Selenium Concentration in Spring Wheat and Leaching Water as Influenced by Application Times of Selenium and Nitrogen

ABSTRACT

Selenium (Se) deficiency in Scandinavian soils is a common problem, and crops generally contain inadequate amounts to meet human need. This study shows a relationship of the Se concentration in spring wheat (Triticum aestivum L., c.v. ‘Helena’) and leaching water with timing of nitrogen (N) [as ammonium nitrate (NH₄NO₃)] and Se [as sodium selenate (Na₂SeO₄)] application. Ammonium-nitrate was applied by two methods (i) whole amount at sowing and (ii) in split application as 75% at sowing and 25% at stem elongation. Selenate was applied at cereal growth stages after sowing, e.g., tillering, stem elongation, head emergence, and milking. Split N application in comparison to one N application increased the grain protein content from 12.1 to 13.7 mg g^{? 1}, and grain Se was increased from 0.8 to 1.1 mg kg^{? 1} when Se was applied at stem elongation and from 0.6 to 0.9 mg kg^{? 1} when applied at heading. The highest Se concentration in plant was achieved with the split N application and Se application at stem elongation or heading. Selenium leaching losses increased with increasing selenium concentration in the wheat grains. No differences in Se leaching losses were obtained with split N application. Applying selenate and ammonium-nitrate together after tillering increased the grain Se concentration, but did not affect the potential leaching of Se, and thus could be considered as an appropriate time of application of these elements.     

Technology selection—the impact of economic risk on decision making

ABSTRACT

Developing an understanding of economic variance (risk) is critical when evaluating alternative aquaculture production technologies. This article assesses the efficacy of employing a quantitative stochastic analysis technique to support technology selection decision making by undertaking a case study investment assessment of three alternative production expansion strategies (offshore sea-pens, land-based RAS growout and larger post-smolt) for the Tasmanian salmon industry. Results demonstrate that salmon aquaculture is undertaken with considerable underlying levels of economic risk, expansion offshore probably represents the lowest initial capital investment and greatest economic return, and that levels of financial uncertainty increase with land-based RAS production. The study highlights stochastic modeling provides significant “added-value” over single-point deterministic analysis and that developing an appreciation of the input variability is a key component in critically evaluating alternative production technologies.     

Prothrombin time and activated partial thromboplastin time using a point‐of‐care analyser (Abaxis VSpro®) in Bennett's wallabies (Macropus rufogriseus)

There are few reports of coagulation times in marsupial species. Blood samples collected from 14 Bennett's wallabies (Macropus rufogriseus) under anaesthesia during routine health assessments were analysed for prothrombin time (PT) and activated partial thromboplastin time (aPTT) using a point‐of‐care analyser (POC) (Abaxis VSPro®). The wallabies had an aPTT mean of 78.09 s and median of 78.1 s. The PT for all wallabies was greater than 35 s, exceeding the longest time measured on the POC. Although PT was significantly longer, aPTT was similar to the manufacturer's domestic canine reference range.     

Energy expenditure and physical activity in domestic fowl kept on standard and interrupted lighting patterns

1. The energy expenditure (H) and physical activity of laying hens were measured under lighting regimes of 14L:10D (standard), 2L:10D:2L:10D (interrupted) and (15 X (13 min L:47 min D]: 9D (fragmented). 2. Neither of the intermittent regimes produced a significant change in total daily energy expenditure, although large alterations occurred in the distribution of H between the lighting phases. The absence of change in total H resulted from the combined effects of greater H in the light in the intermittent regimes, greater H in darkness during the interrupted day than at night and slightly greater H at night in the intermittent regimes. 3. Physical activity count, like H, was redistributed over time but, unlike H, was also significantly reduced in total; changes in the energy cost of unit activity, however, were such that no reduction occurred in the total amount of H attributable to activity. 4. In the standard groups, 90% of total activity costs were incurred in the light; in the fragmented-day and interrupted-day groups, respectively, 7% and 55% of total activity costs were incurred in the light periods and 85% and 30% in daytime darkness. 5. In terms of both H and activity, there was clear differentiation between night darkness and subjective-day darkness. 6. Even when the energy cost of activity was excluded, significant differences remained between H at night, H in the light and H in daytime darkness.     

Thermoregulation at high ambient temperature in genetically fat and lean broiler hens fed ad libitum or on a controlled‐feeding regime

1. Hens of lines divergently selected for fatness and leanness, fed either ad libitum or on a controlled regimen, were compared for susceptibility to heat stress.

2. The rate of increase in deep‐body (rectal) temperature during exposure to 32°C was used as the index of thermoregulatory ability. Comb and foot surface temperatures were measured as indicators of peripheral vasomotor tone.

3. Because body temperature control depends on the balance between heat production and heat loss, heat production was measured to determine whether fat line hens had a higher heat production, which they would then have to dissipate.

4. During the first hour of heat exposure, rectal temperature in the ad libitum‐fed birds increased twice as rapidly as in the corresponding lean line sample and 6 times more rapidly than in the control‐fed fat‐line group.

5. Surface temperatures of comb and foot increased from 27°C to 37°C within the first hour at 32°C, with no effect of either genotype or feeding regimen on rate of increase.

6. Heat production was unrelated to genotype but was reduced by 23% by controlled feeding, largely because of the reduction in body weight.

7. The results demonstrated that ad libitum‐fed fat‐line birds are susceptible to heat stress and that this is related not to increased heat production, but to a decreased ability to lose heat. Elevation of blood viscosity by plasma triglycerides is suggested as a causal factor.