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The growing global emphasis on sustainability has brought renewed focus to innovative approaches in managing animal byproducts and wool. Traditionally seen as waste, materials like hides, bones, fats, and wool are now being recognized for their potential to be repurposed into valuable, eco-friendly products. Wool, in particular, is a renewable resource gaining importance for its biodegradability and versatility in sustainable applications. "Animal Byproducts and Wool Science: Processing, Utilization, and Sustainable Applications" explores transformative practices and research that drive the future of these industries, offering practical solutions for minimizing environmental impact. Through insights from experts in environmental science, material engineering, and sustainable manufacturing, this book highlights the opportunities and challenges in harnessing the full potential of these resources. This work aims to inspire innovation and spark global dialogue on the role of sustainability in shaping our production and consumption practices, showcasing how waste can be transformed into valuable resources for a more sustainable future. I am deeply grateful to my parents, Sri Narayan Chandra Sarkar and Mrs. Arati Rani Sarkar, for their unwavering support in creating this book. Thanks to my sister and brother-in-law for their constant encouragement. I also appreciate my teachers, whose guidance fostered my passion. Special thanks to my students of the College of Veterinary Sciences and Animal husbandry, Tripura, for inspiring me in this journey. I am extremely grateful to my student Bashanti Biswas, for assisting me with the numerous illustrations in this book. Lastly, I am thankful to my friends, family members and colleagues for their support during challenging times, keeping me focused and motivated.

India has a substantial livestock population, with animal husbandry acting as a supplementary occupation for about 67% of the rural population. Unlike the commercially oriented farming systems found in Western countries, livestock rearing in India is intricately linked to rural life, where most farmers maintain a small number of animals. Currently, India’s livestock population surpasses 535 million, which includes 192.49 million cattle, 109.85 million buffaloes, 74.26 million sheep, 148.88 million goats, 9.06 million pigs, and over 850 million poultry birds. Each year, approximately 100 million animals are slaughtered in nearly 4,000 slaughterhouses, resulting in a significant amount of by-products or offals. In tropical regions, a considerable portion of these by-products deteriorates before they can be utilized, primarily due to a lack of knowledge, skills, and infrastructure. Enhancing profitability in the livestock sector could be realized through improved utilization of animal by-products and waste. Many slaughterhouses presently do not have sufficient facilities to collect and preserve these byproducts in a timely manner. Additionally, retrieving fallen animal carcasses from remote rural areas often presents challenges. The competitiveness of the meat industry can be bolstered by more effective use of by-products. It is estimated that by-products such as skin, pluck, head, feet, and gut can recover approximately 30% and 35% of the live animal value for goats and sheep, respectively. Thus, it is crucial to add value to significant by-products.

Given our substantial livestock population, it is essential to efficiently process animal by-products to enhance economic gains and generate employment opportunities for individuals with limited educational backgrounds. To effectively manage the high density of livestock, it is advisable to establish animal by-product processing facilities at intervals of every 50 kilometers. Additionally, situating these facilities in proximity to abattoirs can contribute to the reduction of pollution. Furthermore, the waste generated from both abattoirs and processing plants can be utilized to produce biogas, offering mutual benefits. Incorporating by-product utilization facilities is a critical component of modern abattoirs. This approach not only boosts profits for producers but also mitigates environmental pollution resulting from improper waste management. In nations such as India, where there is a scarcity of modern abattoirs and many operate using outdated practices, it becomes particularly vital to establish facilities dedicated to the management of deceased animals and slaughterhouse waste. Some developing countries have even resorted to employing mobile units to effectively manage dead and fallen animals. While it is frequently asserted that every part of an animal, with the exception of its last cry, holds value when utilized appropriately, the actual utility of byproducts is contingent upon various factors, including the size of the abattoir (the number of animals processed daily), the availability of raw materials, the current applications of by-products, and their significance. A standard by-product utilization facility encompasses various components such as rendering plants, hide/skin storage, and casing processing units. These facilities gather raw by-products and transport them to different processing centers located away from the slaughterhouse. For example, glands may be directed to the pharmaceutical sector, skins to tanning operations, fat to soap production, and bones to gelatine extraction. When designing such a facility, it is crucial to consider the availability and quantity of raw materials to ensure efficient functioning and comprehensive utilization of by-products.

Rendering is the process of transforming deceased animals or condemned meat into valuable products, such as carcass meal. Traditionally, rendering specifically referred to the extraction of fat from animal materials through heating. However, the term has evolved to encompass the production of carcass meal, meat meal, and technical fat. While the traditional method of rendering involved boiling animal remnants to extract fat, contemporary rendering includes the heating or steaming of carcasses to produce a nearly sterilized material that retains nutrients. The animal by-products utilized in rendering consist of excess fat, hooves, and offal. In the past, tallow was employed in the manufacture of soap and candles, while other by-products like heads and hooves were repurposed for fertilizers. Meat packers quickly recognized the potential for profit in processing these by-products. Today, the rendering industry generates a variety of valuable products, including both edible and inedible oils, chemicals, meat meals, and bone meals, derived from materials such as viscera, bones, trimmings, dead stock, and feathers. A substantial portion of these by-products is recycled into useful products. In developed nations, as well as in India, integrated abattoirs and meat processing facilities manage such waste utilizing advanced equipment and sophisticated processes. Pre-rendering operations: It is essential to process raw materials from the slaughter floor swiftly and comprehensively to guarantee the highest quality of the final product. Prior to placing these materials into the cooker, they require adequate preparation. Heads, feet, condemned carcasses, and bones from the boning department are initially reduced or crushed into smaller fragments using shredders. Additionally, bones can be further reduced in size with machines referred to as “pre-breakers.” Intestines and other soft tissues, which may be contaminated with feed or manure, must be opened, cleaned, and reduced in size before being incorporated into the cookers during the inedible rendering process.

Blood serves as a significant byproduct within the meat industry, and the  efficient management of its collection and processing is crucial for improving profitability. The amount of blood obtained from slaughtered animals typically ranges from 5-7% of their live weight. Despite diligent efforts, a portion of blood is inevitably lost during the slaughtering process due to spillage and various other factors. To reduce these losses, several essential practices can be adopted: 1. Effective slaughterhouse design: Enhancing the layout and operational procedures within the slaughterhouse can significantly minimize spillage. This encompasses the implementation of well-structured drainage systems and collection vessels. 2. Training and protocols: It is essential to ensure that personnel are thoroughly trained in blood collection methods and strictly follow established protocols to mitigate accidental loss. This involves appropriate handling and prompt processing to prevent clotting and spoilage. 3. Technology: Allocating resources towards advanced blood collection and processing technologies can enhance operational efficiency. Automated systems facilitate the collection, filtration, and storage of blood while minimizing waste. 4. Regular maintenance: Maintaining equipment and facilities in optimal condition is vital to prevent leaks and other complications that may result in blood loss. 5. Storage and processing: After collection, blood must be processed promptly to prevent coagulation. Efficient cooling and storage practices are essential for preserving its quality and maximizing its potential for subsequent processing into products such as blood meal or plasma. Collection of Blood Blood may be collected directly into metal or plastic drums when animals are suspended for bleeding. In cases where the animals are slaughtered on the ground, small enamel or plastic bowls can be placed under the bleeding site to collect the blood, which can subsequently be transferred into a drum. The anticipated yield of blood from average tropical livestock is generally as follows:

Bones, horns, and hooves represent essential by-products of the slaughterhouse sector. Frequently obtained from deceased or fallen animals, these by-products possess considerable applications both independently and in the production of secondary goods. Their use fosters the development of secondary rural industries, consequently creating employment opportunities for individuals in rural regions. Furthermore, by fully utilizing these by-products, producers can secure higher prices for their livestock, while processors may experience enhanced profitability. Effective management of these by-products could also play a role in reducing the costs associated with meat and meat products. Composition of Bone Bone constitutes roughly 15% of the weight of a dressed carcass, although this figure may fluctuate due to variables such as breed, age, fat content, and overall health. Generally, the percentage of bone in a dressed carcass is assessed as the weight of the bones in relation to the total weight of the carcass post-dressing. The bone content varies as follows: • Young cattle and buffalo: 15% to 20% of carcass weight. • Older cattle and buffalo: 20% to 25% of carcass weight. • Pigs: 15% to 20% of carcass weight. • Sheep and goats: 25% to 30% of carcass weight. • Poultry: 30% to 35% of carcass weight.

The intestines of domesticated animals, which are a byproduct of slaughterhouses, are employed in numerous applications. Intestines that function as food containers are referred to casings. Non-consumable uses encompass catgut, strings for musical instruments and rackets, along with various other specialized applications. Additionally, intestines can be ingested following meticulous cleaning and cooking with spices. Among these applications, sausage casings yield the highest profit. Different nations exhibit distinct preferences for sausages, and these preferences frequently determine the varieties of casings utilized. In addition to intestines, casings can also be sourced from weasands (oesophagus), urinary bladders, stomachs, and rectums. Although artificial casings made from plastic materials and hydro-cellulose are prevalent in Western nations, natural animal casings continue to be in high demand due to their distinctive properties. Natural casings, which are obtained from the intestines or other parts of animals such as sheep, pigs, or cows, undergo processing to become edible and are utilized in the production of sausages and other processed meats. They are esteemed for their elasticity, enabling them to conform to the shape of the sausage filling, and they play a crucial role in enhancing the flavour and texture of the final product. Natural casings, are frequently favored for traditional or artisanal sausages because of their authentic origin and their capacity to improve the taste and visual appeal of the sausages.

Animal organs and glands play a crucial role in both nutrition and medicine. These organs encompass the brain, heart, liver, lungs, spleen, tongue, pancreas, udder, stomach, uterus, testes, thymus, kidneys, parathyroid, adrenal glands, and ovaries. Some of these are consumed as food, while others find application in medical practices. Glands, constituting approximately 0.28% of an animal’s total weight, are regarded as valuable by-products of meat production and are increasingly utilized in contemporary medicine for the extraction of beneficial substances. The secretions from both endocrine and exocrine glands are essential for the growth and functioning of the body, with hormones derived from these glands being employed to address deficiencies and serve as therapeutic agents. 1. Human consumption: The majority of glands are ingested alongside meat; however, in the case of cattle and buffalo, ovaries and testes are typically discarded, while other glands are consumed. In smaller animals, it is common to eat all glands with the exception of the ovaries. The liver is especially prized for its rich nutritional profile, being abundant in vitamins A, D, and B complex, which are advantageous for conditions such as poor vision, bone development, and anaemia. 2. Medicinal uses: Glands are responsible for producing hormones that offer significant medicinal advantages, including the treatment of anaemia, diabetes, and various other health issues. They also contribute to the development of secondary sexual characteristics in both males and females. Extracts derived from these glands are invaluable for restoring hormonal deficiencies within the body. The incorporation of animal glands into pharmaceutical manufacturing represents a notable advancement in modern science. In Western nations, there has been a concentrated effort on the efficient collection and utilization of these glands, acknowledging their economic significance for slaughterhouses and the meatpacking sector.

Historically, humans have utilized animal skins for various purposes including shelter, clothing, weapons, and food containers. In contemporary times, skins and hides significantly contribute to foreign exchange earnings within the animal husbandry sector and are widely employed by the leather industry. At slaughterhouses, hides and skins are generally collected and dispatched to tanneries on the same day. If a tannery is not in close proximity, hides are preserved through salting or curing prior to being transported in batches. A skin (the outer covering) from a fully grown large animal is termed a hide; it is comparatively large, thick, and heavy, typically exceeding 30 lb (13.62 kg) for cattle or buffalo. Conversely, the outer covering of smaller animals such as sheep, goats, pigs, and young calves is known as skin. This type is smaller, thinner, and lighter. The term “slunk” refers to the skin of an unborn calf, which is often utilized for parchment, light suede, or drum skins. Calf skin is derived from young calves that have not yet reached maturity, and it is generally softer and more delicate than the hides of older animals. Its fine texture renders it highly sought after for premium leather goods. In contrast, kip skin is obtained from older but still immature calves. It is thicker and more robust than calf skin while being more refined than adult hides. Kip skin is recognized for its blend of durability and softness, making it ideal for longlasting leather products. Hides and skins constitute approximately 4-11% of an animal’s live weight, influenced by factors such as species, age, breed, and health. In cattle, the average hide yield is about 7% of live weight, whereas in sheep and goats, the average skin yield is around 11% of live weight. Hides and skins rank among the most valuable by-products of animals and are transformed into leather through the tanning process. The trimmings are repurposed for the production of glue, artifacts, or as feed supplements.

The poultry industry generates by-products that encompass all materials derived from farms and processing facilities that are not intended for human consumption. These by-products can be classified as either edible or inedible. The edible by-products primarily consist of tissues and bones extracted from poultry carcasses. Conversely, inedible by-products comprise hatchery waste, which includes infertile eggs, deceased embryos, dead chicks, and eggshells, as well as feathers, blood, offal, fat, and manure. These by-products are typically divided into three categories: 1. By-products from the production phase, which consist of litter and manure sourced from the farm. 2. By-products from hatcheries which include materials originating from the hatchery, such as the shells of hatched eggs, dead embryos, infertile eggs, and deceased chicks. 3. By-products from the poultry processing plant, which encompass blood, feathers, offal (including feet, heads, and intestinal tracts), condemned birds etc. 1. By-products from the production phase: Poultry litter and manure from caged layers are extensively utilized as a protein supplement in the diets of both poultry and livestock. Following sterilization and dehydration, poultry manure can be integrated into feed, containing approximately 27-29% protein. It can be incorporated into the diets of broilers at levels of up to 20% and layers at 25%. In addition to their application in animal feed, poultry manure and litter are valuable as a ‘surface dressing’ for agricultural fields. They function not only as effective fertilizers but also improve soil texture. One ton of deep litter yields approximately 29.48 kg of nitrogen (equivalent to 136.08 to 147.42 kg of ammonium sulphate), 20.41 kg of phosphorus (equivalent to 113.40 to 136.08 kg of ordinary superphosphate), and 20.41 kg of potash (equivalent to 45.34 kg of potassium), along with 6.80 kg of magnesium, 6.80 kg of sodium, and 27.21 kg of calcium. Furthermore, poultry manure is rich in trace elements such as boron, copper, iron, sulphur, and zinc.

In the realm of meat processing, waste is defined as the materials produced during the processing of meat and its byproducts that currently lack economic value and often lead to disposal expenses. This definition may vary depending on market dynamics. The waste generated in meat processing primarily consists of both solid and liquid elements. The solid waste includes manure and residual animal tissues such as meat and fat, while the liquid waste encompasses blood and other bodily fluids. Generally, small remnants of tissue and manure are combined with water and directed to sewage systems. In larger processing facilities, blood is collected and dehydrated for use as animal feed. It is essential to effectively utilize animal farm residues, which include dung, droppings, and urine. Likewise, innovative approaches should be employed to make use of slaughterhouse waste, which consists of ruminal contents, blood, urine, and trimmings of meat and fat, in order to enhance their value. It is vital to discover comprehensive and inventive methods for utilizing all inedible animal parts. The proper management of slaughterhouse waste not only mitigates pollution but can also generate fuel for lighting and heating within the abattoir itself. In rural and suburban areas of India, buffalo and cow dung are frequently dried into cakes and utilized as cooking fuel. Furthermore, dung compost contributes to the enhancement of soil humus and fertility, with approximately two-thirds of dung being used as fuel and one-third as fertilizer. Cow dung, which is abundant in organic matter and nitrogen, is also traditionally employed as a floor plaster. In certain regions, sheep owners receive compensation for allowing their flocks to graze on fields post-harvest, thereby improving soil fertility through their manure. Consequently, the organic waste produced by animal industries can be effectively harnessed in numerous ways.

In textile manufacturing, fibers serve as the fundamental components of raw materials, distinguished by their length, flexibility, and strength, which enable them to be spun into yarns and woven into fabrics. Extremely long fibers are referred to as filaments. Fibers can be classified as natural, derived from plants, animals, or minerals, or artificial, produced through chemical processes. Natural fibers are those sourced directly from animal, vegetable, or mineral origins and can be utilized for creating nonwoven fabrics or spun into yarns for woven textiles. Typically, they are significantly longer than they are wide. Although nature offers a variety of fibrous materials, including cotton, wood, grains, and straw, only a select few are appropriate for textile applications. The appropriateness of a fiber is determined by its length, strength, flexibility, elasticity, abrasion resistance, absorbency, and surface characteristics. Most textile fibers are slender, flexible, robust, and elastic, allowing them to stretch and revert to their original form. During the 18th and 19th centuries, the Industrial Revolution brought about significant advancements in machinery for processing natural fibers, resulting in increased fiber production. This era saw the introduction of regenerated cellulosic fibers such as rayon, which is produced by dissolving and purifying cellulose, followed by the emergence of synthetic fibers like nylon, which began to compete with the supremacy of natural fibers in the textile industry. Synthetic fibers, with their distinct advantages, started to supplant natural fibers across various sectors. In reaction to this shift, there was a surge in research aimed at enhancing natural fibers through improved strains, advanced production techniques, and modified properties of yarns and fabrics. Nevertheless, synthetic fibers, being more economical and less labourintensive, captured a larger share of the market.

Apparel wool: Any wool utilized for the creation of garments, excluding carpet and pulled wool, is referred to as apparel wool. Bale: A bale is a wool package that contains a designated minimum weight of wool. The wool is compactly packed into bales, entirely covered with new gunny cloth, and secured with multiple iron hoops. Each bale typically weighs between 100 kg and 200 kg, which is considered a standard commercial weight. Belly wool: Belly wool is the wool that grows on the underside of sheep. Black wool: Black wool encompasses any wool that is black, brown, or gray in colour. Blending: The process of combining various grades and/or lengths of wool in either their raw or semi-compressed state to produce a specific type of yarn is known as blending. Blood grade: Blood grade initially indicated the percentage of Merino (fine wool) genetics present in a fleece. Break: A break is a noticeable weak point along the locks in fleeces, resulting from a decrease in the diameter of the wool fibers. This condition is usually caused by illness, fever, or significant stress. Bright wool: Bright wool is grease wool that is almost white and exhibits minimal yellow coloration due to excess yolk. Britch or breech wool: Britch or breech wool pertains to the wool harvested from the hindquarters of sheep, which is generally the coarsest section of  the fleece. Buck fleeces: Buck fleeces are those obtained from mature rams. They are usually longer and coarser than ewe wool from the same breed and possess a distinct ram odour. Burr: Burr denotes vegetable matter, such as twigs and straw, that can be found in wool.

Wool serves as a dense, wavy, and fibrous protective layer for sheep, primarily made up of the insoluble protein keratin. The wool fiber develops from follicles located in the dermis, which is the skin’s middle layer. Each wool fiber comprises two distinct layers: 1. Outer layer: This layer consists of flat, irregularly shaped scales that overlap, resembling fish scales. These scales are less tightly bound than those found in hair and are essential to the wool’s characteristics, such as its capacity to shrink, strengthen, and felt. The outer layer also affects the overall quality of the wool. While the sheep is alive, the outer scales are coated with wool sweat or grease (termed suint), secreted by specialized glands to preserve the fiber’s condition. This grease can be partially removed during washing, and its presence influences the wool’s condition, which pertains to the quantity of grease or oil present in the wool. 2. Inner layer: Known as the cortex, this layer is composed of long fibrils that are bonded together. In contrast to hair, which contains an air-filled medulla in its inner layer, wool does not possess this feature, contributing to its superior strength compared to hair. Morphological Structure of Wool: Technically, wool comprises three layers: cuticle or epidermis, cortex and medulla. 1. Cuticle: The outermost layer of the wool fiber, referred to as the cuticle, is made up of flat, irregularly shaped scales that overlap with their edges directed toward the fiber tip. This overlapping configuration, akin to roof tiles, produces a rough texture that increases friction and aids in felting. When disturbed, these scales interlock, leading to the entanglement of fibers and the formation of a matted fabric, which is beneficial for felted textiles. Additionally, the cuticle possesses a waxy coating that offers a water-repellent barrier, preventing water penetration while permitting moisture vapor absorption, thereby enhancing wool’s resistance to water-based stains and improving comfort by wicking moisture away.

Wool, which is sourced from sheep, is a significant protein fibre categorized as an animal fibre. Its hygroscopic nature allows it to absorb moisture effectively. Composed mainly of keratin, a protein created by amino acids linked through peptide bonds, wool possesses unique characteristics due to its sulphur content, setting it apart from other animal fibres. The fibres of wool are crimped and elastic, growing in clusters. This crimping generates air pockets that provide insulation, while the outer surface features overlapping, serrated scales that enable the fibres to interlock and create felt. For thousands of years, wool has been utilized as a textile because of these distinctive attributes. Properties of Wool Fiber: The properties of wool fibre include the following: 1. Composition of amino acids: Wool fibres consist of amino acids that form the protein keratin. 2. Absorbency: Wool exhibits high absorbency, which allows it to effectively take in moisture. 3. Moisture retention: Wool can hold a considerable amount of moisture in relation to its weight. 4. Thermal insulation: Wool fibres offer superior warmth compared to many other fibres due to their crimp and structure. 5. Chemical resistance: Wool fibres show limited resistance to alkalis (such as strong soaps or detergents) but are resistant to acids.

Classifying wool is crucial in the textile sector for upholding quality standards, enhancing processing techniques, and ensuring that wool satisfies particular market demands. Precise classification aids in choosing the appropriate wool type for a variety of products, ranging from apparel to carpets, and guarantees uniformity and performance across diverse applications. Classification of Wool: Wool is categorized in a manner akin to hides and skins, based on its intended application. It is divided into three primary types according to fibre length: combing wool, clothing wool, and carpet wool. Long fibres are combed and twisted to produce worsted yarn, whereas shorter fibres are carded and blended in various directions to create woollens. Carpet wool is characterized by an average fineness of 30 to 50 μm and a medullation percentage between 15% and 68%. The quality of wool is influenced by factors such as breeding conditions, climatic conditions, diet, and overall care. For example, excessive moisture can strip natural grease, while colder climates lead to tougher, heavier fibres. Consequently, wool can be classified in two distinct manners: A. By the sheep from which it is sourced, and B. By fleece

Wool is a natural fiber that possesses numerous outstanding characteristics, rendering it both functional and visually appealing. Nevertheless, not all wool is created equal; there exists considerable variation in the quality found in the marketplace. This explains the significant fluctuations in price, as some wool is of superior quality and therefore commands a higher price. Various factors influence the quality of this fiber and, consequently, its value. Below is a list of some of these factors. a) The diameter of the wool fiber is the most critical factor affecting its quality and price. Generally, merino wool is regarded as the highest quality due to its fine texture, which produces an exceptionally soft fiber. In simple terms, the finer the wool, the greater its worth. b) Consistency in fiber diameter is another vital aspect; the more uniform the fiber, the higher its value. c) The colour of wool also plays a significant role in determining its value. Wool that is white or off-white can accommodate a wider array of dyes used in fabric manufacturing. d) Staple strength is a measure of the fiber’s capacity to endure the production process. A higher staple strength results in less waste during manufacturing. Wool is a valuable by-product of sheep, differentiated from hair by its enhanced elasticity, flexibility, and curliness. The quality of wool is affected by factors such as shrinking, strengthening, and felting conditions. In their natural form, wool fibers are coated with wool grease (sweat) and wool soap or yolk (suint), which are secreted by specialized glands to preserve the wool’s condition. Wool is classified into three primary types of fibers:

The processing of wool encompasses multiple stages that convert raw fleece into functional fabric or yarn. Each phase in the wool processing procedure is vital in influencing the ultimate quality and appropriateness of the wool product for diverse uses. Below is a concise overview of the steps involved in wool processing: 1. Shearing or pulling 2. Skirting 3. Washing or scouring 4. Carding 5. Combing 6. Spinning 7. Dyeing 8. Weaving and knitting 9. Finishing 10. Packaging

Animal bristles are natural fibers derived from the hair or fur of various animals, mainly pigs and horses. Celebrated for their distinctive characteristics, these bristles have been employed for centuries across a range of uses. Bristles consist of stiff, wiry hairs from pigs, hogs, or boars, and are typically utilized in the manufacture of different types of brushes. They are predominantly harvested from the back, neck, and tail, as the hairs located on the flank and belly are too short for effective use. Pig bristles are characterized by their coarse, stiff texture and tapered shape, often featuring split or flagged tips. These flagged tips improve their efficiency in paint and varnish applications due to their capacity to retain paint effectively. Shaving brushes crafted from soft bristles surpass synthetic options owing to their enhanced water absorption and retention abilities. In our nation, bristles are primarily obtained from local and crossbreed pigs. Indian bristles are noted  for their coarseness and durability, although their longer flagged tips (whichcan constitute up to 30% of their total length) necessitate trimming prior to use, potentially diminishing their overall value. Bristles are harvested from live pigs or boars once or twice annually, as well as from slaughtered or deceased animals. In certain bacon processing facilities, bristles are also collected by shaving the skins of slaughtered animals postscalding. Those obtained from live pigs generally exhibit superior lustre and resilience compared to those from deceased animals.