Stabilization and plant uptake of N from N-labelled pea residue 16.5 years after incorporation in soil

The decline of N from ¹⁵N-labelled mature pea residues was followed in unplanted soil over 16.5 yr. Eight years after residue incorporation, 24% of the residue ¹⁵N input was still present in the soil and, after 16.5 yr, 16% of the residue ¹⁵N input remained. A double exponential model successfully described the decay of N from ¹⁵N-labelled pea residues. The total residual ¹⁵N declined with average decay constants of 1.45 yr⁻¹ for the 30 d to 1 yr period and of 0.07 yr⁻¹ for the 1-16 yr period. Sixteen years following incorporation of the residues, indicator plants growing in residues-amended soils were obtaining 1.7% of their N from residue N. This is, to our knowledge, the longest study on decay of N in soils from ¹⁵N-labelled crop residues. The current study thus provides a unique data set for our empirical understanding of N-dynamics in agricultural systems, which is a prerequisite to parameterize and validate N-simulation models.     

Transmission and genetic diversity of Enterococcus faecalis among layer chickens during hatch

Background

Studies on transmission of Enterococcus faecalis among chickens during hatch have not been carried out so far. Information about vertical transmission and subsequent spreading and colonization of the cloacal mucosa through cloacal ''drinking'' during hatch are important to understand the epidemiology of E. faecalis infections. In the present investigation vertical transmission and subsequent spreading and colonization of the cloacal mucosa of chickens by E. faecalis through cloacal ''drinking'' were examined.

Methods

Two different batches of layer chickens originating from 45 weeks old Brown and White Lohmann parents, respectively from the same farm were sampled in the hatcher. Isolates were confirmed to be E. faecalis by polymerase chain reaction (PCR) and further by multilocus sequence typing (MLST) to state their population structure and comparison made to sequence types previously obtained from chicken.

Results

A total of 480 chickens were swabbed from the cloacae just after hatch and after 24 hours. A total of 101 isolates were confirmed as E. faecalis by a species specific PCR. The prevalence of E. faecalis increased from 14% at 0 h to 97% after 24 h for the Brown Lohmann chickens and from 0.5% to 23% for the White Lohmann flock. The 84 isolates analysed by MLST were distributed on 14 sequence types (ST). Three ST (401, 82 and 249) accounted for 64% of all isolates analysed by MLST after 24 h. ST 82 has previously been reported from amyloid arthropathy and other lesions in poultry.

Conclusions

The present findings demonstrated a high potential of a few contaminated eggs or embryos to rapidly facilitate the spread of E. faecalis to almost all chickens during hatch.     

Combining information from surveys of several species to estimate the probability of freedom from Echinococcus multilocularis in Sweden,Finland and mainland Norway

Background

The fox tapeworm Echinococcus multilocularis has foxes and other canids as definitive host and rodents as intermediate hosts. However, most mammals can be accidental intermediate hosts and the larval stage may cause serious disease in humans. The parasite has never been detected in Sweden, Finland and mainland Norway. All three countries require currently an anthelminthic treatment for dogs and cats prior to entry in order to prevent introduction of the parasite. Documentation of freedom from E. multilocularis is necessary for justification of the present import requirements.

Methods

The probability that Sweden, Finland and mainland Norway were free from E. multilocularis and the sensitivity of the surveillance systems were estimated using scenario trees. Surveillance data from five animal species were included in the study: red fox (Vulpes vulpes), raccoon dog (Nyctereutes procyonoides), domestic pig, wild boar (Sus scrofa) and voles and lemmings (Arvicolinae).

Results

The cumulative probability of freedom from EM in December 2009 was high in all three countries, 0.98 (95% CI 0.96-0.99) in Finland and 0.99 (0.97-0.995) in Sweden and 0.98 (0.95-0.99) in Norway.

Conclusions

Results from the model confirm that there is a high probability that in 2009 the countries were free from E. multilocularis. The sensitivity analyses showed that the choice of the design prevalences in different infected populations was influential. Therefore more knowledge on expected prevalences for E. multilocularis in infected populations of different species is desirable to reduce residual uncertainty of the results.     

Factors affecting Eurasian lynx kill rates on semi-domestic reindeer in northern Scandinavia: Can ecological research contribute to the development of a fair compensation system?

Semi-domestic reindeer (Rangifer tarandus) are the main prey for lynx (Lynx lynx) in northern Scandinavia. This causes large, but poorly documented, losses of reindeer. Although the compensation schemes differ between Norway and Sweden, there is a legal requirement in both Scandinavian countries that losses of semi-domestic reindeer to large carnivores should be fully compensated. The current level of compensation payment is based on limited data on lynx kill rates on reindeer. The main goal of this study was to quantify lynx kill rates on reindeer across a range of ecological conditions in northern Scandinavia. A total of 35 lynx were monitored during 3667 days. All lynx individuals killed reindeer. However, we observed a high variation in individual kill rates. Kill rates were strongly affected by sex and social status (i.e. females with and without kittens), as well as season and reindeer availability. The highest kill rates were observed in summer for male lynx, and the lowest were observed during winter for solitary lynx at low reindeer density. In summer, several female lynx switched completely to small prey species even at high densities of reindeer. The present political goals for lynx conservation in Scandinavia require that lynx occur in the reindeer husbandry area where reindeer are the only suitable ungulate prey available. Accordingly, it is therefore impossible to have the total prevention of depredation as a management goal. Rather depredation levels must be limited such that they are considered acceptable, and fair compensation payments should be paid. Our study is the first empirical quantification of the magnitude of lynx depredation on semi-domestic reindeer. This is an important step necessary to enable the setting of fair compensation levels and will hopefully lead to a reduction in conflict level concerning the potential impacts that lynx have on reindeer.     

Amino acid digestibility in low-fat distillers dried grains with solubles fed to growing pigs

The objective of this experiment was to determine the standardized ileal digestibility（SID） of amino acids（AA） in 3sources of distillers dried grains with solubles（DDGS） with different concentrations of fat.Twelve growing barrows（initial body weight：76.1 ± 6.2 kg） were randomly allotted to a replicated 6×4 Youden square design with 6 diets and 4 periods.The fat content of the 3 sources of DDGS were 11.5,7.5,and 6.9%respectively.Diets contained 60%DDGS and fat concentration of the diets were 7.5,52,and 5.2%,respectively.Two additional diets containing the 2sources of DDGS with 75 and 6.9%fat were also formulated,and corn oil was added to these diets to increase the concentration of fat in the diets to levels that were calculated to be similar to the diet containing conventional DDGS with 11.5%fat.A N-free diet was also formulated to calculate endogenous losses of crude protein（CP） and AA from the pigs.Pigs were fed experimental diets during four 7-d periods.The first 5 d of each period were an adaptation period and ileal digesta were collected on d 6 and 7 of each period.The apparent ileal digestibililty（AID） and SID of CP and all indispensable AA,except AID Pro and SID of Trp,were greater（P 〈 0.01） in conventional DDGS than in the 2 sources of DDGS with reduced fat.Adding oil to the diets containing the 2 sources of DDGS with reduced fat did not consistently increase SID of AA.In conclusion,conventional DDGS has greater SID values for most AA compared with DDGS that contains less fat and inclusion of additional oil to diets containing low-fat DDGS does not increase AID or SID of AA.The lower AA digestibility in low-fat DDGS could not be overcome by the inclusion of additional fat to the diets.     

Landscape simplification promotes weed seed predation by carabid beetles (Coleoptera: Carabidae)

Weeds constitute major constraints for farmers by reducing crop yield and quality. However, weeds are managed effectively using herbicides, but this may cause harmful effects on human health and the environment. In an experiment on weed seed predation, we tested the biological control potential of carabid beetles to combat weeds in the absence of herbicides. Seeds from three common weed species were placed in cereal fields on conventional and organic farms located along a landscape complexity gradient (area annual crops within 1 km) in two distinct regions in Sweden. Carabid beetles were sampled in the same fields using pitfall traps. Neither carabid species richness nor seed removal was related to organic farming. Seed removal was significantly related to carabid species richness and both carabid species richness and seed removal was higher in landscapes with large total area of annual crops, although the evenness of the carabid communities was lower. The carabid genera with strongest positive relationship to seed removal differed between regions (Trechus in Uppland and Pterostichus in Scania), as did the preference for the different weed seed species. This study concludes that carabid species richness contributes to weed seed predation and that large scale landscape context explains more variation in the carabids’ responses than local farming practices.     

Trait-dependent responses of flower-visiting insects to distance to semi-natural grasslands and landscape heterogeneity

Protecting semi-natural grasslands may through spill-over benefit species richness and abundance of flower-visiting insects in linear habitats, such as uncultivated field boundaries, in agricultural landscapes. However, whether local diversity increases both with decreasing distance from potential source habitats and increasing landscape heterogeneity is poorly known due to a general lack of studies replicated at the landscape scale. We analysed if local assemblages of bumblebees, butterflies and hoverflies in linear uncultivated habitats increased with increasing distance to the nearest semi-natural grassland in 12 replicated landscapes along a gradient of landscape heterogeneity in Scania, Southern Sweden. Species richness and abundance of bumblebees and butterflies, but not hoverflies, decreased with increasing distance to semi-natural grasslands, but none of these groups were related to increasing landscape heterogeneity. Further analyses on trait-specific groups revealed significant decreases in the abundance of sedentary and grassland specialist butterflies with increasing distance to assumed source populations, whereas this was not the case concerning mobile species and grassland generalists. The abundance of all bumblebee trait groups decreased with increasing distance to semi-natural grasslands, but only some species (those nesting above ground, with long colony cycles and with small colony sizes) also increased with increasing landscape heterogeneity. We conclude that local species assemblages of flower-visiting insects in linear habitat elements were mainly affected by the occurrence of nearby semi-natural grasslands. In order to conserve diverse assemblages of flower-visiting insects, including the ecological services they provide, it is important to conserve semi-natural grasslands dispersed throughout agricultural landscapes.