Farm economic impacts of bovine Johne's disease in endemically infected Australian dairy herds.

OBJECTIVE: To determine the farm economic impact of bovine Johne's disease (BJD) infection and controls in commercial Victorian dairy herds. DESIGN: Benefit-cost analysis of BJD and various control methods in a Victorian dairy herd. RESULTS: Farm losses from BJD occurred from clinical disease. Clinical cases occur on average in 5-year-old cows, resulting in losses of A$1895 in the year of culling and A$221 in the year preceding culling, giving a total loss of A$2116. Early removal also resulted in loss of future profit equating to A$375 per year. This is the annualised value of foregone future income and costs expressed as a net present value (NPV). The total loss from removal of a clinical case was estimated as A$2491. The average clinical incidence in infected dairy herds prior to entry into the Victorian Bovine Johne's Test-and-Control Program (TCP) was 1.8% and the average Victorian dairy herd size was 262 cows in 2013-14, resulting in annual losses of 4.7 clinical cases if infected and implementing no BJD control. Farm annual loss of profit was estimated as A$11,748 ($44.84 per cow/year). Control of BJD using vaccination, test-and-cull or combined approaches was economical but the cost of implementation in initial years would exceed disease costs. Vaccination-based control provided minimal long-term losses and was the most cost-effective control over a 10-year planning horizon. CONCLUSION: Endemic BJD resulted in modest but persistent losses in typical infected dairy herds. Control of disease using test-and-cull, vaccination or combined test-and-cull with vaccination was cost-effective.

Modelling the spread of foot-and-mouth disease in Australia.

Preparedness for an incursion of an exotic animal disease is of key importance to government, industry, producers and the Australian community. An important aspect of Australia's preparedness for a possible incursion of foot-and-mouth disease is investigation into the likely effectiveness and cost-efficiency of eradication strategies when applied to different regional outbreak scenarios. Disease modelling is a tool that can be used to study diseases such as foot-and-mouth disease to better understand potential disease spread and control under different conditions. The Australian Government Department of Agriculture, Fisheries and Forestry has been involved with epidemiologic simulation modelling for more than 10 years, and has developed a sophisticated spatial model for foot-and-mouth disease (AusSpread) that operates within a geographic information system framework. The model accommodates real farm boundary or point-location data, as well as synthesised data based on agricultural census and land use information. The model also allows for interactions between herds or flocks of different animal species and production type, and considers the role that such interactions are likely to play in the epidemiology of a regional outbreak of foot-and-mouth disease. The user can choose mitigations and eradication strategies from those that are currently described in Australia's veterinary emergency plan. The model also allows the user to evaluate the impact of constraints on the availability of resources for mitigations or eradication measures. Outputs include a range of maps and tabulated outbreak statistics describing the geographic extent of the outbreak and its duration, the numbers of affected, slaughtered, and, as relevant, vaccinated herds or flocks, and the cost of control and eradication. Cost-related outputs are based on budgets of the value of stock and the cost of mitigations, each of which can be varied by the user. These outputs are a valuable resource to assist with policy development and disease management.

Copper supplementation, velvet antler production and growth of rising 2-year-old red deer stags.

AIMS: To investigate whether copper supplementation to rising 2-year-old red deer stags (Cervus elaphus) in winter and/or spring improved velvet antler weight, grade and financial value, and liveweight gain. METHODS: Rising 2-year-old red deer stags (n=142) on a commercial deer farm in Hawke's Bay were allocated to two groups on May 14, 1996. One group received 20 g boluses of copper-oxide wire particles. On August 15 each group was reallocated in a crossover design, each sub-group receiving either the same copper-oxide treatment or no treatment, to produce control, winter-only, winter-plus-spring, and spring-only copper treatment groups. Blood samples were collected for serum ferroxidase measurements from seven deer per group and all deer were weighed at 4-6-week intervals. Dates of antler casting and velvet removal, and velvet antler weight and grade were recorded, and the financial value of velvet calculated. Livers from a sample of deer slaughtered at the end of the trial mid-December were analysed to determine copper content. RESULTS: Supplementation with copper did not significantly alter velvet antler weight, daily velvet antler growth rate, days from casting to removal, grade or value, or stag liveweight gain. Serum ferroxidase concentrations averaged 10.0-23.7 IU/l in control deer. Copper supplementation increased mean serum ferroxidase concentrations by approximately 10 IU/l. Mean liver copper concentration in control deer was 99 micromol/kg and ranged from 194 to 386 micromol/kg in the three treated groups. CONCLUSION: Group mean serum ferroxidase concentrations of 10 IU/l and above are adequate for optimum velvet production and liveweight gain in rising 2-year-old stags.

Gonadotrophin-releasing hormone in postpartum dairy cattle: a meta-analysis of effects on reproductive efficiency.

The efficacy of gonadotrophin-releasing hormone (GnRH) or synthetic analogues in improving the reproductive performance of dairy cows less than 40 days postpartum has not been established. It was postulated that disparity observed between the results of similar trials may have arisen from differences in study design, including the dosage of GnRH used; the number of days after calving at which GnRH was administered; the concurrent use of prostaglandins to induce oestrus; and the enrollment of cows with an abnormal puerperium. The results of 24 trials, extracted from 12 research papers were assessed using meta-analysis. When all trials were considered, treatment with GnRH did not significantly alter the number of days to first oestrus or first service or the relative risk of pregnancy at first service (P > 0.05). While treatment did significantly reduce the number of days open by 2.75 days and the number of services per conception by 0.05 services, the results of these studies were heterogenous (P < 0.001) and the validity of pooled estimates questionable. The results of the subgroup of studies that enrolled only cows with a normal puerperium were homogenous for all outcomes examined (P > 0.43), although none of the pooled estimates were significant. Sensitivity analyses, performed by excluding the consistently outlying results of one study, improved the homogeneity of all outcomes (P > 0.03) and produced a significant reduction of 4.52 days to first oestrus in treated cows. Pooled estimates derived without the results of the outlying study were considered more valid indicators of the direction and likely magnitude of effect than those derived in the heterogenous overall analyses. The results of this meta-analysis showed that while blanket treatment of dairy cows in the postpartum period may reduce the number of days to first oestrus, subsequent reproductive performance is unaltered. The study also demonstrated a need to concentrate further research on the potential for treatment with GnRH during the postpartum period to improve the reproductive performance of cows with an abnormal puerperium.

Blood flow to the corpus cavernosum penis in the bull and goat buck during penile quiescence.

Bulls and bucks were used to study the blood flow into and out of the corpus cavernosum penis (CCP) during the non-erect state of the penis. When contrast medium was injected into the dorsal artery of the penis in a bull cadaver and into surgically implanted catheters of anesthetized bucks, it flowed into the cavernous spaces of the CCP via the penetrating arteries. When contrast medium was injected directly into the CCP of the bull and buck there was no evidence of vascular exits along the body of the penis. The only venous outlets from the CCP were in the crus penis area. In the non-erect penis the vascular pressure within the CCP was 17.8 mm Hg higher in the bull and 8.3 mm Hg higher in the buck at the glans area than the crus area. During the non-erect state of the penis most of the blood flow to the CCP is from the dorsal artery of the penis via the penetrating arteries. The results showed that the pressure gradient provides the means for flow of blood from the glans area toward the base or crus penis area. This flow prevents platelet aggregation and clot formation and provides nutrition to local tissue during the long periods of non-erection.

Nervous regulation of the tone of the retractor penis muscle in the goat.

The nervous control of the retractor penis muscle (rp) was investigated in the anaesthetized goat. Also, isolated field stimulated strips of the muscle were studied. The noradrenaline (NA) and acetylcholine (ACh) content of the rp was determined, and histochemistry for adrenergic and acetylcholinesterase (AChE) positive nerves was performed. The muscle exhibited spontaneous activity that persisted after section of all nerves. There was, however, also a tendency of the activity to follow the general vasomotor tone, which disappeared after section of the sympathetic chains. The excitatory adrenergic nerves which innervate the muscle come from the sympathetic chains and run along the pudendal, the hypogastric and the pelvic nerves. The rp has a dense network of adrenergic fibres and is very sensitive to excitatory adrenergic stimulation. It has a fairly large NA content, which is higher in old goats (5.95 +/- 0.42 micrograms g-1) than in young goats (2.87 +/- 0.78 micrograms g-1). Inhibitory non-adrenergic non-cholinergic (NANC) innervation reaches it via the pelvic and the hypogastric nerves. The maximum inhibitory response is reached at low frequencies (2-4 Hz). Cholinergic prejunctional inhibition of the excitatory response to sympathetic chain stimulation was effected by simultaneous stimulation of the hypogastric nerves. In vitro experiments confirmed the presence of endogenous cholinergic muscarinic suppression of the excitatory adrenergic neurotransmission. Significant amounts of ACh (0.81 +/- 0.18 micrograms g-1) are present in the muscle, and it contains strongly AChE positive nerve fibres and nerve cell bodies. It is concluded that the goat rp is innervated by sympathetic adrenergic excitatory nerves and parasympathetic NANC inhibitory nerves. It further has a direct sympathetic inhibitory NANC innervation, and an indirect inhibitory cholinergic innervation which at least in part is sympathetic.

A comparison of interactive videodisc instruction with live animal laboratories.

This study compared interactive videodisc-simulated laboratories with two types of traditional labs: a traditional general cardiovascular physiology participation lab and a traditional fibrillation/positive pressure ventilation demonstration lab. The two laboratory sections (a total of 85 first-year veterinary medical students) were divided into 12 lab groups of 3-4 students per lab section. These groups were randomly assigned to either a traditional live animal laboratory or an interactive videodisc-simulated laboratory to compare the effectiveness and efficiency of these methods in teaching physiology. A 22-item, multiple-choice/short answer test was given to all students after the laboratories. In both the participation and the demonstration laboratories, there were no significant differences between group test scores of the interactive videodisc groups and the live animal laboratory groups, but there were differences in time spent by both students and instructors. It was concluded that the interactive videodisc-simulated lab was as effective as the traditional live-animal labs and was more time efficient than the traditional participation lab.

Rupture pressure of elastic and muscular aortic segments from hypertensive and hypotensive turkeys.

Blood pressures and heart rates were recorded from two groups of turkeys in two trials. In trial one 20 turkeys, 36 weeks of age and in trial two 24 turkeys, 14 weeks of age, were used. Immediately after blood pressures and heart rates had been determined, the turkeys were killed and vascular tissues were excised. Equal numbers from hypertensive and hypotensive lines of turkeys were used in each trial to determine the rupture pressure of both the elastic and muscular segments of the aorta. When values for the two trials were combined, mean hydrostatic pressures of 1478, 1804, and 794 mm Hg respectively were required to rupture the most caudal abdominal aortic segment, the adjacent cranial abdominal segment, and the thoracic aortic segment. There was a significant difference between the two lines for blood pressure in both trials and for heart rate in trial 2. There were no statistically significant correlations between blood pressure, atherosclerotic plaque score and rupture pressure. Birds fed on a diet containing added fat and cholesterol had significantly lower blood pressures than the birds fed on the other two diets. Birds receiving added dietary cholesterol and fat had lower heart rates than birds fed on the diet with added fat only. Lower plaques scores were evident in the caudal abdominal aorta of the birds fed on the control diet compared to birds fed on the other two diets.

Microscopic characteristics of genital end bulbs in the penis of bulls.

Light microscopic sections of Epon-embedded bull penis were examined for nerve endings. Tissue was taken from the dorsal midline of the glans penis and from the free portion of the penis in 6 mature bulls. Genital end bulbs were identified in both regions of the penis and were located from 1 to 500 micron beneath the epithelium, with most end bulbs concentrated next to the epithelium in the glans penis. Occasionally, end bulbs were found within nerve trunks. Other encapsulated endings were not seen. Ultrastructural correlation of the light and electron microscopic appearance of spherical end bulbs and elongated end bulbs indicated that their structure was identical. Two to 6 neurites filled with mitochondria were surrounded by several layers of thin cytoplasmic lamellae. The lamellae were characterized by pinocytotic vesicles, microtubules, and a scant basal lamina. A capsule of differing thickness enclosed the end bulbs. Fewer capsular layers surrounded more superficially located end bulbs. Near the epithelium, there were gaps in the capsule. Nonmyelinated fibers were seen within end bulbs and between end bulbs and the epithelium.

Angiography of the corpus cavernosum penis in the pony stallion during erection and quiescence.

Serial arteriography was used to determine the vascular pattern and blood flow in the penis of the pony stallion. Ponies were anesthetized with pentobarbital sodium, and catheters were surgically introduced into the internal pudendal and obturator arteries. The vascular anatomy was visualized by angiography via image-intensified fluoroscopy and was recorded on 70-mm film at 3 frames/s or by direct radiography. Blood flow into the corpus cavernosum penis (CCP) was limited during quiescence because the blood was immediately shunted into the venous system. After vasodilation with mild stimulation from an electroejaculator, there was increased filling of the CCP and corpus spongiosum penis. Contrast medium injected into the internal pudendal artery entered the bulb of the penis during peak erection, but medium injected into the obturator artery could not enter the crus penis during peak erection. The contrast medium stopped in the obturator artery at the edge of the ischiocavernous muscles due to the occlusion of the deep arteries of the penis by contraction of these muscles. When contrast medium was injected directly into the CCP near the glans to outline the body of the penis, there was no evidence of venous outlets along the body.

Cardiovascular responses in turkeys as affected by diurnal variation and stressors.

Ten hypertensive (hyper) and hypotensive (hypo) turkeys of both sexes were used to evaluate the effect of various stimuli on blood pressure (BP) and heart rate (HR). Blood pressures were recorded from the brachial artery via a catheter and radio telemetric system. After a 48 hr baseline monitoring, the birds were subjected to exercise, fright, and mating and the BP and HR changes recorded. Mean arterial BP was 4.5 mm Hg less during night than day, and the BP of the hyper strain was significantly (P less than or equal to .05) higher than the hypo strain. Tracings from quiescent birds revealed fluctuations in BP that varied by 100 mm Hg. These were unexplainable fluctuations and occurred in both hyper and/or hypo birds at various times. The application of various stressful situations, such as exercise and fright, had little effect on BP but appeared to cause marked changes in HR. The highest recorded BP occurred during one of the mating exercises where systolic BP approached 350 mm Hg and HR increased by approximately 100%. Noises created with dog whistles and a .22 caliber pistol shot did not cause marked changes in BP and HR.

Effect of exercise, phenylbutazone, and furosemide on the plasma renin activity and angiotensin I in horses.

Circulating concentrations of angiotensin I and plasma renin activity (PRA) were determined in 45 Thoroughbreds before prerace medication (at rest), 1 to 1 1/2 hours before racing but after prerace medication (prerace), within 15 minutes after racing (immediately postrace), and between 1 to 2 hours after racing. Angiotensin I was measured by radioimmunoassay, and PRA was determined by the rate of generation of angiotensin I in plasma incubated at 37 C. Irrespective of prerace medication, there was a marked increase in angiotensin I (0.478 +/- 0.034 to 0.848 +/- 0.051 ng/ml) and PRA (0.191 +/- 0.018 to 0.522 +/- 0.061 ng/hour/ml) from the at-rest samples to the immediate-postrace samples, with the exception of anhidrotic horses in which increases in angiotensin I (0.7131 +/- 0.0794 to 0.8081 +/- 0.0608 ng/ml) and PRA (0.1635 +/- 0.0379 to 0.2176 +/- 0.0437 ng/hour/ml) were not as marked as they were in other horses. Administration of 1 mg of furosemide/kg 2 hours before racing caused an increase in PRA from 0.2438 +/- 0.0324 to 0.3706 +/- 0.1110 ng/hour/ml, whereas horses under the influence of 4 mg of phenylbutazone/kg had a decrease in PRA from 0.2090 +/- 0.0440 to 0.0669 +/- 0.0206 ng/hour/ml. Marked increases in angiotensin I and in PRA did not occur when horses were administered furosemide and phenylbutazone as prerace medication.

Angiography of the crus penis in the ram and buck during erection.

Serial angiography was used to determine blood flow patterns to the penis of rams and bucks. Animals were anesthetized and the internal pudendal artery was catheterized so that contrast medium could be injected toward the crus penis area. By comparing vascular patterns of the ram and buck during erection, it was found that flow patterns of the corpus cavernosum penis (CCP) and corpus spongiosum penis (CSP) were similar for both species. Contraction of the ischiocavernosus muscles occluded the arterial inflow and venous outflow to the CCP, making it a closed system during peak erection. However, during erection, the contrast medium continued to flow into the CSP, showing that it is not a closed system. In the vasodilatation phase, the CSP usually filled before and more intensely than did the CCP.

Effect of local anesthesia of the penis and dorsal penile neurectomy on the mating ability of bulls.

Eleven bulls were used to study the effect of the loss of nerve sensitivity in the free portion of the penis and glans penis on their ability to copulate. The loss of sensitivity was induced by topical anesthesia, infiltration anesthesia, and dorsal penile neurectomy. Topical anesthesia of the glans penis reduced the ability of the bulls to search for and to locate the vagina and to complete copulation; however, all bulls eventually copulated. Topical anesthesia of the free portion of the penis and glans penis blocked the ability of all bulls to copulate. Infiltration of the glans penis with lidocaine resulted in bulls failing to ejaculate, indicating the need for input from deep nerve receptors. Ten of the eleven bulls with unilateral neurectomy were able to copulate, but a longer time was required. In the one bull that failed to complete intromission and ejaculation, the sectioned nerve made up 75% of the nerve mass to the distal end of the penis, leaving only a small number of functional fibers. With this small number of fibers, there may have been insufficient sensory input to elicit the thrusting responses and to cause the animal to ejaculate. Bulls with bilateral neurectomy were unable to copulate.

Penile pressures and muscle activity associated with erection and ejaculation in the dog.

A needle-tipped polyvinyl catheter or subminiature pressure transducer was implanted in the corpus cavernosum penis (CCP), corpus spongiosum penis (CSP), or bulbus glandis to determine the pressure during coitus in 42 dogs. Silver ring electrodes were implanted in the ischiocavernosus (IC) and bulbospongiosus (BS) muscles to monitor the electromyographic (EMG) activity of these muscles. The CCP pressure increased from 26 mmHg in the quiescent state to 161 mmHg at mild erection of the penis in the presence of a receptive female. During the intromission phase of coitus, the mean peak CCP pressure was 5,296 mmHg in the dogs with implanted catheters and 7,434 mmHg in the dogs with implanted transducers. The CCP pressure peaks during intromission were more in phase with the contractile activity of the IC muscles than with the BS muscles. Anesthesia of IC muscles with lidocaine significantly reduced the CCP pressures and the dogs with low pressures were unable to copulate because of insufficient erection for intromission, which indicated that the IC muscles were the source of energy for the high CCP pressure. The mean peak CSP and bulbus glandis pressures during the intromission phase of coitus were 579 and 1280 mmHg, respectively. The contractile activity of the BS muscles was in phase with the CSP pressure peaks. Anesthesia of BS muscles with lidocaine reduced the peak CSP and bulbus glandis pressures during attempted coitus. The mean rupture pressure of the CCP was 86,615 mmHg.

Digital stimulator control system for introducing premature stimuli.

A control system to convert a general-purpose stimulator into one which will generate premature stimuli at variable but controlled intervals is described. The control system was developed to sense spontaneous cardiac depolarizations and inject premature stimuli at preset elapsed times after every 10th or every spontaneous depolarization. The delay may be set by an analog circuit or by digital thumb-wheel switches. The output of the stimulator also may be coupled to the input, permitting the use of the system as a standard asynchronous stimulator with digital control of the pulse interval. A block diagram is presented to permit duplication of the system using standard digital and analog integrated circuits.

Corpus spongiosum penis pressure and penile muscle activity in the stallion during coitus.

A needle-tipped catheter or subminiature pressure transducer was implanted in the corpus spongiosum penis (CSP) of Shetland Pony stallions to determine pressure during coitus. Electrodes for monitoring the electromyographic (EMG) activity were implanted in the ischiocavernosus (IC) and bulbospongiosus (BS) muscles. The mean peak CSP pressure recorded with the catheter was 762 mm of Hg, and with the subminiature pressure transducer, it was 994 mm of Hg. The simultaneous occurrence of the CSP pressure peaks and bursts of BS muscle activity indicated that these muscles were the likely source of energy for the increased pressures, which were far greater than the systemic blood pressure. This conclusion was further supported by the finding that anesthesia of the BS muscles greatly reduced the CSP pressures of the stallion during attempted coitus.