African swine fever (ASF) was officially reported in Vietnam in February 2019 and spread across the whole country, affecting all 63 provinces and cities. In this study, ASF virus (ASFV) VN/Pig/HaNam/2019 (VN/Pig/HN/19) strain was isolated in primary porcine alveolar macrophage (PAM) cells from a sample originating from an outbreak farm in Vietnam’s Red River Delta region. The isolate was characterised using the haemadsorption (HAD) test, real-time PCR, and sequencing. The activity of antimicrobial feed products was evaluated via a contaminated ASFV feed assay. Phylogenetic analysis of the viral p72 and EP402R genes placed VN/Pig/HN/19 in genotype II and serogroup 8 and related it closely to Eastern European and Chinese strains. Infectious titres of the virus propagated in primary PAMs were 10⁶ HAD₅₀/ml. Our study reports the activity against ASFV VN/Pig/HN/19 strain of antimicrobial Sal CURB RM E Liquid, F2 Dry and K2 Liquid. Our feed assay findings suggest that the antimicrobial RM E Liquid has a strong effect against ASFV replication. These results suggest that among the Sal CURB products, the antimicrobial RM E Liquid may have the most potential as a mitigant feed additive for ASFV infection. Therefore, further studies on the use of antimicrobial Sal CURB RM E Liquid in vivo are required. Our study demonstrates the threat of ASFV and emphasises the need to control and eradicate it in Vietnam by multiple measures.

The authorisation of tylosin as feed additive was withdrawn for reasons of human health concerning resistance of pathogenic bacteria. An analytical method for the identification and quantification of tylosin in animal feed was developed and validated. The samples were extracted using an acidified methanol:water mixture and solid-phase extraction was employed for the isolation of the antibiotic from diluted feed samples. Tylosin was analysed by liquid chromatography with electrospray ionisation mass spectrometric detection. The method’s performance was evaluated in adherence to the Commission Decision 2002/657/EC. The recovery of the analyte from spiked samples was determined to be in the range from 78.9% to 108.3% depending on tylosin concentrations. The CCα and CCβ values for tylosin in feeds were determined at 0.085 mg kg⁻¹ and 0.091 mg kg⁻¹, respectively. The method detection limit was found to be 0.035 mg kg⁻¹ and the quantification limit 0.05 mg kg⁻¹. The applicability of the developed method was tested by analysing real feed samples. A reliable LC-MS method was developed to identify and quantify tylosin in animal feed with a good repeatability and a high specificity and sensitivity. Because of these characteristics, the proposed method is applicable and could be deemed necessary within the field of feed control and safety.

The rearing of calves is a difficult period for farmers due to health problems to which the animals are prone this time. Since the use of antibiotics as growth promoters has been forbidden, various innovative feed additives have been tested in many countries around the world. In this study, experimental (E) calves were supplemented with a novel feed additive consisting of the pancreatic-like enzymes protease and lipase, a fat-coated mixture of organic fumaric, malic, citric and sorbic acids, sodium butyrate and silicon dioxide nanoparticles. Control (C) calves received feed without additive. During the supplementation, white blood cell (WBC) counts with leukocyte differentiation, percentages of B lymphocytes and T lymphocytes and their subpopulations, phagocytic activity and oxidative burst of circulating monocytes and granulocytes were examined. Body weight (b.w.) gains of the calves were also monitored. The WBC counts in the E and C calves were within the reference ranges throughout the study. In the analysis of the percentages of the lymphocyte subpopulations, phagocytic activity and oxidative burst, no statistically significant differences were reported between the E and C groups. However, higher average daily body weight gains were obtained for the E calves. The study revealed that the examined feed additive did not modulate the immune response of the calves significantly. The tendency to higher daily average b.w. gains in the E calves than in the C calves suggests a beneficial effect of this feed additive.

Some azo dyes, including Sudans I–IV and Para Red, are genotoxic and may be biotransformed to cancerogenic aromatic amines. They are banned as food and feed additives, but their presence has been detected in food. Aromatic amines are also considered potentially toxic. Online EC–MS is a promising tool to study the transformation mechanisms of xenobiotics such as azo dyes. The aim of the study was to investigate emulation of how azo dyes are enzymatically transformed to amines with EC–MS. The reduction reactions of five azo dyes (Sudans I–IV and Para Red) were conducted using a glassy carbon working electrode and 0.1% formic acid in acetonitrile. Reduction results were compared with the literature and in silico to select preliminary candidates for metabolites. The LC-MS/MS method was used to confirm results obtained by electrochemical reactor. A limited number of pre-selected compounds were confirmed as azo dyes metabolites – aniline for Sudan I, aniline and 4-aminoazobenzene for Sudan III, o-toluidine for Sudan IV, and 4-nitroaniline for Para Red. No metabolites were found for Sudan II. Electrochemistry–mass spectrometry was successfully applied to azo dyes. This approach may be used to mimic the metabolism of azo dyes, and therefore predict products of biotransformation.

An observational study was conducted of chicken and turkey flocks slaughtered at federal processing plants in the province of Quebec, Canada. The objectives were to estimate prevalence of drug use at hatchery and on farm and to identify antimicrobial resistance (AMR) in cecal Escherichia coli and Enterococcus spp. isolates and factors associated with AMR. Eighty-two chicken flocks and 59 turkey flocks were sampled. At the hatchery, the most used antimicrobial was ceftiofur in chickens (76% of flocks) and spectinomycin in turkeys (42% of flocks). Virginiamycin was the antimicrobial most frequently added to the feed in both chicken and turkey flocks. At least 1 E. coli isolate resistant to third-generation cephalosporins was present in all chicken flocks and in a third of turkey flocks. Resistance to tetracycline, streptomycin, and sulfisoxazole was detected in > 90% of flocks for E. coli isolates. Antimicrobial resistance (AMR) was observed to bacitracin, erythromycin, lincomycin, quinupristin-dalfopristin, and tetracycline in both chicken and turkey flocks for Enterococcus spp. isolates. No resistance to vancomycin was observed. The use of ceftiofur at hatchery was significantly associated with the proportion of ceftiofur-resistant E. coli isolates in chicken flocks. In turkey flocks, ceftiofur resistance was more frequent when turkeys were placed on litter previously used by chickens. Associations between drug use and resistance were observed with tetracycline (turkey) in E. coli isolates and with bacitracin (chicken and turkey), gentamicin (turkey), and tylosin (chicken) in Enterococcus spp. isolates. Further studies are needed to provide producers and veterinarians with alternative management practices and tools in order to reduce the use of antimicrobial feed additives in poultry.

The aim of this study was to evaluate the antimicrobial activity and determine the minimum bactericidal concentration (MBC) of the essential oils derived from Origanum vulgare (oregano), Melaleuca alternifolia (tea tree), Cinnamomum cassia (cassia), and Thymus vulgaris (white thyme) against Salmonella Typhimurium, Salmonella Enteritidis, Escherichia coli, Staphylococcus aureus and Enterococcus faecalis. The study also investigated the ability of these different bacterial strains to develop adaptation after repetitive exposure to sub-lethal concentrations of these essential oils. The MBC of the essential oils studied was determined by disc diffusion and broth dilution methods. All essential oils showed antimicrobial effect against all bacterial strains. In general, the development of adaptation varied according to the bacterial strain and the essential oil (tea tree > white thyme > oregano). Therefore, it is important to use essential oils at efficient bactericidal doses in animal feed, food, and sanitizers, since bacteria can rapidly develop adaptation when exposed to sub-lethal concentrations of these oils.