Antibiotics in animal nutrition are strongly under debate. In Europe they are no longer allowed but in other countries like the USA, they are still being used. Essential oils, derived from plants, have proven to be good alternatives and reduce antibiotic resistance in poultry.
By Emma Wall, Full Circle Science, Burlington, VT, USA
The use of antibiotic growth promoters (AGP) to enhance the efficiency of agricultural animals has been practised for over 50 years. The types of antibiotics used as growth promoters include tetracyclines, penicillins, sulfonamides, and aminoglycosides, and all of these compounds have been shown to increase efficiency, weight gain and survival.
The action of AGP’s takes place in the gut of poultry animals where they alter the microflora environment. This leads to a decrease in competition for critical nutrients and a reduction in pathogenic metabolites that can depress bird performance. In addition, AGP’s have been shown to increase nutrient absorption and also reduce the occurrence of subclinical infection. Although AGP’s have proven highly effective at improving animal health and performance, bacterial resistance to AGP was first observed in the late 1950’s and subsequently has been well-documented. When antibiotics are added to poultry feed for prolonged periods of time, populations of pathogenic bacterial flora develop resistance to that antibiotic and can become dominant in the gut. The long term result is that the animal is no longer responsive to the antibiotic, and the improvement in animal performance is no longer observed.
Rotation scheme practice
As an alternative to AGP, there are currently many “all natural” products emerging on the market that have the potential to increase the efficiency of poultry animals. These products include probiotics, prebiotics, trace minerals, enzymes and herbs and spices (essential oils). Essential oils (EO) are compounds that give plants and spices their colour and scent. Many essential oils have antifungal, antioxidant, and antibacterial properties that are used to protect their plant of origin. The antibacterial properties of many essential oils present in clove, garlic, oregano and other plants have been known for years, and these oils have been used to flavour and preserve foods. The essential oils responsible for the antimicrobial activity can be isolated and produced commercially.
Recently, the use of essential oils as feed additives for agricultural animals has become an exciting area of study as a means of improving animal productivity. Laboratory research has shown that certain essential oils, including carvacrol (from oregano) cinnamaldehyde (from cinnamon), and capsaicin (from chilli peppers) have been shown to improve the performance of poultry.
Optimise gut microflora
Currently, there are two commercially available EO products for poultry: Regano 500 (Ralco), which is an oregano extract, and XTract Poultry (6930; Pancosma), which is a blend of carvacrol, cinnamaldehyde, and capsaicin. How do they work? The exact mechanisms are not clear, but they appear to alter enzyme activity in the gut, improve the digestion and uptake of nutrients, and optimise the gut microflora.
Some large field trials have been conducted to confirm the beneficial effects of EO on poultry performance, and to compare the efficacy of EO additives to AGP’s. Here we are highlighting two reports. The first is a compilation of data from 13 field trials, and the results were presented at the Poultry Science Association annual meeting in 2008. That report was focused mainly on comparing the efficacy of EO vs. AGP on enhancing poultry performance.
The second report is a research trial that was presented at the Poultry Science Association annual meeting in 2010 and was conducted to establish if EO and AGP could be combined to get additive effects in animal performance. Figure 1
shows the main results of each trial.
Increase in efficiency
In both reports, using an EO feed additive increased daily gain and feed conversion efficiency to a similar degree as AGP. The increase in feed conversion efficiency observed with either additive is particularly relevant during current times with rising feed costs. Feeding the two additives in combination did not appear to have any beneficial effects. Importantly, there was no difference in the effect of EO vs. AGP on breast yield after moisture loss (Figure 2
).In the second trial, financial analysis was conducted to predict the theoretical return on investment for each feeding strategy. Based on the results (Table 1
), using EO or AGP resulted in a similar return on investment.
Based on these experiments, EO have been shown to be as effective as AGP in enhancing animal performance, and the cost of adding them into feed programs would be similar to AGP. Therefore, they represent an exciting opportunity for poultry producers to improve bird performance using an all-natural approach. For farms that still use AGP, EO can be incorporated into rotation to improve the efficacy of AGP by breaking the cycle of antibiotic resistance.