Any new product or idea that promises to reduce costs and improve performance is worthy of closer examination, in the competitive business of producing pork. A good example is the introduction, over the last few years, of new antibacterial treatments that provide a complete course of therapy in just one injection.

Increasing numbers of producers are recognising the advantages of single-shot antibiotic therapy, which can deliver a guaranteed course of treatment with a high cure rate and minimal labour. This new treatment concept is made possible by the recent development of antibacterial drugs that have an exceptional duration of action. In the case of swine respiratory disease, these new generation products remain active within the lungs for a week or more increasing the likelihood of the full elimination of any bacteria present and, as an added benefit, helping to ensure that other bacteria cannot immediately take advantage of the animal's weakened state. The result is extended care which continues while the pig's own defences begin to recover.

This new treatment concept' is undoubtedly based on some very clever science, but can it provide a good return on investment in the commercial setting? To find a clear answer to that question, it is necessary to go back to basics and assess its potential using existing treatment options as a benchmark.

The various approaches used for treating swine respiratory diseases are a good example of how a thorough evaluation of the options can pay dividends. They all have their advantages, but equally come with certain disadvantages. The key in deciding which route to follow must lie with a full understanding of the costs (or absence of costs) throughout the cycle, including those that may occur if a complete cure is not achieved.

Injectable versus oral: To be fully effective, any antibacterial therapy needs to be administered at the correct time and dose. It must also have a broad enough spectrum to tackle the pathogens that are present, bearing in mind that many respiratory disease outbreaks involve a mixture of organisms. The causes of respiratory disease can be various and there will be little chance of a cure if the wrong antibiotic is used. The medication chosen also needs to reach the site of infection and remain there in high enough concentrations to result in a reliable cure.

Delivering reliable outcomes is where injectable antibiotics can be more successful than those administered via other routes. For most diseases, antibiotics reach the site of infection (the lungs, for example) through the bloodstream. To do this, they must first be absorbed into the blood, a process which is typically more efficient and consistent from an injection site than it is from the gut. The injectable route of delivery also offers the security of exact dosing with minimal between-animal variation in the amount of drug received. But it can appear expensive, both in terms of initial purchase price and in the man-hours needed for administration if repeat doses are required although the new single-shot options minimise the latter.

While injectables therefore offer many benefits, a proper evaluation also needs to consider the characteristics of other approaches. In the case of antibiotics delivered through drinking water, the ease of administration is obvious. Suitable for administering to large numbers of animals and for use over long periods of time, they usually disperse well in water and, in the short term, can be viewed as inexpensive. But the administration in water has a number of drawbacks, including the requirement for the farm to have suitable equipment installed.

Additionally, not all drugs dissolve well or are stable in water. They can also give water an unpalatable taste which reduces intake and there can be no guarantee even without taste effects that every animal in the group will drink a sufficient volume for fully effective treatment, especially as sick animals often drink less. Even assuming that all pigs have consumed sufficient volumes of medicated water, there can be a delay before treatment starts to take effect as it takes time for a dose to be absorbed from the gut, distributed to infected tissues and built up to an effective concentration.

Similarly, in-feed antibiotics are easy to administer and commonly used for mass medication and long-term treatment. But the problems with in-feed treatments are not unlike those experienced with water-soluble medications, in that sick pigs are less likely to eat than healthy animals. Also, distribution within the feed may be patchy and the taste may be unappetising. So this apparently cheap option has costs associated with its potentially uneven results.

While in-feed and water-soluble approaches should be ideal for long-term treatment, they clearly present a number of weaknesses that can lead to sub-optimal performance and resultant cost in terms of poor outcomes, follow-up treatments and lost man-hours all being potential causes of additional cost.

Duration of action: Mention of long-term treatment brings us to a further important element that needs to be considered if therapy is to be successful, and this is how long effective antibiotic concentrations should be maintained in the body.

An antibiotic that is present in tissue for only a short period may fail to eliminate bacteria completely, making a follow-up treatment necessary. Moreover, pathogens will probably be present not only within the treated animal itself, but also in the surrounding environment including infected penmates. The risk of re-infection from the environment poses a threat to all animals in the herd, but especially to those that may have weakened immune systems and lower natural defences as a result of a recent infection. These animals are in need of continued protection if they are to return to healthy and productive growth patterns with minimal disruption and minimal additional cost.

Ideally, an injectable treatment should last long enough for pathogens to be eliminated and should provide sufficient protection from re-infection for tissue to repair, physical defences to be restored and immunity to start to develop. These processes may take 7 days or more.

While multi-shot injections offer advantages over the water and feed-based approaches, they too have their associated problems and costs. An all-important consideration with the multi-shot approach is the proper identification of individual animals and the administration of a full course of treatment. Compared with single-shot treatment, repeat dosing is more complicated and mistakes can occur. Of course, animals might be missed even with the single-shot approach. But a full course of treatment requiring, for example, 3 individual shots multiplies the possibility of making an error three-fold. An animal can receive too many injections and, as a result, it is given too high a dosage. Even more easily, an animal can be missed, leading to dosage levels that are too low. Any deviation from the correct dosage can lead to a suboptimal result, such as a dead or underweight pig, which in turn means a loss of income.

Multi-dose injections also mean repeated handling and higher stress levels for the animal, which in turn can weaken the immune system. There is also the repeated risk of tissue damage and the issue of labour and handler safety. Adopting a single-shot approach allows labour to be more productively employed elsewhere.

It is no surprise therefore that single-shot disease management is becoming more widely adopted. Single-shot antibiotic therapies are now being marketed that offer a broad spectrum of activity against the common causes of swine respiratory diseases. They are able to reach high concentrations in tissue and remain there for a sufficiently long period to produce an effective cure before being eliminated and excreted by the animal.

The higher initial cost associated with single-dose therapy is no longer an issue when costs are considered throughout the production cycle, along with the savings made by avoiding relapse, re-treatments and associated production losses. The return on investment can be assessed in terms of reduced inputs, improved outcomes and reduced losses.

In our view, single-shot can be seen as the common sense' approach to disease management. It offers not only broad and thorough protection, but also the simplest and most efficient approach to employ. The future is likely to see more and more pig units adopting this logical approach to animal health. PIGI