Words Matthew Wedzerai

If you’re not familiar with the range of herbs and spices that can be used as sustainable aids to poultry health, it is important to understand that they can be added to animal diets (in feed or water) in different forms and preparations. They can be given in whole or as extracts such as essential oils or phytogenics.

Consumer preferences

There are several reports of consumers who prefer poultry that’s been fed natural ingredients as substitutes for antibiotics. A recent survey (April 2018) carried out in Thailand, for example, indicated that Thai consumers are ready to buy meat products raised with phytogenic feed additives. Phytogenic feed additives are standardised mixtures of herbs and spices, as well as other plants and their extracts. Phytogenics are used for their impact on animal wellness, gut health and greenhouse gas emissions. The survey suggested that when consumers choose a specific brand of meat, 9 out of 10 consider the following:

• Whether meat products come from poultry fed completely natural ingredients, without antibiotics.
• Whether products reduce environmental impact.
• Whether poultry has been raised with phytogenics or similar herb extracts.
• Overall, it is important to them that food choices reflect their values in relation to the environment, animal health and welfare and natural ingredients.

Why use herbs and spices?

Several studies have indicated that herbs, spices and their extracts are important in sustainable poultry production, because: they’re cost effective – cost being a major limitation in the use of synthetic drugs; they’re easily available; they have no known residual effects; and they avoid the risk of developing antibiotic resistance in the human beings who consume the meat.

The beneficial effects of herbs and spices in poultry production are primarily pertinent to improving the birds’ ability to digest feed. Adding herbs to feed has an effect on digestive enzymes which results in an overall improvement in performance parameters such as weight gain and feed conversion. Better utilisation of feed means less excretion, and this helps reduce environmental pressure, with the added benefit that these are natural ingredients. They also offer several health benefits including immune stimulation, anti-bacterial, coccidiostatic, antiviral or anti-inflammatory activity and anti-oxidant properties.

Effects on health

There is growing interest in herbal feed additives in livestock production due to the development of microbial resistance to antibiotic drugs, and the implications this has on human health. As a feed supplement, herbs and spices have the following properties:

They are antimicrobial

Herbs and spices contain flavonoid components such as baicalin, baicalein, limonene, cinnamaldehyde, thymol, carvacrol or eugenol, among others, which exert antimicrobial effects. They act as antimicrobial agents by changing the characteristics of cell membranes, and causing ion leakage, ultimately making microbes less virulent. For bacteria, they act in the bacterial cell-wall structure, denaturing and coagulating proteins.

They are anti-parasitic

Several herbs such as sage, garlic, thyme, echinacea and oregano, possess anti-coccidial properties against Eimeria species, which reduce oocyst excretions from infected birds. Most of these herbs’ anti-oxidant activity, coupled with their alkaloids (eg halofuginones), helps to significantly reduce oocyst production in birds. Studies have shown that different herbs and spices can be used as prophylactic or therapeutic anti-coccidial agents. Another example, Curcuma longa (turmeric), through its phenolic compound, curcumin, exerts its anti-coccidial effect in birds through its anti-oxidant action on the immune system.

Ecto-parasites such as lice and mice can also be controlled by the use of herb extracts. For example, aqueous extract of garlic and cinnamon oil have both been shown to be effective in decreasing lice and mice infestations in chickens (Jacob and Pescatore, 2011; Zenner et al., 2003).

They are anti-viral

Herb catechins, which are a type of natural phenol, administered through feed or drinking water, decrease replication and excretion of the H9N2 virus from chickens in a dose-dependent manner (Lee et al., 2012). The anti-influenza activity of catechins is mainly due to direct interaction with viral HA and the inhibition of viral RNA synthesis. Ginseng stem and its leaf saponins significantly increase the serum antibody response to Newcastle disease and inactivated H5N1 and H9N2 vaccines in chickens (Zhai et al., 2011; Jiang., 2012).

They have anti-oxidant properties

The use of herbs reduces oxidative stress in chickens (Bharavi et al., 2010). Herbs and spices such as thyme, ginger, turmeric, marjoram, peppermint and nutmeg have been shown to have anti-oxidant properties as they contain compounds such as polyphenolics, alkaloids, lignans, flavonoids and terpenoids. These compounds neutralise superoxide, hydrogen peroxide and nitric oxide by scavenging radicals or by increasing the production of enzymes such as catalase, superoxide dismutase and glutathione peroxidase.

They stimulate the immune system

Herbs and spices rich in flavonoids, vitamin C and carotenoids are of benefit to the bird’s immune system. Some of these plants include echinacea, liquorice, garlic and cat’s claw. These plants can improve the activity of lymphocytes, macrophages and natural killer cells; they increase phagocytosis or stimulate the interferon synthesis. In addition, several herbs have been reported to have immunomodulatory effects like histamine release, modulation of cytokine and immunoglobulin secretion.

Effects on production

There have been a number of trials on the use of herbs and spices measuring their impact on production parameters in broiler chickens. Below are highlights from some of these studies.

Growth and feed conversion

Tables 1 and 2 below show the positive effects of garlic, cinnamon, turmeric and ginger on weight gain and feed conversion in broilers. Active compounds in garlic (Table 1) positively in?uence feed consumption, feed utilisation and bodyweight gain. These compounds are allicin, allyl methyl thiosulphonate, 1-propenyl allyl thiosulphonate and γ-Lglutamyl-S-alkyl-L-cysteine.
In addition, aromatic herbs have growth-stimulating, antimicrobial and anti-oxidative properties, which can contribute to better performance on broilers.

Table 1. Comparison of performance of broilers fed with dietary garlic addition (Puvaca et al., 2015)

Table 2. Growth performance of broilers (two to six weeks old) as affected by different herbs (Al-Al-Maaty et al., 2014)

Nutrient digestibility

Improved nutrient digestibility (Table 3) can be attributed to the properties of herbs. A number of herbs possess antibacterial, anti-oxidant and anti-fungal properties, which could improve the utilisation of dietary nutrients in the bird. Feeding herbs to broilers was reported to stimulate the secretion of digestive enzymes, and thus improve nutrient digestibility – ultimately enhancing the birds’ performance (Nadia et al., 2008; Al-kassie et al 2011).

Table 3. Nutrient digestibility and ash retention of five-week broilers fed different herbal supplements (Al-Maaty et al., 2014)

Meat production

The increased meat yield parameters in Table 4 may be induced by the stimulating effect of bioactive compounds on protein and fat metabolism, as reported by Osawa et al (1995) and Zhang et al (2009).

Table 4. Carcass traits of broilers (% of live bodyweight (LBW) at slaughter) fed different herbal supplements (Al-Maaty et al., 2014)

In summary:

• The utilisation of herbs and spices has a high economic efficiency.
• They possess several health-promoting properties that include antimicrobial, anti-parasitic, anti-oxidant and immunomodulatory properties.
• They stimulate the secretion of digestive enzymes, thereby improving nutrient digestibility and growth in birds – with less secretions into the environment.
• The improved parameters of meat yield are induced by the stimulating effect of bioactive compounds on protein and fat metabolism.
• Overall, herbs and spices offer sustainable therapeutic and performance aids to poultry health and production.

This article originally appeared in the May 2018 edition of Poultry Digital Magazine