Optimization of Dietary Manganese for Rainbow Trout,Oncorhynchus mykiss,Fed a Plant‐based Diet

Juvenile rainbow trout were fed a plant‐based diet supplemented with inorganic Mn added at 0, 0.5, 1, 2, 4, 8, 16, or 32 mg/kg diet for 12 wk. Whole‐body Mn concentrations increased with increasing dietary levels. Rainbow trout fed 2–8 mg Mn/kg diet exhibited weight gain that was significantly higher than fish fed 0, 0.5, 1, 16, and 32 mg Mn/kg diet. Feed conversion ratio (FCR) showed a similar trend, where FCR values decreased with increasing dietary Mn until concentrations reached 8 mg Mn/kg, after which they increased. A rational nonlinear model (R² = 0.84) fit to weight‐gain data showed that the optimal predicted supplementation level for Mn was 4.8 mg/kg diet. The optimal predicted supplementation level for Mn was similar for FCR (5 mg Mn/kg diet). The predicted 5 mg/kg diet of supplemental Mn required for the plant‐based diet formulation examined in this study is lower than the National Research Council–recommended supplementation level of 12 mg/kg. However, due to potential differences in bioavailability or retention of Mn among plant‐protein sources, the level of dietary supplementation for optimal growth could be slightly higher or lower depending on the dietary formulation.     

Gradual forest edges can mitigate edge effects on throughfall deposition if their size and shape are well considered

For the protection and promotion of biodiversity in forest edges and interiors, forest edge management practices are put forward like the creation of gradual forest edges (i.e., edges with a gradual increase of vegetation height from open area to forest, e.g., by means of a fringe, a belt, and a mantle). In this study, we tested the mitigating effect of gradual forest edges on the atmospheric deposition of inorganic nitrogen (N) and the potentially acidifying pollutants SO₄²⁻, NO₃⁻, and NH₄⁺ (N + S). We conducted field experiments at three exposed forest edges in Flanders and the Netherlands and compared throughfall deposition at steep edges (i.e., edges with an abrupt transition from open area to forest) and at adjacent gradual edges. Along transects perpendicular to the edges, during three months in both winter and summer, throughfall deposition of Cl⁻, SO₄²⁻, NO₃⁻, and NH₄⁺ was monitored in the forest between 0 and 64 m from the edges and in the gradual edge vegetation. At the smoothest and best fitting gradual edge, the extra N + S throughfall deposition the forest received due to edge effects was lower than at the adjacent steep edge, with on average 80 and 100% in winter and summer, respectively. This was due to a halving of the depth of edge influence and an almost full reduction of the magnitude of edge influence. This decrease in throughfall deposition in the forest was not compensated by the additional throughfall deposition on the gradual edge vegetation itself, resulting in a final decrease in throughfall deposition in the forest edge by 60% in winter and 74% in summer. While this result confirms that gradual edges can mitigate edge effects on atmospheric deposition, the results of the other sites indicate the importance of size and shape of the gradual edge vegetation in mitigating edge effects on deposition: due to insufficient height (‘size’) or inadequate shape of the gradual edge vegetation, only small or insignificant decreases in throughfall deposition were observed. Hence, for mitigating edge effects on N + S and N deposition, our results support the recommendation of creating gradual edges at forests with poorly developed, abrupt edges, but it stresses the importance of a thorough consideration of the shape and size of the gradual edge vegetation in the design and management of gradual forest edges.     

Refining Inclusion Levels of Grain Distiller's Dried Yeast in Commercial‐type and Plant‐based Diets for Juvenile Rainbow Trout,Oncorhynchus mykiss

Recent studies with rainbow trout, Oncorhynchus mykiss, demonstrated that grain distiller's dried yeast (GDDY) at up to 12% inclusion was an effective dietary protein source when replacing fish meal. To examine the effectiveness of GDDY when replacing an increased variety of dietary protein sources, two feeding trials were conducted. In the first trial, six commercial‐type diets were formulated to contain 42% digestible protein and 20% crude lipid with GDDY included at 0, 6, 9, 12, 15, and 18% to replace all dietary protein sources except fish meal. In the second trial, four plant‐based diets with GDDY at 0, 9, 12, and 15% were examined. Experimental diets were fed twice daily, to apparent satiation, to three replicate tanks of fish/diet (initial weight = 22.3 ± 0.7 g) for 10 wk in a 15 C recirculating system. Results demonstrated excellent fish growth and the inclusion rate of GDDY did not negatively affect growth or feed conversion. No significant negative effects of GDDY on body indices or whole‐body proximate composition were observed. Based on these results, GDDY can be included in both commercial‐type diets and plant‐based diets for rainbow trout at up to 18 or 15%, respectively, without decreasing growth performance.     

Infectious bronchitis virus in testicles and venereal transmission

Even though males represent only 8%-12% of the birds of a breeder flock, their role in infectious bronchitis virus (IBV) dissemination is largely unknown. We first assessed the effect of IBV replication in the chicken testes. Ten-week-old males were inoculated with Arkansas (Ark) or Massachusetts (Mass) IBV virulent strains. Seven days postinoculation (DPI) IBV RNA was detected in testicles of 100% of M41- and in 96% of Ark-infected males. Marginal nonsynonymous variation was detected in spike (S) gene of the predominant population of IBV replicating in the testes compared to the S gene of the predominant population of viruses prior to inoculation. IBV M41 and Ark were detected in spermatogonia and Sertoli cells of testicles of infected roosters by immunofluorescence, without evident histopathological changes. We next assessed venereal transmission of IBV by artificially inseminating 54-wk-old hens either with semen from IBV-infected roosters or with IBV suspended in na?ve semen. IBV RNA was detected in the trachea of all hens inseminated with IBV-spiked semen and in 50% of hens inseminated with semen from IBV-infected males. The egg internal and external quality was negatively affected in hens inseminated with semen containing IBV. These results provide experimental evidence for IBV venereal transmission.     

Performance of Post-juvenile Rainbow Trout Oncorhynchus mykiss Fed Diets Manufactured by Different Processing Techniques

Four different methods of pelleting—extruded (EXT), steam pelleted (STM), using a Universal Pellet Cooker (UPC), and expanded (EXP)—were performed on subsamples of a single batch of mash to determine the effects on feed pellet characteristics, in vivo feed digestibility, and performance of rainbow trout Oncorhynchus mykiss fed the diets for 16 wk. Results indicated that the STM feed was the most (851 g/L) and UPC feed the least (672 g/L) dense, and that UPC feed had the highest % float (8.3%) and, of the pellets that sank, the fastest sink rate (15.1 cm/sec). While some differences occurred among pelleted diets in loss of dry matter (% dry loss) after incubation in a water bath for up to 10 min, the overall % dry loss was only approximately 1–2%. The method of pelleting did not affect fish weight gain, feed conversion ratio, or specific growth rate. Measurement of the apparent digestibility coefficient of dry matter of the test diets using Cr₂O₃ as the marker ranged from 71–89%. While it appeared that the method of pelleting can affect feed characteristics and the amount of feed offered to the fish, fish performance was not affected.     

Biological characteristics of chicken anemia virus regenerated from clinical specimen by PCR

Our previous genetic characterization of chicken anemia virus (CAV) in commercial broiler chickens in Alabama revealed a previously undetected polymorphism: a glutamine codon at VP1 position 22, in 7 of the 14 sequences. The novel glutamine codon was always found in association with a VP1 "hypervariable region" identical to CAV field isolates that replicate poorly in culture. The complete genome of CAV73, representative of the sequences with the novel polymorphism, was generated from cloned polymerase chain reaction (PCR) fragments amplified directly from naturally infected tissues. CAV73 had been detected in 31-day-old broilers submitted for examination for reasons unrelated to anemia. After electroporation of the cloned genomes into MDCC-CU147 lymphoblastoid cells, the regenerated CAV caused the culture to fail within 9 days, and the medium contained 5 X 10(6) TCID50 CAV/ml. Use of MDCC-CU147 cells was essential, as identical electroporation of MDCC-MSB1 cells failed to generate CAV able to destroy the culture within 8 wk. Regenerated CAV73 produced anemia and severe lymphocytic depletion of the thymus when inoculated into susceptible 3-day-old chickens and was reisolated from these chickens. Furthermore, it replicated in low- and high-passage MDCC-MSB1 cells similarly to a low-passage CAV field isolate that contains a different VP 1 "hypervariable region." The regeneration of CAV from PCR products directly from naturally infected carcasses, as performed in this study, provides a tool for the evaluation of distinct genetic polymorphisms that may be detected in specimens where infective virions are no longer available. Our results also provide some insight into the differential susceptibility of cell lines for low-passage CAV field isolates.     

Emerging arthropod-borne diseases of companion animals in Europe

Vector-borne diseases are caused by parasites, bacteria or viruses transmitted by the bite of hematophagous arthropods (mainly ticks and mosquitoes). The past few years have seen the emergence of new diseases, or re-emergence of existing ones, usually with changes in their epidemiology (i.e. geographical distribution, prevalence, and pathogenicity). The frequency of some vector-borne diseases of pets is increasing in Europe, i.e. canine babesiosis, granulocytic anaplasmosis, canine monocytic ehrlichiosis, thrombocytic anaplasmosis, and leishmaniosis. Except for the last, these diseases are transmitted by ticks. Both the distribution and abundance of the three main tick species, Rhipicephalus sanguineus, Dermacentor reticulatus and Ixodes ricinus are changing. The conditions for such changes involve primarily human factors, such as travel with pets, changes in human habitats, social and leisure activities, but climate changes also have a direct impact on arthropod vectors (abundance, geographical distribution, and vectorial capacity). Besides the most known diseases, attention should be kept on tick-borne encephalitis, which seems to be increasing in western Europe, as well as flea-borne diseases like the flea-transmitted rickettsiosis. Here, after consideration of the main reasons for changes in tick vector ecology, an overview of each “emerging” vector-borne diseases of pets is presented.     

应用Le Bissonnais法研究黄土丘陵区土壤团聚体稳定性

 以黄土丘陵区森林草原过渡带燕沟流域植被自然恢复过程中6种植被类型为研究对象,应用LeBissonnais(LB)法测定了不同植被类型下土壤水稳性团聚体,对比分析了LB法3种处理的测定结果与传统湿筛法(Yoder)的差异性。结果表明:在LB法3种湿润处理下,快速湿润处理(FW)对土壤团聚体结构的破坏程度最大,处理后土壤水稳性团聚体以0.05～0.5mm为主;慢速湿润处理(SW)对团聚体的破坏程度最小,处理后土壤水稳性团聚体主要以>2mm团聚体为主;而预湿后扰动处理(WS)对团聚体的破坏程度介于FW和SW之间,处理后土壤团聚体粒径分布比较均匀。说明该区土壤团聚体破坏的主要机制是土壤孔隙中的气泡爆破产生的消散作用。退耕100a期间,植被群落由1年生草本(4a)—多年生灌草(16 a)—半灌木(29 a)—灌木(55 a)—乔木(100a)方向演替过程中,土壤水稳性团聚体由小粒径向大粒径方向转变,土壤结构趋于稳定。LB法3种处理中,FW处理与SW处理所测得>0.5mm团聚体含量和平均重量直径与土壤有机质和物理性黏粒之间存在显著的相关性,而WS处理未达到显著水平(P>0.05)。说明土壤有机质和物理性黏粒主要影响消散和黏粒膨胀引起的崩解作用,而对机械干扰引起的团聚体破坏无明显影响。LB法3种处理中,慢速湿润方法所获得土壤团聚体稳定性特征更接近湿筛法,适宜于黄土丘陵区植被恢复过程中土壤水稳性团聚体的测定。     

农田生物多样性对昆虫的生态调控作用

随着农田作物的单一性种植,植食性昆虫暴发、物种流失等问题日益突出,化学农药大量应用于作物有害生物的防治更加剧了对农田生态系统的破坏和不稳定性.因此,从生物多样性-农田生态系统-植食性昆虫的相互关系入手,探讨生物多样性的保护及其在农业有害生物防控上的应用,回归农田生态系统动态平衡的生态调控举措,成为可持续发展农业领域中研究的焦点之一.本文综述了农田生物多样性对昆虫生态影响的重要性及其生态功能,进一步阐述了农田生物多样性在农业生产中的应用及前景.