Light scattering in central arctic ocean: some winter profiles

Measurements for light scattering in an Arctic water column reveal strong gradients and variability of the order of 15 percent in depths of less than 500 meters. The region of variability appears to persist from day to day and is roughly associated with the typical hydrographic features of the region. No definite nephelocline was observed.     

Modeling perspective of the deforestation impact in stream water quality of small preserved forested areas in the amazonian rainforest

A long-term predictive model, MAGIC, was applied to a Central Amazonian catchment area to illustrate large scale deforestation effects on ‘islands’ of preserved areas, for the situations with and without climate changes. In addition, model sensitivity in response to different organic matter levels in the soil and stream waters as well as to different Al solubility constants was evaluated. The model output was strongly dependent on the chosen values of organic matter concentration and Al solubility constant. Application of the model to a 30 yr deforestation program revealed increases in streamwater ionic concentrations with or without climate change, although streamwater ionic concentrations were predicted to be higher as a consequence of climate change. On the centennial scale, streamwater ionic concentrations reach a new equilibrium, with concentrations higher than those prior to the surrounding deforestation. With the assumed increased cation deposition to the preserved forest areas, soil exchangeable cation concentrations increase with time and aluminum is released to solution. At the end of the simulated deforestation program, SO ₄ ^2? in the preserved areas began to be released to streamwater, inducing acidification. Application of the MAGIC model makes possible to estimate, for the rainforest environment, water quality changes as a function of different climate and land use changes.     

Bioelectrical impedance analysis determination of water content and distribution in the horse

A horse’s hydration status is critical to its health. The accurate and quantitative determination of it has been problematic because of size, length and density of hair, and uneven topography. The objective of this study was to validate a bioelectrical impedance analysis (BIA) method for objectively quantifying hydration status. Monofrequency BIA values and simple biometric measurements were used to construct predictive equations for total body water, plasma, extracellular, and intra-cellular fluid volumes. These predictive equations were correlated with standard body fluid dilution reference methods. The result was an accuracy of ±0.64% for total body water, ±0.17% for plasma volume, ±1.91% for extra-cellular fluid, and ±0.57% for intra-cellular fluid compartments. Less than 5 min was required for all of the measurements and determinations. Therefore, it appears that an accurate measurement of body fluid distribution can be performed on horses using a fast, easy, non-invasive, inexpensive BIA method.     

Differences in water-use efficiency among perennial forages used by the dairy industry under optimum and deficit irrigation

The cost and scarcity of water is placing increasing pressure on Australian dairy farmers to utilise water for forage production as efficiently as possible. This study aimed to identify perennial forage species with greater water-use efficiency (WUE) than the current dominant species, perennial ryegrass (Lolium perenne L.). Fifteen perennial forage species were investigated under optimum irrigation and two deficit irrigation treatments, over three years at Camden, NSW, on a brown Dermsol in a warm temperate climate. Under optimal irrigation, there was a nearly twofold difference in mean WUE_t (total yield/evapotranspiration) between forages, with kikuyu (Pennisetum clandestinum Hochst. ex. chiov.) having the highest (27.3 kg ha⁻¹ mm⁻¹) and birdsfoot trefoil (Lotus corniculatus L.) the lowest (14.8 kg ha⁻¹ mm⁻¹). Kikuyu was also the most water use efficient forage under the extreme deficit irrigation treatment, although its mean WUE_t declined by 15% to 23.2 kg ha⁻¹ mm⁻¹, while white clover (Trifolium repens L.) in the same treatment had the largest decline of 44% and the lowest WUE_t of only 8.8 kg ha⁻¹ mm⁻¹. In order to maximise WUE for any forage, it is necessary to maximise yield, as there is a strong positive relationship between yield and WUE_t.     

Acetylene reduction by bacteria isolated from the rhizosphere of wheat

An asymbiotic bacillus possessing N₂-ase activity and capable of growth on low-N media was consistently isolated from the rhizosphere of a chromosome substitution line of spring wheat in which a pair of chromosomes 5D from the cultivar Rescue had been substituted for those of ‘Cadet’. None of the bacilli were isolated from either of the two parent cultivars, Rescue and Cadet, or from the corresponding substitution line involving a homoeologous chromosome 5B. Maximum C₂H₂ reduction to C₂H₄ by pure culture isolates was found to occur at a partial pressure of 0.2 atm C₂H₂. C₂H₂ reduction was diminished in the presence of O₂ and nearly ceased at a partial pressure of 0.08 atm O₂.The data presented suggest that altering the genetics of the wheat plant can change the root environment to favor the establishment of bacilli that exhibit N₂-ase activity in pure culture.     

Field comparison of the interferon-gamma assay and the intradermal tuberculin test for the diagnosis of bovine tuberculosis

An extensive field comparison of the gamma interferon (IFN-gamma) assay and the single intradermal tuberculin test for the diagnosis of bovine tuberculosis was conducted in Australia. The specificity of the IFN-gamma assay was determined by testing more than 6000 cattle from tuberculosis-free herds and varied from 96.2% to 98.1%, depending on the cut-off point chosen to define a positive reactor. For the sensitivity trial, cattle from herds being de-populated because of bovine tuberculosis were examined with both assays. The sensitivity of the IFN-gamma assay was shown to be significantly higher than the single intradermal tuberculin test and varied from 76.8% to 93.6% depending on the method of interpretation. A maximum overall sensitivity of 95.2% was obtained by testing with the IFN-gamma and the tuberculin test in parallel. The superior sensitivity of the IFN-gamma assay and the ability to adjust the sensitivity of the system depending on the task involved, will provide the Australian Tuberculosis Eradication Campaign with a valuable additional test to enable it to accomplish its goals.     

Using a programmable calculator for rationing pregnant ewes

A simple model, using binary variables, for rationing pregnant ewes is described. The model is designed for a programmable calculator for use by staff of the Meat and Livestock Commission in their consultancy work on farms.     

The effects of crossfostering pigs on survival and growth

Data from 254 crossfostered pigs and 753 noncrossfostered pigs of Duroc and Landrace first-parity litters were used to assess the phenotypic effects of crossfostering on baby pigs. Differences between crossfostered and noncrossfostered pigs in the recipient litter were analyzed. Phenotypic correlations were calculated for selected individual pig traits (n = 1007, combined foster and nonfoster data). Birth weight was correlated positively with improved birth vigor (r = .40; P less than .01), survival to 21 d (r = .34; P less than .01) and weight at 21 d (r = .37; P less than .01). Improved birth vigor was correlated positively with pig survival to 21 d (r = .70; P less than .01) and to weaning (r = .66; P less than .01). These correlations indicate that baby pig size and strength are related and that these two characteristics influence survival and performance. Pigs that were not crossfostered (adjusted for birth vigor) had a 4.8% (P less than .10) higher rate of survival to 21 d and a 6.8% (P less than .05) higher rate of survival to weaning (42 d). However, crossfostered pigs had greater birth vigor (P less than .01). Unadjusted for vigor, crossfostered pigs had an 11.3% (P less than .01) higher rate of survival to 21 d and an 8.6% (P less than .05) higher rate of survival to weaning than noncrossfostered pigs. These results indicate that when average-strength pigs were crossfostered, livability was reduced. However, crossfostered pigs that were stronger than average had greater livability than pigs that were not crossfostered.(ABSTRACT TRUNCATED AT 250 WORDS)