A mild outbreak of bovine mastitis associated with Mycoplasma bovigenitalium.

Mycoplasma bovigenitalium was isolated from milk samples from 16 of 99 cows on one farm during a 15-week period in the summer of 1986. One cow was severely affected, four cows had relatively mild signs of mastitis, and three had only altered dry-cow udder secretions. Eleven of the infected cows were dry and three had been calved less than 48 hours. The abrupt method of drying-off and improvements in cleaning of the milking equipment were introduced, but no other control measures were instituted to eradicate the mycoplasma infections. After this mild outbreak of mastitis the herd was monitored for the next 17 months. In total 19 cows had a mycoplasma isolated from udder secretions. Acholeplasmas were isolated from 14 cows but were not associated with clinical mastitis. The udder infections with mycoplasmas apparently resolved without resorting to the segregation and culling of infected animals.     

A computer model study of light interception by orchards in relation to mechanised harvesting and management

The introduction of mechanised harvesting often results in a redesign of the crop canopy. Computer models have been used to predict light interception, and hence potential yield, by a range of hedgerow tree forms and spacings as a guide to the design of orchard systems for mechanical harvesting. Light interception is increased by increasing tree height, thickness and leaf-area density, and by reducing the clear alleyway. Narrow hedgerows less than 2 m high will need straddle harvesting to avoid loss of light interception and yield.     

Virus-like particles in buffy coat cells of normal goats and goats infected with progressive pneumonia virus.

By electron microscopy, virus-like particles (VLP) were seen in neutrophils and lymphocytes from buffy coats prepared from 5 goats inoculated with progressive pneumonia virus (PPV) and 3 noninoculated goats. The VLP were 80 to 120 nm in diameter, limited by a unit membrane, and resembled PPV, visna virus, and other members of the oncornavirus family. Some VLP seemed to have electron-dense nucleoids and external spikes. In neutrophils, VLP were observed budding into vacuoles; rarely, intravacuolar clusters were seen. In lymphocytes, VLP were seen in vacuoles. Free VLP and budding of VLP from external cell surfaces were not seen. In vitro incubation of buffy coat cells with mitogens did not affect the frequency of VLP. Although the VLP are similar to PPV, the exact nature of the particles and their relationship to PPV is not clearly understood.     

Approaches to relieving aeration stress in waterlogged plants

A fertile soil contains sufficient water-filled pores to replenish losses by evapotranspiration and to sustain growth. However, too many such pores can be detrimental because the exchange of gases between the soil, plant roots and the aerial environment is impaired by the water they contain (waterlogging). The consequences include an accumulation of metabolically generated gases (such as ethylene), oxygen deficiency and the production of potentially toxic substances. Knowledge of these effects, and their consequences for growth, hormone production and inorganic nutrient uptake, enhance the prospects for ameliorating flooding injury by prophylactic or restorative means. Theexamples described are (a) the use of more porousmedia for plant containers in the nutrient film technique (NFT) of glasshouse crop production; (b) fungistatic, acid neutralising and oxygen-releasing seed coatings; (c) boron and nitrogen fertilisation; (d)foliar applications of cytokinins and gibberellins; (e) the inhibition of ethylene action or stimulation of ethylene production in aquatic species.     

Whole blood platelet aggregation in uremic dogs

Whole blood platelet aggregation responses to collagen, arachidonic acid, and adenosine diphosphate were determined by use of the impedance method in 22 dogs with serum urea concentrations greater than or equal to 20 mmol/L, which was attributable to renal disease, and in 25 healthy control dogs. The median changes in impedance for the control dogs were 23 ohms for collagen, 18 ohms for arachidonic acid, and 6 ohms for adenosine diphosphate. The median changes in impedance in uremic dogs were 25 ohms for collagen, 21 ohms for arachidonic acid, and 15 ohms for adenosine diphosphate. There were no significant differences in platelet aggregation responses to collagen, arachidonic acid, and adenosine diphosphate between uremic and control dogs. Hemorrhagic tendencies were not detected in uremic dogs by use of whole blood platelet aggregation. Results of this study suggest that platelet aggregation by use of the whole blood platelet aggregometer is not abnormal in uremic dogs, but does not exclude the possibility of a platelet aggregation defect undetected by the whole blood system.     

Immune exclusion of Haemonchus contortus larvae in sheep: dose dependency, steroid sensitivity and persistence of the response

Naive and immune sheep, treated with anthelmintic, challenged directly into the abomasum and killed 48 hours later were used to examine the steroid sensitivity, persistence and dose dependency of immune mechanisms which result in the failure of incoming Haemonchus contortus larvae to establish (immune exclusion). Immune exclusion was almost totally abolished by corticosteroid treatment, the mean percentage of larvae establishing in the mucosa of immune sheep was 1.4 per cent of the challenge infection whereas in those treated with dexamethasone it was 24.4 per cent and in naive sheep 27.3 per cent. Immune animals challenged after seven and 42 days without antigenic experience excluded more than 90 per cent of the challenge larvae from their mucosae, whereas those challenged after 84 days without antigenic experience were as susceptible as naive animals. Immune exclusion was dose dependent, animals challenged with 10(6) and 10(5) larvae excluded 93 per cent and 82.5 per cent of the challenge dose whereas those challenged with 10(4) larvae failed to exclude larvae.     

Remote sensing for agricultural water management and crop yield prediction

Research we have conducted over the past several years relative to agricultural application of remote sensing is reviewed. In addition, new data are presented from recent experiments reported here for the first time.The subjects treated are soil moisture, evaporation, irrigation scheduling, and crop yield estimation. The analyses indicate that we have the technology at hand to successfully integrate remote sensing techniques into agricultural operations designed to enhance production via intelligent water management.Avenues for additional fruitful research are indicated.