Annual cool-season legumes for forage production in mild winter areas

The forage potential of several annual winter legumes – crimson clover ( Trifolium incarnatum L.), faba beans ( Vicia faba L.), forage peas ( Pisum sativum L.), serradella ( Ornithopus sativus Brot.) and vetches ( Vicia sativa L. and Vicia villosa Roth.) – was evaluated over two growing seasons in the wet and mild winter areas of Galicia (north-west Spain) with a moderately acid soil, at the two normal harvesting dates in the region, April and May.
The results indicate that, in April, serradella and crimson clover (in the warmer location), can produce dry-matter (DM) yields of 4–5 t ha⁻¹, which is similar to other winter forages in the same area, with an average growing season of 212–237 d, corresponding to about 339–420 accumulated degree–days above 10°C (GDD₁₀). In May, mainly in the warmer location, fava beans, peas and vetches yielded on average 4·7–8·5 t ha⁻¹ DM, with an average growing season of 166–206 d but with only 233–278 GDD₁₀ units. Faba bean, with an average of 8·5 t ha⁻¹ DM in the May harvest, was the highest producing forage legume. The results also suggest that some cool-season legumes could fit into double-cropping systems based on summer crops, such as maize, because of their forage yields and nutritive value. However, in order to produce consistent DM yields, the date of sowing is crucial; they must either be sown much earlier than the dates in this study or the harvests must be delayed until the end of April.     

The effect of temperature on the development of yolk‐sac larvae of European hake (Merluccius merluccius L.) under laboratory conditions

The effect of temperature (10, 13, 16, 19 and 22°C) on hatching, development and survival of yolk‐sac larvae of European hake, Merluccius merluccius, was studied. At 22°C the experiment was suspended because all eggs died a few hours after incubation. Five morphological indicators of larval development (standard length – SL, yolk‐sac volume – YSV, oil globule diameter – OD, body height – BH and body wet weight – BW) were analysed. SL, YSV, OD and BW of newly hatched larvae were biggest in size and weight at low temperatures (P < 0.05). Throughout the experiments, the rates of changes in SL, YSV and OD varied with temperature (P < 0.05). By contrast, BH and BW remained constant and did not show significant relationship with the effect of temperature (P > 0.05). The potential model showed that the SL growth rate varied from 0.05 to 0.08 mm day^?1 from 10.5 to 19.5°C respectively. However, at all temperatures two growth phases were identified: a rapid growth phase followed by a slow one. Rapid growth rate in length and depletion in yolk‐sac and oil globule occurred at high temperatures. After total YSV and OD consumption (death by starvation), larvae died between 8 and 14 days at 19.5 and 10.5°C respectively, reaching a maximum length of 4.3 mm at 10.5°C. Metabolic indices such as: lowest threshold temperature (T₀); effective larval development (); cumulative thermal units (TC) to complete larval development; the temperature coefficient on growth rate in length (Q₁₀) and the condition factor (K) were also studied.     

Studies on maternally derived antibodies to Aujeszky's disease virus in piglets born to naturally or experimentally infected sows

The concentration of maternally derived antibodies to Aujeszky's disease virus was compared in 10 litters born to infected sows. Four sows had been naturally infected and six were experimentally infected. Both IgG and IgM were present in piglet sera during the first days of life. IgM antibodies went rapidly to undetectable levels; IgG persisted much longer. The duration was dependent upon the original concentration. There was a clear relationship between the clinical disease experienced by the sow and the titre of antibodies in serum and colostrum; sows which had been naturally infected or experimentally infected with a highly virulent strain passed onto their litters a high amount of specific antibodies while sows which after experimental infection presented only mild clinical signs had very low titres of neutralizing antibodies and their litters were virtually devoid of specific antibodies at 3 weeks after birth. A return to detectable levels of IgM was noticed in some litters at around 9 weeks postcolostrum intake suggesting a development of a specific immune response.     

Arrested development of Ostertagia ostertagi: effect of the exposure of infective larvae to natural spring conditions of the humid pampa (Argentina)

The aim of this study was to determine the effect of environmental conditions and the time of exposure to the conditions required for Ostertagia ostertagi to become inhibited in development at the early fourth larval stage in the host. Two comparable experiments were conducted from September to January, experiment I in 1997-1998 and experiment II in 1999-2000. Twenty-thousand third-stage larvae (L3), freshly obtained from coprocultures, were spread in different parasite-free grass plots at the beginning of September, October and November in each experiment and exposed to environmental conditions throughout spring and early summer. Duplicate plots for each exposure period were grazed for 3 days by two dewormed tracer calves after 1, 2, 3, 4 weeks of exposure during the corresponding month, and the remaining plots were grazed for 3 days at monthly intervals until the end of the experimental period. For each month in both experiments, control animals were inoculated orally with 20,000 L3 newly recovered from coprocultures (week 0 animals; infection controls). The control and tracer calves were sacrificed and their parasite burdens analysed. The time required to obtain greater than 50% inhibited larvae (IeL4) in the tracer animals during September and October was 3 weeks, whereas during November around 60% of the parasites were inhibited after one week of exposure. During the period tested, greater than 50% inhibition was found in concurrence with a photoperiod ranging between 13 and 14 h. The highest proportion of IeL4 (75% average) in the animals was found concomitant with a 14 h 43 min photoperiod. A high correlation between the percentage of inhibition and day length was established (0.870 p < 0.001 and 0.815 p < 0.001 for experiment I and II, respectively). In both years, the capacity for developmental arrest was lost by the end of December, when the photoperiod begins to decrease, suggesting either a disappearance of the induction stimulus, or that an excess of the stimulus could block the mechanism of inhibition. The induction time was extended 2 weeks in all months tested when the coprocultures were maintained in the dark (experiment II), suggesting that accumulation of the light stimulus contributes to shortening of the induction time. The data presented here would suggest that photoperiod is a key environmental factor for the induction of hypobiosis.     

Astrophysical opacity

An array of problems in astronomy, cosmology, and particle physics is dependent on our understanding of the evolution and structure of stars. Stellar structure and evolution, in turn, depend on how the nuclear energy generated in the stellar center is transported to the surface. Energy transport by photons is a primary transfer mechanism. Recent improvements in the calculation of the radiative properties of stellar matter have helped resolve several long-standing discrepancies between observations and the predictions of theoretical models.     

Protein analysis of honeys by fast protein liquid chromatography: application to differentiate floral and honeydew honeys

Fast protein liquid chromatography on a Superdex 75 HR column has been applied to analyze the proteins of 29 honeys, 12 of floral origin and 17 from honeydew. The molecular masses were comprised between 13100 and 94000 Da. Seven peaks have been separated; four of them were present in all of the honeys, and three were only present in some honeys. Direct observation of the chromatograms of the floral and honeydew honeys did not reveal any information about their botanical origins. However, both types of honeys can be distinguished with the percentages of the areas of four of the seven chromatographic peaks obtained.     

Variation of quality traits in cassava roots evaluated in landraces and improved clones

About 70 million people obtain more than 500 cal per day from cassava roots. The crop is fundamental as food security of poor rural communities, but little is known about variability of root nutritional and quality traits. Roots from 2457 genotypes comprising landraces and improved clones, were screened for their nutritional (cyanogenic potential, carotene, minerals, and sugars contents) and agronomic (dry matter content, color intensity, and postharvest physiological deterioration) traits. The objective was to assess the range of variation for the traits evaluated to define future research strategies. Results are mostly based on unreplicated measurements. Carotene contents in the roots ranged from 0.102 to 1.040 mg/100 g fresh tissue and correlated positively with color intensity (ρ = 0.860) and cyanogenic potential (ρ = 0.305). Average levels of Fe and Zn were 17.1 and 7.5 mg/kg, respectively. Many clones derived from Meso-America showed high protein levels in the roots, probably as a result of the introgression from wild relatives only found in that region. The observed values for carotene, proteins and minerals contents suggest the potential for improving the nutritive value of cassava.     

Analysis of the variable charge of two organic soils by means of the NICA-Donnan model

We have tested to see if the generic set of NICA‐Donnan model parameters, used to describe isolated humic substances, can also describe soil humic substances in situ. A potentiometric back‐titration technique was used to determine the variable surface charge of two organic peat soils at three different ionic strengths. The non‐ideal, competitive‐adsorption NICA‐Donnan model was used to simulate the surface charge, by assuming a bimodal distribution of H⁺ affinity on the soil solid phase. The model provided an excellent fit to the experimental data. The Donnan volume, V_D, varied slightly with ionic strength, although the variation was less than for humic substances in solution. The values obtained for the parameters that define the affinity distributions, the intrinsic proton binding constant (log K_i^int) and the heterogeneity of the site (m_i), were similar to those observed for isolated soil humic acids. The abundance of carboxylic groups in the whole soil represented 30% of the typical value for isolated soil humic acids. The composition of the organic matter of the whole soils, obtained by ¹³C CPMAS NMR, was comparable to the characteristic composition of soil humic acids.