Nutritional factors of lameness and metabolic bone disease in cattle

Lameness in cattle has numerous causes, and many factors interact to interfere with normal locomotion. The nutrients that have been implicated are protein, energy, calcium, phosphorus, copper, manganese, selenium, zinc, and vitamins A, D, and E. The fact that several nutrients may be involved with the problem should not be overlooked. There may also be factors in the diet that interact with the nutrient (particularly with trace minerals) that must be considered. When congenital skeletal deformities are being investigated, the veterinarian should not overlook the nutrition of the dam during pregnancy. When recommending dietary changes, a veterinarian should be careful that new imbalances have not been created and that the producer is not adding nutrients to the diet other than those suggested.     

Observations on an Outbreak of Infectious Bovine Rhinotracheitis in a Bull Test Station

A clinical outbreak of infectious bovine rhinotracheitis with a morbidity of 11.3% in unvaccinated bulls of a test station is described. The outbreak began explosively in one pen and appeared in others over a period of two weeks. After intranasal vaccination of all bulls, the sporadic occurrence of clinical infectious bovine rhinotracheitis ceased. Although no animals died as a result of infectious bovine rhinotracheitis, the periodic weighing necessary in a bull test station revealed that affected bulls were set back in their average daily rate of gain. While on test, affected Angus bulls never returned to an average daily gain comparable to unaffected bulls of the same breed.     

Optimal Placement of Off-Stream Water Sources for Ephemeral Stream Recovery

Uneven and/or inefficient livestock distribution is often a product of an inadequate number and distribution of watering points. Placement of off-stream water practices (OSWP) in pastures is a key consideration in rangeland management plans and is critical to achieving riparian recovery by improving grazing evenness, while improving livestock performance. Effective OSWP placement also minimizes the impacts of livestock use radiating from OSWP, known as the “piosphere.” The objective of this study was to provide land managers with recommendations for the optimum placement of OSWP. Specifically, we aimed to provide minimum offset distances of OSWP to streams and assess the effective range of OSWP using Normalized Difference Vegetation Index (NDVI) values, an indicator of live standing crop. NDVI values were determined from a time-series of Satellite Pour l'Observation de la Terre (SPOT) 20-m images of western South Dakota mixed-grass prairie. The NDVI values in ephemeral stream channels (in-channel) and uplands were extracted from pre- and post-OSWP images taken in 1989 and 2010, respectively. NDVI values were normalized to a reference imagine and subsequently by ecological site to produce nNDVI. Our results demonstrate a significant (P < 0.05) increase in the nNDVI values of in-channel vegetation within 1 250 m of OSWP following their implementation. The area of piospheres (n = 9) increased with pasture size (R² = 0.49, P = 0.05) and increased with average distance to OSWP in a pasture (R² = 0.43, P = 0.07). Piospheric reduction in nNDVI was observed within 200 m of OSWP, occasionally overlapping in-channel areas. The findings of this study suggest placement of OSWP 200 to 1 250 m from streams to achieve optimal results. These results can be used to increase grazing efficiency by effectively placing OSWP and insure that piospheres do not overlap ecologically important in-channel areas.     

Effects of the paralysis tick, Ixodes holocyclus, on the electrocardiogram of the Spectacled Flying Fox, Pteropus conspicillatus

OBJECTIVE: To evaluate cardiac electrical function in the Spectacled Flying Fox (bat) infested with Ixodes holocyclus. DESIGN: Prospective clinical investigation of bats treated for naturally occurring tick toxicity. PROCEDURE: ECGs were performed on bats with tick toxicity (n = 33), bats that recovered slowly (n = 5) and normally (n = 5) following treatment for tick toxicity, and on normal bats with no history of tick toxicity (n = 9). RESULTS: Bats with tick toxicity had significantly prolonged corrected QT intervals, bradycardia and rhythm disturbances which included sinus bradydysrhythmia, atrial standstill, ventricular premature complexes, and idioventricular bradydysrhythmia. CONCLUSIONS: The QT prolongation observed on ECG traces of bats with tick toxicity reflected delayed ventricular repolarisation and predisposed to polymorphic ventricular tachycardia and sudden cardiac death in response to sympathetic stimulation. The inability to document ventricular tachycardia in bats shortly before death from tick toxicity may be explained by a lack of sympathetic responsiveness attributable to the unique parasympathetic innervation of the bat heart, or hypothermia-induced catecholamine receptor down-regulation. Bradycardia and rhythm disturbances may be attributable to hypothermia.     

Pipes and pipe flow process in an upland catchment,Wales

The results of observations on the spatial localisation, origin and function of soil pipes in an upland catchment are discussed. The pipes occur in distinct zones in the brown earth soils of the lower slopes, and form a hydrological link conducting water between an upslope zone of highly permeable skeletal soils and the stream channel. It is proposed that in this catchment, pipes develop from an initial network of mole burrows, modified by hydraulic activity to produce an efficient downslope transmission network. A conceptual model for the pipe slope segment is proposed which recognises the importance of this transmission role. Slope discharge controls switching between saturated throughflow, pipe flow and overland flow, each of which has a specific threshold value for operation. Attempts to investigate the significance of pipe flow at the catchment scale met with limited success, but it appears to be important in increasing both contributing area and duration of storm flow.     

Two methods for the tracing of pipe flow on hillslopes

Two techniques for the determination of soil pipe networks on hillslopes which avoid the logistic difficulties associated with the unpredictable and ephemeral nature of pipe flow are described. Passive detectors of activated charcoal in conjunction with fluorescent dyes, proved to be most useful for the general definition of networks over moderate areas, whereas artificial injections of water permitted much more detailed information to be obtained. The networks comprised anastomosing bands with definite tributary and distributary zones. The gross network form was stable over a five year period, but the function of individual links could change even during a storm event. Velocities of pipe flow were comparable with those of overland flow in the area, and very much faster than observed rates of throughflow. A complex interrelation between these three flow processes was observed during the experiments.     

Absence of a role for selenium deficiency in the runting syndrome of broiler chickens in Australia

The role of selenium deficiency in the etiology of the runting-stunting syndrome (RSS) of broiler chickens in Australia was investigated. Commercial broiler chickens maintained on selenium-deficient developed signs consistent with selenium deficiency of exudative diathesis and markedly reduced plasma glutathione peroxidase activity, but they did not develop pancreatic atrophy and fibrosis or elevated plasma amylase activity, which are the other lesions associated with RSS. Supplementation of the diets of birds from a RSS-susceptible flock with a mixture of selenium, vitamin E, cysteine, and sulfate had no effect on the incidence of runting in the treated birds. In field outbreaks of RSS there were no observable differences between affected and unaffected birds in the concentration of selenium in tissue samples. Furthermore, evidence is presented which suggests that in cases of RSS, pancreatic atrophy and elevations in plasma amylase precede reductions in plasma glutathione peroxidase activity.