Alfalfa (Medicago sativa L.) water use efficiency as affected by harvest traffic and soil compaction in a sandy loam soil

Summary Traffic during alfalfa harvest operations can cause soil compaction and damage to newly growing stems. Root exploration for soil water and nutrients, forage growth dynamics, and final yield can all be affected. The objectives of this study were to determine the long-term effects of harvest traffic and soil compaction on water-use efficiency (WUE) of alfalfa grown in a Wasco sandy loam (coarse-loamy, mixed, nonacid, thermic Typic Torriorthents). Alfalfa was planted into tilled soil and managed with or without harvest traffic. Plants subjected to traffic during harvest had a significantly lower WUE two out of the three years studied compared to plants that were never subject to traffic. The second experiment examined whether planting alfalfa into compacted soil and managed with or without harvest traffic altered WUE. Soil compaction had no affect on alfalfa WUE. It was significantly lower when grown in compacted soil and subjected to harvest traffic. It is suggested that the decrease in WUE caused by harvest traffic may be explained by plants allocating carbohydrates to damaged shoots and crowns instead of to above ground forage production. The area of the field affected by harvest traffic, which damages newly growing stems, should be minimized to increase crop water use efficiency.     

The effects of continuous photoperiod (24L:0D) on growth of juvenile barramundi (<Emphasis Type="Italic">Lates calcarifer</Emphasis>)

The efficacy of photoperiod manipulation to influence growth and developmental processes is well documented in a range of temperate aquaculture species. However, the application of such techniques with tropical species requires further investigation. This preliminary 20-day study investigated the influence of continuous photoperiod on growth of barramundi (Lates calcarifer). In addition, diel plasma melatonin profiles provided a physiological measure of how the endocrine system of barramundi responded to continuous photoperiod. Juvenile barramundi (1.33 ± 0.02 g) were held in recirculation systems under 12-h light: 12-h dark (12L:12D) or 24-h light (24L:0D) with a light intensity of 1,000 lux throughout the water column. Fish from both treatments grew to more than 14 times their original weight, with final weight (24L:0D = 21.59 ± 0.85 g; 12L:12D = 19.12 ± 0.55 g), total length (24L:0D = 12.67 ± 0.14 cm; 12L:12D = 11.96 ± 0.13 cm) and specific growth rate (24L:0D = 9.60 ± 0.05% bw day⁻¹; 12L:12D = 9.14 ± 0.06% bw day⁻¹) being significantly higher for fish grown on 24L:0D compared with 12L:12D. There were no significant differences in feed intake (24L:0D = 226.46 ± 6.27 g; 12L:12D = 219.02 ± 5.73 g) or feed conversion ratio (24L:0D = 0.71 ± 0.06; 12L:12D = 0.80 ± 0.07) between light treatments. Barramundi held under 12L:12D exhibited diel melatonin secretion, which peaked mid-dark phase (171.83 ± 4.81 pg ml⁻¹) followed by a gradual decrease in base levels at the onset of illumination (68.61 ± 8.77 pg ml⁻¹). When juvenile barramundi were subjected to 24L:0D, the amplitude of peak melatonin secretion was significantly suppressed during the subjective mid-dark phase (129.71 ± 2.36 pg ml⁻¹). This preliminary study confirmed that barramundi respond to photoperiod manipulation in a similar manner to many temperate fish species, thus demonstrating the future potential use of artificial lighting to improve growth in this species commercially.     

Protein and energy nutrition of brook trout (Salvelinus fontinalis) at optimal and elevated temperatures

The digestible protein (DP) and digestible energy (DE) requirements for maintenance and growth of brook trout (Salvelinus fontinalis) were determined using a factorial model at either optimum (15 °C) or elevated temperature (19 °C). Several key parameters of the factorial model were measured using a series of inter‐related studies. The maintenance requirements for DP and DE were 0.10 gDP kg^?0.69 day^?1 (15 °C) and 0.31 gDP kg^?0.78 day^?1 (19 °C), and 34.86 kJDE kg^?0.84 day^?1 (15 °C) and 46.14 kJDE kg^?0.86 day^?1 (19 °C). The total requirements for DP were 0.10 gDP kg^?0.69 day^?1 + 2.14PG (protein gain) (15 °C) and 0.31 gDP kg^?0.78 day^?1 + 1.98PG (19 °C). The total requirements for DE were 36.86 kJDE kg^?0.84 day^?1 + 1.58EG (energy gain) (15 °C) and 46.14 kJDE kg^?0.86 day^?1 + 1.64EG (19 °C). The partial efficiencies for growth were 0.47 (15 °C) and 0.51 (19 °C) for protein, and 0.63 (15 °C) and 0.61 (19 °C) for energy. Nutrient gain was lower at the elevated temperature; however, feed formulation for brook trout should be adjusted to match changes in nutrient requirements at different culture temperatures. The protein and energy requirements model will be useful for developing commercial feeds and feeding charts for brook trout.     

Carbon sequestration and saving potential associated with changes to the management of agricultural soils in England

Abstract. The potential for soil organic carbon sequestration, energy savings and the reduction of the emission of greenhouse gases were investigated for a range of changes in the management of tilled land and managed grassland. These parameters were modelled on a regional basis, according to local soils and crop rotations in England, and avoided the use of soil related indices. The largest carbon sequestration and saving contribution possible comes from an increase in the proportion of permanent woodland, such that a 10% change in land use could amount to 9 Mt C yr⁻¹ in the initial years (arable and grassland). Changes in arable management could make a significant contribution to an abatement strategy if carried out in concert with greater use of permanent conservation field margins, increased returns of crop residues and reduced tillage systems, contributing 1.3 Mt C yr⁻¹ in the initial years. It should be noted, however, that true soil carbon sequestration would be only a minor component of this (125 kt C yr⁻¹), the main part being savings on CO₂ emissions from reduced energy use, and lower N₂O emissions from reduced use of inorganic nitrogen fertilizer.     

Three-dimensional structure of human serum albumin

The three-dimensional structure of human serum albumin has been solved at 6.0 angstrom (A) resolution by the method of multiple isomorphous replacement. Crystals were grown from solutions of polyethylene glycol in the infrequently observed space group P42(1)2 (unit cell constants a = b = 186.5 +/- 0.5 A and c = 81.0 +/- 0.5 A) and diffracted x-rays to lattice d-spacings of less than 2.9 A. The electron density maps are of high quality and revealed the structure as a predominantly alpha-helical globin protein in which the course of the polypeptide can be traced. The binding loci of several organic compounds have been determined.     

Nucleotide sequence of UK and Australian isolates of feline calicivirus (FCV) and phylogenetic analysis of FCVs.

We have determined the first complete genome sequence and capsid gene sequences of feline calicivirus (FCV) isolates from the UK and Australia. These were compared with other previously published sequences. The viruses used in the comparisons were isolated between 1957 and 1995 from various geographical locations and obtained from cats showing a range of clinical signs. Despite these diverse origins, comparisons between all strains showed a similar degree of sequence variation within both ORF1 (non-structural polyprotein) and ORF2 (major capsid protein) (amino acid distances of 7.7-13.0% and 8.8-18.6%, respectively). In contrast, ORF3 (putative minor structural protein) sequences indicated a more heterogenous distribution of FCV relatedness (amino acid distances of 1.9-17.9%). Phylogenetic analysis suggested that, unlike some other caliciviruses, FCV isolates within the current data set fall into one diverse genogroup. Within this group, there was an overall lack of geographic or temporal clustering which may be related to the epidemiology of FCV infection in cats. Analysis of regions of variability in the genome has shown that, as well as the previously identified variable regions in ORF2, similar domains exist within ORFs 1 and 3 also, although to a lesser extent. In ORF1, these variable domains largely fall between the putative non-structural protein functional domains.     

Matrix metalloproteinase-2 and -9 are activated in joint diseases.

A study was performed to identify the activation status of the gelatinase MMPs, MMP-2 and -9, in both normal and diseased equine articular tissues. In addition, the production and activation status of equine MMP-2 and -9 by equine articular cells and tissues in response to increasing IL-1beta concentrations was assessed. The study was performed to test the hypothesis that activation of MMPs is a fundamental step in the pathogenesis of joint diseases; and that this activation is mediated by the cytokine IL-1. Using purified equine MMP-2 and -9, the molecular weights of the zymogen and activated form of equine MMP-2 and -9 were identified by a combination of gelatin zymography and a gelatin degradation assay using aminophenylmercuric acetate as a chemical activator of the molecules. Normal equine articular tissues (cartilage and synovial membrane) maintained in short-term tissue culture produced MMP-2 zymogen alone, while similar tissues obtained from a variety of pathological conditions produce both zymogen and active MMP-2, as well as MMP-9 monomer and dimer. Activated MMP-9 was an inconsistent finding. Normal equine synovial fibroblasts in monolayer culture produced zymogen MMP-2 alone under basal conditions. A mild increase in active and zymogen MMP-2 levels occurred with IL-1beta treatment. Equine synovial membrane explants demonstrated a dose-dependent increase in active and zymogen MMP-2 and MMP-9 levels following IL-1beta treatment. Monolayer chondrocyte cell cultures demonstrated a dose-dependent mild increase in active and zymogen MMP-2 following IL-1beta treatment. Explant cartilage cultures demonstrated a dose-dependent mild increase in zymogen MMP-2 alone following IL-1beta treatment. This study supports the hypothesis that activation of MMPs is occurring in joint disease, and that in vitro stimulation of equine articular cells and tissues causes not only an increase in MMP production, but also an increase in amount of activated enzyme released. Further research is required to investigate the role of MMP activation in joint diseases, and to investigate the potential use of therapeutic agents, which inhibit MMP activation, in the treatment and prevention of joint diseases.     

A Novel Approach to the Treatment and Prevention of Laminitis: Botulinum Toxin Type A for the Treatment of Laminitis

Laminitis is an inflammation of the lamina of hoofed animals. According to the United States Department of Agriculture (USDA), laminitis impacts approximately 2% of the horse population each year. Because of the severity of the inflammation and chronic pain, it is frequently necessary to euthanize these horses. Surviving horses may be left useless, with resultant economic and social impact on the industry. Current interventions for laminitis are based on supportive care and alteration of biomechanical forces on the digit. The transition from laminitis to laminar failure (founder) is believed to be caused by the “weight of the horse and the forces of locomotion driving the bone down into the hoof capsule.” We hypothesize that an important factor is the torsional forces placed on the distal phalanx (coffin bone) by the deep digital flexor muscle and tendon. The paralyzing effect of botulinum toxin will result in a decrease of these torsional forces and therefore will aid in the prevention or treatment of the sequelae of laminitis. Seven horses with varying degrees of laminitis were evaluated. Each underwent pretreatment and posttreatment radiographs as well as pretreatment and posttreatment Obel grading. Each horse received botulinum toxin type A injected into the belly of the deep digital flexor muscle. In all cases there was radiographic stabilization of pedal displacement from the dorsal hoof wall. Obel scores showed improvement of 1 to 2 grades during the time monitored.     

The lipid compositions of two isolates of Cladosporium cucumerinum do not explain their differences in sensitivity to fungicides which inhibit sterol biosynthesis

Isolate 840905 of Cladosporium cucumerinum, when grown on agar or in liqiud medium, was sensitive to triadimenol, HWG 1608 (tebuconazole), fenpropimorph and pimaricin but relatively resistant to terbinafine. Conversely, isolate 49628 was sensitive to terbinafine but relatively resistant to the other fungicides. Changes in sterol composition following treatment with the fungicides reflected the known modes of action of each fungicide. When individual enantiomers of triadimenol were tested against isolate 840905 the order of activity in reducing mycelial growth was 1 S, 2R > 1R, 2R > 1R, 2S ≈? 1S, 2S, and this was paralleled by the depletion of ergosterol and the appearance of 14α-methyl sterols. Isolate 49628 had a greater saturated:unsaturated fatty acid ratio than did isolate 840905 but no major changes in fatty acid composition of either isolate were induced by fungicide treatment. There appears to be no obvious explanation for the differences in fungicide sensitivity of the isolates in terms of their lipid compositions.