(a) Describe molecular marker. Write in detail about different types of DNA markers alongwith their advantages and disadvantages…

(a) Molecular Markers and DNA Markers A molecular marker is a DNA sequence at a known chromosomal location that shows polymorphism between individuals, so it can be used to track a gene or genome region, identify breeds and parentage, and study diversity. A good marker is polymorphic, co-dominant, abundant, neutral and reproducible.

• RFLP: differences in restriction-site fragment length, detected by Southern blot or probe. Advantages: co-dominant, reproducible. Disadvantages: needs large amounts of good DNA, laborious, uses radioactivity, low polymorphism.
• RAPD: PCR with short random primers. Advantages: quick, cheap, needs no sequence information, little DNA. Disadvantages: dominant (heterozygotes not identified), poor reproducibility.
• AFLP: restriction digestion followed by selective PCR amplification of fragments. Advantages: many bands per assay, no prior sequence information, good reproducibility. Disadvantages: dominant, technically demanding, costly.
• SSR (microsatellites): short tandem repeats of 1–6 bp, amplified by PCR with flanking primers. Advantages: multi-allelic, highly polymorphic, co-dominant, used for parentage and diversity studies in cattle. Disadvantages: primer design needs sequence data, null alleles, stutter bands.
• SNP: single base differences; most abundant, stable, suited to high-throughput chip genotyping and genomic selection. Disadvantages: biallelic so low information per locus, so many SNPs are needed, and chips are costly.

(b) Ration for Laying Hens Requirement for layers: about 2,500–2,700 kcal ME/kg, 16–17% CP, 3.5–4% calcium, 0.35% available phosphorus, with lysine about 0.8% and methionine about 0.35%.

Formulation for 100 kg of feed: maize 55 kg, soybean meal 24 kg, wheat bran 7 kg, rice bran 2.75 kg, limestone or shell grit 9 kg, dicalcium phosphate 1.5 kg, salt 0.4 kg, vitamin-mineral premix 0.25 kg, DL-methionine 0.1 kg.

Calculated analysis: about 16.5% CP, about 2,500 kcal ME/kg, calcium about 3.8%, available phosphorus about 0.38%, and lysine about 0.85%.

Economy: maize and brans are locally available and cheap; soybean meal can be partly replaced by groundnut or mustard cake when cheaper, with synthetic amino acids correcting deficits. Cost per kg is calculated from ingredient prices, and the least-cost mix is chosen by Pearson square or linear programming. Add grit and clean water, and avoid mouldy grain to prevent aflatoxin.

(c) Indigenous Cattle Breeds Indian cattle (Bos indicus) are adapted to heat, tick resistance and poor feed. Types:

• Milch: Gir (south Kathiawar, Gujarat; red or spotted, domed forehead, long pendulous ears; about 1,200–1,800 kg per lactation), Sahiwal (Montgomery region; red, loose skin, about 1,400–2,500 kg), Red Sindhi (Sindh; deep red, about 1,250–1,800 kg).
• Dual purpose: Tharparkar (Rajasthan; white to grey; about 1,800–2,600 kg; draft use), Kankrej (Gujarat; lyre horns; about 1,400 kg), Ongole (Andhra Pradesh; white, large hump; about 1,000 kg), Deoni (about 600–1,200 kg), Hariana (about 600–800 kg).
• Draught: Hallikar, Amritmahal, Kangayam, Nagori.

Features: prominent hump, dewlap, loose skin, resistance to ticks and tropical diseases, ability to use poor fodder, higher butterfat, strong draught capacity, and lower yield than exotic breeds. Crossing with Jersey and HF is used for yield, and Gir and Sahiwal are used to conserve and upgrade.

(d) Dairy Development Programmes of Government of India

• Key Village Scheme (1950s): breed improvement through AI and bulls in groups of villages.
• Intensive Cattle Development Projects (1964–65): breed improvement, feed and veterinary services in selected areas.
• Operation Flood (1970–96, NDDB): "white revolution", a national milk grid linking producers to consumers through the three-tier cooperative structure, and raising farmer income.
• National Dairy Plan I (2012 onwards): raise productivity of milch animals and organise rural milk procurement.
• Dairy Entrepreneurship Development Scheme (2010, NABARD): capital subsidy for small dairy units.
• Rashtriya Gokul Mission (2014): conserve and develop indigenous breeds, Gokul Grams, genetic improvement and sex-sorted semen.
• National Programme for Dairy Development (2014): quality milk, chilling and processing infrastructure.
• Dairy Processing and Infrastructure Development Fund (2017–18, NABARD): modernise processing capacity.
• Animal Husbandry Infrastructure Development Fund (2020): incentives for private investment in processing and value addition.
• Supporting Dairy Cooperatives and Farmer Producer Organisations: working capital for cooperatives and FPOs.