What are the best correlates of predicted extinction risk?

Direct estimates of extinction risk are frequently unavailable, so surrogate indicators are used in threatened species categorizations, but there is inadequate information on which best predict vulnerability. We compared the ability of 16 frequently-used factors to predict extinction risk for 45 vertebrate taxa. Median times to extinction were estimated using taxon-specific stochastic population models. Population size (N) and trend were clearly the best correlates of extinction risk in our data set. Stepwise multiple regression with additive and interaction terms identified N, N × trend, plus taxonomic level, number of sub-populations × N × trend, number of offspring (O) and N × O as predictors, and explained 70% of the variation. Trend was important in large, but not in small populations. Population size is the most important data to collect for threatened species and with trend should be the major focus in endangered species categorization and state of the environment reporting.     

Managing lead exposure and toxicity in cow-calf herds to minimize the potential for food residues.

Lead poisoning is commonly diagnosed in cattle. In this study, 3 groups of cattle from different herds accidentally exposed to discarded lead batteries on pasture were intensively studied to determine the extent and severity of exposure. The losses from acute death due to lead toxicity were substantial in all the 3 study groups at 12%, 17%, and 4%. Blood samples were taken from all cattle around the time of the first diagnosis and then later in 2 of the 3 herds to monitor the change in lead concentrations over time. Asymptomatic lead toxicosis was observed in these herds. In these 3 groups, between 4% and 12% of asymptomatic cattle had blood lead concentrations consistent with acute lead poisoning (> 0.35 ppm), and between 7% and 40% of these asymptomatic animals were in the high-normal range (0.1-0.35 ppm). Because of the consistently high number of asymptomatic cattle with elevated lead levels, all cattle potentially exposed to a lead source should be tested before sale or slaughter to minimize the entry of lead into the food chain. The blood lead concentrations, which were monitored for months after the initial diagnosis, decreased slowly after the cattle were removed from the lead source. The prolonged retention of lead may be due to continued release and absorption of lead from metal particles in the reticulum or rumen. The mean reduction in the lead level was 0.046 ppm (95% CI, 0.017-0.075 ppm) every 30 days for these 2 herds. Using a single-component exponential model, the half-life of lead in the animals retested from Herds 1 and 2 was highly variable. The median half-life was 63 days (interquartile range, 34-107 days). One out of 8 pregnant heifers with high blood levels had a stillborn calf. There were no abortions or calf mortalities in this group. Blood samples were'collected from the calves around the time of birth. The concentrations of lead in the blood of the calves exposed in utero were low (0.010-0.095 ppm).     

Pest and disease control on intensive apple trees by overhead mobile spraying

In 3 year field experiments on pest and disease control by mobile overhead spraying of intensive Cox's Orange Pippin apple trees, overhead booms applying 1125 litres/ha and overhead mist-blowing equipment applying 562 litres/ha, each spraying two complete rows from one alley in half the normal time, were compared with conventional automatic mast spraying at 2250 litres/ha and with conventional mist-blowing at 562 litres/ha. The overhead boom application of demeton-S-methyl (0.0036% a.i.) with azinphos-methyl (0.0165% a.i.) or of fenitrothion (0.031% a.i.) at the green cluster stage gave control of the applegrass aphid, Rhopalosiphum insertum, virtually equal to that obtained by conventional application of the same insecticides. Similarly, the overhead mist applications of conventional quantities of insecticides gave equal control, but not when applying one-quarter of the normal amount of insecticides. The conventional methods generally gave better control of apple sucker, Psylla mali. In 1971, when the incidence of apple scab, Venturia inaequalis, was only moderate, the overhead boom method gave equal control to conventional spraying with both dodine/captan (0.03% a.i. and 0.094% a.i.) and benomyl (0.025% a.i.) programmes: in 1972 and 1973, when the scab incidence was heavier, the overhead boom spraying was again equal to the conventional method with the benomyl programme but was less effective with the dodine/captan programme. The overhead mist applications gave control only when the scab incidence was light. Repeated applications of dinocap emulsion (0.025% a.i.), included in the fungicide programme in 1971, gave as good control of the active stages of fruit tree red spider mite, Panonychus ulmi, when applied by the overhead methods as by conventional spraying, but application of the benomyl programme gave poor control. Mobile overhead spraying of small intensive apple trees is a promising method but needs further development before becoming fully acceptable.     

A lysosomal storage disorder in the BALB/c mouse: bone marrow transplantation

The morphological and biochemical consequences of transplanting affected bone marrow from donor BALB/c mice with a lysosomal storage disorder (BALB/c LSD) into normal recipient mice were studied. Bone marrow was removed from normal BALB/c and BALB/c LSD mice and transfused into normal BALB/c recipient mice four hours after the mice received 850 rads of irradiation. Tissues of the recipient mice were examined 240 days later. This study revealed that the defective cells that constituted the visceral lesions of BALB/c LSD could be transplanted to normal BALB/c mice by the use of bone marrow from affected BALB/c LSD homozygote; that the defective cells of BALB/c LSD proliferated and disseminated throughout the mononuclear phagocytic system of the recipient; that there were increases in cholesterol, sphingolipids, and cystine with decreases in sphingomyelinase and glucocerebrosidase activity in tissues of the recipients; and that the recipients survived substantially longer than BALB/c LSD homozygotes and their lifespan was compromised mainly by the secondary effects of irradiation. These lesions, although not as extensive as in homozygous BALB/c LSD, paralleled the lesions which develop in BALB/c LSD. Since the recipient mice were not compromised by the short life span (70 days) of the BALB/c LSD mice, they may be used to study the long-term chronic effects of these metabolic lesions.     

Failure of a recombinant Babesia bovis antigen to protect cattle against heterologous strain challenge

Groups of cattle were inoculated subcutaneously with (i) a recombinant DNA-derived Babesia bovis protein (KaBbl-GZ) fused to beta-galactosidase and combined with adjuvants, or (ii) native beta-galactosidase (GZ) plus adjuvant, or (iii) adjuvant only or (iv) a live, attenuated B bovis vaccine. KaBbl-GZ was produced in the lambda gt11-amp3 system as a 5-10 kD babesial polypeptide linked to GZ. KaBbl has previously been shown to be an immunodominant antigen of B bovis, localised at the apex of the parasite, and present in a range of B bovis strains. High levels of GZ antibodies were observed in KaBbl-GZ and GZ inoculated cattle, but specific KaBbl antibodies could not be detected by ELISA. Five months after primary inoculation, all cattle were blood challenged with a virulent heterologous B bovis strain. Despite four inoculations with KaBbl-GZ, significant protection against the challenge was not observed.     

Effective use of simulations for the teaching and acquisition of veterinary professional and clinical skills

Simulation technology will feature prominently in this exciting, yet challenging, time for veterinary medicine. The profession is evolving to keep pace with rapid changes in clinical practice, scientific discovery, and educational strategy, while ensuring that it follows the public mandate to produce competent veterinarians. Among the challenges to meeting this educational goal are limitations-due to important issues such as animal welfare-on the availability of real patients for training. Drawing chiefly on the experience in human medicine, this article explores the use of simulations in veterinary medical education to provide safe and ethical alternative opportunities for learners to practice essential clinical and professional skills.     

Assessment of the cryopreservation of equine spermatozoa in the presence of enzyme scavengers and antioxidants

OBJECTIVE: To evaluate the effect of the addition of enzyme scavengers and antioxidants to the cryopreservation extender on characteristics of equine spermatozoa after freezing and thawing. SAMPLE POPULATION: 2 ejaculates collected from each of 5 stallions. PROCEDURE: Equine spermatozoa were cryopreserved in freezing extender alone (control samples) or with the addition of catalase (200 U/mL), superoxide dismutase (200 U/mL), reduced glutathione (10 mM), ascorbic acid (10 mM), alpha-tocopherol (25, 50, 100, or 500 microM or 1 mM), or the vehicle for alpha-tocopherol (0.5% ethanol). After thawing, spermatozoal motility was assessed via computer-assisted analysis and DNA fragmentation was assessed via the comet assay. Spermatozoal mitochondrial membrane potential, acrosomal integrity, and viability were determined by use of various specific staining techniques and flow cytometry. RESULTS: The addition of enzyme scavengers or antioxidants to cryopreservation extender did not improve spermatozoal motility, DNA fragmentation, acrosomal integrity, viability, or mitochondrial membrane potential after thawing. Superoxide dismutase increased DNA fragmentation, likely because of the additional oxidative stress caused by the generation of hydrogen peroxide by this enzyme. Interestingly, the addition of the vehicle for alpha-tocopherol resulted in a significant decrease in live acrosome-intact spermatozoa. CONCLUSIONS AND CLINICAL RELEVANCE: The addition of antioxidants to the cryopreservation extender did not improve the quality of equine spermatozoa after thawing, which suggests that the role of oxidative stress in cryopreservation-induced damage of equine spermatozoa requires further investigation. Our data suggest that solubilizing alpha-tocopherol in ethanol may affect spermatozoal viability; consequently, water-soluble analogues of alpha-tocopherol may be preferred for future investigations.