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• Passive Systems


  Medication is received because of the animal's usual, healthy, and voluntary behaviour. Examples include incorporation into feed or drinking water, and application of a topical preparation by animal actions or movements. Passive systems are generally low on labour cost, but less accurate, in terms of dosage, because animal behaviour is not always consistent or predictable. Passive delivery of a product does not generally require the use of custom designed dispensing equipment since simplicity and low cost of administration are its main benefits.
• Active Systems


  Direct application of medication to individual animals. These are more labour-intensive than a passive system, but more accurate dosage is likely to be achieved. For many active dosing situations widely available standard equipment, such as one of the many variants of the hand operated piston and cylinder syringe system, is adequate. Under some active dosing circumstances power is applied to the system to reduce operator fatigue.
• Factors influencing choice of medication formulation and delivery system


  • Purpose: prophylaxis, therapy, or performance enhancement
  • Dose volume: permitted by regulation; commonly accepted practice; expectation; animal tolerance
  • Route and body site of administration
  • Frequency of dosing
  • Number of animals likely to be dosed per session
  • Accessibility of the animal(s) to be dosed
  • Availability of helpful or necessary animal restraints
  • Age and/or size of the animals to be dosed
  • Skill and cost of personnel likely to be dosing the animals
• Cost of a delivery system


  Influences its design
• Preferences and value to the user

  • Reusable vs. disposable equipment
  • Power assistance
  • Automation
  • Comparative novelty
  • User perceptions
• Balling Guns


  Relatively simple. A barrel, holding one or several boluses, is fitted with a flexible constriction at its tip and a plunger which, when gently depressed by hand, dislodges the bolus through its tip into the oesophagus of the animal.
• Syringes (for oral administration)


  Regular injection syringes can be adapted for direct stomach delivery by attaching a dose tube to the barrel outlet. Flexible tubes from 12 in.
• Tubes


  Syringes, injection (stomach) pumps, and funnels may be used to deliver liquid medication through an oesophageal tube inserted into the stomach through a speculum in the mouth or via a nostril.
• Direct administration of a liquid to the stomach


  • The total dose enters the stomach. Most horses will resist a balling gun to a greater degree than a nasogastric tube, and drenching usually results in a loss of some of the fluid administered.
  • Irritating substances that might otherwise cause oesophageal or pharyngeal lesions can be administered.
  • Feed, water, or medication can be delivered to animals that are unable or refuse to eat.
• Drenchers

  The oral administration of liquid medication to livestock (drenching) is facilitated by a variety of equipment. Nonautomatic: Simple calibrated syringes. Automatic: syringe refills automatically after each dose has been dispensed.
• Paste Dosers


  Pastes or gels, presented in a prefilled syringe, cartridge, squeeze tube, or bottle, are popular with formulators of oral medications because insoluble compounds can be suspended in the paste or gel.
• Injection Needles


  The most common routes of injection for liquids are subcutaneous (SC), intramuscular (IM), and intravenous (IV). Operators have their own preferences of needle length, gauge, and bevel. Injection needles for the common routes are available in reusable or disposable form.
• Syringe Systems

  The withdrawal of a plunger from a barrel creates negative pressure within the barrel; the partial vacuum draws liquid medication into the barrel for volumetric measurement and transportation. All syringe barrels carry volume marks so that users can either check or measure filled and dispensed volumes.
• Sterile Syringe Systems


  A syringe injection system should be sterile at the time of use. Systems that are not supplied sterile, or are not prefilled with sterile medication by the manufacturer, must therefore be able to withstand the sterilization processes available to users. Most commonly these are boiling water or autoclave or a chemical treatment.
• Types of Syringe Systems

  • Single Use: Single-use systems dispense one dose of medication and are then discarded.
  • Single Dose: Single-dose syringes require each dose to be separately filled and dispensed.
  • Simple Multiple Dose: These syringes are most convenient for the injection of a small number of animals, each of which may require a different dose volume.
  • Repeater: Repeater syringes are filled the same way as single-use and simple multiple-dose syringes.
• Automatic Refill Syringe Systems

  The syringe is connected to the medication container. The medication reservoir is inverted, and held above the syringe, to provide gravity flow. The barrel automatically refills after each dose has been dispensed. A vacuum is created in the container as medication is withdrawn by the syringe. If the container is not collapsible, air must replace the withdrawn liquid for the syringe to function efficiently. Most automatic systems are therefore provided with an air inlet valve so that rigid containers can be accommodated.
• One-Handed Syringe Systems


  When the animals to be injected cannot be closely restrained and/or the operator prefers a "slap technique," an instrument that automatically injects the dose when the animal is "hit" may be preferred. The manufacturer's instructions state "with a firm thrust hit the animal at the injection site and then withdraw the instrument. The thrusting motion penetrates the hide and forces the plunger forward, dispensing medication."
• Implants


  The sustained release of a chemical dose can be accomplished by solid-form implantation. The dose may be released from one or a number of pelleted implants.
• Implants (Pellets or Silicone-Coated)

  Growth promoting implants are available in preloaded disposable belts or cylinder cartridges.
• Implanters (Also Known as "Guns")


  Each manufacturer produces its own size and shape of pellets; this requires each to make available its own design of implanter.