**1. Introduction**

Surgical husbandry practices carried out on farm animals in many management systems are: castration, docking, disbudding, dehorning, spaying, ear notching, ear tagging, brandinghot, branding-freeze, mulesing, teeth grinding, teeth clipping, tusk grinding, nose ringing, tail nicking, beak trimming. The management of farm animals is based on the ability to control them and many aspects of their environments.

The standards of husbandry and welfare during animal production are becoming important factors influencing consumer perceptions in many markets. Welfare attention on surgical husbandry practices for farm animals focuses on the fact that many of the procedures involve innervated tissues.

One of the approaches available for addressing welfare concerns surrounding these procedures is performing them without pain by the use of local anesthesia.

Food-animal practitioners commonly perform local-anesthetic techniques due to the dangers associated with general anaesthesia. Local anesthetic techniques usually are simple, cheap and have relatively few side effects.

The problems involved in anaesthetizing farm animals for husbandry procedures are usually less complicated than those encountered when local anesthetics have to be used in these animals for experimental purposes where it is important that anesthesia should have little or no influence on the result of the experiment.

Blood serial sampling is required for many applied reproduction and nutrition trials with farm animals. The experimental design of these researches very often includes repeated samplings of large volumes of blood for metabolites and hormones analysis. In addition, the harvested blood can be used for analysis of biochemical, toxicological or immunological parameters, for examination or culture of micro-organisms, for production of antibodies.

The use of topically applied local anesthetics is very useful in removing sensation from the vessel puncture.

There are several features of local anesthesia which render it particularly helpful in veterinary practice. Local anesthetics provide a reversible regional loss of sensation, reduce

Local Anesthesia for Husbandry Procedures and Experimental Purposes in Farm Animals 235

The prilocaine has slower onset of action, and spreads less well compared to lidocaine. The unique ability of prilocaine to cause dose-dependent methemoglobinemia limits its clinical

The proparacaine is used to anesthetize the cornea of the eye. When dropped on the cornea it has a rapid onset of action (within 1 minute) and lasts for about 15-30 minutes. It is

The procaine, an older drug with slow onset of action and poor spreading powers has been

The cocaine is the only one to cause vasoconstriction. It is now not used as a local anesthetic

Newer long acting local anesthetics with less cardiotoxicity, e.g. ropivacaine or lovobupivacaine, are now available for man, but are currently very expensive for veterinary

Reviewing the physiology of nerve conduction is important before any discussion of local anesthetics. Nerves transmit sensation as a result of the propagation of electrical impulses; this propagation is accomplished by alternating the ion gradient across the nerve cell wall,

In the normal resting state, the nerve has a negative membrane potential of -70 mV. This resting potential is determined by the concentration gradients of 2 major ions, Na+ and K+,

The concentration gradients are maintained by the sodium/potassium ATP pump (in an energy-dependent process) that transports sodium ions out of the cell and potassium ions into the cell. This active transport creates a concentration gradient that favors the

In addition, because the nerve membrane is permeable to potassium ions and impermeable to sodium ions, 95% of the ionic leak in excitable cells is caused by K+ ions in the form of an outward flux, accounting for the negative resting potential. The recently identified 2-pore

When a nerve is stimulated, depolarization of the nerve occurs, and impulse propagation progresses. Initially, sodium ions gradually enter the cell through the nerve cell membrane. The entry of sodium ions causes the transmembrane electric potential to increase from the resting potential. Once the potential reaches a threshold level of approximately -55 mV, a rapid influx of sodium ions ensues. Sodium channels in the membrane become activated, and sodium ion permeability increases; the nerve membrane is depolarized to a level of +35

domain potassium (K2P) channels are believed to be responsible for leak K+ currents.

and the relative membrane permeability to these ions (also known as leak currents).

The amethocaine is well absorbed by surfaces and is used on mucous membranes.

usefulness.

use.

or axolemma.

mV or more.

Other local anesthetics are:

nonirritant, and does not affect the size of the pupil.

superseded by the more modern drugs.

**3. Physiology of nerve conduction** 

extracellular diffusion of potassium ions.

because of its potential for abuse.

pain, thereby facilitating surgical procedures. Many surgical procedures can be carried out satisfactorily using different local anesthetics.

Whether or not sedation is necessary as an adjunct will depend on the species, temperament and health of the farm animal, and on the magnitude of the procedure.

Many operations, including some husbandry procedures and practices for experimental purposes, are performed on standing animals. Local anesthesia, enabling protracted operations in standing animals, eliminates the dangers associated with forcible casting and restraint, and prolonged recumbency.

The techniques are not difficult to learn and do not involve the use of expensive or complicated equipment.
