eChapters

• The proportion of bone varies depending on breed and body condition from 12 to 28% in the dressed carcase and approximately 15% in a good large ruminants carcase
• Bone percentage increases with the age and weight of the animal and it is lowest in Aberdeen Angus cattle and it may increase to 28% in low quality large ruminants
• The average bone % in bobby calves is 50%, veal calves 25%, in lamb 17–35%, in pork 12–20% and in poultry 8–17% Important parts of digestive system of meat animals Ox tongue
• Filiform papillae found on the tongue are pointing backward and horny and thus, helps in food prehension
• Actinobacillosis erodes the prominent posterior part of the tongue dorsum
• 10–14 circumvallate papillae are spread in the region of prominent dorsum around the either side of the tongue midline
• Black pigmentation of the tongue surface is fairly normal and not associated with any disease condition
Sheep and goat tongue
• Similar to cattle tongue
• However, papillae are not horny but the centre of the tip is slightly grooved
• Black pigmentation of the surface of the tongue is common in blackskinned sheep.

Bleeding disorders can be either congenital, present from birth, or acquired, developing later in life. Defects in blood clotting proteins typically result in delayed bleeding and deep tissue bruising, whereas platelet defects often lead to superficial bruises, nosebleeds, black stools, and prolonged bleeding at injection sites or during surgery. Blood clotting tests can identify animals with defective clotting proteins, but they are not very sensitive.
Congenital Clotting Protein Disorders
Congenital clotting protein disorders are present from birth, and severe deficiencies or defects in these proteins typically manifest early in life. Such severe defects can be fatal, with affected animals often being stillborn or dying shortly after birth. Additionally, a lack of clotting proteins or vitamin K in a newborn can exacerbate clotting issues. If the level of a specific clotting protein is only 5 to 10% of normal, the newborn might survive but is likely to show signs of illness before reaching 6 months of age.
Hypofibrinogenemia, characterized by an abnormal shortage of fibrinogen in the blood and severe bleeding, has been observed in Saint Bernards. Dysfibrinogenemia, which involves abnormally functioning fibrinogen, has been reported in an inbred family of Russian Wolfhounds. Affected dogs experience mild bleeding problems, such as nosebleeds, but may suffer life-threatening bleeding from injuries or surgeries. The best treatment for this condition is intravenous transfusion with fresh or fresh-frozen plasma.
Factor II (prothrombin) disorders are rare. Prothrombin is a key protein in blood clotting. In Boxer dogs, prothrombin is present in normal amounts but does not function properly. Affected puppies may experience nosebleeds and bleeding gums, which tend to improve with age. In adult dogs, easy bruising and inflamed skin are common. Treatment involves transfusions of whole blood or plasma Factor VII deficiency has been reported in several breeds, including Beagles, English Bulldogs, Alaskan Malamutes, Miniature Schnauzers, Boxers, and mixed-breed dogs. This condition can lead to prolonged bleeding after giving birth and is often diagnosed incidentally during clotting tests.

Introduction
Normal reproduction in the female depends on hormones, which specific chemical substances produced by specialized glands are called endocrine glands. These secretions pass into the blood and lymph fluids and are transported to various parts of the body, where they exert several specific effects. Reproductive hormones may originate in the hypothalamus, pituitary, gonads, uterus, or placenta. Hypothalamic hormones are produced
in the hypothalamus, a portion of the brain that is the neural control center for reproductive hormones. The role of hypothalamic hormones is to regulate the release of other hormones from the pituitary gland, and many hypothalamic hormones are therefore called releasing hormones. The primary releasing hormone of reproduction is gonadotropin-releasing hormone (GnRH). GnRH controls the release of follicle-stimulating hormone (FSH)
and luteinizing hormone (LH) from the pituitary gland, located at the base of the brain. These pituitary hormones regulate the production of estrogen and progesterone from the ovary. FSH stimulates the follicle’s growth, development, and function, while LH causes\= the follicle to rupture and the corpus luteum to develop. The female hormone estrogen is produced by the Graafian follicle on the ovary. Another hormone originating from the
ovary is progesterone, which is produced by the corpus luteum. Each has an important role in the female reproductive process.
A relatively new discovery in reproductive physiology is that follicular growth is not continuous in the bovine, but occurs in waves (2 to 4 waves per cycle). Each wave begins when the dominant follicle in the previous wave gains maximal size, at which time numerous small follicles begin a period of rapid growth. From this group of follicles, one follicle is allowed to grow to a much larger size than the others. This large follicle is called the dominant follicle, because it has the ability to regulate and restrict the growth of the smaller follicles. A few days after reaching maximum size, the dominant follicle begins to degenerate and die.

Introduction
Eye
Visual perception, eyesight, sight, or vision is the ability to interpret the surrounding environment using light in the visible spectrum reflected by the objects in the environment. The eyes are the sensory organs that are extension of the brain; they receive visual information from the environment and transmit them to the visual sensory area of the brain for interpretation.
The pineal and para-pineal glands are photoreceptive in non-mammalian vertebrates. Birds have photoactive cerebrospinal fluid (CSF)-contacting neurons within the paraventricular organ that respond to light in the absence of input from the eyes or neurotransmitters.
Accessory Structure of the Eye
Eyelids - (Palpebrae) The free margins of the eyelids form the palpebral fissure. The edges where the upper and lower eyelids meet are called the lateral and medial canthus. The palpebral margins are lined by eyelashes. The eyelids are supported internally by sheets of connective tissue that form the tarsal plate.
Glands associated with the eyelids
Glands of Zeis - These are sebaceous glands associated with the eyelashes.
Tarsal glands - (Meibomian glands) - These glands line the inner margin of the lid and
produce a lipid-rich product that prevents the lids from sticking together.
Lacrimal caruncle - This is a mound of tissue in the medial canthus that produces thick secretions.
Conjunctiva It is the epithelium that lines the inner surface of the eyelids and continueson to the outer surface of the eye.
Palpebral conjunctiva lines the inner surface of the eyelid.
Bulbar conjunctiva lines the anterior surface of the eye.
Lacrimal Apparatus It produces, distributes and removes tears. Tears reduce friction, remove debris, prevent bacterial infection and provide nutrients and oxygen for the conjunctiva. Lacrimal glands are located near the lateral canthus of the eye. Tears flow over the cornea and are drained into the nose by the nasolacrimal duct.

Introduction
The endocrine system comprises a network of glands responsible for producing and releasing hormones that regulate essential bodily functions, particularly the conversion of calories into energy for cellular and organ function. Endocrinology, a medical branch, focuses on these disorders, which often present complexities involving a combination of hypersecretion and hyposecretion due to intricate feedback mechanisms within
the endocrine system. Glands within this system release distinct hormones into the bloodstream, where they travel to various cells, playing a pivotal role in coordinating and controlling numerous physiological processes. The coordination of normal physiological processes involves the interplay between the endocrine and nervous systems. Neurons with neurosecretory functions in the supraoptic and paraventricular nuclei of the hypothalamus
generate peptides and amines. Endocrine disorders refer to a broad range of conditions that affect the endocrine system, a complex network of glands responsible for producing and regulating hormones in the body.
Hormones play a crucial role in controlling various bodily functions, including growth and development, metabolism, electrolyte balance, and reproductive processes. When the endocrine system fails to function properly, it can lead to a wide range of disorders that can significantly impact an individual's quality of life. The endocrine system comprises several glands located throughout the body, each producing specific hormones that regulate various physiological processes. The main endocrine glands include:
1. Pituitary gland: Often referred to as the "master gland," the pituitary gland regulates the function of other endocrine glands and produces hormones that control growth and development.
2. Thyroid gland: Located in the neck, the thyroid gland produces hormones that regulate metabolism, energy production, and growth.
3. Adrenal glands: Situated on top of the kidneys, the adrenal glands produce hormones that control electrolyte balance, blood pressure, and stress response.

Introduction
In cattle, the digestive system consists of four primary compartments: the rumen, reticulum, omasum, and abomasum, followed by the small and large intestines. The rumen plays a crucial role as a fermentation chamber, maintaining anaerobic conditions and ensuring thorough mixing, as well as regulating temperature and pH levels. Food, which is frequently re-chewed, enters the rumen through the esophagus, where fermentation occurs.
The byproducts of fermentation are either absorbed within the rumen or moved on for further digestion and absorption in other parts of the digestive system. Simple indigestion in ruminants is a temporary disruption in gastrointestinal function, usually caused by a sudden change in the quality or quantity of their diet. Consuming large amounts of indigestible feed can impair rumen function for 24 to 48 hours after ingestion, as the accumulation of this feed can physically disrupt ruminal activity. Additionally, the breakdown of proteins in the rumen can produce toxic substances such as amides and amines, including histamine. This condition can lead to a significant drop in milk production due to a marked reduction in the production of volatile fatty acids in a hypotonic reticulorumen. Ruminal impaction is a condition seen in ruminants like cows, sheep,and goats, where the  rumen’s contents become compacted, obstructing their movement through the digestive tract. This condition can arise from various causes, including the ingestion of plastic waste, grazing habits, mineral deficiencies, negative energy balance, urbanization, inadequate water intake, low-fiber or high-grain diets, changes in feed or grazing patterns, and stress. The accumulation of foreign material can block fermentation, interfere with the mixing of rumen contents, and disrupt the rumen’s microflora, leading to indigestion. Acute ruminal acidosis is often caused by the sudden intake of large amounts of carbohydrate-rich feed, particularly grains. Subacute ruminal acidosis (SARA) occurs in dairy cattle and is characterized by disrupted ruminal fermentation. It typically results from feeding large amounts of concentrates with insufficient fiber, a practice often used to boost milk production during early lactation. This imbalance in diet can disturb rumen pH and microbial populations, leading to various metabolic and digestive problems. Chronic ruminal acidosis can lead to complications such as rumenitis, which is inflammation of the rumen, and laminitis, a painful condition affecting the hooves. Alkaline indigestion, also known as ruminal alkalosis, occurs when the pH of ruminal fluid rises above 7.5.
 

Introduction
The digestive system is essential for the survival and overall health of all animals, and its proper function is crucial for the digestion, absorption, and metabolism of nutrients. In monogastric animals-those with a single-chambered stomach, such as dogs, cats, pigs, and horses-the digestive process is both complex and finely tuned to meet their specific nutritional needs. Understanding the clinical physiology of digestive disorders in monogastric animals is vital for veterinary professionals, animal caretakers, and researchers, as it enables them to recognize, iagnose, and treat various gastrointestinal conditions that may impact these 
species. This introduction provides an overview of the fundamental aspects of digestive physiology in monogastric animals, outlines common digestive disorders, and highlights the importance of this knowledge in clinical practice.
The digestive tract of monogastric animals consists of several organs that work together to break down food, absorb nutrients, and expel waste. The primary components include the mouth, esophagus, stomach, small intestine, large intestine, and associated glands such as the salivary glands, liver, and pancreas.
The digestive process begins in the mouth, where food is mechanically broken down by chewing and mixed with saliva, which contains enzymes like amylase to initiate the breakdown of carbohydrates. The bolus of food is then transported through the esophagus to the stomach via coordinated muscular contractions known as peristalsis. In the stomach, food is mixed with gastric secretions, including hydrochloric acid (HCl) and digestive enzymes like pepsin, which help break down proteins. The stomach’s acidic environment also plays a critical role in killing pathogens and aiding the digestion of certain nutrients, such as vitamin B12. The stomach of monogastric animals differs from that of ruminants, as it does not possess multiple compartments for fermentation but rather relies on enzymatic digestion.
The chyme (partially digested food) passes into the small intestine, where most digestion and nutrient absorption occur. The small intestine is composed of three segments-the duodenum, jejunum, and ileum-each with specialized functions. Enzymes secreted by the pancreas and bile from the liver facilitate the digestion of carbohydrates, proteins, and fats. The intestinal lining, with its villi and microvilli, maximizes the surface area for nutrient absorption.

Introduction
Heart failure can develop as a complication of almost all congenital and acquired cardiac diseases in dogs and cats. Cardiac disease is a significant global health concern, impacting both humans and domestic animals, particularly dogs. In the animal kingdom, the cardiovascular system consists of essential components, including the heart, veins, arteries, and capillary beds. Its proper function depends on complex mechanisms, such
as the atrioventricular valves (mitral and tricuspid) and the semilunar valves (aortic and pulmonic), which ensure that blood flows in only one direction through the heart. The activity of the cardiovascular system, including heart contraction rates and strengths, as well as blood vessel diameter adjustments, is regulated by the autonomic nervous system (both sympathetic and parasympathetic branches) and various hormones.
The strength of ventricular contractions is influenced by several factors, primarily enddiastolic volume (preload) and myocardial contractility (inotropy). Preload is the amount of blood in the ventricles just before they contract, while contractility refers to the ability of the heart muscle fibers to contract. Preload is determined by the difference between the end-diastolic pressure in the ventricle and the pressure in the pleural space, adjusted for the
stiffness of the ventricular myocardium. This pressure is influenced by the ratio of blood volume to the heart muscle’s compliance. Low-pressure volume receptors in the heart and large veins primarily regulate preload. When these receptors detect increased blood volume or vein distension, they trigger responses such as increased urine production and vein dilation, which help reduce blood volume and lower venous pressures. Increased enddiastolic volume (preload) stretches the ventricular wall, enhancing contraction strength through the Frank-Starling mechanism, or Starling’s law of the heart. This stretching activates receptors in the atria and ventricles, leading to the release of natriuretic peptides like brain natriuretic peptide (BNP) from the ventricles and atrial natriuretic peptide (ANP) from the atria) These peptides promote natriuresis, relax smooth muscle, and counteract
vasopressin and angiotensin II. In dogs, levels of BNP and NT-proBNP are directly related to cardiac stretch.

Introduction
India has a well-established fisheries and aquaculture industry that significantly impacts Gross Domestic Product (GDP), foreign exchange, and nutrition. The fisheries sector plays a crucial role in India’s economy, contributing approximately 1.07% to the national GDP and 6.72% to agricultural GDP in 2021-22 (Economic Survey, 2022). India is second-largest producer of fish in the world (after China), with an annual production of around 16.24 million metric tonnes (MMT) in 2022–23, comprising 12.2 MMT from Inland fisheries and 4.04 MMT from marine fisheries. The fisheries sector has experienced remarkable growth over the decades. Fish production surged from 0.75 MMT in 1950-51 to 12.59 MMT in 2018-19, marking a seventeen-fold increase. This growth has been accompanied by a rise in the sector’s contribution to agricultural GDP, which impressively increased from 0.84% in 1950 to 5.7% in 2017. India is one of the largest seafood exporters, with exports reaching INR 63,969 crores ($8.09 billion) in 2022-23 (Marine Products Export Development Authority - MPEDA). Frozen shrimp is the leading export commodity, followed by frozen fish and cephalopods. The USA, China, the EU, and Southeast Asian nations are key export markets. This robust performance underscores the sector’s role in bolstering India’s foreign exchange reserves. The sector supports direct employment to over 28 million people, mainly in coastal and rural communities (National Fisheries Development Board, 2023) and indirect employment, including processing, transportation, and allied workers.
Fish is an important source of protein, essential fatty acids, vitamins and minerals. The harvest, handling, processing and distribution of fish
provide livelihood for millions of people and also provide valuable foreign exchange earnings. In both the industrialized and developing countries, fish is an important and cheaper source of animal protein to local communities (Adewolu and Adeoti, 2010). Fish is also used as source of other nutrients such as micro nutrients, minerals, and essential fatty acids mainly in the Low Income Food Deficit Countries. However, the disadvantage with the fish is that it is highly perishable though it is an inexpensive protein source. Due to these characteristics, the fish suffers 50-60% higher post harvest losses compared to agricultural commodities.

Introduction
The nervous system in animals is a complex group of highly specialized cells capable of collecting and transmitting information in response to external stimuli via receptors and highly specialized sensory organs. It aids in the regulation of muscle coordination, the release of hormones, neurotransmitters, and other chemical mediators, all of which facilitate numerous bodily activities.
The nervous system is divided into two systems: the central nervous system (CNS), which includes the brain and spinal cord, and the peripheral nervous system. Within these systems, there is another autonomic nervous system (ANS), which is distinguished by higher centers of the hypothalamus, midbrain, pons, and medulla, as well as tracts and nuclei in the spinal cord. The ANS is further divided into sympathetic and parasympathetic
systems, which help maintain homeostasis and activate emergency mechanisms in response to external stimuli. The brain is normally covered by three meninges: piameter, arachnoid, and durameter. These meninges create three spaces: the subarachnoid space (between pia mater and arachnoid), the subdural space (between arachnoid and dura mater), and the epidural space (between dura mater and the ligamentum flavum in the spinal canal). The subarachnoid space includes cerebrospinal fluid, which is isolated from cerebral blood by the morphological and enzymatic activity of cells with tight junctions that regulate intercellular diffusion and solute exchange inside the cells. These cells form a barrier known as the “blood-brain barrier”.
The blood-brain barrier works as a selective permeable membrane, allowing only certain chemicals and medications to pass through while excreting essential components from the central nervous system via energy-dependent efflux pumps like p-glycoprotein. These proteins are encoded by genes such as ABCB1, and mutations in them can result in severe effects such as Ivermectin poisoning in the Colie breed of dogs. Similarly, it aids in the relative isolation of the neurological system from the immune system by establishing an immune-suppressive parenchymal milieu. However, various infections, trauma, and developmental defects can result in underdevelopment or damage to different cerebellar structures. As a result, depending on the portion implicated, it might cause changed behavioral changes in animals such as muscle incoordination, depression, and paralysis. These clinical symptoms may be excitatory.

Introduction
The conceptual foundation of environmental DNA (eDNA) can be traced back to French criminologist Edmond Locard’s principle that “every contact leaves a trace.” eDNA, often referred to as the “blueprint of life,” represents the genetic material shed by organisms into their environment. This innovative approach allows scientists to obtain biological information without directly interacting with or disturbing the organisms. eDNA technology is particularly advantageous in studying megadiverse ecosystems, as it enables the isolation and analysis of genetic material from various environmental samples, such as soil, water, and air. The approach of environmental DNA (eDNA) has its roots in metagenomics, which has long been used to study microbial communities
in soil, water, and sediment. The concept of eDNA was first applied in microbiological research on marine environments (Orgam et al., 1987; Handelsman, 2004). Early breakthroughs in biodiversity monitoring included the detection of invasive species, such as Rana catesbeiana (American bullfrog), in French swamps, demonstrating the potential of eDNA in ecological studies
(Díaz-Ferguson and Moyer, 2014). The persistence of eDNA also depends on the species and habitat: in freshwater, it may last between 15 and 30 days for fish and amphibians, while in marine environments, it typically persists for shorter durations, ranging from 0.9 to 7 days for marine mammals. These variations underscore the importance of understanding environmental and biological factors when applying eDNA methods for monitoring biodiversity and ecosystem health. The transport of eDNA in rivers is particularly rapid, with genetic material potentially traveling tens of kilometers from its source. This dynamic propagation must be accounted for when designing experiments and interpreting results.

Introduction
Pesticides play a crucial role in agriculture. During the period of the Green Revolution, the use of pesticides increased dramatically (Matson et al., 1997). According to the Environmental Protection Agency (EPA), pesticides can be defined as compounds that are used for the destruction, repulsion, or prevention of organisms that can be harmful to cultured crops (pests) as well as affect the regulation of plant growth. They are categorized based on several factors, such as their chemical composition (organophosphates, pyrethroids, neonicotinoids, etc.), based on the types of pests they eradicate (herbicides, insecticides, fungicides, etc.), and application methods. Although each pesticide has a distinct purpose, they all have comparable advantages. Some of the primary benefits of pesticide usage are the prevention of disease andan increase in yield, whereas secondary benefits include economic efficiency, an increase in food quality, facilitation of sustainable agriculture, improving public health, etc. However, the extensive use of pesticides has its consequences. These pesticides are meant to control or eliminate pests, but their toxicity could end up in unexpected areas. Its utilization poses significant harm to the environment, particularly to aquatic ecosystems. While they are essential in agriculture, their unregulated application leads to environmental degradation. The level of toxicity is influenced by factors such as pesticide concentration, mode of action, chemical composition, and persistence in the environment. Pesticides can cause both acute as well as chronic health effects. Through runoff or leaching, they indirectly enter water bodies, harming aquatic flora and fauna. A 2001 study revealed that over 90 percent of fish and water samples collected from various streams contained traces of one or more pesticides (Kole et al., 2001).

Introduction
Cell Cycle: Growth at the cellular level involves the cell cycle, which includes phases of growth (G1), DNA replication (S), and cell division (M). During these phases, cells prepare for and execute division to increase cell numbers. Mitosis and Meiosis: Mitosis results in two identical daughter cells, crucial for tissue growth and repair. Meiosis, on the other hand, is essential for producing gametes (sperm and eggs) and ensures genetic diversity.
Hormonal Regulation
Growth Hormone (GH): Secreted by the pituitary gland, GH stimulates liver cells toproduce insulin-like growth factor 1 (IGF-1), which promotes cell growth and division throughout the body.
Thyroid Hormones: Thyroxine (T4) and triiodothyronine (T3) from the thyroid gland regulate metabolic rate and are vital for normal growth and development, particularly in the nervous system.
Sex Hormones: Estrogens and androgens influence the growth of secondary sexual characteristics and contribute to the final stages of skeletal growth during puberty.
Nutritional Factors
Proteins: Amino acids from dietary proteins are necessary for the synthesis of new proteins and enzymes, which are crucial for cell growth and repair.
Vitamins: Vitamins such as A, C, and D are essential for various growth processes. For instance, vitamin D is vital for bone growth and calcium absorption.
Minerals: Calcium and phosphorus are key for bone development, while zinc and iron are important for cellular functions and overall growth.
Genetic Factors
Genetic Blueprint: Growth patterns and potential are largely determined by genetic factors. Genes influence growth rates, final height, and the development of various body structures.
Growth Disorders: Genetic mutations or abnormalities can lead to growth disorders such as dwarfism or gigantism, illustrating the role of genetics in growth regulation.

Introduction
The aquatic ecosystem is full with harmful contaminants like heavy metals. Due to farming, mining, geochemical composition, and anthropogenic wastes, their concentration has dramatically increased. Heavy metals contaminate aquatic ecosystems through multiple pathways, such as industrial effluents, agricultural runoff, and atmospheric deposition. Once released heavy metals into water bodies, these metals undergo bioaccumulation, wherein they accumulate in aquatic organism’s tissue, including fish, gradually over time over time. Toxicity of heavy metals due to their long persistence in the environment and non-biodegradable nature. Additionally, heavy metals undergo biomagnification, leading to increasing concentrations as they ascend the food chain, posing greater risks to higher trophic level organisms, including fish. Fish serve as crucial bioindicators for evaluating the potential risks of pollution (Lakra & Nagpure, 2009). Exposure to pollutants, particularly heavy metals like cadmium (Cd), iron (Fe), lead (Pb), and copper (Cu), can lead to both acute and chronic toxicity, disrupting various physiological functions, including reproduction. A  ealthy reproductive system in fish signifies their ability to maintain population sustainability. Fish are widely consumed due to their desirable taste and affordability, making them a vital and cost- effective source of animal protein.
Fish are more susceptible to heavy metal pollution than other aquatic species, despite being one of the most widely distributed species. Some heavy metals like cadmium, mercury, arsenic, and lead have no biological significance, while some like iron, copper, and zinc are vital to the metabolism of fish. Heavy metals concentration in the water bodies has increased significantly as a result of farming, mining, geochemical composition, anthropogenic wastes, and other factors. Heavy metals are among the most hazardous and widely distributed contaminants, naturally occurring as trace elements in the hydrosphere (Sankhla & Kumar, 2019). Fish, however, breed in environments that are naturally contaminated with heavy metals. Fish reproduction is essential to the natural ecosystem and is required for the development of aquaculture. Several studies show that heavy metals interfere with fish reproduction by preventing the induction of vitellogenin, postponing oogenesis, increasing the secretion of luteinizing hormone, and lowering the parameters of the gonadal somatic index and ovulation.

Introduction
Intracellular transport of molecules plays a crucial role in maintaining cellular function and organization. The genetic and biochemical processes that regulate membrane trafficking, such as membrane bending, budding, fusion, and fission, ensure the efficient movement of molecules within cells. Despite substantial advances in understanding the molecular aspects of these processes, the broader, or “supramolecular,” regulation of membrane trafficking, which coordinates the overall balance and response to environmental changes, remains less explored. This involves the transport and exchange of membranes and proteins betweenorganelles in a highly organized manner, critical for maintaining cellular homeostasis.
Membrane Trafficking Pathways
Membrane trafficking consists of well-defined pathways connecting cellular compartments like the endoplasmic reticulum (ER), the Golgi apparatus, and the plasma membrane (PM). Proteins and lipids are transferred from the ER to the Golgi and then directed either to the PM or other intracellular destinations. These pathways must be tightly regulated to maintain cellular balance, as any disruptions in membrane flow can lead to cellular dysfunction. In addition to routine cellular maintenance, these pathways must adapt to signals from the environment, ensuring that cells respond appropriately to external stimuli.

Introduction
Ageing, a multifaceted and intricate process, is characterized by a series of transformations that occur at various levels of biological hierarchy, ultimately culminating in death. This phenomenon, marked by its complexity, involves numerous factors that interact simultaneously and operate across different levels of functional organization. The diversity of ageing phenotypes among individuals of the same species and the disparities in longevity
among different species underscore the significant roles of both genetic and environmental influences in shaping the lifespan.At its core, ageing is an ontogenic journey—a process of growing old that encompasses all physiological, genetic, and molecular changes occurring from fertilization to death. The biology of ageing pertains to the progressive accumulation of random molecular defects within tissues and cells, leading to age-related functional impairments in tissues and organs. This relentless, deleterious, and intrinsic phenomenon was famously described by Medawar in 1952 as an “unsolved problem in biology.” Despite the enduring mystery of the ageing process, research has advanced significantly since Medawar’s time, expanding our understanding of this intricate biological conundrum.
Goldberger et al. (2002) define senescence as the progressive deterioration of bodily functions over time, noting that normal human ageing is associated with a loss of complexity in various physiological processes and anatomical structures. Although ageing and senescence are often used interchangeably, they encompass distinct concepts. Senescence refers to a post-maturational process that leads to diminished homeostasis and increased vulnerability to death, while ageing encompasses any time-related process that begins at conception and continues until death. The mechanisms driving ageing are partially intrinsic, influenced by genetic and epigenetic factors, and partially extrinsic, shaped by environmental factors such as nutrition, radiation, temperature, and stress. Genetic factors account for approximately 25% of the variance in human lifespan, with the remainder determined by nutritional and environmental influences. 

Introduction
Metabolism encompasses a series of cellular reactions essential for sustaining life in living organisms. These reactions are part of interconnected pathways within cells, ultimately providing the necessary energy for cellular functions. The importance and evolutionary benefits of these pathways are evident as they are conserved across animals, plants, fungi, and bacteria. In eukaryotes, metabolic pathways operate within the cytosol and
mitochondria, with glucose and fatty acids being the primary sources of cellular energy in animals. Metabolism is organized into distinct pathways to optimize energy capture or minimize energy expenditure. It can be divided into two main processes: anabolism, which involves the synthesis of complex macromolecules, and catabolism, which involves their degradation.
Carbohydrates are the major source of energy in the animal’s diet. Absorbed glucose could be utilized by the animal for several functions. The first priority is the formation of glycogen in the liver, which is stored in muscle and hepatic tissue. However, the body stores very little as glycogen (a starch-like compound), and glycogen could be rapidly hydrolyzed back to glucose through a process called glycogenolysis. This helps in maintaining blood
glucose at a narrow range in normal healthy animals. The second priority is oxidation to form energy (a major function) and is described in the next sections. Since glycogen storage is limited, excess glucose is converted to fat and is stored in adipose tissue. This is accomplished by the breakdown of glucose to pyruvate through a process called glycolysis, which is then available for fat synthesis. The catabolism of glucose occurs in two metabolic pathways: glycolysis and the tricarboxylic acid (TCA; also called citric acid or Kreb’s) cycle.
Glycolysis: Enzymes for glycolysis are located in the cytosol of the cell, and glycolysis occurs in this part of the cell. Glycolysis is the breakdown of 6 C glucose into two 3 C end product pyruvates in aerobic metabolism and lactic acid in anaerobic metabolism. It is a catabolic pathway involving oxidation and yields ATP and NADH (reduced NAD) energy. Glycolysis is the pathway by which other sugars (e.g., fructose, galactose) are catabolized by converting them to intermediates of glycolysis. Fructose can be converted to fructose-6- phosphate by hexokinase. Galactose can enter glycolysis by being converted to galactose- 1-phosphate followed by conversion (ultimately) to glucose-1-phosphate and subsequently to glucose-6-phosphate (G6P), which is a glycolysis intermediate.

Introduction
Physiological disorders or dysfunctions in domestic animals are prevalent and can significantly impact the health and well-being of these animals. Understanding the fundamentals of these disorders is essential for veterinarians, animal scientists, and anyone involved in the care and management of animals. This chapter covers a diverse range of physiological disorders, including cardiovascular, respiratory, gastrointestinal, renal, endocrine, musculoskeletal, neurological, dermatological, reproductive, and ocular disorders. These conditions can manifest differently across species and breeds. This MCQ chapter serves as an introduction to the basics of physiological disorders in domestic animals and aims to test your knowledge on this important subject.

Introduction
In the intricate tapestry of life, the relationship between foodstuffs and animal nutrition forms a fundamental thread, weaving its way through the intricate patterns of ecological balance, agricultural practices, and the sustenance of diverse life forms. The intersection of these two realms is not only pivotal for the flourishing of animals but also crucial for the well-being of ecosystems, human societies, and the planet at large. This intricate connection delves into the nuanced interplay between dietary components, physiological mechanisms, and the broader implications for the health of animals, both domestic and wild.
It is imperative to recognize that foodstuffs are not mere sustenance; they are the building blocks of life, the fuel for growth, and the source of energy that sustains the diverse array of creatures inhabiting our planet. From the microscopic organisms in the soil to the majestic mammals roaming vast landscapes, the quest for nourishment is a universal constant, intricately tied to the delicate balance of ecosystems.
At the heart of this relationship lies the fascinating science of animal nutrition—a field that scrutinizes the complex interactions between dietary elements and an organism’s physiological functions. From the intricacies of nutrient absorption to the role of different foodstuffs in promoting health, animal nutrition serves as a compass guiding us through the intricate pathways of biology, agriculture, and environmental conservation. The journey into understanding animal nutrition commences with a closer look at the varied foodstuffs that contribute to the dietary landscape. Foodstuffs, in this context, encompass a vast array of substances ranging from grains and forage to proteins and fats, each playing a distinctive role in the nutritional well-being of animals. The composition and quality of these foodstuffs are crucial determinants of an animal’s growth, reproduction, and overall
health. Unraveling the nutritional value of these components requires delving into the realms of biochemistry, physiology, and the intricate dance between macronutrients and micronutrients.
Macroscopic entities such as carbohydrates, proteins, and lipids stand as the pillars of animal nutrition. Carbohydrates, in the form of sugars, starches, and fibers, serve as the primary source of energy, fueling the metabolic processes that sustain life. Proteins, comprising amino acids, are the essential building blocks for growth, development, and the maintenance of bodily functions. Meanwhile, lipids, including fats and oils, play
multifaceted roles, serving as energy reserves, structural components, and facilitators of nutrient absorption.

Introduction
Toxic inorganic and organic compounds are continuously contaminating our environment, endangering both human health and the planet’s ecosystems. This is a major worldwide problem. Because they persist in the environment, these pollutants which are caused by industrial processes, agricultural practices, urbanization, and over use of natural resources are very hard to control. While inorganic contaminants, including heavy metals, are difficult to break down naturally and need more complex remediation techniques, organic molecules may frequently be broken down into less dangerous components. Among these methods, bioremediation has become a viable, environmentally beneficial option that uses the inherent powers of fungus, bacteria, and plants to purify
and repair polluted soils and streams.
Phytoremediation, a specific form of bioremediation, harnesses the power of green plants to absorb, accumulate, degrade, or stabilize these harmful substances (Wang et al., 2021). This process not only mitigates pollution but also revitalizes ecosystems by improving soil structure, increasing biodiversity, and supporting sustainable land use. Phytoremediation provides a low-cost
and less intrusive substitute for conventional cleanup techniques, which frequently entail high-energy procedures, chemical treatments, or considerable excavation, as the globe struggles with the growing danger of environmental deterioration. Rapid industrialisation, urban waste, and natural activities can introduce large quantities of highly toxic organic pollutants, including
petroleum hydrocarbons, nitro and halogenated aromatic compounds, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), dibenzofurans and dibenzop-dioxins (PCDD/Fs), solvents, explosives, and pesticides, into both aquatic and soil ecosystems (Tanwir et al., 2021). One of the major challenges to reducing water pollution is the presence of heavy metals including cadmium (Cd), lead (Pb), and chromium (Cr) in industrial and agricultural runoff. Associated with other pollutants, these metals disrupt aquatic ecosystems at the species and community levels, which has an array of negative impacts on animal and human health. The World Health Organization (WHO) has emphasized how important it is to keep an eye on these chemicals in drinking water because of their link to serious health concerns including cancer, respiratory disorders, and cardiovascular illnesses.