NOTES ON THE USE OF POLYTHENE BELOW GROUND TO SEPARATE THE ROOTS OF HERBAGE SPECIES

A method is described by which the root systems of herbage species may be separated under field conditions, using a double layer of 500-gauge black polythene. The effect of such a treatment was examined in field trials; tests on the permeability of this material in laboratory and field were also made. Visual, manual and mechanical examinations of the polythene after 2, 3 and 4 years in the soil are reported. From the results obtained it is concluded that polythene used in this manner is not detrimental to either herbage yield or quality, and that it can be expected to remain a satisfactory barrier below ground for at least 4 years. However, the introduction of polythene placed parallel to drilled perennial ryegrass and white clover did reduce total root weight by 20%, with a concomitant loss in yield; this loss was mainly associated with the grass component.     

Detection and genetic diversity of porcine rotavirus A,B and C in eastern Australian piggeries

Rotaviruses (RV) have a high prevalence in piggeries worldwide and are one of the major pathogens causing severe diarrhoea in young pigs. RV species A, B, and C have been linked to piglet diarrhoea in Australian pig herds, but their genetic diversity has not been studied in detail. Based on sequencing of the structural viral protein 7 (VP7) RVA G genotypes G3, G4 and G5, and RVC types G1, G3, G5, and G6 have been identified in Australian piggeries in previous studies. Although occurrence of RVB was reported in Australia in 1988, no further genetic analysis has been conducted. To improve health management decisions in Australian pig herds, more information on RV prevalence and genetic diversity is needed. Here, 243 enteric samples collected from 20 pig farms within Eastern Australia were analysed for the presence of RV in different age groups using a novel PCR-based multiplex assay (Pork MultiPath™ enteric panel). RVA, RVB, and RVC were detected in 10, 14, and 14 farms, respectively. Further sequencing of VP7 in selected RV-positive samples revealed G genotypes G2, G5, G9 (RVA), G6, G8, G14, G16, G20 (RVB), and G1, G3, G5, G6 (RVC) present. RVA was only detected in young (<10 weeks old) pigs whereas RVB and RVC were also detected in older animals (>11 weeks old). Interestingly, RVB and RVC G-type occurrence differed between age groups. In conclusion, this study provides new insights on the prevalence and diversity of different RV species in pig herds of Eastern Australia whilst demonstrating the ability of the Pork MultiPath™ technology to accurately differentiate between these RV species.     

Development and validation of a range of endogenous controls to support the implementation of practical Taqman real-time PCR-based surveillance for fish diseases within aquaculture

The use of Taqman real-time PCR-based technology has recently become more frequent in the detection of pathogens in the aquaculture industry. This interest has necessitated the development of robust and reliable pathogen-detection assays. The development of a range of endogenous control assays to be run alongside these diagnostic assays works to further increase confidence in the latter. This study describes the design of a range of endogenous control assays based on the elongation factor 1-α (EF1-α) gene specific to a range of fish species including Atlantic salmon, Salmo salar; rainbow trout, Oncorhynchus mykiss; brown trout, Salmo trutta; cod, Gadus morhua; haddock, Melanogrammus aeglefinus; saithe, Pollachius virens; whiting, Merlangius merlangus; Norway pout, Trisopterus esmarkii; carp (family Cyprinidae), roach, Rutilus rutilus; European eel, Anguilla anguilla; and herring, Clupea harengus, as well as a number of fish cell lines. Evidence is provided of the validation of these assays for specific species, a range of tissue types and cell lines as well as an example of the potential uses of these assays.     

Prevalence of Cysticercus bovis in Australian cattle

Objective The first national abattoir survey of Cysticercus bovis (‘beef measles’) in cattle was conducted in February 2008. Methods During the data collection period, 493,316 cattle were subjected to standard postmortem procedures, including incision of the masseter and heart muscles. On-site veterinarians were asked to record the location of any C. bovis cysts, as well as the National Livestock Identification System ear tag numbers of infected animals. Veterinarians were asked to submit samples for laboratory confirmation by histology and polymerase chain reaction testing. Results Of the 23 samples submitted, none was positive for C. bovis by either diagnostic method. Conclusions Occasional, isolated diagnoses of beef measles are still made in most states of Australia, but since the last regional surveys were conducted 30 years ago, when the estimated prevalence was 50 to 200 per 100,000 cattle slaughtered, the parasite has become extremely rare.     

Atypical distribution of fowl pox lesions in broilers

An unusual cutaneous fowl pox outbreak occurred in 8-wk-old broilers in California. Rounded and longitudinal, proliferative scratch-associated lesions were found only in feathered areas of the body. Both sides of the hip, the lower abdomen, pericloacal area, and lateral lower neck area were involved. The head, legs, feet, and toes did not have lesions. Birds in only one section of one of five houses were affected. Fifteen percent condemnations occurred in birds from the affected house due to the skin lesions. A diagnosis of fowl pox was achieved by histopathology, viral isolation, and direct electron microscopy. The unusual distribution of pox lesions was assumed to be associated with skin scratches. There was no evidence that mosquitoes or other types of insects were involved in this outbreak. To the knowledge of the authors, this is the first report of this kind of unusual fowl pox in the United States.     

Vitamin A deficiency in turkey poults.

Vitamin A deficiency was diagnosed in a commercial flock of 13,000 4-6-week-old turkey poults in the summer of 2004. The birds were initially submitted for examination because of a 3% increase in the reported daily mortality of the flock. Clinically, affected birds had stunted growth and ruffled feathers, showed signs of incoordination, and were depressed. At necropsy, pale white pseudomembranous to mucoid material was observed on the mucosal surface of the tongue, oral cavity, portions of the esophagus, and the crop of some birds. Histologically, there was squamous metaplasia of the mucosal epithelium of the oral mucosa, esophagus, sinuses, nasal glands, bronchi, proventriculus, and the bursa of Fabricius. Vitamin A was not detected in the feed sample at a detection limit of 0.5 mg/kg. Serum vitamin A concentrations in 7 birds were very low and ranged from 0.05 to 0.1 mg/L. Vitamin A concentrations in livers were extremely low (0.1 mg/kg wet weight, 1/7 poults) or undetectable (< 0.1 mg/kg wet weight, 6/7 poults). A diagnosis of vitamin A deficiency was made based on gross and microscopic lesions and vitamin A concentrations in serum, liver, and feed. To the authors' knowledge, this is the first documented case of vitamin A deficiency in poults submitted from a commercial meat turkey producer comparatively depicting the gross and microscopic lesions with those found in other species of birds and mammals.     

Clinical exercise testing in the normal Thoroughbred racehorse

To evaluate normal cardiorespiratory and metabolic responses of Thoroughbred horses to a standardised treadmill exercise test, we examined 28 horses ranging in age from 1 to 4 years. The group consisted of eight yearlings, eight 2-year-olds and twelve 3 and 4-year-olds. All horses except the yearlings were in training, and either racing or ready to race, at the time of examination. None of the horses had histories of performance problems. On the first day the horses received a full physical examination, resting electrocardiogram, upper respiratory tract endoscopy and either one or two acclimatisation runs on the treadmill. The following day they were given an exercise test on a treadmill inclined at 6 degrees (+10% slope). The test consisted of 3 min at 4 m/sec, 90 sec at 6 m/sec and 60 sec intervals at 8, 10, 11, 12 and 13 m/sec. During the last 15 sec of each step, blood samples were collected for plasma lactate determination, expired respiratory gases were obtained using an open flow mask system for measurement of oxygen uptake, and heart rate was measured using telemetry electrocardiogram. From these measurements, various derived values were calculated, which have been used by others as indices of exercise capacity. These values included: V200 (speed at HR of 200 bpm), VHRmax (speed at which horses reached maximum HR), VO2-200 (oxygen uptake at a HR of 200 bpm), VO2max (maximum oxygen uptake), VLA4 (speed at which horses reached a plasma lactate of 4 mmol/l) and HRLA4 (HR at which horses reached a plasma lactate of 4 mmol/l). The yearlings had significantly lower values than the older age groups for most of the derived values.(ABSTRACT TRUNCATED AT 250 WORDS)     

Physiological and biochemical consequences of electroimobilisation in conscious sheep

An electroimmobilisation device has been developed to facilitate the automated shearing of sheep, but there is little information on its effects on the body. We have studied its effects on the cardiovascular system and on intermediary metabolism in sheep. Electroimmobilisation caused statistically significant increases in mean arterial pressure, heart rate, cardiac output, renal and hepatic and hindquarter glucose and lactate flux, organ and whole body oxygen flux, hindquarter blood flow and core temperature and decreases in arterial and posterior vena cava blood pH, renal and hepatic blood flow and PaCO2. Notably, no change occurred in PaO2. The metabolic changes demonstrated the capacity of sheep to respond to the increased muscular and cardiovascular work induced by electroimmobilisation. Pulmonary function was not compromised during electroimmobilisation as judged from blood gas changes, and the acid/base changes were rapidly reversed after electroimmobilisation. The recovery to control conditions for all perturbations generally took no longer than 30 min, consistent with a rapid and physiologically adequate reversal by the animal's homeostatic mechanisms.     

Clinical and pathological responses of weaned pigs to atmospheric ammonia and dust

Nine hundred and sixty weaned pigs were exposed for five weeks to controlled concentrations of atmospheric ammonia and dust in a single, multifactorial experiment. The treatments were a mean dust concentration of either 1.2, 2.7, 5.1 or 9.9 mg/m3 (inhalable fraction) and a mean ammonia concentration of either 0.6, 10.0, 18.8 or 37.0 ppm, concentrations representative of commercial conditions. The experiment was carried out over two years and the pigs were used in eight batches, each consisting of five lots of 24 pigs. Each treatment combination was replicated once, and an additional control lot (nominally 0 mg/m3 dust and 0 ppm ammonia) was included in each batch. The dust concentration was the same in the other four lots in each batch in which the four concentrations of ammonia were used; thus, the split-plot design was more sensitive to the effects of ammonia than dust. The groups of pigs were kept separately in five rooms in a purpose-built facility, and the pollutants were injected continuously into the air supply. Ammonia was supplied from a pressurised cylinder, and the endogenous dust in each room was supplemented by an artificial dust manufactured from feed, barley straw and faeces, mixed by weight in the proportions 5:1:4; its ingredients were oven-dried, milled and mixed, and then resuspended in the air supply. The health of the pigs was assessed in terms of general pathology, respiratory tract pathology, and the microbiology of the nasal cavity, trachea and lung. In each batch, postmortem examinations were carried out on 40 pigs after five weeks' exposure to the pollutants and on 30 pigs two weeks later to test for carryover and recovery--a total of 560 pigs. These examinations revealed minimal gross pathology and widespread minor pathological changes of little significance. The pigs' turbinate and lung scores were low and unaffected by exposure to pollutants. All the putative bacterial pathogens, with the exception of toxigenic Pasteurella multocida type D, were isolated from the respiratory tract of the pigs of both ages, but there were no differences between the effects of the different concentrations of pollutants.