Calculated forelimb flexor tendon forces in horses with experimentally induced superficial digital flexor tendinitis and the effects of application of heel wedges

OBJECTIVE: To calculate forces in the flexor tendons and the influence of heel wedges in affected and contralateral (compensating) forelimbs of horses with experimentally induced unilateral tendinitis of the superficial digital flexor (SDF) tendon. ANIMALS: 5 Warmblood horses. Procedure-Ground reaction force and kinematic data were obtained during a previous study while horses were trotting before and after induction of tendinitis in 1 forelimb SDF and after application of 6 degrees heel wedges to both forehooves. Forces in the SDF, deep digital flexor (DDF), and the suspensory ligament (SL) and strain in the accessory ligament (AL) of the DDF were calculated, using an in vitro model of the distal region of the forelimb. RESULTS: After induction of tendinitis, trotting speed slowed, and forces decreased in most tendons. In the affected limb, SL force decreased more than SDF and DDF forces. In the compensating limb, SDF force increased, and the other forces decreased. After application of heel wedges, SDF force in both limbs increased but not significantly. Furthermore, there was a decrease in DDF force and AL strain. CONCLUSIONS AND CLINICAL RELEVANCE: The increase in SDF force in the compensating forelimb of horses with unilateral SDF tendinitis may explain the high secondary injury rate in this tendon. The lack of decrease of SDF force in either limb after application of heel wedges suggests that heel wedges are not beneficial in horses with SDF tendinitis. Instead, heel wedges may exacerbate the existing lesion.     

Mepivacaine local anaesthetic duration in equine palmar digital nerve blocks

REASONS FOR PERFORMING STUDY: Perineural analgesics are used for lameness diagnosis but the duration of effect, knowledge of which would provide valuable information when performing subsequent blocks, is unknown. OBJECTIVE: To evaluate the duration of a palmar digital nerve block using force plate measurements. METHODS: Ten horses diagnosed with unilateral navicular syndrome were trotted at range of 3 +/- 0.15 m/sec over a force plate to record ground reaction forces for 5 trials of each forelimb. Data were recorded before nerve block, and then at 15 mins, 1, 2 and 24 h post nerve block. RESULTS: Before nerve block, peak vertical force (mean +/- s.e.) was significantly higher in the contralateral forelimb (CL = 5345 +/- 188 N) than in the lame forelimb (L = 4256 +/- 204 N; P<0.05). At 15 mins post nerve block there was no significant difference between the 2 forelimbs (CL = 5140 +/- 184 N; L = 5126 +/- 129 N), and this remained the case for 1 h. By 2 h, the mean score for the lame leg had decreased (L = 4642 +/- 182 N) but was still greater than preblock. By 24 h, vertical forces had returned to preblock values. CONCLUSIONS: The palmar digital nerve block was fully effective between 15 mins and 1 h. The analgesic effect began to subside between 1 and 2 h but sufficient analgesia persisted to affect gait characteristics beyond 2 h. POTENTIAL RELEVANCE: When using a palmar digital nerve block, it is important to perform lameness evaluations between 15 mins and 1 h to be sure of effective nerve blockade.     

Regional land-cover conversion in the U.S. upper Midwest: magnitude of change and limited recovery (1850–1935–1993)

Land-use legacies can persist for hundreds to thousands of years, influencing plant species composition, nutrient cycling, water flows, and climate. To understand how land use has affected regional land-cover composition in Wisconsin (USA), we assessed the magnitude and direction of change in land cover between: (1) c.1850, at the onset of Euro-American settlement; (2) c.1935, the period of maximum clearing for agriculture following widespread forest logging; and (3) 1993, which, especially in northern Wisconsin, follows farm abandonment and forest recovery. We derived land-cover maps using U.S. Public Land Survey records (c.1850), the Wisconsin Land Economic Inventory (c.1935), and Landsat TM satellite data (1993). We stratified Wisconsin (145,000 km²) into two ecological provinces and used spatial error models, multinomial logistic regression, and non-metric multi-dimensional scaling ordination to examine change. Between 1850 and 1935, forest cover in the North declined from 84% to 56%, cropland increased to 24%, and mixed/coniferous forests and savannas were replaced by deciduous forests. In the South, formerly dominant savannas (69%) and prairies (6%) were mostly converted to cropland (51%) and pasture (11%). Remnant deciduous savannas and coniferous forests and savannas were replaced by deciduous forests. Remarkably little recovery to pre-settlement land-cover classes occurred from 1935 to 1993. Less cropland was abandoned than expected, and there was little net gain in coniferous/mixed forest. Based on these general land-cover classes, current cover is significantly different from that in 1850, but not from that in 1935, and thus continues to reflect historical logging and agricultural patterns. These results provide a historical framework for measuring associated changes in ecosystem function and can be used to guide restoration where desirable and feasible.     

Growth,food conversion,carcass yields and their heritabilities in ducks (anas platyrhynchos)

1. Live weight, food consumption, eviscerated carcass weight, breast muscle mass and ratios of these traits were measured in a strain of ducks of known pedigree. Heritabilities, genetic and phenotypic correlations were estimated for all traits. From the results the following conclusions are drawn.

2. Selection for live weight at market age would be simplest and most effective in improving growth rate and food conversion efficiency though would not necessarily markedly improve carcass lean meat.

3. Selection to increase the proportion of breast muscle (heritability (h ² ): 0.55) should be effective but might depress body weight as a correlated response. The effect on fat content is uncertain.

4. Selection for food conversion efficiency (h² : 0.21) might be expected to increase body weight, but its effect on carcass lean meat (proportion of breast muscle) is uncertain.

5. Selection for breast muscle mass (h ² : 0.41) should improve body weight and food conversion efficiency but its effect on proportion of lean meat is much less certain (rG = 0.45 + 0.17).     

Quantification of Staphylococcus aureus adhesion to equine bone surfaces passivated with Plasmalyte and hyperimmune plasma

OBJECTIVE: To quantify the adhesion of Staphylococcus aureus to 4 equine bone surfaces passivated in a balanced polyionic solution (Plasmalyte) or hyperimmune equine plasma (Polymune plasma). STUDY DESIGN: In vitro comparative study. SAMPLE POPULATION: Third metacarpal bone (MC3) surface explants from 9 equine cadavers. METHODS: Approximately 1 cm(2) sections of periosteum were removed from MC3 and stapled to sterile stainless steel screens. Three bone surface explants were cut using a surgical saw to present 1 cm(2) surfaces of subperiosteal bone, cut cortical bone, or endosteum. Duplicate explants of each surface were immersed for 1 hour in Plasmalyte or hyperimmune equine plasma. Each explant was then placed in a well of a 6-well sterile tissue culture plate with the surface of interest exposed. Each surface was inoculated with approximately 100 colony-forming units of S. aureus in 10 microL of Mueller Hinton broth and incubated for 6 hours at 37 degrees C. After gentle rinsing to remove non-adherent bacteria, samples were sonicated for 5 minutes at 60 kHz to loosen adhered bacteria. The number of adherent bacteria was determined by serial dilutions and incubation of the sonicate. Scanning electron microscopy (SEM) was performed on samples identically treated from an additional horse to confirm bacterial removal by sonication from all surfaces and support quantitative culture results. RESULTS: Less S. aureus adhered to periosteum than to cortical bone, cut cortical bone, and endosteal surfaces, which were all similar. Exposure of all surfaces to hyperimmune plasma reduced S. aureus adherence compared with Plasmalyte exposure; SEM supported these conclusions. CONCLUSION: Less bacteria adhere to periosteum than other bone surfaces. Hyperimmune plasma reduces bacterial adhesion to all bone tissue surfaces. CLINICAL RELEVANCE: Understanding the factors that affect bacterial adhesion to bone will facilitate development of improved intraoperative lavage solutions to reduce the morbidity and mortality associated with postoperative infection.     

A new source of basaltic meteorites inferred from Northwest Africa 011

Eucrites are a class of basaltic meteorites that share common mineralogical, isotopic, and chemical properties and are thought to have been derived from the same parent body, possibly asteroid 4 Vesta. The texture, mineralogy, and noble gas data of the recently recovered meteorite, Northwest Africa (NWA) 011, are similar to those of basaltic eucrites. However, the oxygen isotopic composition of NWA011 is different from that of other eucrites, indicating that NWA011 may be derived from a different parent body. The presence of basaltic meteorites with variable oxygen isotopic composition suggests the occurrence of multiple basaltic meteorite parent bodies, perhaps similar to 4 Vesta, in the early solar system.     

Potential terrain controls on soil color, texture contrast and grain-size deposition for the original catena landscape in Uganda

Inspired by the catena concept, we returned to the landscape of origin for this idea in central Uganda and applied quantitative soil-landscape-modeling techniques to the study of soil formation. In particular, we employed Generalized Least Squares (GLS) regression to identify potential terrain (and other) controls on surface texture with the goal of explaining texture contrast formation for well-drained red soils, and fluvial deposition for yellow-gray lowland soils. Well-drained red soils and poorly drained yellow-gray soils were identified using a high-resolution spectroradiometer and soil redness was highly correlated with a measure of elevation above the valley floor. For the yellow-gray soils, sand content and sand grain size increased with greater slope gradient and in converging areas—evidence supporting fluvial control of surface soil composition. For red soils, texture contrast increased on lower backslopes, decreased over ferricrete-rich parent material, and had no significant association with either infiltration- or runoff-influenced locations. Surprisingly, texture contrast was also reduced or even inverted on fine scale convexities (<18 m in diameter). These findings were consistent with the following theoretical processes: (1) sand deposition on lower-backslopes, increasing texture contrast; (2) ferricrete weathering at the soil surface, reducing texture contrast; and (3) texture contrast inversion through termite turbation. A number of techniques proved useful in this study: (a) the use of GLS regression supported the interpretation of model coefficients in an explicitly spatial context; (b) thin-plate splines provided a flexible means of controlling the spatial scale of terrain index computation; and (c) the development of a new downslope-looking Elevation Above Stream (EASy) terrain index provided a powerful tool for the identification of poorly drained soils—a tool that could have applications in a variety of landscapes and environments. Overall, we found that the catena concept as a soil-terrain-modeling approach worked best on lower, less well-drained, depositional landscape components. For the well-drained portion of this landscape, there was little evidence to suggest that soil formation was controlled by hillslope hydrology as proposed by the catena concept. The catena concept interpreted in a broad sense challenges pedologists to explicitly link soil geographic patterns with specific soil forming processes and environmental controls—an approach that proved valuable in this study.     

The effects of invasive North American beavers on riparian plant communities in Cape Horn, Chile: Do exotic beavers engineer differently in sub-Antarctic ecosystems?

North American beavers (Castor canadensis) were introduced into southern South America in 1946. Since that time, their populations have greatly expanded. In their native range, beavers shape riparian ecosystems by selectively feeding on particular plant species, increasing herbaceous richness and creating a distinct plant community. To test their effects as exotic engineers on sub-Antarctic vegetation, we quantified beaver impacts on tree canopy cover and seedling abundance and composition, as well as their impacts on herbaceous species richness, abundance and composition on Navarino Island, Cape Horn County, Chile (55°S). Beavers significantly reduced forest canopy up to 30 m away from streams, essentially eliminating riparian forests. The tree seedling bank was greatly reduced and seedling species composition was changed by suppressing Nothofagus betuloides and Nothofagus pumilio, but allowing Nothofagus antarctica. Herbaceous richness and abundance almost doubled in meadows. However, unlike beaver effects on North American herbaceous plant communities, much of this richness was due to invasion by exotic plants, and beaver modifications of the meadow vegetation assemblage did not result in a significantly different community, compared to forests. Overall, 42% of plant species were shared between both habitat types. Our results indicate that, as predicted from North American studies, beaver-engineering increased local herbaceous richness. Unlike in their native range, though, they did not create a unique plant community in sub-Antarctic landscapes. Plus, the elimination of Nothofagus forests and their seedling bank and the creation of invasion pathways for exotic plants together threaten one of the world’s most pristine temperate forest ecosystems.     

Statewide modeling of bobcat, Lynx rufus, habitat in Illinois, USA

We used sighting location and remotely sensed habitat data, multivariate statistical techniques, and a geographic information system to model bobcat (Lynx rufus) habitat in Illinois, thereby providing state wildlife managers with information to review the listing of bobcats as a state-threatened species and contribute to the development of a statewide management plan. We used canonical discriminant function analysis to model presence/absence and relative abundance of bobcats statewide. These models suggested that bobcats occurred in moderate to high abundance in 23 of 98 counties statewide (23%). We used stepwise logistic regression (SLR) analysis to model statewide habitat suitability. Spatial modeling of the SLR equation predicted that 29% of Illinois contained suitable habitat classified as P>0.50. Models were accurate when validated with an independent data set and indicated the importance of woods-related habitat variables to bobcats. In conclusion, these models provided tools to rapidly assess status that contributed to delisting bobcats as a threatened species in Illinois and provided further information to guide conservation efforts.     

Soil microbial biomass, functional diversity and enzyme activity in glyphosate-resistant wheat-canola rotations under low-disturbance direct seeding and conventional tillage

As glyphosate-resistant (GR) crops are becoming common in agro-ecosystems, their effects on non-target soil organisms need to be monitored. We evaluated soil microbial biomass C (MBC), bacterial functional diversity and community structure, and dehydrogenase enzyme activity in a field experiment conducted at six sites on the Canadian prairies. Treatments consisted of a factorial arrangement of three GR wheat and GR canola crop frequencies and two tillage systems. GR crop frequencies were arranged in 4-yr wheat-canola-wheat-pea rotations, with GR wheat and GR canola in zero of four, two of four, or three of four possible GR crop frequencies. The two tillage systems were either low soil-disturbance direct-seeding (LDS) or conventional tillage (CT). MBC increased with increasing frequency of GR crops in two of 20 site-years in the rhizosphere, and had no effects in bulk soil. Depending on tillage, GR crop frequency also affected the functional diversity of rhizosphere soil bacteria in only two of 20 site-years, and had no effects in bulk soil. Shifts in the structures of bacterial communities related to GR crop frequency were detected, but they were few and inconsistent. In three of 22 cases (10 in rhizosphere+12 in bulk soil), the activity of dehydrogenase enzyme decreased with increasing frequency GR crops in both the rhizosphere and bulk soil. In five of 20 site-years, soil MBC in the rhizosphere was greater under CT than under LDS, regardless of GR crop frequency. In bulk soil, tillage affected soil MBC in five site-years, three of which had greater MBC under CT than LDS, and vice versa in the other two. Tillage affected the functional diversity of soil bacteria in the rhizosphere in three site-years, but the effects were not consistent. Similar inconsistent tillage-related patterns were observed in the community structures of bacteria. There were no tillage effects on bacterial diversity in bulk soil. Dehydrogenase enzyme activity was greater under LDS than under CT in three of four cases in which tillage had significant effects. Overall, GR crop frequency effects on soil microorganisms were minor and inconsistent over a wide range of growing conditions and crop management.