24 May 2002

DRENCHINGGUNS INSIGHTS

As a tool that may be needed infrequently, but for

long periods when it is used, a sheep drenching gun

needs to be comfortable and efficient as well as

accurate. Mervyn Bailey explores whats on offer

IT MAY be free, but it does not necessarily follow that a complimentary drenching gun is a cheap and cheerful device.

Certainly, cheap throwaway items do come with promotions or as part and parcel of the product. But sometimes, pharmaceutical companies are generous enough to hand out quality gear that is worth looking after.

As a general rule of thumb, that means cleaning it immediately after each days work and storing it ready for the next job in a clean and tidy state. Cleaning is a relatively simple operation that involves setting the drencher to maximum dose and pumping through a solution of washing up liquid and warm water.

Vegetable oil

Then, after rinsing with fresh water and shaking or drying off any excess moisture, it is worth putting some light vegetable or peanut oil around any valves to prevent them sticking. On fully automated guns, there are two valves – one usually located behind the handle or as part of the piston assembly, the second behind the nozzle.

On non-auto guns, it is common to have a single valve, usually located at the nozzle.

Bear in mind that most dosing guns should not be used for applying pour-on treatments, as these tend to be spirit based, in contrast to water based oral doses. Pour-on preparations require a dosing gun with resistant components; otherwise washers and valves will swell and need replacing.

Components becoming worn or damaged can be replaced using service kits including springs, valves and washers.

Most manufacturers can also supply a barrel and piston if the two become seized.

Supplying parts

Local distributors should be able to supply parts, but it will help to provide the exploded diagram and parts list that should be found in the packaging.

When buying a dosing gun, as opposed to taking advantage of a freebie, there are plenty of designs to consider with a range of nozzles and other attachments to suit preferences and different tasks. Key features include total capacity and accuracy of incremental settings so users can be sure of administering the correct dose to animals.

For a drenching gun to be of use throughout the year, it needs to have sufficient volume range to handle a variety of dose volumes and product concentrations. Typically, this will require capacities up to 30ml, but bear in mind that some high capacity drenchers start at 5ml rather than zero, making them useless for low volume administrations.

Auto fill drenching guns, that siphon liquid from a backpack, can be used with a nozzle or needle at high work rates because there is no time wasted refilling. Packs can usually be connected to the gun so neither time nor doses are wasted pouring drench from original packaging to a dedicated container.

For small batches of stock, however, a non-auto fill gun, which needs frequent replenishing, is usually adequate.

The Phillips drenchers available from Cox, the Protector and Defender from Ritchey Tagg and the Sure Shot Dial-a-Dose from Fearing International all have a clear barrel so that when used with a backpack it is easy to see whether the barrel is filling correctly. This can be a problem with thick dosing fluids which sometimes create airlocks in the pipe resulting in inaccurate measures.

Levels of dose are set using a thread or notch arrangement. The notch system has dedicated settings, which are often preferred to screw systems that rely on the operators eye to line up the correct measurement.

When dosing mixed animal groups, it is often easiest to set the chamber to the lowest required setting – for lambs, say – and to give larger animals a sequence of shots adding up to the correct amount.

Dosing technique is also influenced by nozzle type. A standard short nozzle is most popular because it tends to be easier to use in mobile pens where animals are not tightly packed. However, these require the operator to be alongside or in front of the sheep.

A hook nozzle, of the type popular for cattle, allows the operator to work from behind the animal, which may be more convenient in a race or crush. The hook also helps to lift the animals head preventing it from spitting out the dose.

Hook nozzles are either fitted direct to the gun or with a flexible hose between the gun and the metal nozzle.

Some low volume drenching guns are also available with a vaccinating needle attachment; just the thing for making a favourite gun that sits well in the hand more versatile and cost effective to use. &#42

When selecting a drenching gun, it is important to bear in mind handling facilities, animal numbers and dose requirements.

The Ritchey Tagg Defender and Protector dosing guns have a clear barrel so the user can see whether the chamber is filling correctly.