Authors: Drs. Ben Enyetornye, Alfred Adjiri-Awere
POSSIBLE SUBSTITUTES FOR ANTIBIOTICS
NUTRACEUTICALS
A nutraceutical is defined as a product that has been isolated or purified from foods and generally sold in medicinal forms not usually associated with food (Health Canada 1998). Nutraceuticals are, usually, plant-derived biomolecules popularly known as herb extracts, spices or aromatic oils.
It has been suggested that many nutraceuticals help regulate the immune system, when administered in low doses, and as potent cell destroying agents in the treatment of cancer, bacterial and viral diseases, if used at relatively high concentrations.
Nutraceuticals that have been investigated for stimulating the immune system include extracts from garlic (Allium sativum), ginseng (Panax sp.) and oregano (Origanum vulgare). Honey has been investigated for wound treatment.
Ginseng
Ginseng has been extracted from various plant species of the genus Panax. The active ingredients of ginseng fall into two classes – triterpene glycosides (ginsenosides) and unsaturated long-chain alcohols. Standardized mixtures of ginseng saponins are known to greatly stimulate the immune system. Ginseng also enhances the production of signal inducing molecules such as interferon and interleukin-2. After vaccination with a low dose of an antigen (diphtheria toxoid), ginseng potentiated the primary antibody response. On the other hand, vaccination with a high dose of the same antigen, ginseng had only a slight potentiating effect on the immune system. This implies that ginseng can stimulate immune functions that have been curbed and restrain those that have been excited. Research in pigs has demonstrated that ginseng has a synergist effect when combined with aluminum hydroxide as an adjuvant in porcine (pig) parvovirus and Erysipelothrix rhusiopathiae vaccines. In a nutshell, animals exhibit a stronger immune response when ginseng was added to the vaccines.
Garlic
Garlic contains the active ingredients L. allin and the enzyme allinase. Garlic is known to have antimicrobial activity against Bacillus subtilis, Salmonella typhimurium, Staphylococcus aureus, Streptococcus faecalis, and Listeria monocytogenes; although, it has no effect on beneficial intestinal resident bacteria, Lactobacilli spp. Other studies suggest that aged garlic extract could be a promising candidate as an immune modifier to boost immune functions. Garlic fed to weaned piglets at an inclusion rate of 0.05% in the diet-maintained feed utilization efficiency and reduced the incidence of diarrhea and mortality when compared with the antimicrobial growth enhancer, Carbadox
Oregano
Oregano may benefit the development of a healthy immune system in pigs. A commercial oregano feed additive is prepared using the dried leaf and flower of Origanum vulgare enriched with 500 g kg–1 cold-pressed oregano essential oils, carvacrol and thymol. In growth-retarded, low-weight, growing-finishing pigs, enriched-oregano-supplemented feed improved daily gain and feed conversion and reduced mortality rate compared with non-supplemented pigs. This oregano feed additive was also found to stimulate the immune system by increasing the proportion of immune cells, including CD4+CD8+ double positive lymphocytes that have been shown to play a major role in protective immunity in pigs. It has been shown that essential oils of oregano possess in vitro antimicrobial activity against E. coli, S. typhimurium, S. aureus, R. leguminosarum, B. subtilis, Pseudomonae. aeruginosa, Enterococcus faecalis, and Klebsiella pneumoniae.
Honey
Honey is an ancient remedy for the treatment of infected wounds, which has, recently, been ‘rediscovered’ by the medical profession. The use to which honey is put in medical care is increasing with many authors pointing out its importance and role in wound care.
The production of honey as well as the storing process account for the presence of microorganisms in honey. Most of these organisms are said to be in inactive forms as they can hardly survive in honey because of its several properties, including peroxide content and antibiotic activities. Thus, there is the need for caution in the use of honey in wound management.
There is the need to determine the microorganisms present on the wound through laboratory culture and their sensitivity to the honey determined before commencing honey treatment. This procedure will help in carefully selecting wounds that might do well with honey treatment.
MINERALS AND VITAMINS
Zinc
One possible mechanism by which Zn affects immune response is through enhancement of macrophage function at higher levels of Zn inclusion
Significant improvements were observed in the health status (low blood cholesterol level and high ALT) and immunity of the birds by supplementing zinc nanoparticles (nZn) to broiler diets at 0.06 mg/kg compared with the conventional dose of 15 mg/kg of organic and inorganic Zn with the basal diet.
Addition of pharmacological concentrations of ZnO to piglet diets, after weaning, has been documented to prevent and/or alleviate diarrhea and mortality in swine attributable to E. coli infection and in those challenge exposed with Serpulina hyodysenteriae. High dietary ZnO has resulted in improved gut morphology.
Copper sulfate has also been recognized as having antibacterial and antimycotic activity in pigs.
Vitamins
A vitamin is now generally accepted to be an organic compound that is (1) a component of a natural food, but is distinct from other nutrients such as carbohydrates, fats, proteins, minerals and water; (2) present in most foods in a minute amount; (3) essential for normal metabolism in physiological functions such as growth, development, maintenance and reproduction; (4) a cause of a specific deficiency disease or syndrome if absent from the diet or if improperly absorbed or utilized; and (5) not always synthesized by the host in sufficient amounts to meet physiological demands and therefore must be obtained from the diet. Vitamins are differentiated from the trace elements, also present in the diet in small quantities, by their organic nature.
Vitamins are important for maintaining optimum immune response. Higher levels of vitamins (e.g., vitamins A, carotenoids, E and C) have been shown to increase overall health by improving disease resistance as a result of improved immunity.
Some vitamins deviate from the preceding definition in that they do not always need to be constituents of food, e.g Vitamin C.
Vitamin C (ascorbic acid) can be synthesized by companion animals and farm livestock, except fish, humans, nonhuman primates, gunea pigs, capybaras and certain fruit bats. Nonetheless, a deficiency has been reported in some species that synthesize vitamin C, and supplementation with this vitamin has been shown to have therapeutic value for certain disease conditions or for maximizing performance. For example, swine, poultry and ruminants can synthesize vitamin C, but there is a favorable response to supplemental C when these animals are under stress. Also, some swine have been shown to have a genetic defect that limits synthesis of the vitamin.
Based on research findings supplementation of vitamin C at 1000ppm had beneficial effect on Infectious Bursal Disease (Gumboro Disease) vaccination in in chickens for the protection against the Gumboro Disease infection. Supplementation of vitamin C through feed or through water has been adopted before and after vaccination of Gumboro Disease and to offset different stress factors, especially heat stress, in chickens.
Dietary supplementation of vitamin C improved the health of old laying hens by increasing antioxidant status and immunity. The optimum amount of dietary vitamin C supplementation for laying hens is approximately 0.25 g Vitamin C/kg diet.
Vitamin D can be synthesized from the action of ultraviolet (UV) light on a precursor compound in the skin. This is not true, however, for dogs and cats (and possibly other carnivores), which derive little or no vitamin D from UV light activity on skin. Although there is often synthesis of niacin and vitamin D, these normally will be supplemented in modern animal diets to improve resistance to disease.
Ascites is a costly metabolic disease in broilers that is the consequence of pulmonary hypertension. The addition of Vitamin C to broiler diets significantly reduced mortality due to ascites.
Vitamin D3 plays a key role in sow performance, sustainability and profitability, as well as piglet health and growth. However, the latest research strongly supports the idea that significant economic value is created when feeding sows Hy-D (the most bioavailable form of vitamin D), rather than using vitamin D3 directly because it improves vitamin D status. That is because Hy-D ensures more efficient and faster uptake of the required metabolite 25(OH)D3, resulting in a stronger skeleton and healthier, more productive animals and healthier piglets as a result – the key to increased herd profitability.
In conclusion, veterinarians and other professionals in the animal health and production chain should be considering the possible substitutes to antibiotics listed in parts 2 and 3 of this article. Such antibiotic substitutes should, eventually, reduce the frequency and excessive use of antibiotics in veterinary medicine and animal production.
