RESUMO
BACKGROUND: Although Beef Quality Assurance guidelines do not recommend use of darting methods to deliver drugs, cattle in the US may be raised on farms and ranches without restraint facilities, and reports from the field suggest that dart guns are being used to deliver antimicrobial drugs. Few studies report whether this route of administration results in altered drug disposition or carcass quality. METHODS: Forty steers were blocked by sire and then randomly assigned to treatment with saline, ceftiofur crystalline free acid, tildipirosin, or tulathromycin delivered via dart gun. To assess drug disposition, eight ceftiofur, six tulathromycin, and six tildipirosin-treated calves were selected to measure plasma concentrations of drugs up to 10 days after drug administration. Steers were then fed a balanced ration for approximately 6.5 months and slaughtered. To evaluate carcass quality, tenderness of steaks from darted-side and non-darted sides was evaluated via Warner-Bratzler shear force testing. Due to the prohibition of extralabel routes of administration for ceftiofur in the U.S., animals treated with this drug did not enter the food supply. RESULTS: Ceftiofur disposition differed from published reports with lower mean Cmax but similar mean apparent elimination half-life. Tildipirosin disposition differed from published reports with lower Cmax and shorter apparent elimination half-life. Tulathromycin was similar to previous published reports but Cmax and apparent elimination half-life was highly variable. All steaks (from darted and non-darted sides) from cattle treated with ceftiofur and saline were more tender than from cattle treated with tulathromycin or tildipirosin (P = 0.003). There was a trend toward more tenderness in steaks from the non-darted compared to the darted side. Steaks from the darted side for one treatment, tildipirosin, were less tender than the non-darted side. CONCLUSIONS: Pharmacokinetic parameters of ceftiofur crystalline free acid, tildipirosin, and tulathromycin to cattle using pressure-adjustable pneumatic gas-powered dart gun were estimated in this study. Delivery of tildipirosin and tulathromycin to cattle with dart gun may also result in detectable decreases in tenderness of harvested steaks.
RESUMO
BACKGROUND: The objective of this study was to determine the renal clearance of flunixin and meloxicam in pigs and compare plasma and urine concentrations and tissue residues. Urine clearance is important for livestock show animals where urine is routinely tested for these drugs. Fourteen Yorkshire/Landrace cross pigs were housed in individual metabolism cages to facilitate urine collection. This is a unique feature of this study compared to other reports. Animals received either 2.2 mg/kg flunixin or 0.4 mg/kg meloxicam via intramuscular injection and samples analyzed by mass spectrometry. Pigs were euthanized when drugs were no longer detected in urine and liver and kidneys were collected to quantify residues. RESULTS: Drug levels in urine reached peak concentrations between 4 and 8 h post-dose for both flunixin and meloxicam. Flunixin urine concentrations were higher than maximum levels in plasma. Urine concentrations for flunixin and meloxicam were last detected above the limit of quantification at 120 h and 48 h, respectively. The renal clearance of flunixin and meloxicam was 4.72 ± 2.98 mL/h/kg and 0.16 ± 0.04 mL/h/kg, respectively. Mean apparent elimination half-life in plasma was 5.00 ± 1.89 h and 3.22 ± 1.52 h for flunixin and meloxicam, respectively. Six of seven pigs had detectable liver concentrations of flunixin (range 0.0001-0.0012 µg/g) following negative urine samples at 96 and 168 h, however all samples at 168 h were below the FDA tolerance level (0.03 µg/g). Meloxicam was detected in a single liver sample (0.0054 µg/g) at 72 h but was below the EU MRL (0.065 µg/g). CONCLUSIONS: These data suggest that pigs given a single intramuscular dose of meloxicam at 0.4 mg/kg or flunixin at 2.2 mg/kg are likely to have detectable levels of the parent drug in urine up to 2 days and 5 days, respectively, after the first dose, but unlikely to have tissue residues above the US FDA tolerance or EU MRL following negative urine testing. This information will assist veterinarians in the therapeutic use of these drugs prior to livestock shows and also inform livestock show authorities involved in testing for these substances.