THE EFFECT OF GARLIC (Allium sativum L.) MEAL AS A FEED INGREDIENT IN THE DIETS OF BROILER CHICKENS

THE EFFECT OF GARLIC (Allium sativum L.) MEAL AS A FEED INGREDIENT IN THE DIETS OF BROILER CHICKENS

Abstract

This study investigated the effect of garlic (Allium sativum L.) meal as a feed ingredient in the diets of broiler chickens. The specific objectives were to determine the effect of varying levels of garlic meal on feed intake and weight gain; assess the effect on feed conversion ratio (FCR); evaluate the effect on carcass characteristics; determine the effect on blood parameters (cholesterol, glucose); and assess the economicimplications of incorporating garlic meal in broiler diets. A total of 150 day-old broiler chicks were randomly assigned to five dietary treatments (0%, 0.5%, 1.0%, 1.5%, and 2.0% garlic meal inclusion), with three replicates of 10 birds each. The experiment lasted for 8 weeks. Data were collected on weekly feed intake, weekly weight gain, and final carcass characteristics. Blood samples were collected for analysis. The data were analyzed using Analysis of Variance (ANOVA). The findings revealed that garlic meal inclusion had a significant (p<0.05) effect on performance. Weight gain and FCR were significantly improved at inclusion levels of 1.0% and 1.5%. Total cholesterol and blood glucose levels were significantly reduced in birds fed garlic meal. Carcass characteristics were not significantly affected. The economic analysis showed that the 1.0% inclusion level yielded the highest net return. The study concluded that garlic meal can be effectively used as a natural growth promoter and health enhancer in broiler diets at an optimal inclusion level of 1.0-1.5%. It was recommended that garlic meal be incorporated into broiler diets at 1.0% for improved performance and profitability.

Chapter One – Introduction

1.1 Background of the Study

The poultry industry is a vital component of global agriculture, providing a significant and affordable source of high-quality animal protein. Broiler production, in particular, is a major commercial enterprise focused on the efficient conversion of feed into meat. The industry is characterized by continuous efforts to improve growth rates, feed efficiency, and overall bird health. Central to this goal is the formulation of cost-effective and nutritionally complete diets. (Food and Agriculture Organization [FAO], 2021).

For decades, the poultry industry has relied heavily on the use of antibiotic growth promoters (AGPs) to enhance growth performance, improve feed conversion, and prevent diseases. These sub-therapeutic doses of antibiotics in feed alter the gut microflora, reducing the burden of pathogenic bacteria and allowing for more efficient nutrient absorption. However, the widespread use of AGPs has come under intense scrutiny due to the growing threat of antimicrobial resistance (AMR). The emergence of drug-resistant bacteria poses a serious risk to human health. (World Health Organization [WHO], 2021).

The global concern over AMR has led to increased pressure to phase out the use of AGPs in animal production. Many countries have already banned or restricted their use. This regulatory pressure, coupled with consumer demand for “antibiotic-free” meat, has driven the search for safe and effective alternatives. Researchers and the industry have turned their attention to natural products, particularly phytogenic (plant-derived) feed additives, which may offer similar benefits to AGPs without the associated risks. (Adebayo, Oladele, and Sanusi, 2021).

Phytogenic feed additives, also known as phytobiotics or botanicals, are a broad category of plant-derived substances that are added to animal feed to improve performance and health. They include herbs, spices, essential oils, and other plant extracts. These substances contain a complex mixture of bioactive compounds, including alkaloids, flavonoids, and essential oils, which exhibit a range of biological activities, including antimicrobial, antioxidant, and immunomodulatory effects. Their mode of action is often multifaceted. (Hashemi and Davoodi, 2019).

Garlic (Allium sativum L.) is one of the most widely studied and promising phytogenic feed additives. It has been used for centuries for its culinary and medicinal properties. The primary bioactive compound in garlic is allicin, which is formed when garlic is crushed or chopped. Allicin is known for its potent antimicrobial, antiviral, antifungal, and antioxidant properties. These properties make garlic a strong candidate as a natural alternative to AGPs in animal feed. (Amagase, Petesch, Matsuura, Kasuga, and Itakura, 2018).

The use of garlic in poultry diets has been the subject of extensive research. Studies have shown that garlic supplementation can lead to improvements in growth performance, including increased body weight gain and improved feed conversion ratio. The proposed mechanisms for these effects include the stimulation of digestive enzyme secretion, the improvement of gut health by modifying the intestinal microflora, and the enhancement of the immune system. The antimicrobial action of allicin helps to suppress harmful bacteria, creating a more favorable environment for nutrient digestion and absorption. (Hashemi and Davoodi, 2019).

Beyond growth performance, garlic has been shown to have beneficial effects on the health status of broilers. One of the most consistently reported effects is the reduction of serum cholesterol and triglyceride levels. The hypocholesterolemic effect of garlic is thought to be due to its ability to inhibit key enzymes involved in cholesterol synthesis in the liver. This could result in the production of leaner, healthier meat with a better fatty acid profile. This is a significant consumer health benefit. (Amagase et al., 2018).

The effect of garlic on the immune system is another important area of interest. Garlic has been shown to modulate the immune response, enhancing the activity of immune cells and increasing the production of antibodies. This immunomodulatory effect can help birds to better resist infections, reducing the need for therapeutic antibiotics. A stronger immune system contributes to overall bird health and welfare. The antioxidant properties of garlic also help to protect cells from oxidative stress. (Hashemi and Davoodi, 2019).

The response to garlic supplementation is not always linear; it is often dose-dependent. Studies have shown that there is an optimal inclusion level, beyond which the benefits may plateau or even become negative. Very high levels of garlic in the diet can lead to reduced palatability, as the strong flavor and odor may deter birds from eating. The determination of the optimal inclusion level is therefore a critical research question. The form of garlic used (fresh, dried, oil, extract) also influences its potency and effectiveness. (Amagase et al., 2018).

The use of garlic meal (dried and ground garlic) is particularly relevant in the Nigerian context, as it is a stable, easy-to-handle form that can be readily incorporated into feed. The assessment of its effect on broiler performance under local conditions is essential for providing evidence-based recommendations to farmers. The economic viability of using garlic meal is also a key consideration, as its cost must be justified by improvements in performance. (Emmanuel and Okafor, 2022).

This study is therefore designed to provide a comprehensive analysis of the effect of garlic meal as a feed ingredient in the diets of broiler chickens. It will investigate the effects of varying inclusion levels on growth performance, feed efficiency, carcass characteristics, and blood parameters. The study will also conduct an economic analysis to determine the most profitable inclusion level. This will provide valuable evidence for farmers and the poultry industry. (World Bank, 2022).

The findings of this study are expected to be of significant value to a wide range of stakeholders. For poultry farmers, the study will provide a natural, affordable, and effective alternative to antibiotic growth promoters. For researchers, the study will contribute to the scientific literature on phytogenic feed additives. For policymakers, the study will provide evidence to support the promotion of natural feed additives as part of a strategy to combat antimicrobial resistance. Ultimately, the study aims to contribute to a more sustainable and healthy poultry industry. (World Bank, 2022).

1.2 Statement of the Problem

The poultry industry is under increasing pressure to move away from the use of antibiotic growth promoters (AGPs) due to the global crisis of antimicrobial resistance (AMR). The core problem is that while AGPs are effective at improving broiler performance, their continued use poses an unacceptable risk to public health. There is a pressing need to identify and validate safe, natural alternatives. While garlic has shown promise, the specific effects of garlic meal under local conditions and the optimal inclusion level for maximizing performance and profitability are not fully established. (WHO, 2021).

A fundamental problem is the potential for a decline in performance if AGPs are simply removed from feed without a suitable replacement. Farmers have become reliant on these additives to achieve high growth rates and feed efficiency. The problem is that the sudden withdrawal of AGPs could lead to a deterioration in gut health and an increase in disease, resulting in economic losses. The identification of effective alternatives is therefore crucial to ensure a smooth transition. (Adebayo et al., 2021).

The problem of the variability in the effectiveness of natural feed additives is a challenge. Unlike synthetic antibiotics, which have a defined and well-understood mode of action, the active compounds in natural products can vary in concentration and potency. The problem is that the effectiveness of garlic can be influenced by factors like the variety, growing conditions, processing method, and storage. This makes it difficult to standardize results and to make reliable recommendations. The need for local, specific research is therefore evident. (Hashemi and Davoodi, 2019).

There is a significant problem with determining the correct or optimal dosage of garlic meal for broiler chickens. The response to garlic is known to be dose-dependent, but the optimal level can vary depending on the bird’s age, the diet composition, and the specific health status of the flock. The problem is that using too little garlic may not produce the desired effect, while using too much can reduce feed palatability and negatively impact performance. The determination of the “sweet spot” is a key experimental question. (Amagase et al., 2018).

The issue of the potential negative effects of high levels of garlic on feed intake is a practical concern. Garlic has a strong, pungent flavor and odor, which can be off-putting to birds if included at too high a concentration. The problem is that a reduction in feed intake will inevitably lead to a reduction in growth rate. The optimal inclusion level must therefore balance the beneficial health effects against the risk of reduced palatability. This trade-off is a key focus of the dose-response study. (Hashemi and Davoodi, 2019).

The problem of the lack of comprehensive data on the effect of garlic meal on carcass quality in local breeds is a gap. While the effect on live weight is important, the final measure of value is the carcass. The problem is that the effect of garlic on dressing percentage, breast meat yield, and other carcass parameters is not always reported. The inclusion of carcass evaluation is essential for a complete assessment of the economic impact. (Adebayo et al., 2021).

There is a significant problem with the need to validate the health benefits of garlic under local disease conditions. The immunomodulatory effects of garlic are of great interest, but their practical significance depends on the specific disease challenges faced by birds in a given environment. The problem is that a feed additive that is effective in a clean, controlled laboratory setting may not be as effective in a farm environment with higher pathogen loads. Field trials are needed to confirm these benefits. (Hashemi and Davoodi, 2019).

The problem of the cost-effectiveness of garlic meal as a feed ingredient is a key economic consideration. While garlic is a natural and relatively affordable product, adding it to feed still incurs a cost. The problem is that this cost must be justified by measurable improvements in performance (better growth, better feed efficiency, lower mortality) that translate into higher profits. The economic analysis is therefore an essential component of the evaluation. (Heady and Dillon, 2018).

The issue of consumer acceptance of meat from birds fed with garlic is an important market consideration. While some consumers may prefer the idea of natural additives, the potential for the meat or eggs to have a garlicky odor or taste is a concern. The problem is that if the flavor is transferred to the meat, it could reduce its marketability. Studies that include sensory evaluation of the meat are needed to address this concern. This is an area often overlooked. (Lawless and Heymann, 2018).

The problem of the lack of a standardized form of garlic for use in feed is a methodological issue. Different studies have used fresh garlic, dried garlic powder, garlic oil, or garlic extract, making it difficult to compare results. The problem is that the concentration of the active compounds varies significantly between these forms. The use of a well-defined form, like garlic meal, and the precise reporting of inclusion levels are essential for the reproducibility of research. (Amagase et al., 2018).

This study is designed to address these problems by providing a comprehensive, empirical evaluation of the effect of garlic meal in broiler diets. It will test a range of inclusion levels to determine the optimal dose for performance and health benefits. The study will assess feed intake, growth, feed efficiency, carcass characteristics, and blood parameters. The core problem this research aims to solve is the lack of local, evidence-based data needed to guide the use of garlic meal as a natural alternative to AGPs in broiler production. (Emmanuel and Okafor, 2022).

1.3 Aim of the Study

The aim of this study is to determine the effect of garlic (Allium sativum L.) meal as a feed ingredient on the performance and health of broiler chickens.

1.4 Objectives of the Study

The specific objectives of this study are to:

1. Determine the effect of varying levels of garlic meal on the feed intake and body weight gain of broilers.
2. Assess the effect of garlic meal on the feed conversion ratio (FCR).
3. Evaluate the effect of garlic meal on carcass characteristics (dressing percentage, organ weights).
4. Determine the effect of garlic meal on blood parameters (serum cholesterol and glucose).
5. Assess the economic implications of incorporating garlic meal into broiler diets.

1.5 Research Questions

The following research questions were formulated to guide this study:

1. What is the effect of different inclusion levels of garlic meal on feed intake and weight gain?
2. How does garlic meal affect the feed conversion ratio (FCR) of broilers?
3. What is the effect of garlic meal on the carcass characteristics of the birds?
4. What is the effect of garlic meal on serum cholesterol and glucose levels?
5. Which inclusion level of garlic meal is the most economically viable?

1.6 Research Hypotheses

The following null (H₀) and alternative (H₁) hypotheses were tested in this study:

1. H₀: Garlic meal inclusion does not have a significant effect on the body weight gain of broiler chickens.
   H₁: Garlic meal inclusion has a significant effect on the body weight gain of broiler chickens.
2. H₀: Garlic meal inclusion does not have a significant effect on the feed conversion ratio (FCR).
   H₁: Garlic meal inclusion has a significant effect on the feed conversion ratio (FCR).
3. H₀: Garlic meal inclusion does not have a significant effect on the serum cholesterol level of broilers.
   H₁: Garlic meal inclusion has a significant effect on the serum cholesterol level of broilers.
4. H₀: Garlic meal inclusion does not have a significant effect on the carcass dressing percentage.
   H₁: Garlic meal inclusion has a significant effect on the carcass dressing percentage.
5. H₀: There is no significant difference in the economic net return between the different inclusion levels of garlic meal.
   H₁: There is a significant difference in the economic net return between the different inclusion levels of garlic meal.

1.7 Significance of the Study

This study holds significant value for a wide range of stakeholders. For poultry farmers , the findings will provide a natural, effective, and locally available alternative to antibiotic growth promoters. This will enable them to reduce their reliance on antibiotics, address consumer concerns about AMR, and potentially improve their flock’s health and performance. The study will provide clear, evidence-based guidance on the optimal inclusion level of garlic meal, helping farmers to maximize their return on investment.

For researchers and academics in animal nutrition , this study will contribute valuable data to the growing body of knowledge on phytogenic feed additives. The dose-response design provides a robust framework for understanding the effects of garlic. The local data, from a specific context in Nigeria, adds to the global evidence base. The study will also serve as a foundation for further research into the mechanisms of action of garlic and its interaction with other feed components.

For policymakers and regulatory agencies , the study will provide evidence to support the promotion of natural alternatives to antibiotics. This is directly relevant to national and global efforts to combat antimicrobial resistance. The findings can inform the development of policies and guidelines that encourage the use of safe, effective phytogenic feed additives. The study contributes to the broader goal of building a more sustainable and responsible livestock sector.

For the feed industry , the study will provide valuable information on the potential of garlic meal as a functional feed ingredient. The data on performance, health benefits, and economics can inform product development and marketing strategies. The study highlights a potential market opportunity for feed additives that are both effective and align with consumer preferences for natural products.

1.8 Scope of the Study

This study is focused on the effect of garlic meal as a feed ingredient in the diets of broiler chickens. The study involves the use of 150 day-old broiler chicks over an 8-week period. The independent variable is the inclusion level of garlic meal (0%, 0.5%, 1.0%, 1.5%, and 2.0%). The dependent variables include feed intake, body weight gain, FCR, carcass characteristics, and blood parameters (cholesterol and glucose). The study is limited to the use of garlic meal (dried, ground garlic) and to broiler chickens. It does not cover the use of other forms of garlic (oil, extract), other poultry species, or the evaluation of meat organoleptic properties.

1.9 Limitation of the Study

This study is subject to certain limitations. The primary limitation is that the experiment is conducted under controlled conditions, which may not perfectly replicate the challenges of a commercial farm environment. The study uses a single breed of broiler, and the response of other breeds may differ. The study is limited to a single production cycle (8 weeks), and the long-term effects of garlic supplementation are not assessed. The economic analysis is based on a specific set of feed and ingredient prices, which may vary over time and by location. Finally, the study does not include a detailed analysis of the gut microflora, which would provide a deeper mechanistic understanding of the observed effects.

1.10 Definition of Terms

For the purpose of clarity, the following terms are defined as they are used in this study:

1. Garlic Meal: Dried and ground garlic (Allium sativum L.) used as a feed ingredient.
2. Phytogenic Feed Additive: A plant-derived substance added to animal feed to improve performance and health.
3. Antibiotic Growth Promoter (AGP): A sub-therapeutic dose of antibiotics used in animal feed to enhance growth.
4. Feed Conversion Ratio (FCR): A measure of the efficiency with which an animal converts feed into body mass (feed consumed / weight gained).
5. Carcass Characteristics: The physical attributes of the slaughtered bird, including dressing percentage and organ weights.
6. Dressing Percentage: The weight of the carcass expressed as a percentage of the live weight.
7. Allicin: The primary bioactive compound in garlic, responsible for many of its health benefits.
8. Antimicrobial Resistance (AMR): The ability of microorganisms to resist the effects of drugs that were once effective against them.
9. Serum Cholesterol: The level of cholesterol in the blood.
10. Inclusion Level: The percentage of a particular ingredient included in the total feed ration.