The adoption of drones in German agriculture: a structural equation model

Drones are one of the latest tools to have been added to farmers’ precision agriculture technology tool kit. Despite the proclaimed benefits, adoption rates of drones are low and literature regarding the adoption of drones in agriculture is scarce. Therefore, this study investigates whether an extended Technology Acceptance Model (TAM) can contribute to the understanding of latent factors influencing farmers’ intention to adopt a drone. The sample of 167 German farmers was collected in 2019 via an online survey. Using partial least squares structural equation modelling and a binary model, the TAM explains 69% of the variance in the intention to use a drone by German farmers. According to the results, raising farmers’ awareness of farm-specific areas of drone application and the confidence level of using a drone can increase farmers’ intention to adopt a drone. The results are of interest for agribusinesses developing drones as well as selling or providing drones. Furthermore, the results are of interest for researchers in precision agriculture technologies.

     

Experimental enteric infection of gnotobiotic piglets with Chlamydia suis strain S45

Enteric chlamydial infections of pigs with Chlamydia (C.) suis are frequent and often subclinical. The enteric pathogenicity of C. suis strain S45 was investigated in gnotobiotic piglets. Piglets from three litters (n=31) were inoculated with egg-grown chlamydiae at 2-3 days of age (n=17) or used as controls (n=14). They were observed for clinical signs, killed and necropsied sequentially at 2-13 days postinoculation (DPI). Feces were collected daily and investigated with an ELISA for chlamydial antigen. At necropsy, specimens were collected for histopathology and for immunohistochemical, PCR-based, and serological (complement fixation test, ELISA) detection of chlamydiae. Chlamydial replication and associated symptoms and lesions were observed from 2 to 13 DPI and were particularly pronounced within the first week PI. Clinical symptoms consisted of moderate-to-severe diarrhea, slight and transient anorexia, weakness and body weight loss. Immunohistochemistry and ELISA revealed that chlamydial replication was particularly marked at 2-4 DPI and primarily located in the small intestinal villus enterocytes. Further sites of replication included large intestinal enterocytes, the lamina propria and Tunica submucosa, and the mesenteric lymphnodes. Histopathological changes included moderate-to-severe villus atrophy with flattened enterocytes and focal villus tip erosions, and moderate mucosal inflammatory cell infiltrates and lymphangitis in the small intestine. PCR of spleen tissue and blood was mostly negative for chlamydiae, indicating that they did not substantially disseminate into the host up to 13 DPI. All sera were negative for anti-chlamydial antibodies. In conclusion, C. suis strain S45 elicited significant enteric disease and lesions in gnotobiotic piglets indicating its pathogenic potential for swine.     

OmpA and antigenic diversity of bovine Chlamydophila pecorum strains

Infections with the intracellular bacterium Chlamydophila (C.) pecorum are highly prevalent worldwide in cattle. These infections cause significant diseases such as polyarthritis, pneumonia, enteritis, genital infections and fertility disorders, and occasionally sporadic bovine encephalomyelitis. Subclinical respiratory infections of calves with C. pecorum have been associated with airway obstruction, pulmonary inflammation, and reduced weight gains. This investigation examined four chlamydial strains with biological properties of C. pecorum isolated from feces of clinically normal cattle, from calves with pneumonia, and from bulls with posthitis. The objective was to characterize the evolutionary relationships of these bovine chlamydial isolates to other chlamydiae by genetic analysis of the ompA gene, and by the immunological cross-reactivities in Western immunoblot analysis. PCR typing of the ompA gene identified these isolates as C. pecorum. The OmpA-deduced amino acid dissimilarities between these four strains spanned 10-20%. In phylogenetic analysis, the four isolates clustered with C. pecorum ruminant, porcine, and koala strains of different geographic origins rather than with each other. All four isolates showed different patterns of Western immunoblot reactivity with antiserum against bovine C. pecorum strain LW63, and, interestingly, no cross-reactivity of the OmpA proteins with the anti-LW613 OmpA antibodies. These data underscore the polyphyletic population structure of C. pecorum and suggest that the spectrum of C. pecorum OmpA proteins in a host species can occupy the entire evolutionary bandwidth within C. pecorum. The variant immunoblot reactivities support the notion of considerable genomic plasticity of C. pecorum.     

Course of infection and immune responses in the respiratory tract of IBV infected broilers after superinfection with E. coli

Colibacillosis results from infection with avian pathogenic Escherichia coli bacteria. Healthy broilers are resistant to inhaled E. coli, but previous infection with vaccine or virulent strains of Infectious Bronchitis Virus (IBV) predisposes birds for severe colibacillosis. The aim of this study was to investigate how IBV affects the course of events upon infection with E. coli. Broilers were inoculated with IBV H120 vaccine virus or virulent M41 and challenged 5 days later with E. coli 506. A PBS and E. coli group without previous virus inoculation were included. Sections of trachea, lung and airsacs were stained for CD4, CD8, gammadelta-TCR, alphabeta1-TCR, and for macrophages (KUL-01) and both pathogens. Changes in the mucociliary barrier of trachea, lung and airsacs did not predispose for bacterial superinfection. The disease in the lungs of the E. coli group and both IBV/E. coli groups was similar. Lesions in the airsacs were more pronounced and of longer duration in the IBV/E. coli groups. The immunocytological changes differed substantially between the E. coli group and both IBV/E. coli groups. In trachea, lungs and airsacs the CD4+ and CD8+ populations were significantly larger than in the E. coli and PBS groups. In the lungs and the airsacs the macrophages were more numerous in the IBV/E. coli and the E. coli groups than in the PBS group. The presence of high numbers of T cells and macrophages in IBV infected birds most likely induced an altered immune response, which is responsible for the enhanced clinical signs of colibacillosis.     

Dingeman van der Vliet,veterinary artist, 1792-1866

Dingeman van der Vliet (1792-1866) from Zierikzee in province of Zeeland, was one of the first officially trained veterinarians in the Netherlands. He was sent to Paris on the order of Louis Napoleon, king of Holland, at the expense of the Dutch government. In the period of his stay at the Veterinary School in Alfort (1808-1811) he wrote a great number of letters to his parents and friends. His letters give insight in the daily life of the school in Alfort and the festivities in Paris during the reign of the emperor Napoleon Bonaparte. In a second article, the laborious built-up of a veterinary practice in those days will be described.     

Feeds and Feeding Schedules for Indoor Nursery Culture of Postlarval Freshwater Prawns Macrobrachium rosenbergii1

Potential feeds, feeding schedules, and feed supplements for growing M. rosenbergii postlarvae to a juvenile size of 0.5 g were evaluated. Postlarvae were grown in 69 L aquaria for 6 to 9 weeks at densities of 1.3 or 2.0/L at a water temperature of 28 C. An experimental diet (HFX-EXD-86X) and four commercially available feeds (Purina Trout Chow No. 2, Silver Cup Fish Feed—Salmon No. 3, Zeigler Shrimp Post Larval Granules No. 3, and MFC Clover Brand 38% Catfish Fingerling Crumbles) were tested. Prawns fed Purina Trout Chow No. 2 had the best survival and yield. Four feeding schedules were then evaluated with Purina Trout Chow No. 2 as the only food: once daily (at 1600 h), twice daily (at 0800 and 1600 h), twice daily (at 0800 and 2000 h), and three times daily (at 0800, 1600, and 2400 h). Prawns in the oncedaily treatment exhibited the best survival, final weight, yield, and food conversion ratio. A oncedaily frequency was then used to test the effects of supplementing the Purina diet with beef liver, squid mantle, codfish muscle, or cooked (scrambled) chicken egg, at 20% dry weight of the total diet. Prawns fed the beef liver supplement had the best final weight and yield.     

A wind density model to quantify the airborne spread of Culicoides species during north-western Europe bluetongue epidemic, 2006

Increased transport and trade as well as climate shifts play an important role in the introduction, establishment and spread of new pathogens. Arguably, the introduction of bluetongue virus (BTV) serotype 8 in Benelux, Germany and France in 2006 is such an example. After its establishment in receptive local vector and host populations the continued spread of such a disease in a suitable environment will mainly depend on movement of infected vectors and animals. In this paper we explore how wind models can contribute to explain the spread of BTV in a temperate eco-climatic setting. Based on previous work in Greece and Bulgaria filtered wind density maps were computed using data from the European Centre for Medium-Range Weather Forecasts (ECMWF). Six hourly forward wind trajectories were computed at pressure levels of 850hPa for each infected farm as from the recorded onset of symptoms. The trajectories were filtered to remove wind events that do not contribute to possible spread of the vector. The suitable wind events were rastered and aggregated on a weekly basis to obtain weekly wind density maps. Next to this, cumulated wind density maps were also calculated to assess the overall impact of wind dispersal of vectors. A strong positive correlation was established between wind density data and the horizontal asymmetrical spread pattern of the 2006 BTV8 epidemic. It was shown that short (<5km), medium (5-31km) and long (>31km) distance spread had a different impact on disease spread. Computed wind densities were linked to the medium/long-distance spread whilst short range spread was mainly driven by active Culicoides flight. Whilst previous work in the Mediterranean basin showed that wind driven spread of Culicoides over sea occurred over distances of up to 700km, this phenomenon was not observed over land. Long-distance spread over land followed a hopping pattern, i.e. with intermediary stops and establishment of local virus circulation clusters at distances of 35-85km. Despite suitable wind densities, no long range spread was recorded over distances of 300-400km. Factors preventing spread Eastwards to the UK and Northwards to Denmark during the 2006 epidemic are discussed. Towards the east both elevation and terrain roughness, causing air turbulences and drop down of Culicoides, were major factors restricting spread. It is concluded that the proposed approach opens new avenues for understanding the spread of vector-borne viruses in Europe. Future developments should take into consideration both physical and biological factors affecting spread.     

Water quality and waste production in a recirculating trout-culture system with feeding of a higher-energy or a lower-energy diet

Higher-energy fish feeds can reduce waste discharges and might also improve water quality in recirculating fish-culture systems. A higher-energy diet, Zeigler Salmon High Energy feed (HE; 45% protein, 20% fat, 17.4 MJ digestible energy kg^-1) and a lower-energy diet, Zeigler Hi-Fat Trout Grower (LE; 38% protein, 12% fat, 14.6 MJ digestible energy kg ^-1) were fed ad libitum at different times to rainbow trout, Oncorhynchus mykiss (Walbaum), in a semi-closed recirculating culture system by means of demand feeders. The system contained two 10-m³ fish-culture tanks, each with a downstream microscreen (80 μn) filter. Feeding rates per day and per unit biomass were not significantly different between diets. In general, use of HE was associated with higher levels of total ammonia nitrogen (TAN) and NO₂-N, lower BOD₅ and total suspended solids (TSS), and lower effluent releases of suspended solids per unit feed, NO₃-N per unit feed, and dissolved phosphorus per unit feed. Although total effluent P per unit feed or P fed did not differ significantly between diets, HE had significantly more of the total effluent P in the settleable solids, 85% vs. 76%. Differences in water quality in the system were probably not of great importance with respect to fish health.