Abstract
Piglet castration and tail-docking are routinely performed in the United States without analgesia. Pain medications, predominately non-steroidal anti-inflammatory drugs, are used in the EU/Canada to decrease pain associated with processing and improve piglet welfare, however, past studies have shown the efficacy and required dose remain controversial, particularly for meloxicam. This study assessed the pharmacokinetics of three NSAIDs (meloxicam, flunixin, and ketoprofen) in piglets prior to undergoing routine castration and tail-docking. Five-day-old male piglets (8/group) received one of 3 randomized treatments; meloxicam (0.4 mg/kg), flunixin (2.2 mg/kg), ketoprofen (3.0 mg/kg). Two hours post-dose, piglets underwent processing. Drug concentrations were quantified in plasma and interstitial fluid (ISF) and pharmacokinetic parameters were generated by non-compartmental analysis. Time to peak concentration (Tmax) of meloxicam, flunixin, and S(–)-ketoprofen in plasma were 1.21, 0.85, and 0.59 h, compared to 2.81, 3.64, and 2.98 h in the ISF, respectively. The apparent terminal half-life of meloxicam, flunixin and S(–)-ketoprofen were 4.39, 7.69, and 3.50 h, compared to 11.26, 16.34, and 5.54 h, respectively in the ISF. If drug concentrations in the ISF are more closely related to efficacy than the plasma, then the delay between the Tmax in plasma and ISF may be relevant to the timing of castration in order to provide the greatest analgesic effect.
Highlights
Consumers are becoming increasingly concerned with welfare issues associated with castration and tail-docking of piglets, and this has prompted an increase in the investigation of pain medications to provide analgesia during these procedures
The plasma pharmacokinetics of meloxicam after IM administration were characterized by rapid absorption and a brief apparent terminal half-life (4.46 ± 1.52 h), compared to interstitial fluid (ISF) in which meloxicam persisted for a longer time
Mean plasma and ISF ketoprofen concentrations over time following a single IM injection of 3.0 mg/kg are presented in Following intramuscular administration of 0.4 mg/kg meloxicam, the peak plasma concentration was reached in 1.21 h, which was delayed compared to the previously reported 0.50 h in 8-day-old piglets given an intramuscular dose of 1 mg/kg [17]
Summary
Consumers are becoming increasingly concerned with welfare issues associated with castration and tail-docking of piglets, and this has prompted an increase in the investigation of pain medications to provide analgesia during these procedures. In the United States, husbandry procedures such as castration, tail-docking, teeth clipping, ear notching/tagging, and injections are collectively referred to as “processing” of piglets. Commercial farms in the United States routinely perform processing procedures (including castration and tail docking) without anesthesia or analgesia, despite the fact that these procedures are painful and distressing to piglets [1,2,3,4,5,6,7]. While currently there is no requirement for the provision of analgesics for piglets in the US, legislation in the EU and Canada requires that surgical castration of piglets should be performed with anesthesia and/or analgesia [8, 9]. Routine tail docking is forbidden in the EU and may only be performed when there is evidence that tail biting has occurred [10]
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