the calving season.

Feedlot cattle pneumonia.

The etiology, epidemiology, clinical signs, and pathology of feedlot cattle pneumonias are discussed. This information enables a clinician with a feedlot cattle pneumonia problem to give prompt, useful advice on cause, prevention, and treatment based on findings of the feedlot visit.

Investigation planning and data gathering.

The goal of outbreak investigation is the identification of the risk factors over which management has control; these factors are known as key determinants. The risk factor approach to disease causality is much more functional than simplistic theories such as agent causality. Many outbreaks, even of infectious disease, do not have simple microbiologic explanations. In the planning of an outbreak investigation, the most critical step is the identification of management procedures that have been found, by scientific studies, to influence risk of the type of disease present. During the investigation, specific disease data, rather than the client's impressions, should be collected so that temporal and risk group analyses may be performed. Performance evaluation should be conducted to determine the breadth of management systems involved and the duration of involvement. Management evaluation must be specific, comprehensive, and targeted by scientific studies, risk group and temporal analyses, physical examination, and laboratory diagnosis. The entire investigation--the planning, the data gathering, the sample collection--must be concentrated on identifying the ways in which management should be changed to restore equilibrium to a herd experiencing excessive losses due to disease.

Nutritional and dietary interrelationships with diseases of grazing beef cattle.

This article describes current methods of controlling acute bovine pulmonary emphysema (ABPEE) and edema, lungworm and gastrointestinal nematodes, and bloat in grazing beef cattle. Success in handling outbreaks of these conditions and in their prevention depends on an understanding of their epidemiology and pathogenesis. Supplementation with ionophore antibiotics is effective in prevention of ABPEE and bloat and may also prevent other diseases of cattle that graze lush pastures.

The incidence, causes, and financial impact of perinatal mortality in North American beef herds.

This article contains a brief overview of the magnitude and causes of perinatal calf mortality (PCM). A PATH model chart of the risk factors of PCM is presented as a foundation for preparation of herd-management programs to prevent PCM, for herd investigations to control excessive PCM, or to plan seminars for livestock producers on control of PCM. The financial impact of PCM is explored through discussions of expenses associated with PCM, management decisions after calf deaths, and a comparison of the financial losses of PCM with losses incurred through pregnancy failure.

Investigating perinatal calf mortality in beef herds.

This article summarizes the information presented in this issue to identify the reasons for a perinatal calf mortality (PCM) problem through a risk-factor-evaluation approach. The benefits of necropsies in PCM investigations are discussed, and the gross lesions of the major causes of PCM are described. The use of 2 x 2 tables to calculate odds ratios and the Chi-square method to test the validity of the odds ratios are presented as methods to determine suspected risk factors. The article concludes with a discussion of the management plan used to solve a PCM problem.

Bovine teat atresia associated with horn fly (Haematobia irritans irritans (L.))-induced dermatitis.

Mammary gland lesions characterized primarily as mammary teat atresia were observed in a Limousin beef cattle herd in eastern Texas. Atresia of multiple teats per mammary gland was reported in first-calf heifers at the time of calving. Pathogens were not identified in eight mammary glands collected at slaughter. Histology of affected glands demonstrated superficial and deep perivascular inflammation and fibrosing dermatitis of teat and mammary gland skin that resulted in formation of the atretic lesions of glandular tissue. Institution of a horn fly (Haematobia irritans irritans (L.)) control program using insecticide-impregnated ear tags was associated with elimination of the problem from the herd.