How to Drench a Sheep or Calf Correctly

Knowing how to drench a sheep — or a calf — correctly is a basic but high-stakes skill on any livestock farm. Drenching delivers liquid medicine (usually a wormer) straight into the animal's mouth with a drenching gun, and done properly it is fast, cheap and effective. Done badly, it can send liquid into the lungs, under-dose animals and breed drug-resistant worms. The difference is a handful of techniques that every stockman can learn: the right tool, the right hold, the right head position and honest dose calibration. This guide walks through each step for sheep and calves.

What a Drench Gun Does — and How It Fails

A drench gun meters a set dose of liquid and delivers it through a nozzle into the mouth, over the tongue and toward the back of the throat, where the animal swallows it into the esophagus — not the windpipe.

Three common failures:

1. Aspiration — liquid enters the trachea and lungs, causing pneumonia or sudden death. This is the most serious risk and is usually caused by the head being tipped too far back.
2. Under-dosing — an uncalibrated gun or guessing doses by eye leaves worms alive and selects for drench resistance.
3. Injury — a worn or jagged nozzle can cut the mouth and throat, and repeated stress makes animals harder to handle next time.

Choosing the Right Drenching Gun

Match the gun to the animal class and dose volume:

Practical buying points:

• Volume accuracy matters more than capacity. An adjustable gun that locks per-dose volume lets you set the exact ml per animal.
• Automatic (trigger) guns suit large mobs — they refill and re-dose continuously for fast throughput.
• Choose a gun with a smooth, rounded nozzle tip and replace worn nozzles before they roughen.
• Buy from a supplier who stocks replacement parts (seals, nozzles, tubes) — a drench gun you cannot repair is a disposable cost.

Prepare Before You Start

• Weigh or assess animals first. Dose to the heaviest animal in the mob (or per label and veterinary instruction); under-dosing light animals is a resistance risk.
• Calibrate the gun before the run: pump the measured volume into a graduated container and adjust until it delivers exactly the intended ml.
• Restrain the animal safely.
  • Sheep: stand the sheep against your legs or a solid race, holding its chin lightly — you need control of the head, not a wrestling match.
  • Calves: use a calf crate, head gate or a strong helper holding the head steady.
• Time it right. Drenching when animals are hungry and thirsty can cause gulping; follow label guidance on feeding and withholding periods.

The Correct Drenching Technique

1. Position the head at a natural horizontal line. Tilt the nose up slightly — but never tip the head far back. A fully raised head opens the windpipe and invites aspiration.

2. Insert the nozzle at the side of the mouth. Slide it past the corner of the lips, behind the teeth, and lay the nozzle over the tongue, angled toward the back of the throat.

3. Squeeze slowly and let the animal swallow. Deliver the dose in a steady stream; watch the throat move. If the animal coughs, stop immediately, lower its head and let it recover before continuing.

4. Never force it. If the animal is fighting, release and re-restrain. A drench that goes down the wrong pipe in seconds can kill an animal that took months to raise.

5. Keep a rhythm and a record. In a race or crate, work smoothly from animal to animal and note which mob was treated, with what product and on which date.

Avoiding Drench Resistance

Resistance is the single biggest threat to worm control worldwide: if a wormer stops working on your farm, no tool change will fix it. Australia's WormBoss program — a respected industry authority — emphasizes that the smartest farms do not drench every animal on a fixed calendar. Instead, they:

• Use worm egg counts to decide whether a mob actually needs treatment.
• Practise targeted treatment: leave a proportion of healthy adult animals undrenched so susceptible worms survive as "refugia" and dilute resistant ones.
• Always dose accurately to the heaviest animal — under-dosing is how resistance accelerates.
• Rotate products only under veterinary advice; random switching can worsen resistance.

The lesson for buyers: the drenching gun is a delivery tool, but drench discipline is a management system. Buying an accurate, adjustable gun is step one; using it selectively and recording results is what keeps wormers working for the next decade.

Gun Care and Maintenance

• Rinse the gun with clean water after every use. Drench formulations can crystallize and clog valves, wrecking dose accuracy.
• Disassemble and clean the nozzle, seals and barrel regularly; lubricate seals lightly per the manual.
• Re-check calibration periodically during long runs — seals wear and doses drift.
• Store the gun out of direct sun and freezing conditions; UV and frost damage plastic and rubber parts.
• Inspect nozzles before each season and replace them at the first sign of roughness or wear.

The Professional View

From a supplier's perspective, the most common mistake we see is a farm buying one gun for every class of animal — dosing 3-week-old lambs and 200 kg calves with the same tool and the same nozzle. The second mistake is treating the gun as a lifetime purchase with no spare seals or nozzles in stock. Buy the correct capacity per animal class, keep a spare nozzle and seal kit on hand, and — above all — treat dose accuracy as a non-negotiable: an uncalibrated drench gun is worse than no drench gun, because it quietly builds resistance you will only discover years later.

For guidance on reducing drench resistance through targeted treatment, see WormBoss's Targeted Treatment Drenching Guidelines. Always follow the veterinary medicine label and local veterinary advice.