A herd of 277 beef-breed calves in three age groups was mistakenly given the poultry coccidiostat maduramicin in a total mixed ration. It caused an acute toxicosis in which sudden death was the sole clinical finding in most cases. One group of 212 calves aged five to eight months suffered a mortality of 51 per cent in eight days and a total mortality of 56 per cent during the 40 days in which mortality was recorded. Mortality of only 3 per cent was recorded in two other groups of calves aged nine to 16 months in eight days and a total mortality of 11 per cent over the 40-day period.

Broiler chickens are raised under extremely intensive conditions with the emphasis in utilizing every day of their short 35-40 day lifespan to realize the potential of maximum weight gain. If the birds fall behind the planned growth rate there may be reduced profits for the fanner. Therefore, in many modern systems. mean body weight is constantly monitored, and within hours ofdetecting a reduction in projected weight gain, veterinarians and nutritionists can be alerted to fiid the cause of the setback. If a bacterial disease is diagnosed, the whole flock is o h n given feed or water medicated with an antibacterial drug. Ifthe response to this drug is not optimal. or antibiotic sensitivity tests indicate otherwise, another antibacterial agent may be administered. The emcacy of these drugs is dependent upon the dosage administered, the susceptibility of the pathogenic organism to that drug, the pharmaccdynamics of the drug in the broiler (a fairly constant factor which would have been examined in detail by the manufacturer), its pharmacokinetics in the broiler, and acquiring and maintaining a minimum inhibitory concentration (MIC) in the blood. Pharmacokinetics largely involves phase 1 metabolism in the liver mediated by enzymes, collectively called mixed function oxidases (MFO). The activity of the MFO can be elevated or depressed after exposure to many xenobiotics, and the metabolism of certain drugs given concomitantly or thereafter might also be changed.In view of the above facts, it is surprising that the topic of the effects of xenobiotics on MFO in broilers has been so little investigated. Our literature search revealed only three publications on MFO in commercial broiler chickens (Takahashi & Jensen, 1984; Brenes et d., 1985; Brenes et PI., 1990), with no mention of chemotherapeutic agents. Although considerable data exist on the effects of xenobiotics on MFO activity in laboratory animals (Yang et d., 1992), species dflerences (Walker, 1980) preclude a valid extrapolation to broilers and there clearly exists a tremendous knowledge deficit on this topic. Quinolones have been shown to inhibit Ndemethylation In humans (Staib et d.. 1987) and in laboratory anfmals (Mizukl etal.. 1989). but no such studies have been published on this promising group of antimicrobials which are now used in broilers. This work presents data on the d e c t of the ff uomquinolone antibiotic emfloxacin on the activity of MFO in broilers. Onedaydd male commercial broiler chicks were housed in electrically heated battery brooders. Broiler feed was supplied ad libitum throughout. When the birds were 25 days old, they were weighed and birds were chosen in a weight range of 525-650 g. Five gruups of 6-10 birds w e n randomly constituted. Four groups were dosed per os with emfloxacin (Barn, Bayer, Germany), according to the manufacturers' recommendations, at a dose of 10 mgkg body weight each day for 3 consecutive days: these groups diflered only in the time between emfloxacin dosage and MFO determination. One control group received no tr...

No abstract

ABSTRACT:A captive hottlelmose dolphin (Tursiops tfliflcatUS)

The fluoroquinolone antimicrobials norfloxacin and enrofloxacin were found to inhibit hepatic microsomal cytochrome P-450 monooxygenases in the livers of broiler chickens using dosages as given in commercial flocks. Norfloxacin inhibited the process of N-demethylation of aminopyrine to a greater degree, while enrofloxacin more markedly inhibited hydroxylation of aniline.