Natural Antioxidants in Poultry Nutrition

All recognised vitamins with the exception of vitamin C are dietary essentials for poultry nutrition, and each is required for normal metabolism, health and growth. Feed ingredients such as corn, soybean meal and meat meal, all contain natural sources of vitamins and in some situations could theoretically contain enough to meet the nutritional needs of poultry.

However the concentration of vitamins contained in these raw materials are affected by factors such as exposure to high temperatures and storage conditions. Therefore we cannot rely on regular feed ingredients to supply vitamins, and consequently, vitamin premixes are designed to supply all necessary levels for poultry.

It is a well-known fact that the main cause of vitamin activity loss comes from a process known as oxidation, due to the exposure to oxygen. This can easily be prevented with the use of suitable antioxidants in feed.

But there remains the question of what type of antioxidants to use in feed. Antioxidants for feed can be categorised into two main groups, synthetic and natural. Synthetic chemicals such as butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) are widely used as preservatives, but have been linked to liver and kidney dysfunctions as well as allergies and skin disorders.

Ethoxyquin is another chemical preservative that is commonly used as a feed grade antioxidant. It is regulated by the USFDA as a pesticide, with possible carcinogenicity. While ethoxyquin is disallowed in human foods, it continues to be used in livestock feeds around the world. Ethoxyquin has been found to promote kidney carcinogenesis and significantly increases the incidence of stomach tumours and enhanced bladder carcinogenesis, according to several studies, including a recent one by the Department of Pathology, Nagoya City University Medical School, Japan.

Such synthetic antioxidants have long been used to prevent excessive oxidation of vitamins in animal feed, but recent concern over their use has created a need and prompted research for natural alternatives. Due to increased public awareness of the importance of food safety, there is increasing consumer pressure to discontinue the use of synthetic chemicals as feed preservatives in livestock feeds.

Therefore, the search for suitable antioxidants derived from natural sources have turned the interest of the industry towards plants and essential oils, which have been known to possess high levels of antioxidant properties for a long time now. I wish to bring across to the readers of this forum the potential benefits of using oregano essential oil for its antioxidant properties to protect vitamins in poultry feed.

Throughout the last few years, a range of naturally-occurring antioxidants including extracts of herbs and spices have been studied for their potential to protect lipids and vitamins in feed from the process of oxidation. Herbs of the Labiatae family were found to exhibit substantial antioxidant activity and showed potential for use in animal diets.

According to Joseph Mercola, who reported his findings in the Journal of Agricultural and Food Chemistry in November 2001, oregano was the herb with the highest antioxidant activity, which had 3-20 times higher antioxidant activity compared to all the other herbs studied.

On a per gram fresh weight basis, oregano ranked even higher in antioxidant activity than most fruits and vegetables known to be high in antioxidants. In comparison to the antioxidant activities of a few select fruits and vegetables, oregano had 42 times more antioxidant activity than apples, 30 times more than potatoes, 12 times more than oranges and 4 times more than blueberries.

An example of a feed additive that contains pure and natural oregano essential oil is Orego-Stim^®, produced by Meriden Animal Health Limited (UK). The phenolic ingredients, mainly comprising carvacrol and thymol, are bioflavonoids that act as powerful antioxidants. These help combat free-radical damage, while protecting cells, lipids and vitamins such as A, C and E from the process of oxidation.

An evaluation of antioxidant activities of different substances and the margin of deterioration of oxidation by UVA-VIS radiation showed that the antioxidant activity of oregano essential oil was higher than those of coriander and rosemary at various concentrations. In fact, it was even higher than ascorbic acid (vitamin C) and d-alpha tocopherol (vitamin E).

Because carvacrol and thymol are more reactive, they sacrifice themselves in the presence of a free radical in the peroxidation process, thus protecting more valuable antioxidant vitamins and increasing their bioavailability as nutrients for dietary absorption.

The use of oregano essential oils not only enables lower inclusion levels of vitamin premixes in the feed, thus lowering feed costs, but it also provides better performance in terms of growth, feed conversion, hatchability, egg production and egg quality. Due to its antibacterial properties, it also offers protection from intestinal diseases, reduces incidences of diarrhoea and decreases mortality rates.