Introduction

Prompt diagnosis and control of disease is essential if an enterprise is to remain profitable while maintaining welfare standards. Sick pigs are generally treated with injectable, in-feed or water medication:

• Injectable medications are often used for treating individual or small groups of pigs.
• Medicated feed is suitable for large numbers of pigs.
• Medicated drinking water is suitable for small or large group sizes.

Water medication is the administering of chemicals via the drinking water supply, using soluble powder or suspended formulations. Water medication has a number of benefits when compared with injections and in-feed medication (Table 1).

Quality assurance and medication systems

The pig industry has made excellent progress towards ensuring the quality and food safety of pork under the Australian Pig Industry Quality (APIQ) program. One of the key goals of the program is to reduce the risk of antibiotic residues. Accurate identification of all treated animals and adherence to minimum withholding periods is fundamental to the APIQ program. The industry is endeavouring to reduce the total use of medications.

Water medication systems are being increasingly used to minimise hazards relating to residues in pigmeat. Water medication systems can be used to target individual pens or whole sheds for the treatment of sick pigs. This flexibility reduces the risk of treating healthy stock by mistake. Water medication also reduces the likelihood of cross-contamination of medication that occurs with in-feed medication via the feed mill, feeders or feed trolleys.

Uses of water medication

Preventative medication and pulse medication
Water medication has significant advantages in preventing disease outbreaks. Medicated water can be provided to pigs in regular doses or pulses, keeping disease in check. A well-organised medicated-water program can be more effective for disease prevention than an in-feed medication program, and in many cases may be more cost-effective. Rather than providing a constant supply of preventative antibiotics to animals, as occurs using in-feed medication, medicated water can be provided as required. The advantages of pulse medication include less antibiotic usage, lower cost and less build-up of antibiotic resistance.

Treating disease
Water medication can also be used to treat and cure disease by promptly and easily providing medication to sick animals. The benefits of water medication begin almost immediately, as water intake is normally unaffected during illness. With the use of in-feed medication there is a delay before sick pigs consume enough feed to allow the medication to have the desired impact. This delay can be further increased when the illness causes a reduction in feed intake.

Electrolytes, acidifiers and probiotics
Water medication systems have potential uses beyond supplying soluble medications. A range of electrolytes, acidifiers and probiotics can also be administered using water medication systems. For example, if pigs have been trucked a long distance or have been withheld from water for a period of time, the inclusion of an electrolyte in the water can aid the restoration of body water balance

Probiotics are live microbial feed supplements that improve the intestinal microbial balance to help provide protection against disease.

Electrolytes are typically provided to sucker and weaner pigs to prevent or treat scours. Dissolved electrolytes provide an energy source (glucose or other sugar) for the pigs, and mineral salts assist with stabilising blood mineral levels. Electrolytes are effective in reducing sucker and weaner deaths from dehydration following a scour outbreak.

Acidifiers may be provided to weaner pigs to control post-weaning E. coli scours. Acidifiers supply a range of organic acids, such as lactic acid, which lower gut pH or acidity and thus discourage E. coli growth. Acidifiers can also be used in older pigs to reduce the incidence of salmonella.

Water medication systems

Water medication systems used in piggeries include the use of overhead tanks and proportioners.

Overhead tank systems
Overhead tank-water medication systems are simple and effective. They rely on having a header tank capable of holding enough water to treat pigs for 12–24 hours. Header tanks with variable volume can be created by using an adjustable float valve to limit tank capacity to the volume required. Header tanks are plumbed into shed water systems so that medicated water can be directed to individual pens or to groups of pigs that require treatment. The system generally includes the use of shut-off valves and/or detachable polypipe fittings.

Many existing water systems readily adapt to the installation of an overhead tank medication system as there is very little initial cost and there are low maintenance costs. However, this system may be cost-prohibitive for some larger and more complex facilities — these units may choose to install separate medication lines. A simple system for the treatment of weaners is to place a 20–80 L plastic container above the weaner pen and connect the container to pen drinkers.

The calculation of dose rates when using overhead tanks for medication is detailed in Table 2. To ensure the effective medication treatment of pigs, turn the pen/shed water supply off to avoid medication dilution which results if pigs also consume non-medicated drinking water. It is obviously essential to switch the normal water supply back on after consumption of the medicated supply. It is important for all piggeries to have at least a 24 hour backup supply of drinking water to cover any emergencies that may arise.

Proportioners

Proportioner medication systems rely on a pump to deliver measured amounts of a stock solution of dissolved medication into a water line at a typical dilution of 1% (1:100) or 2% (2:100). Proportioner pumps include piston and diaphragm pumps which both work at almost identical pressures. Pump design should aim for long life without losing proportioning accuracy. Ideally, pumps should include a chemical bypass to minimise pump wear. Proportioners have the benefit of being portable. One unit can be moved from shed to shed on a hand cart and plugged into the water line using quick-release fittings to medicate pigs as required.

Proportioners cost around $650 to $1100 (including GST) and maintenance requirements can be minimised with regular cleaning. To accurately measure the amount of medicated water to pens, a portable in-line water meter at a cost of about $120 can be used. The more advanced proportioners will monitor water flow and allow dose rates to be easily changed. Also, they can operate over a much larger range of flow rates and pressures.

Table 3 provides examples of calculating dose rates when using proportioners for medication. Examples of cost-effective and durable proportioners include the Dosatron, Chemilizer and Gator systems. An example of a more advanced unit capable of a wider range of applications is the Select Dosing System. The advanced systems provide very accurate dosing through water systems, and a replaceable pump tube can be used to protect the pump’s moveable parts from corrosion. With the more complex systems, an electronic pump can be activated by signals from a water flow sensor fitted in the medicated water line. Continuous monitoring and adjustment allows increased accuracy of medication.

Water medication tips

In hot weather, pigs will have higher water intakes (Table 4) and will waste water trying to keep cool. Reduce wastage by medicating pigs in the cooler periods of the day — early mornings and evenings. Installation of spray cooling systems will also reduce wastage, and the installation of cup-style drinkers can reduce water wastage by up to 60% when compared to the use of nipple drinkers. The amount of medication may need to be increased to compensate for wastage. For example, if administering the medication through nipple drinkers, the level of chemical may need to be increased by up to 20%. Water quality may affect medication efficacy (Table 5). For example, bore water with high salt levels may inhibit the activity of some medications. Further advice on medication efficacy can be obtained from a veterinarian or drug company representative.

Some medications are quite hard to dissolve, particularly in cold, hard water. When mixing medicated water, it is important to fully dissolve all of the medication prior to use. To increase the rate of dissolving the medication, the use of warm, purified or distilled water is recommended. Avoid combining drugs or formulations unless it is done under the direction of a veterinarian. Many combinations are incompatible and the effectiveness of combined drugs may be reduced.

Avoid residues

The treatment of sick pigs with medication can result in residues in the pig meat if the medications are not used correctly. Always read the drug label before use. If you are in doubt about the correct dose rate, the withholding period or anything else on the label, contact your veterinarian for advice.

Drug residues in carcases can lead to prosecutions and heavy fines as well as damage to consumer confidence. The Stock Medicines Act 1989 and the Stock Medicines Amendment Bill 2004 provide for fines of up to $22 000 and $44 000 (corporations). Offences include failing to follow stock medicine label directions and breaching withholding periods.

Checklists and tips

Key features of proportioners

• Robustness. Units should be strong and durable to withstand high pressures. This will minimise the likelihood of breakage and therefore increase longevity.

• Accuracy is paramount when dealing with medications. For example, piston pumps require a long stroke to minimise ‘short cycling’, which will maintain accuracy for a longer lifespan.

• Resistance to harsh chemicals. Ideally, a bypass can be used so that chemicals are not mixed in the motor chamber. Harsh chemicals and poorly dissolved additives can damage and clog motors.

• Easy, low-cost maintenance is essential. This includes minimal or no adjustments (stronger dosages can be obtained by increasing the chemical concentration of the medication).

• Low capital cost of proportioner units.

• To avoid costly downtime and repairs, install an 80 micron/200 mesh filter in-line prior to the proportioner.

• Choose a medicator that will operate at a wide range of pressures.

• Inspect the medicator regularly, and periodically check that the in-line filter is operating at maximum efficiency.

• Change injector seals at least once a year.

• After use, flush injectors with clean water.

• Dismantle the medicator once a year to remove any foreign material that has built up.

• Follow the directions on the label or the instructions provided by your veterinarian.

• Correctly calculate the dose rate for treated animals.

• Only sell animals after any withholding period has passed.

Further reading

A wide range of information sources can also be found on many pig industry websites:

• Australian Pork Limited (APL) is the national representative body for Australian pig producers. It is a producer-owned not-for-profit company combining marketing, export development, research, innovation and strategic policy development to assist in securing a profitable and sustainable future for the Australian pork industry. Resources and contacts are listed on their website: http://www.australianpork.com.au/ or they can be contacted on 1800 789 099.

• NSW Farmers’ Association’s NSW Pork Committee have resources and contacts listed on their website: http://www.nswfarmers.org.au/pig or they can be contacted on 02 8251 1700.

• Queensland Department of Primary Industries and Fisheries (QDPI&F) have a large range of fact sheets available on their website, and their PigTech notes can be obtained on CD.