Development of an indirect fluorescent antibody test, using microfluorometry as a diagnostic test for bovine anaplasmosis

The indirect fluorescent antibody test for the diagnosis of Anaplasma marginale infection in cattle was modified for use with microfluorometry. The test was standardized by use of a fluorometer that measures intensity of fluorescence. Standardization included A marginale-infected blood smears on microscope slides as antigen, serum from an inoculated calf as a positive control containing specific antibody, and an affinity-purified fluorescein-conjugated anti-bovine immunoglobulin as 2nd antibody. The modified test and microfluorometry allowed for titration of sera from A marginale (Florida isolate)-inoculated cattle with a degree of accuracy exceeding visual determinations. In addition, the fluorometric test was more sensitive than the complement fixation or card agglutination tests in identifying cattle that had previous Anaplasma infections.     

Multiple embryo-transplant offspring produced from quartering a bovine embryo at the morula stage

A non-surgical embryo collection was completed on a day 7 superovulated Chianina donor cow. Because all but two of the ova from the collection were unfertilised and a surplus of potential recipients was available, one embryo (an excellent quality late morula) was dissected into four equal portioned 'quarter' embryos using a simplified micromanipulation procedure. Each quarter embryo was then placed in a 0.25 ml French straw and non-surgically transplanted to four different crossbred beef recipient females. The remaining embryo was similarly transplanted to a herd mate recipient as an intact embryo. One recipient returned to oestrus, one recipient had an extended post transfer cycle and the two remaining recipients produced a live quarter embryo transplant calf each within 24 hours of the other. The intact embryo placed in a herd mate recipient did not produce a transplant calf. To the authors' knowledge, these transplant offspring are the first live births reported from a non-surgically collected later-stage bovine morula (day 7), which had been dissected into quarters and then individually transplanted non-surgically to recipient females. The procedure was relatively simple to perform and was completed in less than one hour.     

Changes in photosynthesis and water status of developing leaves of Brachystegia spiciformis Benth

Changes in net carbon assimilation and water status were studied during leaf development in the deciduous, tropical species Brachystegia spiciformis Benth. In this upland savanna African tree, bud-burst and leaf development occur approximately two months before the rainy season. The newly formed leaves synthesize anthocyanin until the fully expanded leaves of the whole canopy are red. This foliage is referred to as "spring flush" foliage. Subsequently, the anthocyanins are metabolized and the pre-rain leaves become green. Carbon dioxide assimilation exhibited a bimodal diurnal pattern and was similar for pre-rain green leaves and fully expanded flushing leaves, although pre-rain green leaves showed a net uptake of carbon throughout the daylight period, whereas flushing leaves exhibited only brief periods of net photosynthesis in the morning and early afternoon. Measurements of leaf water potential and relative water content showed a diurnal pattern with considerable variation throughout the day. Leaf water potential and relative water content values decreased soon after sunrise reaching a minimum at a time corresponding to the afternoon peak in CO(2) assimilation. Stomatal conductance was closely related to transpiration rate in both flushing and pre-rain green leaves, although flushing leaves had lower stomatal conductances than pre-rain green leaves. Pre-rain green leaves exhibited a compensation irradiance of approximately 180 micro mol m(-2) s(-1), whereas flushing leaves had positive net photosynthesis only at PPFDs greater than 300 micro mol m(-2) s(-1). Rate of photosynthesis (expressed per leaf area or chlorophyll unit) increased as anthocyanin concentration decreased, although the photosynthetic rate continued to increase long after the leaf anthocyanins had been degraded to low, visually undetectable amounts. Post-rain green leaves had chlorophyll concentrations, transpiration rates and stomatal conductances similar to those of pre-rain green leaves; however, photosynthetic rates in post-rain leaves were more than three times higher. Thus, during the early stages of the spring flush, carbon asimilation rates of the flushing leaves were inversely related to leaf anthocyanin concentrations. In pre-rain green leaves, photosynthesis was limited by other non-stomatal factors.     

Carbon dioxide enrichment improves growth, water relations and survival of droughted honey mesquite (Prosopis glandulosa) seedlings

Low water availability reduces the establishment of the invasive shrub Prosopis on some grasslands. Water deficit survival and traits that may contribute to the postponement or tolerance of plant dehydration were measured on seedlings of P. glandulosa Torr. var. glandulosa (honey mesquite) grown at CO(2) concentrations of 370 (ambient), 710, and 1050 micro mol mol(-1). Because elevated CO(2) decreases stomatal conductance, the number of seedlings per container in the elevated CO(2) treatments was increased to ensure that soil water content was depleted at similar rates in all treatments. Seedlings grown at elevated CO(2) had a greater root biomass and a higher ratio of lateral root to total root biomass than those grown at ambient CO(2) concentration; however, these seedlings also shed more leaves and retained smaller leaves. These changes, together with a reduced transpiration/leaf area ratio at elevated CO(2), may have contributed to a slight increase in xylem pressure potentials of seedlings in the 1050 micro mol mol(-1) CO(2) treatment during the first 37 days of growth (0.26 to 0.40 MPa). Osmotic potential was not affected by CO(2) treatment. Increasing the CO(2) concentration to 710 and 1050 micro mol mol(-1) more than doubled the percentage survival of seedlings from which water was withheld for 65 days. Carbon dioxide enrichment significantly increased survival from 0% to about 40% among seedlings that experienced the lowest soil water content. By increasing seedling survival of drought, rising atmospheric CO(2) concentration may increase abundance of P. glandulosa on grasslands where low water availability limits its establishment.     

Acacia cyanophylla for forage and fuelwood in North Africa

Forage and wood yield of Acacia cyanophylla, also known as Acacia saligna, was studied in a 300–400 mm precipitation zone in Tunisia. Yields were measured during and after drought. This short (2–8 m) evergreen leguminous tree is used as a forage drought reserve in frost free regions where mean annual precipitation exceeds 250 mm. The standing crop of leafy forage builds up year after year for at least four years or until the tree is cut. It rapidly regrows after cutting from coppice shoots. The leaves provide high protein forage for sheep and goats during the long dry summer season typical of the Mediterranean climate as well as emergency forage during drought. The tree is used to stabilize moving sand dunes, and as a windbreak to protect cropland. It also provides fuelwood and increasaes soil nitrogen by fixation. The need for supplemental irrigation during establishment is a major constraint. Research in the 350 mm precipitation zone of Tunisia found 3.2 year old trees to yield over 1400 kg of forage standing crop per hectare after a severe drought. Trees harvested at 2.5 years of age in May, during the worst drought in over 30 years, yielded a standing forage crop of 724 kg per hectare. Forage regrowth 8 months after cutting and 4 months after rains returned was 700 kg/ha. The forage standing crop for trees harvested only once during the 3.2 year period was double the amount of forage regrowth from trees harvested the previous year, but mean annual forage yield similar. This demonstrates that it is possible for forage to be conserved as a living forage reserve for later use during drought. Total wood yield was only 1621 kg/ha for trees cut twice compared to 3683 kg/ha for trees cut only once. Annual cutting will substantially reduce the amount of forage available during drought and reduce the production of fuelwood. It may also reduce the vigor, productivity and life of the tree. Acacia cyanophylla alley cropped on cereal farmland can protect the soil from erosion, protect the associated crop from wind damage, fix nitrogen, provide fuelwood and provide a reserve of high quality forage for use during drought. This work was supported by the Government of Tunisia and the U.S.A.I.D. Tunisia Range Development and Management Project (664-0312.8).     

ASSESSMENT OF RESPIRATION‐INDUCED DISPLACEMENT OF CANINE ABDOMINAL ORGANS IN DORSAL AND VENTRAL RECUMBENCY USING MULTISLICE COMPUTED TOMOGRAPHY

Respiratory‐induced organ displacement during image acquisition can produce motion artifacts and variation in spatial localization of an organ in diagnostic computed tomography (CT) examinations. The purpose of this prospective study was to quantify respiratory‐induced abdominal organ displacement in dorsal and ventral recumbency using five normal dogs. All dogs underwent CT examinations using 64 multidetector row CT (64‐MDCT). A “3‐dimensional (3D) apneic CT exam” of the abdomen was acquired followed by a “4‐dimensional (4D) ventilated CT exam.” The liver, pancreas, both kidneys, both medial iliac lymph nodes, and urinary bladder were delineated on the 3D‐apneic examination and the organ outlines were compared to the maximum alteration in organ position in the 4D‐ventilated examination. Displacement was measured in dorsal‐to‐ventral (DV), right‐to‐left (RL), and cranial‐to‐caudal (CC) directions. Respiratory‐induced displacement of canine abdominal organs was not predictable and showed large variability in the three directions evaluated. For most canine abdominal organs, dorsal recumbency provided overall the least amount of displacement among all directions evaluated except for liver and urinary bladder. For liver, a large variability was found for all directions and a statistically significant difference was found only in the RL direction with ventral recumbency exhibiting less displacement (P = 0.0099). For the urinary bladder, ventral recumbency also provided less displacement but this was statistically significant only in the RL direction (P < 0.0001). Findings from this study indicated that dorsal recumbency may be preferred for minimizing respiratory motion artifacts in whole abdomen studies, but ventral recumbency may be preferred for liver and urinary bladder studies when respiration cannot be controlled.