Determination and kinetics of enrofloxacin and ciprofloxacin in Tra catfish (Pangasianodon hypophthalmus) and giant freshwater prawn (Macrobrachium rosenbergii) using a liquid chromatography/mass spectrometry method

Determination and kinetics of enrofloxacin and ciprofloxacin in Tra catfish (Pangasianodon hypophthalmus) and giant freshwater prawn (Macrobrachium rosenbergii) using a liquid chromatography/mass spectrometry method. J. vet. Pharmacol. Therap. 34, 142-152. The fluoroquinolones enrofloxacin (EF) and ciprofloxacin (CF) residues were investigated in the edible tissues of two important Asian aquacultured species such as Tra catfish (Pangasianodon hypophthalmus) and giant freshwater prawn (Macrobrachium rosenbergii) using a sensitive liquid chromatography-electrospray ionization-tandem mass spectrometry method. Fish and prawn were treated with medicated feed with multiple doses of EF, in field conditions. A validation study of the analytical method was realized in terms of linearity, specificity, precision (repeatability and within-laboratory reproducibility), recovery and decision limit (CCα). The time needed before the antibiotic disappears from animal tissues or reach the maximum residue limit (MRL, 100μg/kg) was assessed. The concentration values of EF detected in Tra catfish tissue were between the MRL and 2×MRL concentrations, according to the fish density, 7days following the end of the enrofloxacin treatment (20mg/kg body weight per day, for seven consecutive days). The concentration value of ER in prawn tissue was lower than the MRL and the limit of quantification (LOQ, 14μg/kg) 5 and 7days after the stop of the EF treatment (50mg/kg body weight per day, for five consecutive days), respectively. The mean detected levels of CF was much lower in comparison with that of EF, indicating that only a small part of EF is metabolized into CF (<5%) in both Tra catfish and prawn.     

Technical note: Development of an enzyme-linked immunosorbent assay for the determination of florfenicol and thiamphenicol in swine feed

One polyclonal antibody against florfenicol and thiamphenicol was produced and a competitive ELISA was developed for the detection of florfenicol and thiamphenicol in swine feed. The ELISA gave a 50% inhibiting concentration of 1.02 ng/mL for florfenicol. For swine feed fortified with 0.05 to 3.0 mg/kg, the interassay recoveries of florfenicol and thiamphenicol ranged from 86.4 to 118.6%, whereas intraassay recoveries of both drug ranged from 90.1 to 126.5% with less than 15% CV. Results obtained from HPLC-tandem mass spectrometry indicated this ELISA procedure could be used as a convenient method for rapid screening of florfenicol and thiamphenicol in swine feed.     

全球禽肉生产和贸易中的沙门菌风险评估与控制

1 禽源沙门菌对公共卫生的影响 在许多国家,沙门菌仍是引发食源性肠道疾病的主要原因.沙门菌通常存在于家畜、家禽中,也可在啮齿类、爬行类和鸟类等野生动物中发现.当农场的禽群感染沙门菌后,通常会有一部分家禽的消化道中携带沙门菌,但并无症状.随后,沙门菌可能会通过粪便污染感染动物屠体.     

Metabolism of microbial nitrogen in ruminants with special reference to nucleic acids

Characteristically the metabolism of microbial nitrogen (N) compounds in ruminants involves the degradation of dietary N and synthesis of microbial protein (MP), compounds including a small amount of peptides and free amino acids, which may account for 75–85% of total N and the remainder are nucleic acids (NA: DNA and RNA). Generally rumen microbes contain 10–25% NA‐N of the total N while 70–80% is in the form of RNA. This paper describes the degradation and synthesis of NA in the rumen and their fate in the lower digestive tracts. Their physiological and nutritional significance in different types of ruminant animals is also discussed. The research works on NA metabolism in ruminants has been mainly on metabolism of purines after rumen microbial digestion and absorption in the lower gut. Subsequently, the fate of absorbed purines has been intensively investigated to assess the extent of MP synthesis in the rumen. The method for predicting ruminal synthesized MP and subsequently digested MP has been proposed using urinary purine derivative (PD) excretion in sheep and cattle fed on ordinary feed. The latter approach has now been adopted for calculation of protein supply in some feeding standards, although there are still difficulties in predicting representative samples of rumen microbes, and also uncertainties in variations of non‐renal and endogenous purine losses.     

Monoclonal antibodies to sheep MHC class I and class II molecules: biochemical characterization of three class I gene products and four distinct subpopulations of class II molecules

The availability of a panel of monoclonal antibodies to sheep MHC class I and class II gene products has allowed for the first time an assessment of the relative complexity of the sheep MHC. By using four monoclonal antibodies to MHC class I, and seven monoclonal antibodies to MHC class II molecules together with one-dimensional SDS-PAGE, sequential immunoprecipitation and 2-dimensional gel analysis, three class I gene products and four distinct subsets of class II molecules have been identified. Sheep class I molecules showed heterogeneity on 2-dimensional gels and as in mouse and man, represented the products of at least three different non-allelic class I genes. Interestingly, the sheep beta 2 microglobulin molecule also displayed heterogeneity, consistent with either two primary gene products or allelic variation. Four sheep class II monoclonal antibodies identified distinct, non-overlapping subsets of sheep class II molecules of Mr 32-36 K (alpha chain) and 25-28 K (beta chain). These class II molecules were co-expressed on sheep B lymphocytes and represented the primary products of different sheep MHC class II genes. The class II molecules within three of these subsets displayed allelic polymorphism essentially restricted to their beta polypeptides, while the fourth subset of class II molecules showed allelic variation in both their alpha and beta polypeptides. The results of this study represent the first evidence for gene duplication and heterogeneity within the sheep MHC. The identification of three primary class I gene products and four distinct subsets of class II molecules suggests three class I loci and up to four distinct class II subregions within the sheep MHC. Potentially large numbers of allelic variants of these different gene products may be expressed in normal sheep.     

Two cases of IgA multiple myeloma in the dog

Clinical and laboratory findings are presented from two cases of canine IgA multiple myeloma. One of these animals presented with typical clinical and pathological changes including haematological abnormalities and skeletal lesions with secondary invasion of other organs. In contrast, the primary focus of disease in the second dog was the anterior alimentary tract and there were no skeletal changes. In this respect this second case was similar to the condition in man known as alpha chain disease. The two paraproteins differed in electrophoretic mobility.     

Use of ev loci as a measure of inbreeding in domestic fowls

1. The endogenous avian leukosis virus (ev) loci present in 9 lines of domestic fowls have been partially characterised and the average heterozygosity of the loci in each line calculated. 2. Using these data an estimate of the coefficient of inbreeding of the lines was derived; this estimate of the extent of inbreeding is compared with the mating history of the lines. 3. This method provides the first means of directly assessing the degree of inbreeding of fowl lines: assumptions implicit in the method are discussed.     

A zinc-containing intraruminal device for facial eczema control in lambs

A zinc-containing intraruminal device has been developed for protecting lambs against facial eczema. The rate of release of zinc from the device has been optimised, and its safety in use established. Under both experimental and farm conditions, the device gave excellent protection against the liver injury associated with facial eczema. The device relies upon erosion for release of zinc, and disappears completely when its charge of zinc has been released, leaving no metal or plastic residue in the rumen. This device has the potential to greatly ameliorate the problem of facial eczema in New Zealand.