Stable isotopes and gut contents indicate differential resource use by coexisting asp (Leuciscus aspius) and pikeperch (Sander lucioperca)

Differential use of habitat and prey resources is an important mechanism that may allow coexistence of sympatric species. Unlike interactions between smaller cyprinid and percid fishes, the resource use by coexisting predatory asp (Leuciscus aspius) and pikeperch (Sander lucioperca) is relatively unknown. Here, gut content and stable isotope analyses were used to study ontogenetic dietary shifts and interspecific trophic niche overlap between asp and pikeperch coexisting in two reservoirs. The hypothesis that both species show an ontogenetic dietary shift from small invertebrates to large fish prey, but at the same time use different prey resources to reduce potential competitive interactions, was validated. The isotopic niches of the two predators showed no, or only a moderate, degree of overlap (0%–65%). The ontogenetic changes in the degree of interspecific isotopic niche overlap were different in the two reservoirs, suggesting that trophic segregation can be dynamic and variable among systems. Gut contents revealed that small (<100 mm standard length) asp consumed mostly terrestrial invertebrates and emerged aquatic insects, whereas small pikeperch foraged on zooplankton, larval and pupal stages of aquatic insects and fish. Larger individuals (>100 mm) of both species were predominantly piscivorous, with asp consuming more cyprinid prey and pikeperch more percid prey. Coexisting asp and pikeperch populations are able to utilise different prey resources, thereby reducing potential negative competitive interactions.     

Depletion study and estimation of withdrawal periods for florfenicol and florfenicol amine in pacu (Piaractus mesopotamicus)

The intensive production of farmed fish is at a global all‐time high, and the control of bacteria proliferation in fish farms requires the frequent use of antimicrobials. This practice raises important environmental concerns related to the emergence of antimicrobial‐resistant bacteria strains. Only a few antimicrobial drugs have been approved for use in aquaculture, one of which is florfenicol. This work studies the depletion and withdrawal period of florfenicol and its main metabolite, florfenicol amine, in pacu (Piaractus mesopotamicus), a neotropical characin widely farmed in the southern hemisphere. Juvenile pacu (average weight of 724 g) were stocked in a closed‐loop laboratory system with controlled water temperature (25.8°C), and were fed for 10 consecutive days with a diet containing an intended dose of 10 mg/florfenicol per kg bw. Muscle and skin tissues were collected at 1, 3, 6, 8, 10, 12 and 16 days post‐treatment, and florfenicol and florfenicol amine were quantified using a validated ultra‐high performance liquid chromatography‐tandem mass spectrometry (UPLC‐MS/MS) method. The limits of quantitation for florfenicol and florfenicol amine were 10 ng/g in muscle and 50 ng/g in skin. Considering a maximum residue limit of 1000 ng/g for the sum of florfenicol and florfenicol amine in muscle with skin in natural proportions a withdrawal period of 5 days (water temperature 25.8°C) or 129 degree days was calculated on the basis of the upper limit of the one‐sided 95% confidence interval for the 99^th percentile derived from the residue depletion study.     

Bemerkungen über die Populationsbewegungen der Mittelmeerfruchtfliege (Ceratitis capitata Vied.) an der jugoslawischen Adriaküste

Zusammenfassung Untersuchungen über den Massenwechsel und die Biologie der MittelmeerfruchtfliegeCeratitis capitata Vied. während der letzen 5 Jahre führten zu folgenden Ergebnissen:1. Die Mittelmeerfruchtfliege, die bis 1947 in ganz Jugoslawien unbekannt war, kommt seit mindestens zehn Jahren auch an der Adriaküste vor.2. Erst im Jahre 1958 erwies sich die Fruchtfliege als Schädling verschiedener Obstarten.3. Wie aus Beobachtungen in Obstanlagen an der Adriaküste hervorgeht, befällt die Fliege in erster Linie Pfirsich, ferner auch Birne, Kaki, Feige, Apfel, Pflaume, Orange und grünen Paprika. Im Laboratorium gelang die Zucht außerdem noch an Banane, nicht aber an Tomate und Trauben.4. ObwohlC. capitata ein polyphages Insekt ist, befällt sie an einigen Stellen, wo sie regelmäßig große Häufigkeit aufweist, nur Pfirsich (Split, Debeli Rti) bzw. nur Kaki (Ankaran). In manchen Obstgärten lebt sie aber an verschiedenen Früchten (Podstrana, Stroanac). Es gibt bei der Fruchtfliege also auf Obstarten spezialisierte Populationen und solche, die an verschiedenen Obstarten vorkommen.5. Unter den in unserem Küstenland herrschenden Klimabedingungen kann die Fruchtfliege in einem Jahr 4–5 Generationen entwickeln. Die Herbstgeneration verpuppt sich Ende Oktober/Anfang November in der Erde, die Imagines verlassen bis Januar die Puppen und warten auf das Reifen der ersten, frühen Pfirsichsorten. Die gleiche Überwinterungsweise wurde auch an der Olivenfliege beobachtet.6. Mit Angelica-Öl versehene Fanggläser brachten nur zum Teil befriedigende Ergebnisse, da dieser Lockstoff nur die Männchen anzieht, aber auch nur in der Zeit, in der die Fliegen überhaupt selten sind. Im Spätsommer und Herbst wirkt ein aus Kleie und Biammonphosphat bereiteter Köder auf beide Geschlechter stark anlockend.     

Evaluation of the effectiveness of Duddingtonia flagrans and Monacrosporium thaumasium in the biological control of gastrointestinal nematodes in female bovines bred in the semiarid region

Brazil has a herd of 212 million cattle and 171 million hectares of pastures that produce approximately 96 % of Brazilian beef. The Brazilian production system enables animal infection by endoparasites, which are considered one of the main obstacles for the development of this industry and are responsible for considerable economic losses. The control of parasitic diseases is performed via the administration of antiparasitic drugs, but they leave residues of the products in the treated animal, affect non-target organisms and select resistant strains of the parasites. The species D. flagrans and M. thaumasium are promising and sustainable alternatives for controlling gastrointestinal helminths of ruminants and other herbivores. In this study, we evaluated the efficacy of isolates of these species, formulated in a sodium alginate matrix and administered twice a week, to reduce the number of environmental infective larvae of gastrointestinal nematodes that affect prepubescent zebu females. The treated animals presented fewer eggs and a lower number of infective larvae per gram of faeces (p?<?0.05). The pastures occupied by treated animals showed a statistically significant reduction (p?<?0.05) of the number of L₃ and, furthermore, the genera Cooperia sp., Haemonchus sp., and Oesophagostomum sp. were the most prevalent. The average weight of the animals did not differ statistically (p?>?0.05) among the treated and control groups. The use of sodium alginate pellets as vehicle for delivery of the fungus mycelia D. flagrans (isolate AC001) and M. thaumasium (isolate NF34A) proved effective in controlling trichostrongylids in prepubescent cows bred in the semi-arid region, with an effective reduction in the number of infective larvae in the pastures.     

Long-term effects of good handling practices during the pre-weaning period of crossbred dairy heifer calves

The aim of this study was to determine whether applying good practices of handling during the pre-weaning period have long-term effects on behavioral and physiological indicators, health status, and average daily gain (ADG) of crossbred Bos taurus × Bos indicus heifer calves. During the pre-weaning period, 98 crossbred of Holstein × Gir heifer calves were allotted into three treatments: (1) good practices of handling + brushing (GPB; n?=?25), (2) good practices of handling (GP; n?=?25), and (3) control (n?=?48). Every 2 months, four evaluation periods (EV₁ to EV₄) were conducted to record data. Behavioral indicators comprised time to drive (TD), flight speed (FS), flight distance (FD), and composite reactivity score (CRS). Physiological indicators of acute stress during handling comprised respiratory and heart rates. Health status comprised data regarding occurrence of most common diseases (i.e., pneumonia and anaplasmosis). Collected data were analyzed by using a linear mixed model for repeated measures, Tukey’s test, and chi-squared procedures. Treatment influenced (P?<?0.05) TD, FS, and FD but not CRS (P?=?0.78). From EV₁ to EV₃, the control calves had the lowest TD. The GPB group had lower FS than the control but did not differ from GP. The GPB group had lower FD means than the other two groups in EV₂, EV₃, and EV₄. No differences (P?>?0.05) due to treatment were observed on heart and respiratory rates, ADG, or occurrence of pneumonia and anaplasmosis. It was concluded that adoption of good practices of handling during pre-weaning period may lead to long-term positive effects.     

Impact of controlled redox conditions on nickel in a serpentine soil

Purpose  

Serpentine soils exist in many regions around the world; they are naturally enriched with nickel (Ni). An adequate understanding of soil processes determining Ni solubility is a special need particularly since less research has been addressed to Ni behavior under dynamic and controlled redox conditions. Our aim was (1) to characterize the properties of a serpentine soil and (2) to determine the impact of predefined redox windows on the mobility and dynamics of Ni in a serpentine soil.     

Nutrient Digestibility of Cereal Grain Products and By‐products in Extruded Diets for Nile Tilapia

Apparent digestibility coefficients (ADCs) provide estimates of nutrient availability in feedstuffs and can be used as a tool for selecting ingredients to compound cost‐effective diets for fish. Extrusion process is one factor that could influence ADC values. Thus, a digestibility trial was undertaken to evaluate ADC of protein, energy, and dry matter, and apparent amino acid availability (AAAA) in five cereal grain products/by‐products (corn, wheat middlings, broken rice, rice bran, and sorghum) in compounded diets for Nile tilapia. Chromic oxide was used as an external inert marker. The digestibility values of energy and dry matter in ingredients, in decreasing order, were highest for broken rice (95.34 and 96.45%), sorghum (82.37 and 87.29%), corn (67.34 and 82.21%), rice bran (57.58 and 55.59%), and wheat middlings (48.94 and 45.88%). Protein digestibility value was higher for corn (72.86%) and the lowest value was observed for sorghum (56.77%), while broken rice, wheat middlings, and rice bran presented values ranging from 63.01 to 66.88%. AAAA values were higher for corn (70.05%) and the lowest methionine and cystine availability values were recorded for wheat middlings and broken rice, respectively. Broken rice appears as one of the most indicated ingredient for using in Nile tilapia diets because of its highest values of nutrient digestibility when compared to the other energetic sources. The use of this information should aid more precise and economic diet formulation for Nile tilapia.