Civil Service Examination - Questions and Answers (from 1996 onwards) - 2 | Animal Husbandry & Veterinary Science Optional for UPSC PDF Download

Q6: Describe the circulatory and respiratory adjustment in warm environments and during exercise.
Ans: 

• Adjustments in the circulatory system in response to temperature changes are influenced by a complex interplay of reflex regulation, including both unconditioned and conditioned reflexes. Vascular reactions to temperature shifts are intricately regulated, with conditional reflexes observed in the dilation and constriction of vessels due to stimuli like heat and cold applied to the skin. An increase in heart rate is a consistent response to elevated body temperature.
• In a warm environment, the circulatory adjustment involves a reduction in heat production, increased perspiration, and enhanced heat loss through convection, marked by the dilation of cutaneous vessels. This response is accompanied by a decreased water consumption, crucial for maintaining the balanced salt composition of blood often disrupted by excessive perspiration. There is also a perceived decrease in the intensity of muscular movements in animals. The body's cooling mechanism through water evaporation is a highly effective process, with approximately 0.58 calorie lost for every gram of water evaporated.
• The significance of sweating as a heat dissipation mechanism varies among species. For example, in dogs, sweating is insignificant compared to the importance of panting. In cows, maximum evaporation from the skin surface occurs at about 150 g/sq.m/hr at an external temperature of 40°C. Sheep rely less on sweat secretion compared to cows, and evaporative heat loss through respiratory passages becomes more crucial in sheep than in cows.
• In camels, the balance between evaporation from the skin and respiratory tracts has been studied, revealing that even under desert heat exposure, respiratory frequency increases only slightly, while sweating is substantial. The camel's sweat evaporates under the fur rather than on the fur's surface, leading to more efficient water economy.
• Despite these adaptations, sweat gland function in domestic animals is less remarkable than in humans. Humans can experience high heat loss, up to 1000 calories per hour, through sweating. Panting is another heat dissipation mechanism observed in many species, triggered by a rise in body temperature or local warming of the anterior hypothalamus, and it may occur both reflexively and centrally.

Q7: Write short notes on: Physiologic response to heat in domestic animals
Ans: 

• A thermal equilibrium occurs when the overall heat gain is counteracted by the heat loss. Cutaneous vasomotor reactions, responding to thermal changes, are primarily mediated by sympathetic vasoconstrictor nerves. Peripheral vasodilation is achieved by an inhibition of sympathetic vasoconstrictor tone. 
• Warmth can reduce vasoconstrictor tone either through an elevation in hypothalamic temperature or reflexively through thermoreceptors in the skin. Local skin vasodilation may also happen due to the direct impact of warmth on blood vessels or the presence of bradykinin, a potent vasodilator released from activated sweat glands in humans.
• However, beyond an environmental temperature of around 31°C, skin vasodilation no longer increases heat dissipation, and a rise in body temperature will occur unless other means of enhancing heat loss are employed.
• In the case of a decrease in environmental temperature, regulation is achieved through a reduction in heat loss as a primary physical regulatory mechanism. If this proves insufficient, the secondary defense involves an increase in heat production through chemical regulation.

Q8: Write short notes on Seminal fluid
Ans: 

• Semen is composed of spermatozoa or sperm cells suspended in a fluid medium known as seminal plasma, alternatively referred to as seminal fluid. The major portion of the seminal plasma is derived from the secretions of various reproductive organs, including the epididymis, vas deferens, and accessory sex glands such as the seminal vesicles, prostate, and bulbourethral glands. This fluid provides an ideal environment for the viability and motility of male germ cells and serves as a storage medium for sperm.
• Seminal plasma comprises a diverse array of substances in varying proportions, including water, sugar (primarily fructose), proteins, non-protein nitrogen, cholesterol, phospholipids, fatty acids, salts, enzymes (such as phosphatase, dehydrogenase, hyaluronidase), vitamins (ascorbic acid and various B-complex vitamins), hormones (testosterone, androgens, with traces of estrogen and progesterone), trace minerals, and inositol.
• The testicular fluids play a crucial role in transporting spermatozoa from the testis to the epididymis. Seminal vesicles contribute a significant portion, around 20 percent or more, to the volume of seminal plasma or fluid. Specific components include glyceryl-phosphorylcholine from the epididymis, ergothioneine and citric acid from ampullae and seminal vesicles, respectively. Seminal vesicles also secrete inositol and fructose.
• It's important to note that the composition of seminal fluid can vary among different species in terms of the quantities of the various components mentioned above.

Q9: Describe the 'Deep Frozen Semen' technique as applied to artificial Insemination of farm animals. Write a critical note on its success under field conditions in India.
Ans: The concept behind frozen semen is an extension of the principle that at low temperatures, metabolic reactions slow down, allowing for the extension of the functional life of sperm. Freezing semen takes this idea further by almost suspending metabolic reactions, significantly extending the functional life of sperm. The success of the frozen semen technique can be attributed to the remarkable discovery by British scientists in 1948. They found that the death of sperm cells during freezing could be prevented by suspending the cells in a medium containing glycerol.
Although bull spermatozoa were successfully frozen over 25 years ago, subsequent modifications in the technique and the transition from using solid carbon dioxide (dry ice) at -79°C to using nitrogen at -196°C for freezing and storage have created a more stable environment for preserving cells.
The methodology for freezing semen has been relatively consistent across species, with only minor modifications.
The semen freezing technique involves several steps:

• Preparation of Diluent:
  • Tri-yolk glycerol is the chosen diluent for semen freezing.
  • It is created by mixing one part fresh egg yolk, four parts Tris buffer, and seven percent glycerol.
  • This diluent is prepared and maintained in a water bath at 30°C for dilution.
• Collection of Semen:
  • Semen is collected in the early morning.
  • Pre-collection stimulation, using a false mount, is applied to ensure high-quality semen.
• Evaluation of Semen:
  • Immediately after collection, semen is assessed for color, consistency, and the presence of foreign matter.
  • Motility is examined under a microscope, and samples with over 50 percent motility are selected for further processing.
  • Sperm concentration is estimated using a photo-electric calorimeter.
• Dilution of Semen:
  • The dilution rate is determined based on motility, sperm concentration, and straw capacity.
  • Typically, a minimum of 20-33 million live sperm per straw is set before freezing.
  • Diluted semen is gradually cooled to 5°C in a refrigerator.
• Equilibration of Semen:
  • Diluted semen is stored at 5°C for a 6-hour equilibration period.
  • This allows glycerol to exert its beneficial action on spermatozoa.
  • Glycerol permeates sperm, modifying ice crystal formation and dissolution, reducing damage due to pressure and other mechanical effects, providing better resistance to freezing stress.
• Filling of Straws:
  • Semen is filled into straws during the equilibration period using an automatic filling and sealing machine or a manual method with a vacuum pump.
  • The filled straws are coated in polyvinyl alcohol powder in French straws.
• Cleaning and Drying:
  • At the end of the equilibration period, straws are carefully rolled and dried using a clean towel to remove water.
• Freezing of Straws in Liquid Nitrogen Vapor:
  • Freezing is conducted in wide-mouthed nitrogen containers, such as LR 320 or LR 250, specifically designed for freezing straws.
  • Straws are held about 4-5 cm from the liquid nitrogen level during freezing.
  • The recommended temperature for freezing in an LR 320 container is -150°C to -160°C for 7 minutes.
  • Afterward, straws are plunged into liquid nitrogen for storage.

Post-Thaw Motility Examination: After freezing, post-thaw motility of the semen is evaluated 24 hours later. Samples with less than 40 percent motility are discarded, while good samples are transferred to permanent storage containers for preservation.
Storage: The frozen semen straws are stored in canisters within liquid nitrogen containers for extended periods until needed.
Frozen Semen across Different Species:

• Bull semen is found to be the most easily frozen without significant loss of fertility, and the success of the Tris diluent for bull semen freezing is noted.
• Buffalo spermatozoa have a lower survival rate compared to bulls, and freezing buffalo semen is less successful.
• Ram semen, lambing rates of 50-60 percent have been reported using rapid freezing methods.
• Goat semen has an enzyme in seminal plasma that affects fertility, and the use of frozen semen is not common.
• Boar semen, initially with low fertility, showed improved results after adopting the pellet technique with less than three percent glycerol.

Field Conditions and Constraints:

• Frozen semen is widely successful in cattle and buffaloes, but results in buffaloes are less uniform.
• Initially, the constraint for frozen semen use was the limited availability of Liquid Nitrogen containers and straws, leading to improper preservation.
• With awareness and improved infrastructure, frozen semen has become a useful tool, especially in cattle and buffaloes.
• The success of milk schemes like Operation Flood is attributed to the use of frozen semen.
• While frozen semen is less commonly used in sheep, goats, swine, and poultry, it has become a permanent part of cattle and buffalo breeding, allowing the use of semen from exceptional sires even after their death.

Q10: Write short notes on: Role of Hormones in Milk Secretion
Ans: 

• Lactation is regulated by a variety of hormones, with prolactin playing a central role in this process. Additionally, growth hormones have been found to enhance established lactation in cows. Adequate levels of ACTH (adrenocorticotropic hormone) and subsequent adrenal hormones are crucial, as they help maintain the required levels of milk precursors in the blood. It is noteworthy that large amounts of adrenal hormones, which are released during stressful conditions, can suppress lactation.
• While thyroid hormones are not deemed essential for lactation, the provision of thyroactive substances (thyroproteins) along with sufficient nutrients during the peak of lactation has been associated with an increase in milk production. Furthermore, parathormone is considered essential for maintaining optimal levels of calcium, and insulin plays a crucial role in regulating carbohydrate metabolism, contributing to the overall process of lactation.