Evaluation of urinalysis as an aid in the diagnosis of equine grass sickness

To determine whether urinalysis can aid the diagnosis of equine grass sickness, samples of urine from 15 horses with acute grass sickness, eight horses with subacute grass sickness, 17 co-grazing horses and 17 stabled control horses were analysed. The samples from all of the horses with grass sickness had a significantly higher specific gravity, higher protein and creatinine concentrations and a significantly lower pH; the samples from the horses with acute grass sickness also had significantly higher glucose concentrations. These differences may support a diagnosis of grass sickness but they are not pathognomonic for the disease.     

Herbage potassium levels in a permanent pasture under grazing

Herbage potassium levels were measured in 1986 in a permanent pasture under continuous grazing with cattle and receiving 200 kg N ha⁻¹. In April, before grazing started, K concentration in the herbage was relatively uniform across the pasture, with a value of 1·9 ± 0·038% K in the herbage dry matter. In July, a significantly lower concentration of herbage K was found in the grazed areas of the pasture (1·8 ± 0·10%) compared with the level (2·4 ± 0·088%) found in the rejected areas of the sward. The difference between the grazed and rejected areas was similar in September, with 1·6 ± 0·087% and 2·2 ± 0·172% K, respectively, in the herbage dry matter. This result suggests that herbage growth in the grazed areas might have been limited by K supply and highlights the need for more information on the K requirements of grazed grassland.     

Periodicity and gradients in dispersal ofAlternaria linicola in linseed crops

Conidia ofAlternaria linicola produced on infected linseed crops were mainly dispersed by wind. The numbers of conidia in the air above linseed crops collected by a Burkard spore sampler were greatest between 1200 h and 1300 h, when the relative humidity was lowest. Although numbers of conidia collected decreased with increasing height within and above the crop canopy, air-borneA. linicola conidia were present up to 80 cm above the crop canopy. Conidia ofA. linicola were transported by wind up to at least 40 m downwind from an artificial line inoculum source, but their numbers decreased with increasing distance from the source. In 1991, 1992, and 1993, the dispersal ofA. linicola conidia above linseed crops followed a seasonal periodicity which was influenced by weather conditions and cultural practices. The greatest numbers of conidia were collected during July, August and early September and coincided with periods favourable for sporulation and with an increase in the incidence of the disease in the senescent crop. Air-borneA. linicola conidia produced on point or line inoculum sources (naturally infected linseed stem debris) were responsible for the spread of the disease in linseed crops. In 1992 and 1993, the disease was first detected downwind from the sources, but by the end of the growing seasons, it had spread in all directions and up to 20 m and 60 m from the sources, respectively. Disease gradients were initially steep near the inoculum sources but they became flatter with time due to the secondary spread of the disease.     

Effect of cutting height and frequency on Leucaena leucocephala forage and wood production

Abstract

Leucaena leucocephala is a fast‐growing tree that can provide both high quality forage and firewood. The objective of this trial was to determine the optimum height and frequency of cutting for both wood and forage production. Cutting heights at 0.3 m, 0.6 m and 1.0 m were superimposed on 3‐month and 6‐month cutting frequencies on mature rows of L. leucocephala for three years. Effects of year or its interaction with the other factors were not significant (P≥0.10). There was an increase (P=0.07) in wood production but not forage production (P≥0.10) with the longer interval. Cutting height had an effect on forage (P<0.001) production, with 5.47 t ha^?1 a^?1 for the 0.3‐m height, 7.62 t ha^?1 a^?1 for the 0.7‐m height, and 8.71 t ha^?1 a^?1 for the 1.0‐m height. Cutting height also had an effect on wood production (P<0.001), with 7.22 t hd^?1 a^?1 for the 0.3‐m height, 9.33 t ha^?1 a^?1 for the 0.7‐mheight, and 11.55 t hd^?1 a^?1 for the 1.0‐m height. In this experiment, the six‐month interval produced more wood than the three‐month interval, but there were no differences in quantity of forage dry matter in L. leucocephala; there were advantages in both wood and forage production with the taller trunk base.     

Infection of primary cultures of mammary epithelial cells by small ruminant lentiviruses.

The caprine arthritis-encephalitis virus (CAEV) and Visna Maedi virus cause persistent infections with long latent periods and induce degenerative and chronic inflammatory lesions of the central nervous system, joints, lungs and udder. Monocyte/macrophage lineage is the main target cell for CAEV and Visna Maedi virus but we speculate that mammary epithelial cells may also be infected. Primary cultures of milk cells, mammary tissues of experimentally and naturally infected goats and ewes were used. Primary cultures of mammary tissue from ewes and goats were infected with the CAEV Cork strain. The lentiviral infection of the primary culture was demonstrated by a typical cytopathic effect in mammary epithelial cells and the presence of an infectious virus in coculture with permissive fibroblasts. To identify the epithelial cells in explants and demonstrate the antigenic expression of CAEV, primary cultures were immunostained with polyclonal anti-keratin and monoclonal anti-CAEV p30. Colocalisation studies under a UV fluorescence microscope and by epifluorescence microscopy showed the expression of specific viral antigens in mammary epithelial cells from the eight animals used. Infected mammary epithelial cells may act as a reservoir for the virus which may play an important role in the virus dissemination and in the pathogenesis of the mammary lentiviral disease.     

Effects of Supplementing a Basal Diet of Chloris gayana Hay with One of Three Protein-rich Legume Hays of Cassia rotundifolia,Lablab purpureus and Macroptilium atropurpureum Forage on Some Nutritional Parameters in Goats

Growth and digestibility experiments were conducted on growing East African type goats offered Chloris gayana hay supplemented with one of three high-protein (119–128 g CP/kg DM) legume hays, Cassia rotundifolia (cassia), Lablab purpureus (lablab) or Macroptilium atropurpureum (siratro), and crushed maize to investigate the feed intake, digestibility, growth and urinary excretion of purine derivatives. Goats in the supplemented groups had higher total dry matter and nitrogen intakes and higher N retention and body mass gains than unsupplemented counterparts. The digestibility of dry matter, organic matter and neutral detergent fibre were increased by protein supplementation. Animals on supplemented diets had higher fractional outflow rates of particulate matter from the rumen. The production of protein by ruminal microbes and the efficiency of microbial N production were increased by supplementation. It was concluded that a mixture of low-quality grass hay (61.9 CP/kg DM) and either cassia, lablab or siratro hay, and maize grain can provide a productive balanced diet for growing goats.     

Clearance of ovine isolates of Bordetella parapertussis from murine trachea and lungs

Thirty-six mice were inoculated intranasally with Bordetella parapertussis organisms (isolated from sheep with chronic non-progressive pneumonia) to study their deposition and clearance in the lower respiratory tract. The deposition of the organism was greater in the trachea than in the lungs. At 48 hours after inoculation, almost 100% of organisms were cleared from the trachea but only 55% of organisms were cleared from the lungs. This result correlates well with the morphological changes seen previously in the pulmonary parenchyma and airways of mice and lambs experimentally infected with this organism.     

Impacts of insect herbivores on rare plant populations

Population-level impacts of insect herbivory on rare and endangered plants are poorly understood, being frequently suggested but seldom quantified. We compiled 37 studies from the primary literature encompassing 35 rare plant species and at least 63 insect herbivore species, and assessed patterns in the effects of insect herbivores on rare plant populations and vital rates. Only three studies directly quantified effects of insect herbivory on population size or growth rate, with the vast majority instead extrapolating from vital rates to population size. Few studies (eight) studied herbivory experimentally, and feeding guilds other than seed predators have been relatively neglected. Estimates of population-level impacts vary extremely widely, but for many rare plants insect herbivores cause major reductions in survivorship or fecundity or can even drive local extinctions. Four studies documented positive (plant-) density dependence in insect attack, suggesting that herbivores may have a stabilizing influence on plant populations and thus may play a role in regulating rare plant population size. Most reported herbivores of rare plants are oligophagous or polyphagous, but monophagous herbivores of rare plants do exist, and there was no detectable difference in impact among specialization classes. Attack on rare plants by escaped biocontrol agents can sometimes have significant population-level effects, but such cases appear uncommon. Because insect herbivory can strongly suppress rare plant populations or vital rates, we need to know much more about what ecological and evolutionary factors determine the population-level impacts of insect herbivores. We suggest several ways in which the results of such research could inform conservation practices for rare plant species – for example, the possibility of different management regimes for plants under attack by monophagous, oligophagous, and polyphagous herbivores.