UPSC Animal Husbandry & Veterinary Science 2026 — Paper I

(a) Two linked demands: (i) 'Classify' the minerals needed by animals — give a proper classification scheme (macro/major vs micro/trace, essential vs non-essential, acid- vs base-forming) with the elements listed under each; and (ii) 'discuss the functions of calcium' — structural, physiological and regulatory roles plus consequences of deficiency. Both halves must appear; an answer only on calcium cannot score more than half. (b) Two demands: (i) trace the growth of the compound/commercial animal feed industry in India — its phases, drivers, present structure and constraints; and (ii) describe the specific activities of CLFMA (CLFMA of India, the Compound Livestock Feed Manufacturers' Association). Both parts carry marks; naming CLFMA's full form is expected. (c) Explain how blood participates in thermoregulation — as a heat-carrying medium, through vasomotor redistribution of blood flow between core and shell, through countercurrent exchange, by delivering heat to evaporative surfaces and by carrying thermal and hormonal signals to and from the hypothalamus. Both heat loss and heat conservation must be covered. (d) 'Explain' with a comparison: show how the dam's plane of nutrition and the uterine environment (placental function, uterine capacity, dam age/size, heat stress) shape prenatal growth, and contrast this with postnatal growth where the animal's own genotype, feeding and management dominate and compensatory growth is possible. The comparison between prenatal and postnatal is the crux. (e) Explain how the composition of different semen extenders (egg yolk-citrate, Tris-egg yolk-glycerol, skim milk, soya-lecithin/chemically defined, Caprogen, BTS) and different preservation methods (liquid at 5 C or ambient, frozen in liquid nitrogen) act on sperm survival, membrane integrity, acrosome status and hence on fertilising capacity. Both 'extenders' and 'preservation methods' must be discussed.

• Macrominerals (Ca, P, Mg, Na, K, Cl, S) versus microminerals (Fe, Cu, Zn, Mn, Co, I, Se, Mo)
• Calcium: bones and teeth (about 99%)
• Calcium: blood clotting, nerve and muscle function, enzyme activation, milk and eggshell
• Regulation and deficiency (PTH, calcitonin, vitamin D; rickets, milk fever); Ca:P ratio
• Origin: crop residues and oilseed cakes; 1960s cooperative cattle-feed plants
• Growth through Operation Flood and the poultry, aqua and pig industries
• Present state and problems: raw materials, quality and adulteration, standards
• CLFMA: industry body; policy representation, quality, conferences, information, research
• Blood carries heat from core organs to skin and respiratory tract
• Vasodilation and vasoconstriction of skin vessels controlled by the hypothalamus
• Evaporative heat loss depends on blood supply; countercurrent exchange and AV anastomoses
• Selective brain cooling (carotid rete) and hormonal effects; dehydration and heat stress
• Maternal nutrition: two-thirds of fetal growth in late gestation; effects on birth weight and vigour
• Mid-gestation under-nutrition and muscle fibre number; fetal programming
• Uterine factors: size, blood flow, placenta, litter size, maternal age and parity, heat stress; embryo-transfer evidence
• Comparison: postnatal growth depends on own genes, milk, feed and management, and is more modifiable
• Extender components: energy, buffers, egg yolk or milk, cryoprotectant, antibiotics
• Protection against cold shock and ice damage; glycerol level and toxicity
• Preservation methods: liquid, chilled, frozen in liquid nitrogen with species examples
• Effects on motility, acrosome, membrane and fertility; only about half survive freezing

(a) 'Discuss the salient features' of broiler feeding for meat production — the phase-feeding schedule with nutrient specifications, energy-protein relationship and ideal amino acid balance, minerals and vitamins, feed additives, physical form of feed, feeding management (ad libitum, water, heat stress, withdrawal periods) and the economics measured by FCR and feed cost. (b) 'Describe the feeding of sheep for good quality wool production' — link wool as a sulphur-rich keratin to specific dietary requirements: sulphur and sulphur amino acids (cystine, methionine, preferably rumen-protected), total DM and energy intake, bypass protein, and the trace minerals copper, zinc and cobalt; and explain how continuity of nutrition prevents staple break and fibre-diameter variation. A practical ration schedule is expected. (c) Two parts: (i) define 'bulk' precisely as a feed property — the volume occupied by a unit weight of feed (the reciprocal of bulk density), governed by fibre content, particle size and water-holding capacity; and (ii) discuss its importance in ruminant feeding — control of voluntary intake through rumen fill, physically effective fibre, rumination and salivary buffering, and the consequences of both too little and too much bulk.

• Phase feeding: starter, grower, finisher with protein and energy levels
• High energy with balanced protein and amino acids (lysine, methionine)
• Minerals, vitamins and feed form (crumbles, pellets); ad libitum feed and clean water
• Additives, aflatoxin-free feed, feed withdrawal before catching; feed conversion and cost
• Wool is keratin, rich in sulphur amino acids; protein, sulphur and energy needed
• Good pasture, browse and legumes; concentrate supplement in dry season and pregnancy
• Rumen-bypass protein and N:S ratio; minerals (copper, zinc, cobalt, iodine, selenium)
• Steady plane of nutrition; effect of poor feeding on fibre; ewe nutrition and follicles
• Definition: volume occupied per unit weight of feed; low bulk density; roughages versus concentrates
• Rumen fill limits intake; high-yielding animals need concentrates
• Rumination, saliva buffering, pH and prevention of acidosis
• Milk fat, gut motility, roughage:concentrate ratio, effect of too much or too little bulk

(a) 'Explain why' — a causal, comparative physiology answer. Show that a high metabolic rate means a high rate of oxygen and nutrient consumption, heat production and nitrogenous waste generation, that simple diffusion cannot service this, and therefore that both a high-capacity convective circulatory system (double circulation, four-chambered heart, high cardiac output) and an elaborate excretory system (metanephric kidney with glomerular filtration and counter-current concentration) are required. Both systems must be argued. (b) 'Explain the three major stages' of coagulation in the classical scheme — (1) formation of prothrombin activator by the intrinsic and extrinsic pathways converging on factor X, (2) conversion of prothrombin to thrombin, (3) conversion of fibrinogen to fibrin and its stabilisation — and, as explicitly required, the specific roles of platelets and of fibrinogen within these stages. (c) Explain the chemoreceptor reflex in hypoxia: identify the peripheral (carotid and aortic body) and central chemoreceptors and their stimuli, distinguish the primary chemoreflex effect on the heart (bradycardia with vasoconstriction) from the secondary effect mediated by hyperventilation and sympathetic activation (tachycardia and rise in cardiac output), and state the net effect on heart rate, cardiac output and the distribution of blood flow, including what happens when hypoxia becomes severe or chronic.

• High metabolic rate means greater oxygen use and greater production of CO₂, heat, water and nitrogenous and acid wastes
• Circulatory: four-chambered heart with complete separation, high pressure, high heart rate and cardiac output, dense capillaries, haemoglobin
• Excretory: many nephrons, high renal blood flow and GFR, long loop of Henle and urine concentration, uric acid in birds
• Comparison with fish, amphibians and reptiles with lower rates
• Stage 1: formation of prothrombin activator by extrinsic and intrinsic pathways (factor X, Va, Ca²⁺, platelet phospholipid)
• Stage 2: prothrombin to thrombin
• Stage 3: fibrinogen to fibrin, cross-linked by factor XIII
• Platelets: plug formation, adhesion, aggregation, phospholipid surface, clot retraction
• Peripheral chemoreceptors: carotid and aortic bodies, stimulated by low PO₂ (also high PCO₂, H⁺)
• Afferents via glossopharyngeal and vagus nerves to the NTS in the medulla
• Respiratory response (hyperventilation) and sympathetic vasoconstriction raising blood pressure
• Heart: direct bradycardia but net tachycardia and increased cardiac output through lung inflation reflex and catecholamines

(a) 'Critically evaluate' means take a position on both sides. Establish what silent heat (suboestrus) is and how it differs from true anoestrus, marshal the evidence that it is essentially a heat-detection and management failure, then present the genuine physiological, endocrine, seasonal, genetic and pathological components that the statement understates, and end with a reasoned verdict and remedies. (b) Two linked demands: (i) 'explain the role' of early embryonic mortality in producing the repeat breeding syndrome — including why loss before day 16-17 gives a normal return to oestrus while later loss gives a delayed return; and (ii) 'enlist the main factors' affecting early embryonic mortality, grouped as genetic, endocrine/maternal, nutritional, environmental, infectious, immunological and managemental. (c) Explain the effect of a high temperature-humidity load on three named outcomes: spermatogenesis, libido, and semen quality parameters, specifically sperm motility and morphology. All three must be addressed, with the mechanism of scrotal thermoregulatory failure and the time course of damage and recovery. (d) 'Explain why' chickens are uricotelic rather than ureotelic: give the biochemical basis (absence of a functional ornithine-urea cycle, uric acid made through the purine pathway), the water-economy argument (insoluble urate paste, poor renal concentrating ability), and above all the cleidoic-egg argument (non-toxic solid waste in a closed shelled egg), plus the anatomical and flight-related advantages.

• Definition: ovulation with absent or weak behavioural signs
• Support: detection failure, short oestrus, observation and record gaps, nutrition and heat stress
• Against: physiological silent first ovulation, buffalo and heifer, endocrine and pathological causes
• A reasoned verdict and remedies (frequent observation, aids, timed AI, cooling, nutrition)
• Definition of repeat breeder (regular cycles, normal tract, three or more services)
• EEM: fertilisation occurs but the embryo dies before maternal recognition of pregnancy, so the animal returns to heat
• Genetic, gamete-age, semen and AI factors; uterine environment; hormonal (progesterone)
• Nutrition, heat stress, infections and management stress
• Thermoregulation of testis (2–6 °C below body); humidity reduces evaporative cooling
• Spermatogenesis: damage to spermatocytes and spermatids with lag and slow recovery
• Libido: lower testosterone and LH, less feed intake
• Semen: lower volume, motility and viability, more abnormal forms, acrosome and DNA damage
• Cleidoic egg: closed system with limited water; ammonia toxic, urea soluble
• Uric acid insoluble, precipitates in allantois, harmless
• Water conservation and weight saving in birds; semi-solid paste, no bladder
• Four nitrogen atoms per molecule; purine synthesis in liver, xanthine dehydrogenase; energy cost

(a) A focused note connecting genetic drift to conservation: define drift and its inverse dependence on effective population size, show its consequences (loss of heterozygosity and alleles, fixation of deleterious alleles, inbreeding depression, loss of adaptive potential, extinction vortex), and translate these into conservation strategy for endangered species and threatened livestock breeds. (b) Explain and justify the statement. Define a threshold trait through the underlying-liability model, show with the scale relationship between observed and underlying heritability that the efficiency of selection depends on the incidence (frequency) of the trait in the population, being greatest near 50% incidence and negligible at extreme incidences, and draw the breeding consequences. (c) 'Mention the salient features' - an organised listing, with brief explanation, of the socio-economic dimensions of livestock farming in India: contribution to income and GVA, equity and asset distribution, employment and the role of women, nutritional security, cultural and religious factors, institutions and risk, and the main socio-economic constraints and policy responses. (d) List and briefly explain the factors determining the production efficiency of dairy animals, organised as genetic, physiological/reproductive, nutritional and environmental-managerial, and indicate the measures by which production efficiency is actually judged (milk per day of calving interval, feed conversion efficiency, lifetime production, cost per litre). (e) 'Describe the steps' of recombinant DNA production in order: isolation of the gene of interest, choice of vector, restriction digestion, ligation, transformation of a host cell, selection and screening of recombinants, and multiplication/expression with recovery of the product. Named enzymes, vectors and screening methods are expected.

• Definition: random change of allele frequencies by sampling in a finite population; stronger in small populations
• Loss of alleles and heterozygosity, fixation, inbreeding depression
• Bottleneck and founder effects; extinction vortex
• Conservation measures: large N_e, even sex ratio, gene flow or translocation, studbooks, gene banks
• Threshold trait: discrete expression from a continuous underlying liability
• Observed-scale heritability depends on incidence (h² = h²liability × z²/pq)
• Response to selection is greatest at intermediate frequency and falls at extremes
• Selection changes the incidence; use liability-scale or threshold models
• Livelihood, income and employment for small and marginal farmers and landless
• Contribution to economy (about 30% of agricultural GVA) and world's largest milk producer
• Women's role and empowerment; nutrition security
• Risk cover and assets, cooperatives, cultural aspects, constraints and policy support
• Genetic: breed and selection
• Nutrition: balanced ration, fodder, water
• Reproduction: age at first calving, calving interval, service period
• Health, management, environment (heat stress) and records
• Isolation of the gene (restriction digestion, cDNA, PCR, synthesis)
• Vector with ori, marker and cloning site
• Cutting with same restriction enzyme and ligation with DNA ligase
• Transformation, selection and screening (blue-white), expression and purification

(a) Two linked demands: (i) 'explain the genetic mechanism' of inbreeding depression - the rise in homozygosity measured by the inbreeding coefficient, and the dominance/partial-dominance and overdominance hypotheses with the quantitative relation between depression and F; and (ii) explain 'why continuous inbreeding' specifically reduces fertility and viability/life capacity, i.e. why fitness traits are most affected and why the damage accumulates and cannot be fully purged. (b) Two parts: (i) state and explain the Hardy-Weinberg law of equilibrium with its algebra (p + q = 1; p^2 + 2pq + q^2 = 1), its attribution and its assumptions; and (ii) 'describe the factors that alter this equilibrium' in a livestock population - selection, mutation, migration, genetic drift and non-random mating - with the mechanism of each and its practical form in animal breeding. (c) Explain how repeated records on the same animal permit permanent environmental effects (those that influence every record of an individual) to be separated from temporary ones (those influencing a single record). The answer must define the variance partition P = G + Ep + Et, define repeatability as the intraclass correlation among repeated records, show that temporary environmental variance is the within-animal variance (1 - r)Vp and that r - h2 estimates permanent environmental plus non-additive genetic variance, and mention the repeatability animal model and the practical uses.

• Inbreeding raises homozygosity by F and lowers heterozygosity
• Dominance hypothesis: unmasking of deleterious recessives; overdominance and epistasis as further explanations
• Depression is proportional to F and to dominance; larger for fitness traits with directional dominance
• Effects on fertility, embryo and calf survival, growth, immunity and longevity; control measures
• Statement: gene and genotype frequencies constant in a large, randomly mating population without mutation, migration, selection or drift
• Genotype frequencies p², 2pq, q² with a numerical example
• Factors: selection, mutation, migration or gene flow (AI, crossbreeding), genetic drift
• Non-random mating changes genotype but not gene frequencies; small population
• Model: record = genetic value + permanent environment + temporary environment
• Permanent effects common to all records of an animal; temporary effects specific to a record
• Variance between animals versus within animals; repeatability r as intraclass correlation
• Temporary fraction 1 − r; permanent fraction r − h²; uses of repeatability (accuracy, culling)

(a) 'How do you estimate' - a methodological answer. Set out the cost structure and cost concepts, the actual steps of estimation (unit of measurement, valuation, allocation of joint herd costs, by-product credit, cost per litre or per kg FCM), and then contrast the method for the organised sector (cost accounting from records) with that for the unorganised sector (survey/cost-route with imputation of non-monetised family inputs), ending with the ratios used to interpret the result. (b) 'Explain the significance' - not merely list record types but show what each class of record makes possible: genetic improvement and sire evaluation, reproductive and feeding management, health management with drug withdrawal and traceability, economic decision-making and culling, and legal, insurance and institutional requirements. (c) Both halves must be covered: the feeding of commercial layers (phase feeding with nutrient specifications, the special calcium requirement for eggshell and how it is delivered) and the management (brooding, beak trimming, vaccination, cage space, lighting programme, uniformity, culling, biosecurity and heat-stress control). (d) 'Give the criteria' for formulating a swine ration that is both practical (feasible with locally available ingredients, palatable, safe, of the right physical form) and economic (least cost, good feed conversion, no loss of carcass quality). Requirements by class of pig, the ideal-protein/lysine basis, use of by-products and swill with their safety limits, fibre and antinutritional constraints, additives, feeding systems and economic yardsticks are all expected.

• Cost per litre = (total cost − by-product credit) ÷ milk output, on fat-corrected milk
• Variable costs (feed 60–70%, labour, veterinary, AI) and fixed costs (depreciation, interest, insurance, rent)
• Imputation of family labour and home-grown feed in the unorganised sector; cost concepts A₁, B₁, C₁, C₂, C₃
• Organised versus unorganised sector differences, and costing over the lactation and calving interval
• Types of records: identification, production, reproduction, health, feeding, financial
• Selection, culling and breeding decisions (pedigree, progeny testing)
• Management, disease control and economic analysis
• Uses in marketing, registration, insurance, credit, traceability and research
• Phase feeding with protein and energy levels: starter, grower, layer
• Layer ration: protein 16–18%, calcium 3.5–4%, intake 100–115 g
• Housing (cage or deep litter, space), 16 h lighting, temperature
• Vaccination, beak trimming, culling, egg handling and peak production timing
• Nutrient requirements by stage (protein, energy) and amino acid balance (lysine)
• Minerals and vitamins (Ca:P), limits on fibre
• Palatability, digestibility, freedom from moulds and anti-nutritional factors
• Least-cost formulation with local and by-product ingredients (Pearson's square, linear programming); safe feeding of kitchen waste (ASF)

(a(i)) Explain how a training need is assessed - define the need as a knowledge/skill/attitude gap, describe participatory and diagnostic methods of identifying it, show how needs are prioritised, and specifically address how relevance and practicality are ensured (felt versus unfelt needs, client segmentation including gender, situational and feasibility checks, timing and location, skill-based content, pre- and post-training evaluation). (a(ii)) 'Discuss in what way' - show the mechanism by which socio-economic characteristics of the clientele (literacy, farm size and income, caste and class, gender, tenancy, social participation, media access) determine which extension teaching method works, using the individual-group-mass classification as the framework and ending with the practical implication of matching method to audience. (b(i)) Discuss the philosophical proposition that extension empowers rather than creates dependency: state the philosophy of extension education, support it with the thinkers and the practical mechanisms through which empowerment happens, present the counter-case in which extension practice has produced dependency, and reach a reasoned position. (b(ii)) A practical extension answer: first diagnose why livestock farmers resist a method demonstration on their own animals (the animal is a major asset, fear of harm or milk loss, distrust, fear of ridicule, social and gender barriers), then set out concrete strategies to overcome that reluctance - rapport building, low-risk starter demonstrations, demonstration on the worker's or a volunteer's animals, assurance and indemnity, group and peer approaches, evidence and follow-up. (c) 'What role do you think gender plays... Explain' - an evaluative answer. Establish the gap between women's very large share of livestock labour and their low ownership and control, identify the specific barriers that limit their access to improved technologies, explain the consequences for adoption and for workload, and propose the institutional and policy correctives, using the access-versus-control distinction.

• Training need as the gap in knowledge, skill or attitude
• Participatory data collection: PRA, surveys, focus groups, observation, key informants
• Gap analysis, separating training from non-training problems, and ranking needs with farmers
• Design: local language, timing, hands-on, low-cost technology; pre-test and feedback
• Education and literacy determine choice of written, audiovisual or demonstration methods
• Age, experience and receptiveness
• Farm size, income and resources determine affordability of technology
• Social status, participation, risk orientation and culture; mix of individual, group and mass methods
• Extension as education for self-help: knowledge, skills, confidence and decision-making
• Participatory methods, groups (SHGs, cooperatives, FPOs) and local para-professionals (Pashu Sakhi)
• Conditions under which dependency arises: top-down, free inputs, no exit strategy
• A reasoned conclusion supported by an example
• Diagnosis of reasons: fear of harm, low trust, risk aversion, past experience
• Building rapport through leaders and progressive farmers; explaining benefits
• Starting with low-risk, visible practices, volunteer or institutional animals; safety by a qualified veterinarian, with insurance or compensation
• Active participation, farmer-to-farmer visits, convenient time and place, follow-up
• Women do a large share of livestock work but men control large animals, income, credit and decisions
• Barriers: literacy, mobility, workload, social norms, ownership and credit, few women extension staff
• Effects: lower adoption and benefit; technologies designed for men
• Remedies: women workers (Pashu Sakhi), groups, timing and venue, drudgery-reducing tools, credit and ownership