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Summaries of recent papers on bovine medicine and surgery

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01 May 2014, at 1:00am

Eliminating chorioptic mange from a dairy herd without milk withdrawal

Aurora Villarroel and Megan Halliburton, Oregon State University

Many antiparasitic drugs require lengthy withdrawal times which make them impractical for use in treating an entire dairy herd. The authors carried out a study on the efficacy of eprinomectin (one of only two such drugs approved in the US for treatment of lactating cattle) to tackle an outbreak of chorioptic mange in a commercial dairy herd.

All cattle on the farm were treated on the same day and at dry-off, and lesion scoring was performed five times over a 12-month period. Three months post-treatment there was a reduction in the proportion of cattle with lesions but the numbers increased at 12 months. Factors associated with the presence of persistent lesions included older cows, late lactation and recent treatment. No increase in milk production was apparent but the overall welfare of affected cattle was improved.

The study demonstrated that chorioptic mange can be controlled in entire herds although multiple treatments may be required to eliminate the parasite. The study also demonstrates that mange can be controlled at herd level without recourse to non-licensed products. 

The Veterinary Journal 197 (2): 233-237.

Effectiveness of interventions to reduce claw lesions in 40 dairy herds 

Zoe Barker and others, University of Warwick 

Various risk factors have been identified in connection with lameness in dairy cattle but there is little reliable data on the impact of management changes to address those factors.

The authors investigated the impact of veterinary advice on reducing such risks on the prevalence of lameness on 40 dairy units. They found no significant differences in the prevalence of lameness or the incidence of white line disease, sole ulcers or digital dermatitis between those farms where recommendations were provided and the control units where locomotion was recorded but no advice given.

The overall uptake of veterinary recommendations by the farmers was only 41.3%. 

Animal Welfare 21 (4): 563-576. 

Impact of an internal teat sealant on the incidence of bovine mammary infections 

Volker Kroemker and others, University of Hannover, Germany 

Intramammary antimicrobial treatment has long been the mainstay of preventive measures to control mastitis in dairy herds but there is political pressure to find alternative approaches. The authors examined the efficacy of a newly introduced product (Orbeseal, Zoetis) which aims to seal off the teat canal to prevent invasion by environmental pathogens. 

Rates of new infections in treated and untreated quarters in 128 cattle from nine dairy units was 3.5% and 10.5%, respectively. Therefore, internal teat sealants are a viable option for a drying-off treatment in healthy dairy cattle.

Journal of Dairy Research 81 (1): 54-58.

Milk flow obstruction caused by varicose veins in the teats of dairy cattle

Helene Larde and others, University of Montreal, Canada 

Varicose veins may occur uncommonly in the teats of dairy cattle but, where present, they can reduce milk production and increase the risk of mastitis. The authors recorded the clinical features of 22 such incidents and review the therapeutic options and eventual outcome for these patients. 

The three treatment approaches used were sclerotherapy, ligation of the vein associated with sclerotherapy, and phlebectomy. The overall prognosis was good with the restoration of normal milk flow six months post- treatment in 84% of cases and there were no discernible differences between treatment groups. There was a recurrence of the obstruction in three cases.

Veterinary Surgery 42 (7): 885-891.

Monitoring body temperatures in cattle using infrared thermography cameras 

Gundula Hoffman and others, Free University of Berlin, Germany 

Body temperature measurements using rectal thermometers provide valuable information on an animal’s physiological state but the process is time-consuming and potentially disruptive for the animal concerned. 

The authors examined the possible application in herd health monitoring of infrared thermography cameras. They compared the results of video recordings, particularly of the eye and the back of the ear, in 22 cows and nine calves with those from conventional rectal or vaginal thermometer readings. 

An increase in the maximum temperature recorded on thermography correlated well with changes measured using conventional thermometers and the technique appears to have promise in monitoring body temperatures in housed cattle. 

Veterinary Research Communications 37 (2): 91-99.

Association between haematological variables and bovine respiratory disease risk 

John Richeson and others, Texas A&M University 

Bovine respiratory disease complex in beef calves is the leading cause of economic losses in the US feedlot industry. The authors looked at haematological variables in 1,179 beef calves arriving at university research facilities to identify possible risk factors associated with the later development of the disease syndrome. 

The results indicate that low eosinophil and high red blood cell counts in blood samples taken on arrival may be useful for the identification of calves with a high risk of developing BVD. Bull calves also appeared to be at a higher risk than those that were castrated before arrival. 

Journal of the American Veterinary Medical Association 243 (7): 1,035-1,041.

Diagnosis and management of Staphylococcus aureus mastitis in cattle

James Breen and others, University of Nottingham

Staphylococcus aureus is the most frequent cause of contagious mastitis in most UK dairy herds and will often result in a persistent subclinical infection. However, the isolation of this organism from individual cases or bulk milk tank samples should not necessarily lead to a herd diagnosis. 

The authors explain how systematic analysis of clinical mastitis and somatic cell count data is required to understand the impact of this pathogen on the herd. They review procedures for the diagnosis of infected individuals and herds, and propose measures for treating infected animals and identifying control priorities for infected herds. 

Cattle Practice 21 (3): 189-197.

Detection and potential effects of Ureaplasma diversum in bull semen 

Naomi Hobson and others, Charles Sturt University, New South Wales

Ureaplasma diversum is a common mycoplasmal inhabitant of the vagina
and prepuce of cattle which is known to be an occasional cause of abortion.
The authors investigated the frequency that U. diversum could be identified in semen samples from Australian bulls using direct culture and PCR analysis.

Nine of 29 visually healthy bulls tested positive for the organism. Sperm from infected bulls showed an increased incidence of abnormal gametes with bent or coiled tails, as well as surface abnormalities, such as small protuberances or lumps. These findings suggest a possible association between U. diversum infection and impaired sperm function.

Australian Veterinary Journal 91 (11): 469-473.

Campylobacter foetus isolations from preputialsamples with various preparatory methods

Bonnie Chaban and others, University of Saskatchewan, Canada

Bovine venereal campylobacteriosis is a venereal disease of cattle causing infertility and abortion. The causative organism Campylobacter foetus subsp. venerealis has reduced viability in normal atmospheric conditions and so can be difficult to culture from preputial scrapings. 

The authors compare the isolation rates from 217 samples from 12 infected bulls with passive filtration on selective medium versus non-selective medium, with and without transport medium. Their results show that the use of transport medium and the choice of culture medium can have significant effects on C. foetus recovery rates and both factors should be considered when animals are tested for this organism. 

American Journal of Veterinary Research 74 (8): 1,066-1,069.

Association between MAP culture results and tuberculin test responses in US dairy herds

Barbara Brito and others, University of California, Davis 

Bovine tuberculosis has been eradicated from cattle in most states of the USA although occasional cases are identified at slaughter or using the standard causal fold tuberculin test. 

The authors examined the association between tuberculin test results and the Mycobacterium avium subsp. paratuberculosis status of nearly 7,000 cattle on four units in California and Colorado. They found there was a strong association between positive MAP test results and being classified as a suspect by CFT testing. Within- herd MAP prevalence may affect the specificity of CFT testing for bovine tuberculosis.

Journal of the American Veterinary Medical Association 244 (5): 582-587.

Comparative efficacy of gamithromycin and tulathromycin in treating BRD

Siddartha Torres and others, Kansas State University

Bovine respiratory disease is a multifactorial syndrome involving various bacterial and viral pathogens along with environmental and management factors. The authors examine the relative efficacy of gamithromycin and tulathromycin in treating BRD in feedlot calves. 

Calves given a single subcutaneous dose of 6mg/kg gamithromycin needed more frequent secondary treatment than those given 2.5mg/kg tulathromycin, also by subcutaneous injection. Other parameters such as the mean case fatality rate, final bodyweight, average daily weight gain and clinical score 10 days post-treatment did not differ between the two groups.

American Journal of Veterinary Research 74 (6): 847-853.

Genetic analysis of Mannheimia haemolytica isolates from fatal BRD cases 

Jared Taylor and others, Oklahoma State University

Mannheimia haemolytica is the most common bacterial pathogen isolated from cases of the bovine respiratory disease complex in most developed countries. However, as the bacterium may be present in the upper respiratory tract of healthy animals, it has been suggested that the organism is an opportunistic infection that only causes disease in individuals weakened by other factors. 

The authors analysed ribosomal DNA from bacteria isolated from fatal BRD cases in the US and Australia. The findings may eventually help in assessing whether the organism is an opportunistic pathogen or in identifying features that distinguish commensal isolates from those more likely to be associated with disease. 

Australian Veterinary Journal 92 (1-2): 15-23.