Gastrointestinal nematode parasites of sheep: a dynamic model for their effect on liveweight gain

This paper presents an individual-based model for gastrointestinal nematode parasites of sheep and includes the effect of these parasites on the liveweight performance of young sheep. Parasitism is known to affect the host animal in at least two ways. The first induces a loss of appetite in the host, which reduces pasture consumption compared with the parasite-free animal. This effect is examined in the first part of the study. The second major effect of parasitism is a reduction in the metabolic efficiency of the host which decreases nutrients available for maintenance and growth. The latter part of the paper examines the consequences of incorporating this effect on the liveweight changes in individuals in a group of sheep. Previous models addressing this issue have only given mean liveweight and worm burden changes.

Tree water use and rainfall partitioning in a mature poplar-pasture system

Traditionally, poplars (Populus) have been planted to control erosion on New Zealand's hill-slopes, because of their capacity to dry out and bind together the soil, by reducing effective rainfall and increasing evapotranspiration and soil strength. However, the effect of widely spaced poplars on the partitioning of soil water and rainfall has not been reported. This study determined rainfall partitioning for 18 mid-spring days in a mature P. deltoides (Bart. ex Marsh, Clone I78)-pasture association (37 stems per hectare, unevenly spaced at 16.4 +/- 0.4 m) and compared it with a traditional open pasture system in grazed areas of a hill environment. Tree transpiration was measured by the heat pulse technique. A time-driven mathematical model was used to set a zero offset, adjust anomalous values and describe simultaneous sap velocity time courses of trees. The model showed that daylight sap flow velocities can be represented with a nonlinear Beta function (R(2) > 0.98), and differences in the parameters representing the initiation, duration and conformation of the sap velocity can be tested statistically to discern tree transpiration differences during the day. Evapotranspiration was greater for the poplar-pasture association than for the open pasture (2.7-3.0 versus 2.2 mm day(-1)). The tree canopy alone contributed 0.92 mm day(-1) as transpiration and 1.37 mm day(-1) as interception, whereas evapotranspiration of the pasture understory was only 0.4-0.6 mm day(-1). Despite the higher water use of the poplar-pasture association, soil water in the 0-300 mm soil stratum was higher than, or similar to, that of the open pasture. Tree shading decreased evapotranspiration and pasture accumulation under the trees.

Effect of topographical aspect and farm system on the population dynamics of Trichostrongylus larvae on a hill pasture

The population dynamics of Trichostrongylus colubriformis larvae were compared over two years on contrasting topographical aspects north (warm and dry) and south-facing (cool and moist) hill slopes) on paddocks which form part of the 'non-chemical' and conventional' farm systems at the AgResearch Ballantrae Hill Country Station located in a summer-moist region of New Zealand. Sheep faeces containing 50,000 Trichostrongylus eggs were incubated for 4 days at 25 degrees C and then deposited on each of 36 sub-plots in each of 8 plots in a 2 x 2 factorial design in the summer (summer trial) and again in autumn (autumn trial). Pasture was removed to ground level and larvae extracted from six sub-plots from each plot 2, 4, 6, 8, 11 and 14 weeks after contamination in all trials. Larvae were recovered from two strata, 0-5 cm above the soil surface and > 5 cm above the soil surface. Fewer (p < 0.001) larvae were recovered from herbage (47 vs. 118) and residual faeces (28 vs. 246) from the autumn than from the summer trials. This coincided with more rapid (p < 0.001) faecal disappearance in the autumn trials. In the summer trials, fewer (p < 0.003) larvae were recovered from the herbage (101 vs. 182) and residual faeces (140 vs. 352) from plots on the south than the north facing aspect. In the autumn trials there was a rapid (p < 0.0001) faecal disappearance from the south-facing aspect. In the autumn trials there was a non-significant (p < 0.10) trend for fewer larvae to be recovered from the south-facing aspect (2 vs. 54). This also coincided with more rapid faecal disappearance from the south-facing aspect. There was no effect of farm system on the number of larvae recovered. Despite greater (p < 0.0001) numbers of larvae recovered from the bottom stratum of herbage, the density of larvae (L3/kg DM) tended (p < 0.12) to be higher in the top stratum of herbage. It was concluded that season and aspect have a marked effect on the number of larvae recovered from herbage and that this was inversely related to the rate of faecal disappearance.

Genetic variation for macro- and micro-nutrient concentration in perennial ryegrass (Lolium perenne L.)

A perennial ryegrass breeding pool showed significant genetic variation for concentrations in leaf of 8 of 16 macro- and micro-nutrients measured. Narrow sense heritabilities (h2) ranged from 0 (B, Zn) to 0·9 (Mn, Na). Families selected for high and low herbage P concentrations (h2 = 0·4) showed consistent behaviour over a range of soil P treatments in a separate experiment. Families similarly selected for herbage K concentrations (h2 = 0·15) did not show such consistent response in a later experiment. High soil K reduced herbage Mg concentrations, but family means for herbage Mg and herbage K concentrations were not correlated. The data show that selection for herbage content of Mg, Na, or P is likely to be successful, but that herbage K is not simply regulated. These results have implications for livestock Mg metabolism, for efficiency of P and K use in mixed legume-based pastures, and for P and K wastage from pastures.

Controlling internal parasites in grazing ruminants without recourse to anthelmintics: approaches, experiences and prospects

Interest in ways of raising stock without using anthelmintics has been stimulated by the desire for intensive grazing systems to adopt more sustainable methods of internal parasite control and by potential premiums for "organic" produce. This requires grazing management systems which are practicable and achieve levels of parasite control sufficient to meet realistic production objectives. This paper will summarise 3 years experience of lamb and cattle production without a recourse to anthelmintics on 2 production systems: a mixed cropping, lamb finishing, and cattle rearing unit and an all grass, mixed-stock, hill country unit in which all non-replacement lambs are sold at weaning. On both units parasite control was almost entirely dependent on integrated grazing management of sheep and cattle and strict systems of grazing management had to be rigidly applied. Acceptable productivity could be more readily achieved in sheep than cattle. Rams selected for resistance to nematodes were also used in both sheep flocks. Their influence on lamb production was equivocal. There is a need for more information on factors influencing parasite epidemiology and for consideration of strategies other than alternate grazing. The impact of pasture species on parasite epidemiology needs to be clarified. Current research indicates substantial differences between grasses in terms of parasite burdens acquired and production losses suffered by lambs grazing them. Grazing management may need to vary with pasture species. Also, specialty forage crops, particularly those containing condensed tannins (i.e. Hedysarum coronarium, Lotus pedunculatus and Lotus corniculatus) hold special promise as a means of countering parasite-induced production losses and dagginess. Using biological control of free-living larval stages and vaccination, may in the long term, also prove useful. Developing effective and acceptable systems for raising stock without using anthelmintics presents a considerable challenge, to parasitologists, as well as to plant breeders, agronomists, and farming systems researchers.

Accumulation of cadmium with time in Romney sheep grazing ryegrass-white clover pasture: effect of cadmium from pasture and soil intake

Cadmium (Cd) concentrations in various tissues of Romney sheep and rates of accumulation, as affected by Cd concentrations in pasture and soil, DM intake, and animal age, were determined in a 25-month study. After weaning, 6 groups of 10 wether lambs were grazed on a low Cd (0.l8 � 0.08 8g Cd/g DM) or high Cd (0.52 � 0.17 8g Cd/g DM) pasture in 3 replicates. The rate of accumulation of Cd (8g /day) into the liver and kidney was greatest in sheep aged about 6 months (for the low and high Cd pastures: kidney 0.27 and 0.56; liver 0.35 and 1 I), after which it declined with age (kidney 0.02 and 0.03: liver <0901 and 0.05; at 28 months of age). Total content of Cd in the organs continued to increase. In 6-month-old animals, 0.25% of total Cd ingested was retained by the kidney and liver, but this proportion decreased to about 0.05% of Cd intake with 28-month-old animals. Net retention of Cd in the fleece-free body as a percentage of daily Cd intake for both the control and treatment animals was estimated between 0- 35 and 0 5%. Except for muscle tissue from sheep in the treatment group, for which the mean Cd concentration was lower than that of the control group (2.0 � 0.24 and 3 9 � 0.63 r)g Cd/g fresh tissue, respectively), Cd concentrations in kidney, liver, thymus, muscle, and lung tissue increased over the first 3 months for both groups of animals. After 2 years, animals on the treatment pastures had approximately 3-fold greater Cd concentrations in liver, kidney, and duodenal tissue tissue than those grazing the control pastures (liver, 361 � 58 v. 97 � 11; kidney, l485 � 200 v. 352f48; duodenal tissue, 32f 4 v. 18f 2.5 t)g Cd/g FW, respectively). At higher Cd intakes, the adaptive effect of increased metallothionein synthesis enabled the animal to be more efficient in binding Cd, which restricted accumulation of Cd in muscle. The regression ([Cd] kidney = -205 + 0. 981Cdintake + 0 - 726Time; r = 0.82, P < 0.001) gave the best fit for the observed Cd concentration in the kidney tissue. Daily Cd intake was also a better predictor of the Cd concentration in liver tissue than the concentration of Cd in pasture by itself ([Cd]liver, = 24.7 + 0.353Cdintake; r = 0.81, P < 0.001). Accurate predictions of the potential for Cd accumulation in young grazing animals will enable more effective management strategies to be implemented to reduce Cd accumulation and therefore minimise the potential impact relating to both environment and market.

Theophylline analysis at the chest clinic--comparison of a portable versus conventional system

The running cost and clinical application of a new, portable, direct-injection, high-performance, liquid chromatograph for the measurement of theophylline was compared with conventional laboratory-based analysis by studying the two methods in two parallel chest clinics. Thirty-six patients were managed with the portable method and 33 by the conventional system. They were already receiving theophylline preparations for treatment of their asthma or chronic airflow limitation. Over the 12-week period of study, the percentage of patients with levels in the therapeutic range rose from 33% to approximately 87% in both clinics, but this change was achieved in only 6 weeks using the portable system. Patients whose theophylline levels were increased into the therapeutic range had improved symptom scores as measured by visual analogue scales but we were unable to demonstrate any significant change in spirometry. The cost of the portable system compared favourably with laboratory analysis, and had the additional benefit of quicker detection of non-compliance and facility for discussion with the patients at the time of consultation.

Changes in hospital management of acute severe asthma by thoracic and general physicians in Birmingham and Manchester during 1978 and 1985

Hospital management of acute severe asthma in 14 large hospitals in Birmingham and Manchester was audited in a random 20% of 1196 patients aged 15-45 years admitted in 1985. Of the 239 admissions randomised, 192 were suitable for study. Results were compared with those from a study in the same hospitals using the same methods in 1978. The age and sex of the patients and their smoking history, duration of asthma, and hospital attendance were similar in 1978 and 1985. A much smaller proportion of patients presented with symptoms of over seven days' duration in 1985 (8.5%) than in 1978 (26%). The inpatient management of asthma appears to have improved in both thoracic and general units, with more thorough functional assessments, more frequent performance of relevant investigations (arterial blood gases and peak expiratory flow rates) and more frequent use of recommended treatment (nebulised bronchodilators, oral and intravenous corticosteroids). Less difference was found in 1985 between units with a specialist thoracic interest and those without, though some differences remained in 1985 in monitoring of peak expiratory flow rate and arterial blood gases, outpatient prescribing, and follow up arrangements. Inhaled preventive medication was prescribed more frequently than in 1978. In 1985 there was a 56% increase in admissions for asthma. The proportion of severely ill patients was similar to that in 1978, but in the most severe functional grade mean arterial carbon dioxide tension was higher in 1985 and more patients were ventilated. Our results suggest that hospital management by thoracic and general physicians has improved over the period 1978-85. Patients presented earlier in 1985, though there seems to have been an increase in asthma of all grades of severity.

Action of intravenously administered aminophylline on normal airways

The changes in airway caliber and plasma cyclic-AMP levels after intravenously administered aminophylline, and the effect of DL- and D-propranolol on these responses have been investigated in a double-blind manner in normal subjects. Aminophylline 5.6 mg/kg was given intravenously over a 10-min period and the airway response was measured as change in specific airway conductance (delta SGaw) in the body plethysmograph. In the initial study in 6 subjects, orally administered placebo or propranolol was followed 2 h later by intravenously administered aminophylline. Neither placebo nor propranolol alone caused any change in SGaw at 2 h. After placebo, intravenously injected aminophylline produced a 30% increase in SGaw, reaching a peak 5 min after injection. This response was equivalent to 77% of the maximal response to 400 micrograms inhaled albuterol in the same subjects. After propranolol, the airway response to aminophylline was attenuated, with a 53% reduction in delta SGaw at the time of peak response. In a further study on 6 subjects, intravenously given aminophylline produced a 25% increase in SGaw and a 51% increase in plasma cyclic-AMP levels after placebo tablets. Pretreatment with 40 and 80 mg DL-propranolol caused a dose-dependent reduction of both the airway and plasma cyclic-AMP response to aminophylline. The airway response to aminophylline was not attenuated by D-propranolol so the effect of DL-propranolol is thought to be due to beta-adrenoceptor blockade. The absence of any detectable change in SGaw after DL-propranolol suggests there is little resting sympathetic tone to the airways in normal subjects. In the absence of sympathetic stimulation, the rapid response to aminophylline is unlikely to be due to phosphodiesterase inhibition. The attenuation of the airway and cyclic-AMP response by propranolol suggests that part of the action of aminophylline may be due to beta-agonist activity.

How important is the sequence of administration of inhaled beclomethasone dipropionate and salbutamol in asthma

Sixty patients with fairly stable asthma of mild or moderate severity entered a multicentre, double-blind cross-over trial, comparing the efficacy of inhaled beclomethasone dipropionate preceded 10 minutes earlier by inhalation of salbutamol with that of beclomethasone followed 10 minutes later by salbutamol during two consecutive three-month periods. Patients received beclomethasone 100 microgram and salbutamol 200 microgram four times daily. Analysis of occurrence of exacerbations, usage of additional inhaled salbutamol, peak expiratory flow rate and symptom scores showed no evidence that regular beclomethasone was more effective when preceded by salbutamol rather than when followed by it.

Bronchial and cardiac beta-adrenoceptor blockade--a comparison of atenolol, acebutolol and labetalol

Bronchial and cardiac beta-adrenoceptor blockade have been compared in six normal subjects after three beta-adrenoceptor antagonists. Single and double doses of atenolol (50 and 100 mg), acebutolol (100 and 200 mg) and labetalolol (150 and 300 mg) were studied on separate occasions. 2 Salbutamol airway dose-response curves were obtained by measuring the airway response as the change in specific airway conductance (sGaw) after increasing doses of inhaled salbutamol. Bronchial beta-adrenoceptor blockade was assessed after each drug as the dose of salbutamol needed to cause a 50% increase in sGaw (sGaw D50). 3 Cardiac beta-adrenoceptor blockade was assessed after the same doses of each beta-adrenoceptor antagonist, by measuring the percentage reduction in exercise heart rate from control, after exercise for 5 min at 70% of the subject's maximum work rate. 4 Atenolol 50 and 100 mg caused least bronchial beta-adrenoceptor blockade and the greatest reduction in exercise heart rate. 5 Acebutolol 100 and 200 mg and labetalol 150 and 300 mg produced more bronchial beta-adrenoceptor blockade than atenolol. 6 With this approach new beta-adrenoceptor antagonists can be assessed without putting asthmatic patients at risk.

Assessment of bronchial beta blockade after oral bevantolol

We have applied a new method for quantitative measurement of bronchial beta adrenoceptor blockade to a new beta adrenoceptor antagonist, bevantolol. Dose-response curves to a beta agonist, albuterol, were obtained in six normal subjects by measuring specific airway conductance (sGaw) after increasing doses of inhaled albuterol. These were repeated on three separate occasions 2 hr after subjects had taken oral placebo or bevantolol (75 or 150 mg), double-blind in random order. The dose-response curves after bevantolol 75 mg were displaced in the right of placebo in four subjects and after 150 mg were displaced to the right of placebo in all subjects. The mean dose ratios for bevantolol 75 or 150 mg were 1.02 and 2.77, much the same as those obtained in the same subjects after practolol 100 and 200 mg and considerably less than that after propranolol 40 mg. The mean reductions in exercise heart rate were 25% and 29% after bevantolol 75 and 150 mg. Our data show that bronchial beta blockade after a beta blocking drug can be assessed quantitatively in many by a double-blind technique.

Amoxycillin versus ampicillin in treatment of exacerbations of chronic bronchitis

To compare the efficacy and unwanted effects of amoxycillin and ampicillin in the treatment of acute exacerbations of chronic bronchitis, 199 patients were recruited from 28 centres into a double-blind between-patient comparison of four regimens: ampicillin 250 mg or 500 mg, amoxycillin 250 mg or 500 mg, each given orally three times daily for seven days. In these doses, amoxycillin and ampicillin were equally effective and there was no apparent advantage in using the higher dose of either drug in preference to the lower dose. Unwanted effects were few. Only in five patients did diarrhoea lead to withdrawal of therapy and there was no significant difference between the two drugs in this respect. Rashes occurred in four patients, all on ampicillin.

Ketotifen in adult asthma

The efficacy and adverse effects of ketotifen 1 mg twice daily and 2 mg twice daily were compared with placebo in 50 patients with atopic asthma in a multicentre, double-blind study. Ketotifen in the higher dosage caused a slight reduction in salbutamol usage and a modest improvement in breathing in patients not already receiving inhaled corticosteroids. The drug was ineffective in patients receiving inhaled corticosteroids. Drowsiness was a troublesome effect causing withdrawal from treatment or reduction of dosage in seven patients while receiving ketotifen compared with only three while receiving placebo.

Two oral beta-adrenergic stimulant drugs, pirbuterol and salbutamol, in reversible airway obstruction

Pirbuterol and salbutamol capsules were compared in a multi-centre, double-blind, crossover study. Pirbuterol 10 mg four times daily and salbutamol 4 mg four times daily produced a similar increase in peak expiratory flow rate, matched by the patients' subjective appreciation of decreased beathlessness. Both drugs produced the same incidence of tremor.

A solitary cardiac metastasis involving the tricuspid valve ring

An unique case of solitary metastasis to the region of the tricuspid valve is described. The mechanisms of formation and symptomatology of cardiac neoplasms are discussed. Tumour spread in this case was probably embolic.

Haemophilus aphrophilus endocarditis in pregnancy

The clinical and microbiological features of a case of Haemophilus aphrophilus endocarditis in pregnancy are described. The complicating effect of pregnancy on treatment and the difficulties in identifying the organism in the laboratory are discussed.

Myocarditis associated with Mycoplasma pneumoniae infection

A 48-year-old patient presented with pneumonia and pleural effusion due to Mycoplasma pneumoniae, and subsequently developed pharyngitis and electrocardiographic evidence of myocarditis. The sparse literature on mycoplasma myocarditis is reviewed. The clinical features, electrocardiographic changes and prognosis are discussed.