Sow removal in Swedish commercial herds

The objective of this study was to describe the sow removal pattern in Swedish commercial piglet producing herds, with group-housing of non-lactating sows. The data collection, based on a PC herd monitoring program used in 21 piglet producing herds in the south-central part of Sweden, was prospective, started in 2002 and continued for 3 years. During this period, information on 14 234 removed sows was recorded. For all parameters studied a large variation between herds was found. The average annual removal rate was 49.5% (range 33.6–66.3%). Among the removed sows, 85.2% were sent to slaughter, 10.5% were euthanised and 4.3% were found dead. The most common removal reasons were ‘reproductive disorders’ (26.9%), ‘old age’ (18.7%) and ‘udder problems’ (18.1%), followed by ‘low productivity’ (9.5%), ‘lameness and/or foot lesions’ (8.6%) and ‘traumatic injuries’ (7.1%). The proportion of sows sent to slaughter was higher than the proportion euthanised for all categories of removal except ‘traumatic injuries’ (in which 81.6% of the sows were euthanised). The average parity number at removal for all sows was 4.4. Lowest average parity numbers were found for sows removed due to ‘traumatic injuries’ (2.6). Among removed sows, the proportion removed per parity decreased up to parity 6. Sows removed due to ‘old age’ had the highest piglet production, while sows removed due to reproductive disorders had the highest number of non-productive days (NPD) per parity and the longest interval from last farrowing to removal. With increasing removal parity number, the number of piglets produced increased and NPD decreased. In lower parities (1–3) most sows were removed due to ‘reproductive disorders’, but this proportion fell as parity number rose. Removals due to ‘udder problems’ were most frequent in medium parity numbers (4–6). Most sows removed after parity 7 were removed due to old age. The proportion of the sows found dead was highest just after farrowing; otherwise only a low percentage of sows were removed during the lactation period. The proportion of euthanised sows was high in the week after farrowing and during the 4-week period following weaning. The proportion of sows sent to slaughter increased considerably 4 weeks after farrowing (i.e. after weaning) and stayed high during the subsequent 3 weeks. The study revealed a considerable amount of unplanned removal of young sows. Not only the sows sent to slaughter, but also those euthanised and found dead, must be included in studies on sow removal.     

Characterization of Streptomyces spp. Isolated from the Sea Surface Microlayer in the Trondheim Fjord, Norway

The water surface microlayer is still poorly explored, although it has been shown to contain a high density of metabolically active bacteria, often called bacterioneuston. Actinomycetes from the surface microlayer in the Trondheim fjord, Norway, have been isolated and characterized. A total of 217 isolates from two separate samples morphologically resembling the genus Streptomyces have been further investigated in this study. Antimicrobial assays showed that about 80% of the isolates exhibited antagonistic activity against non-filamentous fungus, Gram-negative, and Gram-positive bacteria. Based on the macroscopic analyses and inhibition patterns from the antimicrobial assays, the sub-grouping of isolates was performed. Partial 16S rDNAs from the candidates from each subgroup were sequenced and phylogenetic analysis performed. 7 isolates with identical 16S rDNA sequences were further studied for the presence of PKS type I genes. Sequencing and phylogenetic analysis of the PKS gene fragments revealed that horizontal gene transfer between closely related species might have taken place. Identification of unique PKS genes in these isolates implies that de-replication can not be performed based solely on the 16S rDNA sequences. The results obtained in this study suggest that streptomycetes from the neuston population may be an interesting source for discovery of new antimicrobial agents.     

Blood vessel melanosis: a physiological detoxification mechanism in Atlantic cod (<Emphasis Type="Italic">Gadus morhua</Emphasis>)

Melanin deposits in white muscle represent a potentially serious quality problem for farmed cod. Black lines of deposited melanin are associated with blood vessels and consist of layers of melanin-filled cells. Despite numerous anecdotal reports of melanosis in farmed cod no detailed investigations into the underlying mechanisms have been undertaken. In this study we have confirmed that melanosis is present in both farmed and wild cod. However, the incidence of melanosis in wild fish is much lower than that in farmed fish. In addition, we have demonstrated that tyrosinase, a copper-dependent metalloenzyme that is the primary enzyme of melanin synthesis, is present in cod tissues. Copper levels are significantly different in the white muscle of farmed (0.5 ± 0.03 mg/kg wet weight) and wild (0.34 ± 0.01 mg/kg wet weight) cod (P < 0.05) and in the blood vessels of farmed (2.23 ± 0.37 mg/kg wet weight) and wild (0.32 ± 0.02 mg/kg wet weight) cod (P < 0.05). Similarly, differences in the levels of tyrosinase activity were observed in both muscle and blood vessels. Melanised tissues contain higher copper concentrations than tissue containing little or no melanin. Furthermore, we have shown that the addition of copper to protein extracts from fish muscle causes an increase in tyrosinase activity in vitro. Our results suggest that overabundance of copper in commercial feeds leads to increased melanin synthesis via increased tyrosinase activity. We propose that melanin is deposited at sites of high copper exposure and subsequently sequesters copper as a means of reducing the overload stress on other homeostatic mechanisms.     

Embryonic and larval development in the semelparous Nereid polychaete Hediste diversicolor (OF Müller, 1776) in Norway: Challenges and perspectives

Knowledge of broodstock manipulation, gametogenesis, artificial fertilization and larval nutrition is a prerequisite to reach a large‐scale production of the polychaete Hediste diversicolor. In this study, the characteristics of oogenesis and spermatogenesis and embryonic and larval development were observed. Moreover, the effect of temperature on embryonic development and effect of diets and sediment on earlier juvenile development were tested. Mature oocytes were characterized by a spherical shape with a diameter of about 200 μm. They showed radial symmetry with a large centric nucleus surrounded by four distinctive layers. Embryo cleavage started between 4 and 10 hr after fertilization, and developed to the swimming trochophore stage after 5–6 days after fertilization at 11°C. The rate of embryonic development increased with a temperature increase from 6.1 to 21.2°C. The trochophore larvae increased in length from day 9 and commenced differentiation into 3‐setiger stage larvae at day 12. The length growth of larvae until 7‐setiger stage was 0.43 mm/day when fed with fish feed, while those fed shellfish diet and smolt sludge both grew around 0.21–0.23 mm/day. The results suggest that fish feed is a superior diet compared to shellfish diets and smolt sludge for the early larval stage of H. diversicolor.     

Artificial upwelling to stimulate growth of non‐toxic algae in a habitat for mussel farming

Large‐scale artificial upwelling was tested as a method to enhance the environmental conditions for the growth of non‐toxic algae in a Norwegian fjord (61°0′N, 6°22′E). The experiment was designed to evaluate if nutrient‐rich seawater, brought up from below the mixed zone of a stratified fjord to the euphotic zone by air bubbling, would stimulate the growth of non‐toxic relative to toxic algae. Pumping 44 m³ min^?1 of air at 1 atm through a pipe diffuser submerged at 40 m depth formed a buoyancy flux that lifted 60 m³ s^?1 of deep water to the upper 17 m over a period of 21 days. The supply of silicate, inorganic nitrogen and phosphate to the upper 10 m in the fjord increased, and a significant increase in the biomass of non‐toxic algae was observed. The upwelling gave an increased growth of the non‐toxic dinoflagell ates Ceratium furca and C. tripos. After termination of the experiment, the phytoplankton biomass decreased significantly, whereas a distinct increase occurred in the relative biomass of the potentially toxic Dinophysis spp. The result is considered promising when it comes to creating controlled geographical areas with non‐toxic food for mussel production.     

The effect of physiological and environmental conditions on smolt migration in Atlantic salmon Salmo salar

Hydropower development has negatively influenced Atlantic salmon (Salmo salar) populations. Compensatory hatchery‐rearing programmes exist, but released fish suffer from high mortality that may be related to the lack of experience from natural environments in hatchery‐reared smolts and their large body size and high energetic state. Here, we used acoustic telemetry to test how body size, energetic state, and the environmental conditions of the river affect migration in hatchery‐reared smolts. The study was conducted in three consecutive years between 2011 and 2013 in the lower part of the River Umeälven, Sweden. For individual fish, there was no effect of body size but the energetic state of the fish had a negative effect on sea entry. The most important factor affecting sea entry rate was the water discharge in the old river bed that differed among years. Smolts were more likely to enter the sea in years when the discharge was high or when the discharge increased substantially shortly after release. Hatchery‐reared fish had higher migration speed at a slower flowing section compared with a faster flowing section, which was likely a result of large hesitation to enter the rapid section. The increase in water discharge led to an increase in fish migration speed disproportional to the increase in water velocity. Our results highlight the importance of water discharge for the smolts during smolt migration, and we argue that concern should be given to migrating fish when managing regulated rivers.     

Prevalence of Trichinella larvae and extra-intestinal nematodes in Norwegian red foxes (Vulpes vulpes)

A survey of the parasitic fauna of the Norwegian red fox (Vulpes vulpes) population was carried out in 1994/1995 and 2002-2005. All foxes were killed during the licensed hunting season from October to April and, in total, 393 animals from all regions of the country were examined. The present study details the results of extra-intestinal nematode and Trichinella larvae examinations. All individuals were examined for Trichinella, using routine digestion methods. Parasitological examination of the internal organs of some of the foxes also identified a number of different extra-intestinal nematodes. The following prevalences were identified (number positive/number foxes examined): Trichinella larvae 19/393 (4.8%); Capillaria b?hmi (C. b?hmi) 88/174 (51%); Capillaria aerophila (C. aerophila) 160/181 (88%); Crenosoma vulpis (Cr. vulpis) 105/181 (58%) and Capillaria plica (C. plica) 81/154 (53%). No evidence of Angiostrongylus vasorum infection was found. The 19 different Trichinella isolates were species typed by PCR and sequence analysis; 18 isolates were identified as Trichinella nativa and one as Trichinella britovi. A wide geographical distribution of the parasites was seen. The following exceptions were recorded: C. b?hmi, the prevalence of which was significantly lower in northern Norway (6%) compared to other regions (central Norway, eastern Norway and southern and western Norway; 52-57%). There was a significantly higher prevalence of Trichinella infection in eastern Norway (8.1%), when compared with the rest of the country (0.6%). Cr. vulpis prevalence was significantly higher in central Norway (83%) than in other regions (41-56%). There were no significant differences in age and sex distribution of the parasites with the exception of Cr. vulpis where juvenile foxes had a greater likelihood of infection. The data also indicated that adult foxes were more commonly infected with Trichinella larvae (5.8%) than juveniles (3.3%) (no statistical significance).     

The Potential of High-Oil Oats under Cool Temperate Conditions

Abstract

Genetic and growth temperature effects on the oil content of oats have been studied. A line with high oil content was crossed to a line with low oil content, and the progenies from parental and F₂ plants were studied in two replicated experiments, one in the field, the other combined field/greenhouse. Interactions between greenhouse and field were found for oil content as well as for other characters. High heritability estimates and additive gene action were found for oil content. Insignificant genetic correlations were found between oil content and grain yield. F₃ families which on average had the same oil content as the highest parent were recovered. The results from two independent phytotron experiments indicate that genes conferring high oil content and low temperatures during grain filling seem to work additively towards higher oil content.     

Effects of tractor weight,wheel placement and depth of ploughing on the infestation of perennial weeds in organically farmed cereals

To ensure optimum conditions for organic cereal growing, it is important to minimize both compaction and soil inversion depth. The relative effects of using light versus heavier tractors, shallow versus deeper ploughing and on-land versus in-furrow wheel placement during ploughing were investigated in three-year organic rotations dominated by cereals with naturally infested stands of perennial weeds. The second part of the experiments was carried out in continuous barley with transplanted root fragments of Cirsium arvense (L.) Scop. and rhizome pieces of Elymus repens (L.) Gould. Ploughing was performed in spring under favourable weather conditions. Neither tractor weight nor wheel placement influenced decisively the numbers and above-ground biomass of perennial weeds. Depth of ploughing, on the other hand, affected both perennial weed infestation and yield levels consistently. Weed numbers and the total above-ground weed biomass were mostly 50% lower with deep ploughing (25 cm) than with shallow ploughing (15 cm). The greatest advantage of deep ploughing appeared in the control of C. arvense, which in some cases was reduced by more than 90% compared to shallow ploughing. In organic rotations dominated by cereals, therefore, combating of perennial weeds by deep ploughing may be more important than factors such as tractor weight and wheel placement.     

Long-term study of Sarcoptes scabiei infection in Norwegian red foxes (Vulpes vulpes) indicating host/parasite adaptation

The red fox (Vulpes vulpes) population, in Norway, was na?ve to Sarcoptes scabiei prior to the late 1970s when this parasite was first recorded and a still ongoing epidemic started. During the course of this protracted epidemic some degree of host/parasite adaptation, with the occurrence of healthy antibody positive foxes, might be expected. In the present study the prevalence of sarcoptic mange and serologically identified S. scabiei exposure was investigated in 363 Norwegian red foxes, shot by hunters during two different study periods (1994-1995 and 2002-2005). The sarcoptic mange diagnosis was based upon the presence of clearly visible lesions in the skin of the cadaver with confirmatory demonstration of S. scabiei. The serodiagnosis was based on an indirect-ELISA. There was a significant decrease in prevalence of both mange cases and seropositive animals from the first to the second study period. Whilst the mange prevalence fell more than threefold, from 30.0% to 6.6%, the seroprevalence dropped less dramatically from 53.3% to 19.1%. The smaller decrease in seroprevalence compared to mange cases reflected a significantly higher ratio of seropositive-mange negative versus seropositive-mange positive foxes, during the second study period, 40:18, compared to the first, 14:18. These findings indicate that the red fox population is adapting to live with the parasite and that low-grade or sub-clinical infections, and even recoveries, occur amongst exposed foxes. Mange positive foxes had significantly poorer body condition than those without sarcoptic mange. No significant difference in body condition was seen between seropositive-mange negative versus seronegative-mange negative foxes. The ELISA sensitivity was found to be 95% and proved a useful tool for investigating the exposure to S. scabiei in wild foxes. This study is believed to be the first pointing to a long-term Sarcoptes/fox adaptation, combining long-term prevalence studies of clinical sarcoptic mange and serological evidence of exposure to the parasite in the general fox population.