Country‐wide analysis of large wood as a driver of fish abundance in Swedish streams: Which species benefit and where?

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Long-term effect of photoperiod manipulation on growth, maturation and flesh quality in Atlantic halibut

The aim of this study was to investigate the effect of continuous light at different stages during the production cycle of Atlantic halibut Hippoglossus hippoglossus L. on growth, age at first maturity, endocrine parameters and flesh quality. A group of juvenile halibut [mean (SD), initial weight 191.3 g (44.7)] was reared in indoor tanks under ambient temperature conditions for 38 months until harvesting (mean final weight, 4.6 kg). The entire photoperiod experiment was divided into four phases, where the fish in each phase were exposed to either natural photoperiod (62°33'N) or continuous light (L). Thus, the following five photoperiod combinations were tested: (a) Control group (NNNN), (b) Group 2A (NLNN), (c) Group 2B (NNLN), (d) Group 2C (NNNL) and (e) Production group (LNNN). Exposure to continuous light stimulated growth, and the final mean weights of Groups 2A and 2B were 23% and 11% higher than those of the Control group (NNNN). The final plasma 11-ketotestosteron levels were lower in Groups 2A (2.94 ng mL⁻¹) and 2B (2.46 ng mL⁻¹) compared with the Control (5.29 ng mL⁻¹), Group 2C (5.09 ng mL⁻¹) and the Production group (4.78 ng mL⁻¹) during spring 2007 (age 4 years), indicating higher age at first maturity in Groups 2A and 2B. Photoperiod regime had only a minor, and transient, effect on flesh-quality traits of the fish, whereas a significant seasonal effect was seen with a tendency towards increased gaping, lower pH, lower hardness and lower shear force in July compared with December and March.     

Degradation and effect of hydrogen peroxide in small‐scale recirculation aquaculture system biofilters

From an environmental point of view, hydrogen peroxide (HP) has beneficial attributes compared with other disinfectants in terms of its ready degradation and neutral by‐products. The rapid degradation of HP can, however, cause difficulties with regard to safe and efficient water treatment when applied in different systems. In this study, we investigated the degradation kinetics of HP in biofilters from water recirculating aquaculture systems (RAS). The potential effect of HP on the nitrification process in the biofilters was also examined. Biofilter elements from two different pilot‐scale RAS were exposed to various HP treatments in batch experiments, and the HP concentration was found to follow an exponential decay. The biofilter ammonia and nitrite oxidation processes showed quick recuperation after exposure to a single dose of HP up to 30 mg L^?1. An average HP concentration of 10–13 mg L^?1 maintained over 3 h had a moderate inhibitory effect on the biofilter elements from one of the RAS with relatively high organic loading, while the nitrification was severely inhibited in the pilot‐scale biofilters from the other RAS with a relatively low organic loading. A pilot‐scale RAS, equipped with two biofilter units, both a moving‐bed (Biomedia) and a fixed‐bed (BIO‐BLOK^®) biofilter, was subjected to an average HP concentration of ～12 mg L^?1 for 3 h. The ammonium‐ and nitrite‐degrading efficiencies of both the Biomedia and the BIO‐BLOK^® filters were drastically reduced. The filters had not reverted to pre‐HP exposure efficiency after 24 h, suggesting a possible long‐term impact on the biofilters.     

Use of a cyclic high-pressure sodium lamp to inhibit flowering of chrysanthemum and velvet sage

Photoperiod is commonly controlled in the commercial production of ornamental crops to induce or prevent flowering. Flower induction in short-day (SD) plants can be prevented or delayed when the natural daylength is short by providing low-intensity lighting during the dark period. A stationary high-pressure sodium (HPS) lamp with an oscillating aluminum parabolic reflector (cyclic HPS) has been developed to provide intermittent lighting to greenhouse crops. We determined the efficacy of a cyclic HPS lamp at preventing flowering in SD plants garden chrysanthemum [Chrysanthemum × grandiflorum (Ramat.) Kitam.] ‘Bianca’, pot chrysanthemum ‘Auburn’, and velvet sage (Salvia leucantha L.) relative to traditional night interruption (NI) lighting strategies. Plants were grown in a glass-glazed greenhouse at a mean daily temperature of 19.5–20.7 °C with natural SD photoperiods. NI lighting was delivered during the middle of the night (2230–0230 h) from a 600 W cyclic HPS lamp mounted at one gable end of the greenhouse or from incandescent (INC) lamps that were illuminated for the entire 4 h (CONT INC) or for 6 min every 30 min for 4 h. Plants under cyclic HPS were grown at lateral distances of 1, 4, 7, 10, or 13 m from under the lamp. Control plants were grown under an uninterrupted 15 h skotoperiod. As the distance from the cyclic HPS lamp increased from 1 to 13 m, the maximum irradiance measured during the NI decreased from 25.4 to 0.3 μmol m⁻² s⁻¹ and time to visible inflorescence (VI) and the number of nodes at VI decreased. All species had a VI within 54 d, but ≤10% of plants flowered when grown at a lateral distance of 1 or 4 m from the cyclic HPS lamp or under CONT INC. Plants grown without NI had a VI 2 to 15 d earlier and flowered 7 to 24 d earlier than plants grown at 10 or 13 m from the cyclic HPS. All garden chrysanthemums flowered under cyclic INC, whereas velvet sage and pot chrysanthemum had 15% and 35% flowering, respectively. These results indicate that a cyclic HPS lamp can be used effectively to delay flower induction and prevent flowering in these species when NI is delivered at ≥2.4 μmol m⁻² s⁻¹.     

The combined effects of temperature and GnRHa treatment on the final stages of sexual maturation in Atlantic salmon (Salmo salar L.) females

Atlantic salmon (Salmo salar L.) females (2 SW), maturing for the first time, were reared under one of three temperature regimes (high: 14.3 ± 0.5°C; natural: 10.6 ± 1.0°C; and cold: 6.9 ± 1.0°C) in combination with one of two experimental treatments; an injection of GnRH analogue (GnRHa) contained in biodegradable microspheres, or a sham injection (microspheres only). The six experimental groups were then reared under simulated natural photoperiod for 4 weeks. Blood samples were drawn for analysis of plasma steroid levels and the fish were inspected for ovulation weekly. Batches of stripped eggs were incubated in triplicate incubators in raceways until the eyed stage. Treatment with GnRHa resulted in a substantial advancement and synchronization of ovulation at all temperatures, while exposure to cold water also appeared to advance ovulation slightly. While 75% (warm and cold) to 90% (natural) of GnRHa fish ovulated during the 4-week trial, only 30% of sham-treated females exposed to cold water, and none of the sham-treated fish held at higher temperatures, ovulated during this period. Survival rates of embryos to the eyed-stage were significantly higher for broodstock exposed to cold water. Plasma levels of testosterone (T), 17β-oestradiol (E₂), and 17α,20β-dihydroxy-4-pregnen-3-one (17,20βP) were all significantly affected by treatment with GnRHa and, to a lesser extent, temperature. The efficiency of GnRHa in counteracting the negative effects of high temperature on ovulation and the associated changes in circulating sex steroids suggest that temperature inhibition operates at least in part at the brain or pituitary.     

Effects of Soil Characteristics on Spring-Harvested Switchgrass Biomass Composition

Switchgrass (Panicum virgatum L.) is a promising bioenergy crop for temperate regions. Overwintering has been used to improve biomass quality, resulting in a more efficient combustion, partially due to a reduction in minerals concentration. This study examines the effects of soil composition on overwintered switchgrass composition. Samples were collected in the spring from 58 environments in Southern Quebec to determine possible relationships between soil composition and biomass quality. Principal component analysis and stepwise regressions were used to identify relationships between soil and biomass compositions. Soil parameters monitored explained 74% of the variation in biomass silicon (Si) concentration, 45% of the variation in ash, and 32% of the variation in magnesium (Mg). Soil composition had limited effects on the concentration of other elements in switchgrass biomass. Switchgrass biomass quality is influenced by soil composition and appears well suited to biomass combustion when overwintered and harvested in the spring.     

Nodulation and root growth increase in lower soil layers of water‐limited faba bean intercropped with wheat

Below‐ground niche complementarity in legume–cereal intercrops may improve resource use efficiency and root adaptability to environmental constraints. However, the effect of water limitation on legume rooting and nodulation patterns in intercropping is poorly understood. To advance our knowledge of mechanisms involved in water‐limitation response, faba bean (Vicia faba L.) and wheat (Triticum aestivum L.) were grown as mono‐ and intercrops in soil‐filled plexiglass rhizoboxes under water sufficiency (80% of water‐holding capacity) and water limitation (30% of water‐holding capacity). We examined whether intercropping facilitates below‐ground niche complementarity under water limitation via interspecific root stratification coupled with modified nodulation patterns. While no significant treatment effects were measured in intercropped wheat growth parameters, water limitation induced a decrease in shoot and root biomass of monocropped wheat. Likewise, shoot biomass and height, and root length of monocropped faba bean significantly decreased under water limitation. Conversely, water limitation stimulated root biomass of intercropped faba bean in the lower soil layer (15–30 cm soil depth). Similarly, total nodule number of faba bean roots as well as nodule number in the lower soil layer increased under intercropping regardless of water availability. Under water limitation, intercropping also led to a significant increased nodule biomass (48%) in the lower soil layer as compared to monocropping. The enhanced nodulation in the lower soil layer and the associated increase in root and shoot growth provides evidence for a shift in niche occupancy when intercropped with wheat, which improves water‐limited faba bean performance.     

Molecular breeding for virus resistant potato plants

To engineer resistance against potato virus X (PVX), the viral coat protein (CP) gene has been introduced into two potato cultivars. Stable expression of the gene in transgenic clones throughout the growing season has been obtained and resulted in considerably increased virus resistance. With varying frequencies depending on the original cultivar used, true-to-type PVX resistant transgenic clones have been obtained. Since deviant light sprout characteristics were invariably associated with aberrations in plant phenotype, they can be used in procedures to early screen for deviations. Furthermore, it has been possible to unequivocally discriminate between the original untransformed and independent transgenic cultivars. Although no relation has been found between the presence, if any, of the CP of potato virus Y (PVY) or potato leafroll virus (PLRV) in CP gene transgenic potato, appreciable levels of resistance to these viruses has been obtained. This suggests that the mechanism by which a viral CP gene in the potato genome evokes resistance, differs amongst various viruses.     

Nonendoscopic Antegrade Percutaneous Gastrostomy: The Effect of Preplacement Gastric Insufflation on Tube Position and Intra-Abdominal Anatomy

Nonendoscopic tube gastrostomy was performed on 41 anesthetized dogs using the technique of Fulton and Dennis with or without gastric insufflation prior to tube placement. Immediately after tube placement, dogs were euthanized and postmortem examinations performed. When gastric insufflation was not performed (group I), gastrostomy tubes penetrated the visceral surface of the stomach in 25% of dogs. The deep leaf of the omentum was interposed between stomach and body wall in the majority of these dogs, exposing other intra-abdominal organs to potential injury. Additionally, displacement and tethering of the spleen cranial to the gastrostomy site were observed in 33% of dogs in group I. Similar results were obtained when preplacement gastric insufflation was performed after the orogastric tube was inserted sufficiently far to displace the stomach laterally against the body wall (group II). In contrast, consistent positioning of gastrostomy tubes through the parietal surface of the stomach was achieved when the stomach was insufflated prior to lateralizing the left abdominal wall with the gastric end of the orogastric tube (group III). It was concluded that the blind percutaneous gastrostomy technique is made safer by insufflating the stomach immediately prior to pushing the gastric wall laterally into contact with the parietal peritoneum. J Vet Intern Med 1996;10:15–20. Copyright © 1996 by the American College of Veterinary Internal Medicine .     

Dietary calcium-phosphorus ratios for growing pigs in relation to serum levels and bone development

Two experiments comprising a total of 80 Danish Landrace pigs in the period 20–90 kg live-weight were carried out to study the effect of dietary levels and ratios of Ca and P on serum values of Ca, inorg. P, and alkaline phosphatase and on the development of degenerative arthritis and atrophic rhinitis.In both experiments each kg feed (Table 1) was supplemented with 600 i. u. vitamin D₃ and 80 p. p. m. Zn.In the first experiment the Ca:P ratio was 1.2 and the amount of Ca increased from 0.48 % to 1.20 % without influencing daily gain, feed conversion, carcass performance (Table 2) or frequency of atrophic rhinitis (Table 3). The Ca:P ratio in scapula was 2.15. Only when the diet was supplemented with 1.20 % Ga and 1.00 % P the bone quality was histomorphologically adequate (Figs. 1–4).In the second experiment various Ca:P ratios (ranging from 0.1 to 3.0) were compared with the recommended level and ratio of 0.72 % Ga and 0.60 % P. Performance of pigs on the normal level was better than for the other pigs (Table 4). Clinically, various degrees of leg-weakness and -deformation occurred, most pronounced in the high Ca — low P group. Very little lameness and no convulsions were observed. Marked hypocalcemia was not found. Unilateral high Ca intake increased serum Ca significantly, and serum alkaline phosphatase slightly, and decreased serum P (Figs. 5–7). Advanced pericytic osteolysis, poor mineralization and generalized osteodystrophia fibrosa were found in the low Ca groups (Figs. 8–13). The groups showed no differences in frequency of atrophic rhinitis (Table 5), and rickets was not observed.The incidence of degenerative joint lesions was not increased in pigs on the unfavourable Ca:P ratios, and depended apparently more on litters than on diets.