Civil Service Examination - Questions and Answers (from 1996 onwards) - 1 | Animal Husbandry & Veterinary Science Optional for UPSC PDF Download

Q1: Write short notes on Derivatives of embryonic veins.
Ans: 

• Blood vessels and cells originate from mesenchyme, with the earliest formative tissue being the angioblast. In the developing embryo, all veins in the body are modifications of a basic plan and include the following pairs:
  (1) Umbilical veins,
  (2) Vitelline veins,
  (3) Anterior cardinal veins,
  (4) Posterior cardinal veins,
  (5) Supra cardinal veins, and
  (6) Subcardinal veins.
• The proximal ends of vitelline and umbilical veins are assimilated by the developing liver, forming the portal system. Mesenteric veins, draining venous blood from the gut into the liver, persist as the portal vein.
• The anterior cardinal veins manage the drainage of venous blood from the head and neck. The posterior, sub, and supra cardinal veins handle venous blood drainage from the posterior regions of the body.
• The cranial segment of the anterior cardinal vein transforms into the sinus venosus of the dura mater, and the cervical segment persists as the internal jugular, giving rise to the external jugular vein. The thoracic segments unite to create the anterior vena cava.
• The posterior cardinal veins undergo degeneration, contributing only a small part to the azygos vein. The subcardinal veins combine to form the posterior vena cava. The supracardinal veins transform into the azygos vein on the right side and the hemiazygos vein on the left side.

Q2: Write short notes on role of tissue fixatives.
Ans: 

• Before examining body tissues and organs for histo-pathological changes using a microscope, it is essential to adequately prepare them. This preparation involves a series of steps including fixing, hardening, dehydration, de-alcoholization, clearing, embedding, section cutting, mounting, staining, and more.
• The primary goal of fixation is to preserve the cell structure in a condition as close to life-like as possible.
  The fixative serves several functions:
  (a) It sets or fixes parts of organs or tissues in a normal position, ensuring that subsequent operations like cutting the material into thin slices or teasing it out do not significantly alter the micro-anatomical arrangement.
  (b) It sets intracellular bodies, allowing for the study of intimate histology and cytology of cells.
  (c) It arrests post-mortem, autolytic, osmotic, and other changes in the tissue.
  (d) It highlights differences in the refractive indices of organ parts.
  (e) It renders insoluble as much of the cell constituents as possible, ensuring resistance to subsequent technical processes needed to create the final slide.
• It is crucial to fix tissues promptly after the death or destruction of the animal, as delaying the process can lead to distortion and dehydration of surface layers. Keeping tissues in normal saline at room temperature can allow autolysis to progress to a confusing extent. Tissue blocks should not be thick, and the volumes of the fixing fluid should be 15 to 20 times that of the tissue being fixed.
• Various reagents can be used for fixing, including formaldehyde, alcohol, acetone, mercuric chloride, chromates, osmic acid, and picric acid. Formaldehyde in a 10 percent solution is commonly used, with adequate fixation achieved in 48 hours at 20-25°C or 24 hours at 35°C. A 20 percent solution hardens in 3 hours at 55°C. It is preferable to expose tissues to the fixative for a longer time at lower temperatures (0-5°C).
• For rapid fixation, a small tissue piece can be placed in 10 percent formaldehyde and warmed to approximately 45°C. This process takes about half an hour, making the tissue ready for sections using the freezing method. Alternatively, the tissue piece can be transitioned from formal solution to increasing strengths of alcohol and finally to xylol, preparing it for embedding in paraffin within an hour.

Q3: Write short notes of the following in about 200 words each:
(a) Differential staining of cytoplasmic elements
Ans: 

• Various cellular components can be identified through cytochemical stains that react to their chemical compositions and enzymatic activities. For protein analysis, stains like naphthol yellow S and mercuric bromophenol blue are used, targeting proteins with basic amino acids such as lysine, arginine, and histidine. 
• Millon's reagent is employed to stain the amino acid tyrosine. Lipid content can be visualized using fat-soluble dyes like Sudan Black B, osmium tetroxide, and Sudan red. Carbohydrates in cellular components, such as plant cell starch, cellulose, and hemicellulose, or animal cell mucoproteins and chitin, can be stained red with Schitt's reagent.
• Enzymes, usually concentrated in mitochondria, are studied using tetrazolium salt, which remains colorless until acted upon by mitochondrial dehydrogenase enzymes, causing it to change color. Riboflavin, vitamin A, and thiamine are detected using fluorescent dyes like berberine, acridine-orange, and yellow and coriphosphine.
• In light microscopy, both acidic and basic stains are utilized to stain cells or tissues. Acidic stains highlight cytoplasmic proteins and carbohydrates, while basic stains are specific for staining the nucleus, chromosomes, and other organelles within the cell.

Q3: (b) Cell Differentiation
Ans: 

• In the early stages of cellular differentiation, cells at one pole of the blastocyst, known as the germ disc, undergo specialization, forming an outer ectodermal layer and an inner endodermal layer with an intermediate layer of mesoderm. These three primary germ layers play distinct roles in the development of various tissues and organs.
• The somites, or body segments, emerge from the outer layer (somatic layer) of the mesoderm and serve as the foundation for the majority of the axial skeleton and musculature. The somites undergo differentiation into three regions. The first region gives rise to vertebrae that encase the neural tube. The second region, situated near the neural tube, develops into skeletal muscles. The third region, the lower part of the somites, forms the connective tissues of the skin.
• Somite differentiation typically begins around 19 days after ovulation in cattle. The number of somites rapidly increases to 25 on day 23, 40 on day 26, and 55 on day 32 of gestation. In cattle, the formation of most organs and body parts occurs between the second and sixth week of gestation. During this period, the digestive tract, lungs, liver, and pancreas develop from the primitive gut. 
• The initiation of muscular, skeletal, nervous, and urogenital systems occurs, with the heart beginning to function and initiate circulation on the 21st day of gestation. The progressive differentiation and divergent specialization of cells lead to the origin of various fetal organs, all traced back to the primary germ layers originating from the inner cell mass.

Q3: (c) Housing of pregnant sows and cows
Ans: 

• Farrowing pens are essential for confining pregnant sows during the farrowing process. Newborn piglets are nearly naked and highly susceptible to cold, requiring an artificial heat source to maintain a temperature of 32°C for the first week after birth. Farrowing pens should be divided into sow and piglet areas, with additional heat provided to piglets as needed. Temperature becomes less critical for piglets after the first week, with a recommended range of 29-30°C from the second to the sixth week of age. Pigs, despite having a thick coat, are more temperature-sensitive compared to other farm livestock.
• Environmental temperature during the early stages of life significantly influences performance, body leanness, and the weight of thyroid and adrenal glands. Mature sows need slightly more space than gilts, with each sow requiring approximately 50 sq. ft. in the pen, excluding space for feeders and guard rails. Guard rails, positioned about 22 centimeters from the floor along three pen walls, protect piglets from accidental harm.
• A farrowing crate with creep provisions is a beneficial addition to the farrowing pen, allowing the sow to farrow safely without endangering the piglets.
• In the case of pregnant cows, they should be moved to maternity pens or calving boxes two to three weeks before the expected calving date. The number of required calving boxes or maternity pens is approximately 5% of the breddable female stock on the farm. These pens should be conveniently located near the farmer's living quarters or milking barn for constant observation of down-calving cows. The pens can be constructed in rows or groups of two or four.
• Each calving pen should have dimensions of 3 x 4 meters for the covered area and an additional 3 x 4 meters for the open paddock. The covered area should have a 1.25-meter high wall with a 1.2-meter wide gate opening into the open lot. Properly sized mangers and water troughs should be installed in each pen, and the floor should be morum, brick-on-edge, or cement paved with a 1 in 40 slope towards the drain.

Q4: Write short notes on the following in about 200 words each
(a) Cyclozoonoses
Ans: 

• Zoonoses are illnesses that can be transmitted from animals to humans, and this can occur either commonly or incidentally. Diseases like Leishmaniasis, Trypanosomiasis, and even Malaria, prevalent in humans, likely originated as animal diseases. The classification of zoonoses is based on the infectious organism's life cycle.
  • Direct Zoonoses: Involves only a single vertebrate host species for the organism's life cycle.
  • Cyclozoonoses: Requires more than one vertebrate host species to complete the organism's life cycle.
  • Metazoonoses: Involves both vertebrate and invertebrate host species for the life cycle.
  • Saprozoonoses: Requires a vertebrate host and a non-animal reservoir or developmental site for completing the life cycle.
• Wild animals and birds often serve as hosts for various microorganisms. Rats, monkeys, and mice are particularly important in zoonotic epidemiology. Despite not being domesticated, these species are attracted to human habitats, seeking food or shelter in or around human dwellings. Certain wild animals like rabid bats, foxes, wolves, or those used as food can directly transmit infections to humans.
• More than 90 diseases are identified as cyclic zoonotic diseases with domestic animal reservoirs. Diseases such as Hydatid disease, Coenurosis, Taeniasis, Cysticercosis, Anthrax, Brucellosis, Salmonellosis, and Pasteurellosis can be transmitted from dogs, swine, cattle, poultry, and sheep. This type of zoonosis involves two vertebrate hosts for the infective organism.

Q4: (b) Placenta
Ans: 

• In all mammals except monotremes and marsupials, there exists an organ that connects the fetus to the uterine wall, known as the placenta. Essentially, it forms through the close association of the uterus' epithelium (endometrium) and the fetal membranes (chorion and allantois). The structure and characteristics of the placenta vary significantly among species. There are two main types: deciduate, where the fetal and maternal parts are closely linked and shed entirely after birth (e.g., in humans and primates), and indeciduate, where the association is not as tight, and the maternal part is not shed (e.g., in domestic animals).
• The attachment between maternal and fetal membranes is simple and diffuse in animals like horses and pigs. In ruminants, there are more complex areas called placentomes, where fetal cotyledons and maternal caruncles interdigitate. Carnivores also exhibit zones of attachment. The proximity of maternal and fetal circulation allows for the exchange of nutrients, waste products, and respiratory gases. Additionally, the placenta secretes hormones that help maintain pregnancy and initiate parturition. While the placenta is typically expelled shortly after birth, retention can occur, especially in cattle, necessitating prompt removal.
• The complete set of fetal membranes includes the yolk sac (vestigial in mammals), chorion, allantois, and amnion. The amniotic sac, containing fluid that suspends the embryo, protects it from drying and helps maintain its shape. The allantois serves as a temporary sac for storing the fetus's urine. The chorion, adorned with villi, closely associates with endometrial crypts, facilitating functions such as nutrition, respiration, excretion, and embryo protection.

Q5: Write short notes on: Role of endoderm in development of embryo in bovines
Ans: 

• The endoderm, one of the three germ layers in the early embryo, is responsible for forming the lining of various vital structures in the body. It gives rise to the lining of the alimentary tract, including associated glands such as the liver, gall bladder, and pancreas. Additionally, the endoderm contributes to the lining of the bronchi and alveoli in the lungs and a significant portion of the urinary tract.
• Key derivatives of the endoderm include the primary tissues of the entire digestive tract, the pharyngeal part of the mouth, the thymus, pancreas, liver, and respiratory epithelium. The mouth and tooth, however, are the result of a combination of ectodermal and endodermal contributions.
• As the embryonic disc expands, the endoderm underneath transforms into the gut endoderm. The gut endoderm then extends into the head and tail ends, forming two internal blind tubes known as the foregut and hindgut. The intermediate region, which connects to the yolk sac, is referred to as the midgut. At each end, the gut interfaces with invaginations of the ectoderm, creating the pharyngeal membrane in the front and cloacal membrane behind, both lined with endodermal epithelium.
• The digestive tube comprises an internal layer of endoderm that evolves into the epithelial lining and glandular structures of the mucous membrane. Surrounding this is the investing layer of splanchnic mesoderm, which differentiates into connective tissue, muscle, and peritoneum. The liver develops from the ventral diverticulum of the endodermal epithelium lining the posterior part of the foregut, which later transforms into the duodenum. Outpocketings from the endodermal lining of the foregut represent the early forms of the pancreas. The respiratory system's epithelium is also derived from the endoderm.