(a) Discuss the various methods of preservation of hides and skin. Elaborate the different steps involved in conversion of hides…

(a) Preservation of Hides and Skins, and Conversion into Leather Hides are from large animals (cattle, buffalo, horse), and skins from small animals (goat, sheep, calf). Raw stock putrefies within hours, so after flaying it is preserved.

Methods:

• Wet salting: salt (about 40% of weight) is rubbed on the flesh side, and hides are stacked for 2–3 weeks.
• Dry salting: wet-salted pelts are dried.
• Brining: immersion in saturated brine, with bactericide, for 16 hours or more.
• Drying: sun or shade drying on frames, cheap, but risk of insects and hard, brittle pelts.
• Chilling or freezing: short-term for tannery-bound hides.
• Pickling (acid-salt) mostly for sheep skins, and bactericidal treatment with salt.

Conversion to leather:

1. Soaking: rehydrates and removes salt, blood and dirt.
2. Liming (lime and sodium sulphide): unhairing, swelling and opening up fibres. Then fleshing.
3. Deliming: removes lime with ammonium salts or weak acids.
4. Bating: proteolytic enzymes remove non-collagen protein and soften the grain.
5. Pickling: acid and salt, to prepare for tanning.
6. Tanning: stabilises collagen and gives resistance to putrefaction and heat. Vegetable tanning (babul bark, avaram, myrobalan, mimosa) gives firm leather for soles and saddlery. Chrome tanning (basic chromium sulphate) gives soft, light, heat-resistant leather for shoe uppers and garments; combination tanning also used.
7. Post-tanning: neutralising, retanning, dyeing and fatliquoring for softness.
8. Drying, finishing (buffing, pigment coating, embossing), and grading by defects such as scars, pox marks and flay cuts.

(b) Poultry Housing Systems

• Deep litter: birds on 5–10 cm of litter (rice husk, sawdust). Merits: cheap, good manure, comfortable, vitamin B12 from litter, suits broilers and layers. Demerits: litter wetness, coccidiosis, ammonia, dust, labour, and soiled eggs.
• Cage (battery) system: layers in wire cages. Merits: high stocking density, clean eggs, easy disease control, easy culling and recording, better feed efficiency. Demerits: high cost, behavioural restriction and welfare concern, fatty liver, cage layer fatigue, and foot problems.
• Slatted or wire floor: raised floor over the pit. Merits: manure falls through, less parasite contact, less labour. Demerits: capital cost, foot lesions, and draught in winter.
• Free range or semi-intensive: access to land. Merits: natural behaviour, good welfare, cheap, premium eggs and meat. Demerits: predators, disease and parasite exposure, lower output, large land need, and difficult biosecurity.

Choice depends on capital, climate, flock size and market. Proper ventilation, lighting, stocking density and biosecurity are needed in every system.

(c) Mastitis in a High-Yielding Crossbred Jersey Cow Etiology: contagious pathogens (Staphylococcus aureus, Streptococcus agalactiae, Mycoplasma) spread between cows during milking; environmental pathogens (E. coli, Klebsiella, Streptococcus uberis, Trueperella pyogenes, and fungi such as Candida) come from bedding, water, mud and faeces. Predisposing factors: high yield, large pendulous udder, hot and humid climate, wet bedding, poor milking hygiene, faulty machines and teat injury.

Pathogenesis: organisms enter via the teat canal, multiply in the gland, and release toxins (leukocidins, alpha-toxin, LPS). Neutrophils flood the milk, raising somatic cell count. Tissue damage and secretory-cell loss reduce yield, with fibrosis and gland atrophy in chronic infection; Gram-negative endotoxaemia causes severe systemic illness.

Symptoms: clinical form: swollen, hot, painful udder, abnormal milk with flakes, clots, blood or watery secretion, fever, and dullness; subclinical form: no visible signs, but high SCC, low yield, and positive CMT.

Diagnosis: strip-cup test, California Mastitis Test, SCC (above 2 lakh per mL), electrical conductivity, culture and sensitivity, and PCR.

Treatment and control: antibiotics by sensitivity (intramammary and parenteral), NSAIDs, fluids and frequent stripping in acute cases. Control: post-milking teat dipping, dry cow therapy, treatment of clinical cases, culling of chronic cases, milking machine maintenance and hygiene, balanced nutrition with vitamin E and selenium, and clean bedding.