Preface

In 1945, the American grocer Atlantic & Pacific Tea Company (A&P) organized the first of its "Chicken of Tomorrow" contests with the national finals held in 1948. For the finals, breeders submitted a case of 30 dozen hatching eggs to an Eastern Shore hatchery, where the eggs were hatched and the offspring fed until they reached the market weight and were then slaughtered. Broilers were judged on several factors, including growth rate, feed conversion efficiency, and the amount of meat on breast and drumsticks. Because the original purpose of most birds was to grow large quickly, breeders used weight as the primary selection criterion. Genetic line companies found that weight was moderately heritable, with 20 to 40 percent of the trait genetically controlled. Though simple, this selection process helped improve broiler breeder performance across generations. Market forces have changed selection criteria over the years. A more integrated and consolidated industry learned that weight and growth rates alone could not be the only selection criteria considered. This was particularly true as feed costs increased. Today, feed accounts for between 65 and 70 percent of the input cost for a broiler. Newborn chicks grow 31% (55 g/bird) on day one, and 5,902% (2,521 g/bird) on day 35. This astonishing performance of the modern chicken comes from: (1) intensive selection for growth rate, (2) meticulous attention to health and husbandry, and (3) advances in feed formulation, matching the nutrient contents of the feed with the nutrient requirements of the bird. That is why gut health and feed efficiency are so crucial for broiler chickens since feed efficiency is considered "the money saver." In today's broiler industry, subclinical forms of coccidiosis or necrotic enteritis are often financially more devastating than acute, short-term infections. Likewise, dietary factors that modulate the immune system and gut microbiota should be considered when formulating diets and managing feeding practices. As the growth period is progressively shortened and feed efficiency continuously improved, the health care and nutrition of the bird are becoming more demanding. This makes it more important to pay attention to the minute changes that occur in the gut, which are often overlooked because the damage is subtle and usually characterized by microscopic changes in the mucosal layer. This book presents updated information on this fascinating industry in the areas of management, nutrition, health, diseases, and hatchery and incubation.

The editors express their sincere appreciation to all of the authors who contributed to this book for their hard work and dedication, as well as to the IntechOpen editorial team for allowing us to complete this project.

> **Guillermo Tellez-Isaias and Juan D. Latorre** Department of Poultry Science, University of Arkansas Agricultural Experiment Station, Fayetteville, AR, USA

> > **Yordan Martínez-Aguilar** Zamorano University, Tegucigalpa, Honduras

**1**

**Chapter 1**

**Abstract**

The Impact of Heavy Metals on the

Chicken Gut Microbiota and Their

It is important to consider the health and well-being of birds in various production methods. The microbial makeup and function of a bird's gastrointestinal (GIT) system may vary based on the bird's food, breed, age, and other environmental conditions. Gut flora play a critical role in maintaining intestinal homeostasis. Environmental exposure to contaminants such as heavy metals (HMs) has been linked to a wide range of disorders, including the development of dysbiosis in the gut, according to many studies. Changes in the gut microbiota caused by HMs are a major factor in the onset and progression of these illnesses. The microbiota in the gut is thought to be the first line of defense against HMs. Thus, HMs exposure modifies the gut microbiota composition and metabolic profile, affecting HMs uptake and metabolism by altering pH, oxidative balance, and concentrations of detoxifying enzymes or proteins involved in HM metabolism. This chapter will focus on the exposure of chicken to HMs from their feed or water and how these HMs affect the immune

**Keywords:** poultry, chicken, broiler, GIT, heavy metals, microbiota, diseases

greater risk of infection and speeds disease transmission [2].

Among the most popular types of poultry raised for human consumption are domestic chickens. At 35–40 days of age, a typical broiler chicken will weigh around two kilograms [1]. During this period, they require approximately 3–4 kilograms of feed per day because of their rapid growth. While raising chickens in close proximity is necessary to meet the demand for chicken meat, this practice puts the birds at

There is a wide range of microorganisms that colonize an animal's digestive system as soon as it is born or hatches, and these microorganisms change over time [3]. The gut microbiota of an animal, a human of the same species, and the location of the host's body all differ [4]. In the gut microbiota, which is a complex, interconnected community of organisms, the actions of all microbial components have a direct effect on its functions [5]. When the host and microbes interact in a way that benefits both of them, an ecological system is created [6]. As with humans, animals' gut microbiome serves many of the same functions: scavenging energy from undigested feed

Health and Diseases

*Selina Acheampong*

system resulting in various diseases.

**1. Introduction**
