Comparison of three methods for assessing varietal differences in resistance to common scab disease (Streptomyces scabies) of potato

Summary Consistent varietal differences in scab severity were obtained when plants were grown in an open field or under a polythene tunnel in soil naturally infested withStreptomyces scabies, or in a glasshouse in pots filled with artificially inoculated sand. It was concluded that the glasshouse pot-inoculation technique would be the most suitable method to use in a breeding programme in which there are many clones to be tested, because a large number of plants can be grown in a small area under closely controled conditions.     

Modelling and costing BVD outbreaks in beef herds

Results from an epidemiological model of an outbreak of Bovine Viral Diarrhoea (BVD) within a Scottish beef suckler herd are presented. These results concurred with field observations and encouraged us to fulfill the objective of providing an estimate of losses due to BVD to assist decision makers. Using the output from the model, estimates were made of losses associated with the outbreak. Without taking into account any financial premiums associated with disease-free status, the estimate of pound 37 (58) mean loss per cow per annum suggests that health schemes and vaccination should be of immediate financial interest to farmers and veterinary advisors.     

Epidemiological modelling of chlamydial abortion in sheep flocks

Chlamydophila (C.) abortus, responsible for chlamydial abortion (commonly known as Enzootic Abortion of Ewes [EAE]), causes major financial losses to the sheep industry worldwide. There remain many uncertainties surrounding the epidemiology of EAE. The aim of this study was to construct an epidemiological model to simulate EAE based on current knowledge of the disease, and in doing so, identify knowledge gaps that need to be addressed through further research. Key parameters that impact upon the development of the disease, such as the rate of contact between na?ve ewes and infected material, are defined. Sensitivity analysis was undertaken for parameter values that are unknown to explore their impact upon the pattern of disease. The simulated results show the importance of the transmission rate (i.e. contact) and the number of infected replacements introduced at the start of an outbreak. Depending upon the rate of transmission, the year in which the peak number of affected ewes occurs and the number of years over which a high number of animals are affected varies. This suggests that a better understanding of the underlying processes that drive transmission of C. abortus is needed. Furthermore, if infected ewes could be identified prior to parturition, when they shed the organism in large numbers, the impact of EAE on sheep flocks could be greatly reduced.     

Effects of zeranol on protein turnover in L6 myotubes

Protein synthesis and degradation were measured in cultures of L6 myotubes to determine the direct anabolic activity of zeranol on muscle. Zeranol, dexamethasone, insulin and zeranol-dexamethasone combination, at various concentrations from 10(-8) to 10(-6) M, were added to cultures at either 18 hr prior to or at the beginning of a 6 hr synthesis or degradation measuring period. Protein synthesis was measured by determining the incorporation of radioactivity into trichloraoacetic acid precipitable cell protein following incubation with [3H] leucine. Protein synthesis was expressed as cpm incorporated in 6 hr per mg protein. Protein degradation was measured by a pulse-chase procedure using [3H] leucine. Protein degradation was expressed as the percent labeled protein degraded in 6 hr. Results from the study indicate that zeranol did not stimulate protein synthesis or inhibit proteolysis (P greater than .01). Stimulation of proteolysis observed with 10(-8) M dexamethasone was 13% and 18% (P less than .01) at the 6 hr and 24 hr incubation period, respectively. Dexamethasone-stimulated protein degradation was not altered appreciably by zeranol. In contrast, 10(-6) M insulin significantly (P less than .01) stimulated protein synthesis (16%) and inhibited protein degradation (15%). These results suggest that the anabolic action of zeranol does not occur by directly regulating muscle protein synthesis or degradation, or by altering the glucocorticoid-induced catabolic response in muscle.