Anti-inflammatories are one of the most administered drugs in livestock species and they can be used as adjuvants in the treatment of infectious diseases (e.g., sepsis), as antipyretics or to deal with localized inflammatory processes (such as arthritis).
Trends and opinions about animal welfare have changed over the years increasing the focus on the pain management in livestock.
Nowadays it is thought that even minor surgical procedures should be performed using combinations of different types of anesthesia, such us regional, local and general, and also with uninterrupted post-surgical analgesia.
Tail docking, castration and/or ear tattooing/tagging are procedures that require pain control, but this is not always implemented. For instance, although castration is known to be a painful procedure, based on specific behavioral and physiologic indicators, yet piglets do not generally receive any anesthesia for pain relief. Furthermore, there are situations such as prolapses, fractures or bites where animals suffer and pain could be reduced or eliminated.
Besides any ethical consideration, economical losses associated to reduction in appetite and growth retardation are also a problem. For example, Swine Respiratory Disease (SRD in growing and finishing pigs limits herd profitability, due to:
Types of anti-nociceptive drugs that can be administered to swine include:
• Non-steroidal anti-inflammatory drugs (NSAID): they are broadly used in animal production practice to relieve the adverse effects associated with the inflammatory cascade such as excessive swelling, fever or pain. The aim of using NSAIDs is to improve the welfare of the animals and recover their performance, that is often impaired by chronic pain, inflammation and fever. NSAIDs inhibit cyclooxygenase in a reversible and non-selective way and they have less secondary effects than SAIDs.
• Local analgesics. This class of drugs, such as lidocaine, are useful in reducing nociception signs during castration.
• Steroidal anti-inflammatory drugs (SAID): they are indicated for the treatment of muscular and joint inflammatory processes, meningitis, etc. Dexamethasone is one of the drugs most used in pigs within this category.
The principal mechanism of action of NSAIDs is the inhibition of cyclooxygenase (COX), which inhibits the synthesis of prostaglandins (PG). Pro-inflammatory PGs have two important roles in the inflammation process:
1. Hyperalgesia (abnormally increased sensitivity to pain). 2. Dilate the arterioles, increasing blood flow to the area of injury
There are many COX inhibitors, and among the non-selective ones two main groups of NSAIDs are present:
Many studies show that NSAIDs administered to:
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