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Abstract

The aim of this study was to determine to what extent the ions present in hard water (125 mg/L of MgCl2 and 500 mg/L of CaCl2) may intensify the feed-induced decrease in oxytetracycline (OTC) absorption rate in broiler chickens after single oral administration at a dose of 15 mg/kg. Drug concentrations in plasma were determined by liquid chromatography-tandem mass spectrometry and combined, compartmental and non-compartmental approach was used to assess OTC pharmacokinetics. The administration of feed decreased the absolute bioavailability (F) of OTC from 12.70%±4.01 to 6.40%±1.08, and this effect was more pronounced after the combined administration of OTC with feed and hard water (5.31%±0.90). A decrease in the area under the concentration- time curve (AUC0-t), (from 10.18±3.24 μg·h/ml in control to 5.13 μg·h/ml±1.26 for feed and 4.26 μg·h/ml±1.10 for feed and hard water) and the maximum plasma concentration of OTC (Cmax) (from 1.22±0.18 μg/ml in control, to 1.01 μg/ml ±0.10 for hard water, 0.68 μg/ml±0.10 for feed and 0.61 μg/ml±0.10 for feed and hard water) was observed. The results of this study indicate that feed strongly decreases F, AUC0-t and Cmax of orally administered OTC. The ions present in hard water increase this inhibitory effect, which suggests that, therapy with OTC may require taking into account local water quality and dose modification, particularly when dealing with outbreaks caused by less sensitive microorganisms.
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Abstract

The aim of this study was to determine the influence of feed on the pharmacokinetics of flumequine (FLU) administered to broiler chickens as follows: directly into the crop (10 mg/kg of BW) of fasted (group I/control) and non-fasted chickens (group II), or administered continu- ously with drinking water (1 g/L for 72 h) and with unlimited access to feed (group III). Plasma concentration of FLU was determined by high-performance liquid chromatography with fluo- rescence detection. In group II, a significant decrease in the maximum concentration (Cmax = 2.13±0.7 μg/mL) and the area under the concentration curve from zero to infinity (AUC0→∞ = 7.47±2.41 μg·h/mL) was noted as compared to the control group (Cmax = 4.11±1.68 μg/mL and AUC0→∞ = 18.17±6.85 μg·h/mL, respectively). In group III, the decrease in AUC was signifi- cant only in the first 3 hours (AUC0→3 = 5.02±1.34 μg·h/mL) as compared to the control group (AUC0→3 = 7.79±3.29 μg·h/mL). The results indicate that feed reduced the bioavailability of FLU from the gastrointestinal tract by at least 50% after the administration of a single oral dose. However, continuous administration of FLU with drinking water could compensate for the feed-induced decrease in absorption after single oral dose.
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Abstract

The present study was conducted to characterize the infectious bursal disease virus (IBDV) circulating in clinically diseased broiler chicken flocks with previous vaccination history during 2015-2016 in Egypt. IBDVs were isolated from 48 out of 63 of the investigated bursae from 10 flocks onto embryonated chicken eggs (ECEs) and verified by reverse transcriptase-poly- merase chain reaction (RT-PCR). Histopathologically, bursae lesions revealed some lymphocytes depletion as well as the presence of vesicles in the lining epithelium. The hyper variable region (HVR) of VP2 and VP1 genes of the 10 isolates (1 isolate/flock) were partially sequenced and subjected to comparative alignment and phyologenetic analysis. Phylogenetically, IBDV isolates were clustered into two distinct genetic lineages: variants of classical virulent (cv) and very viru- lent (vv) IBDV strains based on VP1 and VP2 amino acid (aa) sequences. Alignment analysis of HVR-VP2 aa sequences has demonstrated that the vvIBDV isolates have the conserved residues of the vvIBDV pathotype (A222, I242, and I256), while, the cvIBDV isolates have the same aa sequences of the classical attenuated vaccine strain (D78). Expected single point mutation occurred at position 253 (H253N). All previously characterized isolates were re-subjected to molecular analysis with VP1 protein due to its correlation with virulence and pathogenicity of IBDVs. vvIBDV isolates have the conserved tripeptide (TDN), while, the cvIBDV isolates have aa substitutions at conserved tripeptide including NEG at 145-147 amino acid. The present study has demonstrated that variants of classical virulent and very virulent IBDV circulated among vaccinated flocks in Egypt during 2015-2016.
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