The effects of agricultural fields and human settlements on the use of rivers by wildlife in the mid-Zambezi valley,Zimbabwe

After the eradication of the Tse-Tse fly in the Mid-Zambezi valley, human settlements and fields extended mainly along the main rivers. In order to investigate the consequences of this human development on wildlife diversity we monitored three rivers of the Mid-Zambezi valley in Zimbabwe: Angwa, Manyame and Kadzi. The rivers were divided in segments of 200 m which were checked for spoors in order to assess the number of species and the number of individuals that used the segments. Human settlements were also recorded. We used a GIS to define the spatial characteristics of the fields present along the rivers, and related them to the distribution and abundance of wild species spoors in the river beds and banks. Our results show that the number of species in one segment of the river decreased with the increasing size of the field area bordering the segment. For all the major ungulate species, the numbers of individuals recorded per segment decreased with increasing field area. A similar trend was observed for small and medium-sized carnivores, though they were in lower numbers when present. Our analyses thus confirm that the extension of human agriculture in wildlife areas has an impact on most wild species, but we also define some threshold value of field size above which there seem to be an acceleration of the decrease in wildlife density and diversity: 3.2 ha for medium and small herbivores and carnivores; only the elephant seem to tolerate larger field area with a threshold value of 32 ha.This revised version was published online in May 2005 with corrections to the Cover Date.     

Influence of four soil maintenance practices on Collembola communities in a Mediterranean vineyard

We studied the influence of four soil maintenance practices on Collembola communities in the soil of a Mediterranean vineyard: (a) postemergence herbicide with glyphosate; (b) postemergence and pre-emergence herbicides with glyphosate, terbuthylazine, diuron and oryzalin; (c) natural flora and (d) tillage to a depth of 10–15 cm. Total Collembola abundance, species diversity and species richness significantly varied between the four practices. Notably, the practice using postemergence and pre-emergence herbicides had significantly lower values. Identification of Collembola at species level allowed an interspecies comparison and revealed significant differences for the most common species between the four practices, with each practice being characterized by a different set of species. None of the species were found to be significantly more abundant in the plots treated with postemergence and pre-emergence herbicides.     

Assessment of regional systolic and diastolic myocardial function using tissue Doppler and strain imaging in dogs with dilated cardiomyopathy

BACKGROUND: Tissue Doppler Imaging (TDI) or strain (St) imaging could provide sensitive indices for early detection and treatment follow-up of canine dilated cardiomyopathy (DCM). Analysis of TDI and St features in dogs with overt DCM is a prerequisite before using these new criteria in prospective screenings of predisposed families or in clinical trials. HYPOTHESIS: Radial and longitudinal right and left myocardial motion, assessed by TDI and St variables, is altered in dogs with DCM. ANIMALS: Case records for 26 dogs; 14 with DCM and 12 healthy controls of comparable age and weight were reviewed. METHODS: A retrospective analysis was conducted of conventional echocardiography, 2-dimensional color TDI, and St imaging data. RESULTS: The DCM group was characterized by decreases in radial and longitudinal systolic velocity gradients of the left ventricular free wall (LVFW), radial and longitudinal absolute values of peak systolic St of the LVFW, and longitudinal systolic right ventricular (RV) velocities (all P < .001 versus control) associated with longitudinal postsystolic contraction waves in 7/14 dogs. Early diastolic LVFW velocities also were decreased for longitudinal (P < .01) and radial (P < .05) motions. All radial LVFW, longitudinal basal LVFW, and RV systolic velocities were negatively correlated with heart rate (P < .01). CONCLUSIONS AND CLINICAL IMPORTANCE: LV contractility along both the short and long axes is impaired in dogs with spontaneous DCM, as is systolic RV and diastolic LVFW function. These myocardial alterations are associated with an inverse force-frequency relationship. Studies now are needed to determine the comparative sensitivity of TDI and St variables for the early detection of canine DCM.     

Buyer beware! Disease testing newly arrived cattle to dairy farms in Ontario

The objective of this cross-sectional study was to evaluate the presence of infectious disease in newly arrived cattle on dairy farms in Ontario. Cattle that were more than 2 years old and arrived at dairy farms within the previous year were tested. A total 321 cattle from 56 dairy farms were sampled and had blood submitted to a diagnostic laboratory. Of all sampled cattle, 0.0%, 39.6%, 2.2%, and 1.3% tested positive for Anaplasma, bovine leukemia virus, Mycobacterium avium subsp. paratuberculosis, and Salmonella Dublin, respectively. Based on these results, it is imperative that dairy producers are vigilant to ensure they do not purchase animals with these important and untreatable infectious diseases.     

Mutualism between euryhaline tilapia Sarotherodon melanotheron heudelotii and Chlorella sp.—Implications for nano-algal production in warmwater phytoplankton-based recirculating systems

The West-African euryhaline tilapia, Sarotherodon melanotheron heudelotii shift from visually feeding on zooplankton when juveniles to mostly filter feeding on phytoplankton when adults. When reared using an appropriate ration in intensive aquaculture systems, S. m. heudelotii also consume algal-based detritus, and contribute to sediment mineralization, clean up their environment, and ultimately stimulate and sustain algal growth. We analysed such practical advantages for phytoplankton-based recirculating systems, using S. m. heudelotii and Chlorella sp. as biological material originating from the prototype of such a system operated in Senegal. We performed a 24-h factorial design experiment in 36 tubs, cross-classifying three levels of S. m. heudelotii (fishless control, unfed fish, and fed fish) with four levels of Chlorella initial density.Chlorella overall mean density increased significantly from fishless, to unfed fish, and fed fish treatments, and with Chlorella initial density. S. m. heudelotii did not alter nitrogen nor phosphorus concentrations, only affected by algal initial densities. Most ammonia excreted by fish was probably uptaken by Chlorella. Bacteria-mediated diurnal nitrification was possibly an alternative ammonium loss mechanism at highest oxygen concentrations. Algae were not limited by nitrogen or phosphorus but most likely by low dissolved organic carbon availability. Chlorella differential responses with fed vs. unfed Sarotherodon suggest that CO₂ supplied by heterotrophic S. m. heudelotii respiration played a key role. Observed Chlorella growth rates were similar to the highest rates obtained in algal mass cultures, enriched with CO₂, nitrate and phosphate, under artificial lighting.Our results suggest the existence of a Sarotherodon-Chlorella mutualism in our systems, where S. m. heudelotii provide CO₂, the major limiting factor of Chlorella growth, whereas Chlorella oxygenate and detoxify the water media from ammonia, promoting S. m. heudelotii production. This mutualism could be used to optimize photosynthetic suspended-growth aquaculture systems, particularly in the Tropics where light is abundant and temperature is continuously high.     

Total arsenic in foods after sequential wet digestion, dry ashing, coprecipitation with ammonium pyrrolidine dithiocarbamate, and graphite-furnace atomic absorption spectrometry

A graphite-furnace atomic absorption (GFAAS) method is described for determining total arsenic (organic and inorganic compounds) in foods. Samples ranging from 1 to 40 g (depending on moisture content) were digested with HNO3 and dry-ashed at 500 degrees C overnight after addition of MgO. After dissolution in HCl, the arsenic was reduced with iodide and ascorbic acid and precipitated with ammonium pyrrolidine dithiocarbamate (APDC) in the presence of nickel carrier. Precipitates were collected on 0.3 micron cellulose acetate filters and dissolved in 10% HNO3 containing modifier. Ba(NO3)2 was added to remove a sulfate interference resulting from decomposition of APDC. Arsenic was determined using GFAAS. Accuracy of the method was good for 7 U.S. National Bureau of Standards (NBS) Standard Reference Materials and 3 National Research Council of Canada (NRCC) round-robin samples. Recovery of arsenic(V) from foods averaged 99.2% for peak heights and 97.1% for peak areas, with relative standard deviations (RSD) of 2.2% for peak heights and 3.3% for peak areas for all NBS and NRCC materials. Detection limit of the method was ca 10 ng arsenic.     

Aspects of the antiluteolytic activity of the conceptus during early pregnancy in ewes

Experiments were undertaken to determine whether the conceptus renders a corpus luteum resistant to the luteolytic action of prostaglandin F2 alpha (PGF2 alpha), and modulates release of this prostaglandin by the uterus of early pregnant ewes. Prostaglandin F2 alpha was luteolytic when administered to indomethacin-treated ewes on d 10 and 11 of the estrous cycle. The same PGF2 alpha treatment was not luteolytic when applied on d 19 and 20 of pregnancy in ewes treated with indomethacin. Pulsatile release of PGF2 alpha (measured by 15-keto-13,14-dihydro PGF2 alpha-PGF2 alpha plasma level, PGFM) was observed between d 14 and 16 of the cycle but not during the same period of pregnancy. Ablation of the conceptus on d 17 resulted in progressive restoration of PGFM surges and subsequent luteolysis. Estradiol-17 beta (E2-17 beta) administration on d 12 of the cycle induced earlier PGFM surges and luteal regression. The same E2-17 beta treatment administered on d 14, 19 and 33 of pregnancy failed to induced PGFM pulses and luteolysis. In the absence of the conceptus (surgical ablation), E2-17 beta treatment was luteolytic (PGFM surges) on d 17 but not on d 33. We conclude that the conceptus controls the amount and pattern of PGF2 alpha released by the uterus, as well as the sensitivity of the uterus to E2-17 beta as early as d 14 of pregnancy. Simultaneously, an embryonic protective effect takes place at the luteal level.     

Use of Akaike information criteria for model selection and inference. An application to assess prevention of gastrointestinal parasitism and respiratory mortality of Guinean goats in Kolda,Senegal

A field experiment was carried out in Kolda (southern Senegal) from July 1986 to July 1988. Its goals were to: (1) describe the patterns of mortality of female Guinean goats by age, season and year; (2) assess preventive measures against respiratory diseases and gastrointestinal parasitism in reducing mortality; and (3) estimate the overall impact of these measures on survival to 1 year of age. Preventive measures for respiratory disease included vaccination against peste des petits ruminants (PPR) and pneumonic pasteurellosis (Pasteurella multocida types A and D). Control of gastrointestinal parasites was by deworming does with morantel (7.5 mg kg⁻¹, three times during the rainy season). The effects of vaccines and deworming were tested in a randomised factorial field experiment with villages being the experimental units. A total of 19 villages, 113 goat herds and 1458 goats were included in the study.

Generalised linear models of survival for five cohorts of goats (defined by five different birth seasons) used a binomial assumption for the response distribution and a complementary log–log link. Explanatory variables included age, season, year, vaccination, deworming and their interactions. A complex a priori model was built on the basis of previous epidemiological knowledge; a purposively selected set of simpler models was compared to this full model by the Akaike information criterion (AIC) and derived statistics. Inference on 1-year survival and treatment effects accounted for model-selection uncertainty. It was carried out with a bootstrap procedure and used information from the whole set of selected models.

Large variations in mortality by year and season were observed but no regular seasonal pattern was apparent. Mortality probabilities of kids in dewormed groups decreased quickly after birth, but remained elevated up to 9 months of age in the non-dewormed groups. Deworming lowered the risk of mortality. Vaccination alone was not protective (except during an observed outbreak of PPR).     

Radial strain and strain rate by two-dimensional speckle tracking echocardiography and the tissue velocity based technique in the dog

ObjectivesTwo-dimensional (2D) speckle tracking echocardiography (STE) is a new angle-independent ultrasound technique based on tracking of speckles within the myocardium on 2D grayscale images. The aims of this prospective study were as follows: (1) to assess the variability of left ventricular peak systolic radial strain (St) and strain rate (SR) in awake dogs using STE (Protocol 1); and (2) to quantify these variables in a healthy canine population and compare them with tissue Doppler imaging (TDI)-based St and SR values (Protocol 2).BackgroundSt and SR may be assessed using TDI, which is limited by angle dependency.Animals, materials and methodsThirty-six STE examinations were performed on 6 healthy dogs for Protocol 1 and 37 healthy dogs were recruited for Protocol 2. In both studies, STE measurements were obtained offline from the right parasternal short-axis view by the same trained observer using automatic frame-to-frame tracking of grayscale speckle patterns.ResultsAll within- and between-day coefficients of variation were <10% (Protocol 1). In Protocol 2, St (46.7 ± 12.2%) and SR (2.7 ± 0.6 s⁻¹) measured by STE were correlated with heart rate (p < 0.01), but not with the ratio of early mitral inflow velocity to early mitral annular velocity. There was a good correlation between STE and TDI for both St and SR values (p < 0.001).ConclusionsSTE is a repeatable and reproducible non-Doppler method for assessing radial St and SR. The combination of these indices with conventional echo-Doppler variables could provide a new approach for accurately quantifying canine systolic function.