The Search for Alternative Feed Additives

At the Agriculture's Role in Managing Antimicrobial Resistance Conference, Will Nap, the chair of Ontario Pork, discussed building a strategy to address antimicrobial resistance for the swine industry. In reference to antimicrobial use he commented, "we must assume that an outcry against their use in production practices will require some form of abatement in Canada." As consumer acceptance shifts away from antimicrobial use in livestock production, alternatives are being explored and minds are opening up to new, and even some old, possibilities.

Countries such as Sweden and Denmark have experienced firsthand the limiting of antimicrobial use and the resulting effects on pig production and management. In Sweden, antimicrobial growth promoters were banned in 1986. In the first year, post-weaning mortality increased by 1.5% and age at 25 kg increased by 5-6 days. After experiencing significant clinical problems in piglet production very early, the industry re-learned the basics of pig production, made the necessary adjustments and stabilized considerably. However, a comparison of 1997 and 1987 national production parameters indicated that the swine industry had not yet fully recovered the losses experienced after the ban. Overall, total use of antimicrobials for animals in Sweden has decreased by 55% in the past 13 years.

If livestock producers in Canada were told tomorrow that subtherapeutic levels of antimicrobials could no longer be used for the purpose of growth promotion, what alternatives would they have?

Non-Nutrient Feed Additives

Non-nutrient feed additives are compounds that can cause a response without directly contributing to the pig's requirement for energy, amino acids, minerals and/or vitamins. Some non-nutrient feed additives and their functions are summarized in Table 1. These compounds are typically added in small quantities. The response to feed additives is usually greatest in starter pigs (5-25 kg) so this is where efforts to come up with alternatives are usually concentrated. As pigs grow beyond 25 kg, the effect usually decreases, unless there are challenges associated with disease or stress that enhance the response.

Some nutrients, like zinc and copper, are added at pharmacological concentrations to swine rations. This is because these minerals act as growth promotants when included at levels much higher than minimum requirements. In Canada, the federal Feeds Act limits the level of copper and zinc in the diet to a maximum of 125 ppm and 500 ppm respectively, unless it is prescribed by a veterinarian. In the US, much higher levels are common. In some countries, like the Netherlands, growth-promoting levels of copper and zinc are no longer allowed in finisher pig diets due to the impact on the environment. Following the ban in Sweden, zinc oxide use increased dramatically for a period of time and then gradually decreased as environmental pressures grew.

John Gadd, a world-renowned swine consultant from the UK, thinks that, "consumers are crying out for more natural ingredients in the human food chain". He feels that "nutritional biotechnology is a good thing because it is user-friendly" and will satisfy both the producer's and the consumer's needs. This is why interest is currently growing for the use of compounds, like probiotics and botanicals or herbs, in swine rations.

Probiotics

Probiotics are thought to increase the population of desirable microorganisms, instead of killing or inhibiting undesirable organisms. The most common microorganisms included in probiotic products are Lactobacillus, Streptococus, Saccharomyces, and Bacillus species, which are normal inhabitants of the digestive tract of healthy animals. By encouraging the proliferation of these bacteria in the intestinal tract, it is possible to improve animal performance. However, research results to date have been mixed. Experiments carried out under controlled conditions have shown little response with the addition of probiotics to feed. Experiments conducted under field conditions have shown that probiotics can be beneficial, but generally only when high-stress conditions exist.

Botanicals

Herbal remedies were used thousands of years ago to treat infectious diseases, making use of an individual herb's natural antibacterial properties. Some herbs are thought to promote growth by preventing or limiting pathogenic bacteria in the digestive system, just like a conventional antimicrobial. Advancements in science and technology eventually replaced these natural remedies with man-made products, as scientists learned more and more from the compounds found in herbs.

Although the use of botanicals in swine rations is uncommon in North America, elsewhere around the world they have received considerable attention from feed manufacturers and producers. A large feed manufacturing cooperative in Denmark, where there is a national testing program in place for assessing new products, has been involved in developing its own additive. Their herbal product is now recommended for use in starter diets, accompanied by an organic acid. As a result of their proactive approach, Danish nutritionists are world leaders in the area of botanical growth promoters.

To date, research results with botanicals in pigs have not been very conclusive. Although some experiments have shown positive results, there is generally very little information available on specific compounds and their effects. This may be because it is unusual to find a commercial feed additive that uses only one herb, no matter how complex the herb. Natural growth promoters seem to lend themselves more to synergies of action, where a number of components come together, in a formula of sorts, to create the desired effect.

The Greek Example of Oregano Essential Oils

In Greece, researchers have completed a series of experiments with the essential oils from oregano in the hopes of preventing and controlling post-weaning diarrhea in pigs. Results showed significant improvements in diarrhea score and live weight, with increases of 7-8% in daily gain and feed intake. A separate study, in pigs from weaning through to slaughter, found that pigs fed the oregano essential oils weighed 6-9 kg more than the untreated controls, showed a higher daily weight gain (6.5-10.5%) and improved feed efficiency (12-17%).

Does it sound too good to be true?

When evaluating feed additives, use common sense, and ask to see the results of scientific experiments. Look for consistent results from research trials under controlled and field conditions. If something sounds too good to be true, chances are it is! Ask a fellow producer, extension agent or veterinarian for an impartial evaluation when considering an additive.

Feed additives have to pay their way by providing a higher return through improved health, feed efficiency or faster growth. Weigh the pros and cons of any additive prior to making changes by performing a cost:benefit analysis. For example, if an additive will improve feed efficiency by 0.1 unit in the growing/finishing phase, at a cost of $190/tonne for feed, it is worth $1.50/pig. This means that the breakeven cost of including that feed additive is about $6/tonne of feed. When feed additives are used, be sure to follow manufacturer and federal guidelines to ensure they are handled properly. No matter what the situation, it is important to realize that feed additives cannot compensate for poor management.

Table 1: Function of several non-nutrient feed additives used in swine rations