Tylosin [HRP]

A new multi-compound method for the analysis of veterinary drugs, namely tiamulin, trimethoprim, tylosin, sulfadiazine and sulfamethazine was developed and validated in medicated feeds. After extraction, the samples were centrifuged, diluted in Milli-Q water, filtered and analysed by high performance liquid chromatography coupled to tandem mass spectrometry. The separation of the analytes was performed on a biphenyl column with a gradient of 0.1% formic acid in acetonitrile and 0.1% formic acid in Milli-Q water. Quantitative validation was done in accordance with the guidelines laid down in European Commission Decision 2002/657/EC. Method performances were evaluated by the following parameters: linearity (R-2 < 0.99), precision (repeatability <14% and within-laboratory reproducibility <24%), recovery (73.58-115.21%), sensitivity, limit of detection (LOD), limit of quantification (LOQ), selectivity and expanded measurement uncertainty (k. = 2). The validated method was successfully applied to the 2 medicated feeds obtained from the interlaboratory studies and feed manufactures from Spain in August 2017. In these samples, tiamulin, tylosin and sulfamethazine were detected at the concentration levels declared by the manufacturers. The developed method can therefore be successfully used to routinely control the content and homogeneity of these antibacterial substances in medicated feed.

Red osier dogwood (ROD; Comas sericea) is an abundant native shrub plant across North America and it is rich in bioactive compounds with total phenolic concentration up to 220 g/kg dry matter (DM) depending on the season. The phenolics include anthocyanins, gallic acid, ellagic acid, quercetin, and cyanin, which have both antioxidant and antimicrobial properties. The objective of this study was to determine the effect of increasing substitution of ROD for barley silage in a high-grain diet on DM intake, ruminal pH and fermentation, digestibility in the total digestive tract, blood metabolites and acute phase response in beef heifers. Five ruminally cannulated Angus heifers (averaged body weight of 660 +/- 40.8 kg; initial age of 18 months) were used in a 5 x 5 Latin square design with 21-d periods including 14 d for adaptation to new diets and 7 d for data collection. Treatments were a control diet containing 150 g/kg barley silage and 850 g/kg barley concentrate mix (DM basis), the control diet substituted with 30, 70 or 100 g/kg of ROD for equal proportions of barley silage, respectively, and the control diet supplemented with antibiotics (330 mg monensin +110 mg tylosin/heifer/d). Apparent digestibility was determined using Cr2O3 as external marker by sampling feces from the rectum. Intake of DM quadratically (P < 0.02) increased with increasing the substitution of silage for ROD. Mean ruminal pH were not affected by diets, and no effects of diets on total volatile fatty acid (VFA) concentration were observed. However, ruminal NH3-N concentration linearly (P < 0.01) decreased with increasing ROD feeding. Digestibility of DM linearly (P < 0.04) increased with increasing dietary ROD. Increasing ROD feeding also linearly increased plasma concentration of haptoglobin (P < 0.01) and concentration of serum amyloid A (P < 0.06). Compared with antibiotic group, feeding ROD resulted in greater (P < 0.01) intake and digestibility of DM, and greater (P < 0.05) VFA concentration. These results indicate greater feed value of ROD versus barley silage in high-grain diets. Feeding ROD potentially improves immune status and antioxidant activity in finishing beef heifers. Beef cattle fed ROD performed better or at least equal to antibiotics currently used in beef cattle rations and it could be used as a natural alternative for beef cattle production.