Accumulation of sugars in microtubers of potato node cuttings (cv. Kennebec) during cold storage

Summary Microtubers of potato cultivar Kennebec were stored for two months at 2 or 8°C and sampled at selected intervals for the determination of glucose, fructose, sucrose and sprout weight. The aim of this experiment was to determine whether these microtubers show the same response to storage temperature with respect to sweetening as field grown tubers. During storage at 2 °C, reducing sugars and sucrose increased rapidly to a concentration of over 1.0 and 0.7 g/100 g fresh weight, respectively. In contrast, in tubers kept at 8°C, only a relatively slight increase in reducing sugar concentration to 0.3 g/100 g fresh weight was observed and sucrose concentration remained virtually the same.     

The effects of lactation on the fertility of dairy cows

Lactation has been negatively associated with fertility because pregnancy rates in maiden heifers exceed those obtained after first or subsequent calvings. The extent of this difference is less in pasture-fed dairy cows (<10%) than in American Holsteins (>20%) fed grain and conserved forages. The latter cows have pregnancy rates to first insemination and oestrus detection rates of only 40 to 45%. This suggests that the subsequent fertility of inherently fertile Holstein heifers may be severely compromised by high levels of milk production. International comparisons show that pasture-fed dairy cows may experience extended periods of anovulatory anoestrum but have normal fertility (60% pregnancy rate to first insemination) once cycling. The high-producing American Holstein may ovulate within 4 weeks postpartum but is more likely to continue ovulating without being detected in oestrus. Both situations are associated with negative energy balances (NEB) during early lactation. The severity and duration of this NEB may vary with body condition at calving, age or parity, ration formulation, production level and environmental factors. Relative daily milk yield is not an absolute indicator of NEB, because some lower producing cows within a herd have lower feed intakes and more severe energy deficits. NEB is not simple to measure; nonetheless, it is correlated with genetic improvement for milk yield. A positive energy balance, greater weight gain and higher body condition score have all been shown to be positively correlated with plasma progesterone concentrations in early lactation. No studies have investigated the possibility that the rapid increase in metabolic rate at this time may also alter steroid concentrations with consequent effects on oestrous behaviour and fertility. Studies to more precisely define the effects of increasing milk yields in early lactation, especially in Holsteins, may need to be completed in Australia and New Zealand. Oestrus detection rates and pregnancy rates for American Holsteins of less than 50% are accepted widely in the USA. Such low detection rates confound studies on fertility. The objective should be to increase these 2 rates to at least 80% and 60% respectively. This may involve the use of controlled breeding, especially if oestrous behaviour is less overt in high-producing Holstein cows.     

Behavioural and EEG changes in sheep in response to painful acute electrical stimuli

Objective To measure acute pain in sheep, based on a human pain model, and examined changes in both electroencephalogram frequency spectrum and behavioural responses to increased electrical stimulation in sheep. Design Analysis of variance (treatment and animal effects) for stimulus intensity where each animal received each electric shock treatment given in the order 0, 5,10 and 20 mA. Procedure Eight sheep with electrodes implanted over the surface of the brain were examined for escape-avoidance and electroencephalogram responses to four levels of electrical stimulation from 0–20 mA. Results With increasing stimulus intensity at the time of feeding, the sheep were more hesitant to return to the feeder or remain near the feeder following stimulation. There was little difference between the 0 and 5 mA stimuli for any of the behaviour variables (P > 0.05). However, there were marked increases in the time taken to re-approach the feeder after receiving an electric shock of 5 mA and of 20 mA (P < 0.05; mean values 3 and 119 s, respectively) and remaining near the feeder for 5 s (P < 0.001; mean values 10 and 167 s, respectively). Following the stimulus, there was an overall increase in the electroencephalogram power spectrum in the first four seconds, which then rapidly returned to normal. In particular, the 20 mA stimulus resulted in higher absolute power values than in the control (0 mA) treatment for delta 2 (P < 0.001), theta 1 (P < 0.05), theta 2 (P < 0.05), alpha 1 (P < 0.001), alpha 2 (P < 0.001) and beta 1 (P < 0.01) band-widths. Similarly, for the 10 mA stimulus, the absolute power values were greater than the control treatment for delta 2 (P < 0.05), alpha 1 (P < 0.01), alpha 2 (P < 0.001) and beta 1 (P < 0.01) bandwidths. Conclusion The experiment suggests that a human acute pain model is applicable to sheep and that these electroencephalogram changes may provide a good measure of acute pain in sheep.     

Root production and root mortality of winter wheat grown on sandy and loamy soils in different farming systems

Winter wheat was grown over 2 years (1995, 1996) in an organic and integrated cropping system on sandy and loamy soils. Root growth was measured on five to six occasions each year with an auger sampling procedure and the ingrowth core method. The first resulted in an estimate of net root development, while the latter revealed gross root growth (GG) or root production. Total root production was about 80-150 km m^-2 (0- to 30-cm soil layer) between April and July and exceeded the net size of the root system at harvest by a factor of between 2 and 4. The C input into the soil could be estimated as 1.4-2.6 t ha^-1 by this root production. The cropping systems had nearly no influence on root production. The largest differences occurred between the years. The net root length tended to be lower on sandy soils compared to the loam, but total root production was higher. Root mortality, which is the difference between GG and net root growth, was also higher on sandy soils. The turnover index, which is the mean of the relative root production rates and relative root mortality rates, was positively related to the soil sand content in both years.     

Phosphate Diffusion Coefficients in Soil as Affected by Bulk Density and Water Content

Phosphate diffusion coefficients (D_e) were determined by the quantity of P that diffused from a soil block with P addition into a soil block without P addition. To compare the results with theoretical concepts and to quantify the influencing factors, D_e was also calculated using the equation of Nye (1968). This equation takes into account the P diffusion coefficient in water, D₁, the volumetric water content, θ, the impedance factor, f, and the buffer power, b, of the soil. The results show that D_e strongly depends on volumetric water content whereas the effect of bulk density on D_e values was relatively small. If the weighted average buffer power was used, calculated D_e values were in good agreement with measured values at higher soil moisture contents. At θ < 0.22 g cm^?3 the measured values for D_e were smaller than the calculated. This effect is attributed to incomplete contact between the two soil blocks. The only small influence of bulk density on D_e is caused by the fact that bulk density affects both θ and b in a way which compensates each other.     

Höhe der Erhaltungsdüngung und Ausnutzung von Düngerphosphat vor dem Hintergrund der P-Alterung im Boden

Phosphorus fertilizer rate to maintain the soil P status and the utilization of fertilizer P Once a soil has a P status adequate for optimum plant growth the aim of the farmer is to maintain it. Fertilizer phosphate, even water soluble, is utilized by crop plants generally by less than 20% only in the year of application. Furthermore, the solubility of residual P in soil decreases with time, a process known as “aging” of P. These observations have led to the widespread assumption, that fertilizer P is partly converted into a status unavailable to plants. This would mean that the amount of P necessary to maintain the soil P status has to be permanently higher than P removal of plants. The objective of this work was to test the validity of this conclusion. For this purpose long-term P fertilizer field and pot experiments were carried out on different soils. The results show that the soil test values, lactate (DL or CAL) and water extractable P, remained almost at the same level if fertilizer P was applied in amounts equal to those removed by the crop harvest products. A tendency of decreasing the soluble soil P level was only observed if the soluble soil P content was much higher than necessary for plants. However, the easily extractable P decreased or increased if P applications were less or higher than the amount of P removed by crops, respectively. Desorption studies have revealed that the amount of P desorbed within one week also remained constant if P application was equal to P removal. However, if P was applied in excess of plant removal this proportion was not fully desorbed within one week, whereas the plants were able to utilize it on the long run. We conclude that the “aging” of fertilizer P in soil does not result in a loss of P for crop plants. On the contrary, fertilizer P applied to the soil in a soluble form is fully utilized by the plants in extended periods of time. The rate of P application to maintain the P status of the soil is therefore equal to the quantity of P removed by the plant material.     

A simple method to study the oxidizing power of rice roots under submerged soil conditions

A method was developed to visualize and to study the oxidizing power of rice roots growing under submerged soil conditions. The experimental set up consisted of a transparent jar with an inner core containing the submerged soil surrounded by a coarse (500 μm) and a fine (30 μm) meshed nylon net and a plastic folio. The space of about 1 cm between the jar wall and the soil column was either filled with water (before removing the plastic folio) or with agar containing the redox indicator. Three-week-old rice (Oryza saliva L.) seedlings grown in a sandy soil under controlled growth chamber conditions were transplanted into the jars between the plastic folio and the fine-meshed (30 μm) nylon net. The agar medium (0.5% agar) containing 10 ppm leuco melhylene blue redox indicator or 5 mM ferrous sulphate or precipitated ferrous sulfide (10 m M ferrous sulphate + 4 m M Na₂S) was filled in the transparent jars immediately after sucking out water. Within 4 h the oxidizing power of rice roots became visible by bluish coloration all along of roots and the agar medium around roots due to oxidation of leuco methylene blue. In case of ferrous sulphate reddish brown coloration was observed after one day around the roots and on the surface of roots because of ferrous iron oxidation. When agar medium blackened by precipitated FeS was used the root zone first became transparent because of oxidation of FeS and after few days the roots became reddish brown indicating iron oxyhydroxide deposition. The use of ferrous sulphate and ferrous sulfide enables to study the oxidizing power of rice roots for extended periods, whereas it is not possible to grow rice plants in leuco methylene blue for more than a few hours. However (results not shown), rice cultivars showed differences in oxidizing power of the roots.     

A reduction in the duration of infection with Tritrichomonas foetus following vaccination in heifers and the failure to demonstrate a curative effect in infected bulls

Seven batches of 25% water-phase, oil-in-water vaccine were prepared from whole cultures of Tritrichomonas foetus. Two inoculations were given, spaced 6 weeks apart, to virgin heifers and infected bulls. A significant reduction (P less than 0.01) in the duration of infection in vaccinated heifers was seen when they were challenged by being bred to a bull infected with the same isolate as that contained in the vaccine. Only 1/12 vaccinated heifers were pregnant 4.5 months after the end of the breeding season compared to 2/12 in the control group. The vaccine, therefore, has no practical advantage. Vaccine was supplied to 2,724 bulls on properties where the infection was present. From these bulls, 110 reliable results were obtained, where bulls had been infected, been inoculated and tested 1 month later. No curative effect was demonstrable with 69/110 (62.7%) bulls, remaining infected after the course of inoculations. There was also no difference between vaccine batches or between bulls of different ages. Further work on improving the vaccine is indicated. Three media suitable for the culture of T. foetus are described in detail.