(a) Write about the risk factors, pathogenesis, clinical symptoms and management of organophosphorus poisoning in dairy animals…

(a) Organophosphorus Poisoning in Dairy Animals Risk factors: accidental access to freshly sprayed fodder, pasture or crops; dips, sprays and pour-ons used at too high a concentration or too frequently, especially on young, debilitated or wet animals; contaminated feed or water, and empty containers; storage of pesticides near feed; malicious use; and use of OP ectoparasiticides (malathion, diazinon, chlorpyrifos, coumaphos) with other cholinesterase inhibitors such as carbamates.

Pathogenesis: OPs are absorbed through skin, gut or lungs and phosphorylate the serine hydroxyl of acetylcholinesterase (AChE), inactivating it. If not reactivated, the enzyme "ages" and the inhibition becomes irreversible. Acetylcholine accumulates at muscarinic, nicotinic and central synapses, causing a cholinergic crisis.

Clinical signs: muscarinic: salivation, lacrimation, diarrhoea, frequent urination, colic, bronchial secretion with dyspnoea, miosis and bradycardia; nicotinic: fasciculations, tremor, weakness and paralysis of respiratory muscles; central: restlessness, ataxia, convulsions, coma and death from respiratory failure. Diagnosis is by history and signs, AChE depression in blood, and chemical analysis of rumen contents, feed and liver.

Management: stop exposure; wash the skin with soap and water; for ingestion give activated charcoal orally and a saline purgative. Antidote: atropine, about 0.2–0.5 mg/kg, a quarter of the dose IV and the rest SC or IM, repeated as needed until secretions dry; pralidoxime (2-PAM) 20–50 mg/kg slowly IV early, before enzyme ageing. Give fluids and oxygen, and control seizures. Avoid morphine and phenothiazines. In dairy animals, discard milk until residues fall to the withdrawal period, as OPs are lipophilic and excreted in milk.

(b) Conversion of Muscle to Meat and Factors Affecting Meat Quality Steps after slaughter:

1. Exsanguination stops oxygen supply, so muscle uses anaerobic glycolysis, producing lactic acid from glycogen; pH drops from about 7.2 to an ultimate 5.4–5.7.
2. Creatine phosphate and then ATP fall; actin and myosin form permanent cross-bridges, giving rigor mortis (onset a few hours after death, with a duration varying by species and temperature).
3. Resolution: with ageing (conditioning), calpains and cathepsins degrade myofibrillar proteins, so meat becomes tender, and flavour develops. Chilled storage at 0–4°C for several days.

Factors affecting quality:

• Ante-mortem: species, breed (Bos indicus beef is tougher than Bos taurus), age, sex, nutrition, and pre-slaughter stress, lairage and handling. Stress and low glycogen cause DFD meat (pH above 6.0), and rapid glycolysis with high temperature causes PSE (pale, soft, exudative) meat, especially in pigs.
• Slaughter: stunning, bleeding efficiency, and carcass hygiene.
• Post-mortem: chilling rate (rapid chilling before rigor causes cold shortening), electrical stimulation (speeds glycolysis and prevents cold shortening), ageing time, thaw rigor after freezing, and packaging. Meat quality is judged by pH, WHC, colour, shear force and microbial load.

(c) Systems of Wool Grading Wool grading classifies fleeces or fibres by fineness, length, strength, colour and purity to set price and use.

Systems:

• Bradford count (English system): the number of 560-yard hanks spun from a pound of clean combed top; higher count (60s, 64s, 70s) means finer wool.
• American blood system: fleece graded by the proportion of Merino blood: Fine, half-blood, three-eighths, quarter, low quarter, common and braid.
• Micron or objective system (IWTO): mean fibre diameter in microns measured by projection microscope, air-flow, OFDA or laser scanning; fine wool is below 24 µm, medium 24–30 µm, coarse above 30 µm.
• Staple length, strength, crimp, colour, yield, and vegetable-matter content are also considered, and fleeces are sorted by hand into grade lots.
• Indian system: mainly by fibre type and diameter, with fine apparel wool and carpet wool, such as Chokla, Magra and Nali; coarse carpet wool has more medullation.

Objective measurement is more consistent than visual grading.