Abstract

The absolute reliance on imported feed additives for livestock production in Africa and Cameroon in particular, and the increasing resistance of pathogens to antibiotics, has made livestock production relatively expensive. Hence the need to exploit cheaper options.

This research studied the effects of three plants on feed intake, digestibility, weight gain, gut microbiota and survival of Cameroon Kabir chicken roosters. Eighty Cameroon Kabir chicken roosters aged eight weeks were distributed to 8 treatments using the completely randomized design (CRD) with ten chickens per block which were fed for 4 months.

The chickens were fed with the powders of 0.75% Euphorbia hirta, 1.5% Euphorbia hirta, 0.5% Thymus vulgaris,1.0% Thymus vulgaris, 0.5% Alium sativum and 1.0% Alium sativumin, in blocks A, B, C, D, E and F respectively. Block G (positive control) was given feed and the antibiotic oxytetracycline (0.5g/L of water), while block H (negative control) was given feed that contained neither the plant powders nor the antibiotic. The plants had no significant effects on average feed intake, feed conversion ratio and average weight gain of the chickens.

Although their effects on carbohydrate, ash and cellulose digestibilities were significantly different at P< 0.01, P< 0.006 and P< 0.002 respectively, they showed no significant effects on protein, fats and dry matter digestibilities. Euphorbia at 0.75% produced the highest effect on carbohydrate digestibility (86.6 %) while 0.5% Garlic had the least effect (77.9 %).  The ash digestibility values for 1.5 % Euphobia, 1.0% Thyme, and 1.0% Garlic were higher than that for the positive control. Euphobia at 1.5 %, Thyme at 0.5% and Garlic at 1.0% had values for cellulose digestibility which were higher than that for the negative control. The effects of the plants on the birds’ gut microbiota were very significant (P< 0.001). Birds that received the three plants had the highest effects on microbial load than the negative control.

The effects of the plants on the survival of Kabir chickens were not significantly different (P> 0.762). Thymus vulgaris, Euphorbia hirta and Allium sativum can be recommended as feed additives.

CHAPTER ONE

INTRODUCTION

1.1 Background to the study

Herbs and plant extracts, also known as phytogenic or herbal feed additives, are defined as compounds of plant origin incorporated into animal feed to enhance livestock productivity through the improvement of digestibility, nutrient absorption and elimination of pathogens resident in the animal gut (Athanasiadou et al., 2007).

Feed additives are non-nutritive substances used in poultry feed including antibiotics, enzymes, antioxidants, pellet-binders, antifungal, coloured pigments and flavouring agents, and they generally play the role of improving feed intake and increasing the growth rate in broilers (Scott et al., 1982; Fadlalla et al., 2010; Bali et al., 2011; Abouelfetouh et al., 2012).

Feed intake is the amount of feed voluntarily consumed by an animal. It is determined by the availability, palatability and digestibility of feed, for instance, feed intake is depressed when a diet contains inadequate amounts of minerals, vitamins and various sources of nitrogen, or when it is poorly digestible (Davies, 1982). Stobbs (1973) found that the amount consumed per bite tends to increase with the amount of green leafy material in the food, the physiological status of an animal (for instance, pregnant animals have different intake requirements according to litter size and stage of gestation), environmental conditions (for instance, the availability of water will affect the amount of feed an animal consumes, as will temperature and humidity), infectious, parasitic and metabolic diseases, which may depress intake.

The wide use of antibiotics in poultry feed as growth promoters has led to the increasing resistance of pathogens to antibiotics and the accumulation of antibiotic residues in animal products and in the environment.

This situation has led to restriction on the use of antibiotic growth promoters in animal feed (Nisha, 2008). Scientists are therefore trying to find alternatives and one of the best options is herbs (Yadgar et al., 2015).

For many years feed additives have been widely used to increase animals’ performance and, recently, they have been used in poultry industry to improve growth, feed efficiency and layer performance (Collington et al., 1990; Khan et al., 2007).

Scientific evidence suggests that herbs, spices and various plant extracts have appetite and digestion-stimulating properties, promoting the growth of beneficial bacteria and inhibiting the growth of unfavourable ones in the gut. This would ensure that at all times the animal would have the proper microbial balance (Wenk, 2000; Kamel, 2001). A study of medicinal plants helps us to understand plant toxicity and protect animals and humans from natural poisons (Hosseinzadeh, 2015).

Plants and their metabolite constituents have a long history of use in modern “western” medicine and in certain systems of traditional medicine, and are the sources of important drugs such as atropine, codeine, dioxin, morphine and quinine.

Herbs, spices and their extracts were already in use thousands of years ago in Mesopotamia, India, China and old Greece, where they were appreciated for their specific aroma and various medicinal properties (Greathead, 2003). Scientists recently discovered that the appetizing and stimulating activity of herbs and plant extracts on animal digestive and immune system could benefit performance and health of farm animals (Lopez-Bote et al., 1998).

Antimicrobial (Guo et al., 2004a), antioxidant (Hashemi et al., 2009), anti-stress, gut micro flora manipulation, nutrigenomic effect (Franco-Jimenez et al., 2007) and immune enhancement (Guo et al., 2004b) properties probably are the major mechanisms by which herbal plants exert positive effects on the growth performance and health of animals.

Many plant products and their constituents have a broad antimicrobial activity, antioxidant and sedative properties. Herbal extract supplements have been shown to have beneficial effects on broiler performance and carcass quality (Schleicher et al., 1998).

A variety of herbal supplements have been widely used to maintain and improve health of birds (Gardzielewska et al., 2003) and humans (Freeman et al,. 1995). Aromatic plants and essential oil extracted from these plants have been used as alternatives to antibiotics. For this reason, these plants are becoming more important due to their antimicrobial and stimulating effect on animal digestive system (Osman et al., 2005); they have also been used in poultry diets as feed additives to increase poultry growth performance, health and the quality of their products.

Their extracts have been tested in the diets of poultry as potential alternatives to antibiotics on growth promotion (Yadgar et al., 2015). Mukherjee (2002) established the fact that, with the emerging interest of the world in adopting and studying traditional systems, and in exploiting their potential from different healthcare perspectives, there is need to explore the possibility of evaluating these systems for their therapeutic potential as originally practised, as well as to help generate data to put them in national healthcare programmes.

The usual method to quantify and qualify dietary feed is to conduct digestibility studies and growth performance trials with birds (Khieu et al., 2002). The digestibility of a feed determines the amount that is actually absorbed by an animal and therefore the availability of nutrients for growth, reproduction, muscle building, manufacture of enzyme, antibodies, blood cells and hormones. Sibbald (1987) revealed that, ideally, the bioavailability of a nutrient should be a characteristic of the feedstuff in which it is contained and independent of the animal to which it is fed.

It is recognized that amino acid digestibility is a sensitive indicator of amino acid availability in dietary ingredients for poultry bioavailability is a function of two processes: digestion and metabolism (Khieu et al., 2002).

According to Athanasiadou et al. (2007), herbs and plant extracts can be incorporated into animal feed to enhance livestock productivity through the improvement of digestibility and nutrient absorption.

1.2 Problem Statement

The absolute reliance on western drugs and feed supplements, which are often very expensive for livestock production in Africa and Cameroon in particular, has made livestock production relatively expensive and this has kept the level of production so low that demand can only be met through import and so there is a need to search for cheaper sources of drugs. In addition, the large utilization of antibiotics in poultry feed as growth promoters has led to the increasing resistance of pathogens to antibiotics and the accumulation of antibiotic residues in animal products and in the environment. This situation has led to restriction on the use of antibiotic growth promoters in animal feed (Nisha, 2008). Scientists are therefore trying to find alternatives and one of such options is herbs.

According to Raza et al. (2015), medicinal plants have the ability to prevent a variety of infectious and non-infectious diseases. There are instances in Cameroon in which animal diseases that have defied modern drugs were healed by ethno veterinary practices, but the problem with the Cameroon traditional systems is that those involved in traditional medicines always hide the herbs from people for fear that when other people come to know about these herbs, it would kill their power of monopoly in the market.

Hence, the only way they can maintain this so-called monopoly is by restricting them away from people. In addition, they do it in a traditional manner (unknown dosages, no prescription guides, no analysis of the active ingredients involved).

There is therefore the need for Cameroon scientists to undertake research that will collaborate with ethno veterinary practitioners to identify, analyse and determine the active ingredients and their effects and the dosages at which they exert their optimal therapeutic effects in order to come up with new approaches in the use of local herbs as feed additives, growth promoters and medicinal herbs.

This research was therefore designed to study the effects of three of such herbs; Thymus vulgaris, Euphorbia hirta and Allium sativum and the dosages at which they exert their optimal therapeutic effects, with the goal of knowing whether they could be used in place of imported feed additives and antibiotics.

1.4 Research Objectives

1.4.1 Main Objective

To assess the effects of Thymus vulgaris, Alium sativum and Euphorbia hirta as feed additives on feed intake and digestibility, weight gain, gut microbiota and survival rates of Cameroon Kabir chicken roosters.

1.5.2 Specific Objectives

1. To determine the effects of Thymus vulgaris (Thyme), Euphorbia hirta (Euphorbia) and Allium sativum (Garlic) on feed intake, feed conversion ratio and weight gain, of chickens in the various treatment groups.
2. To assess the effects of Thyme, Euphorbia and Garlic on the digestibility of feed by the chickens in the various treatment groups.
3. To evaluate the effects of Thyme, Euphorbia and Garlic on the gut microbiota of the chickens in the various treatment groups.
4. To assess the effects of Thyme, Euphorbia and Garlic on the survival rate of chickens in the various treatment groups.