(a) Discuss the etiology, clinical signs, diagnosis and treatment of abomasal displacement in cows. (20 marks) (b) Describe the…

(a) Abomasal Displacement in Cows Etiology: abomasal displacement is a disorder of high-yielding dairy cows, about 80–90% of cases occurring within the first month after calving, and most (about 85–95%) are left displacements (LDA). The underlying problem is abomasal atony with accumulation of gas, which lets the organ float to an abnormal position.

• Atony and gas: high-concentrate, low-fibre rations raise volatile fatty acids and gas in the abomasum and reduce its motility.
• Periparturient disease: hypocalcaemia, ketosis and fatty liver, retained placenta, metritis and mastitis all reduce motility; negative energy balance and low dry matter intake reduce rumen fill.
• Space after calving: the uterus no longer holds the rumen up, so the abomasum can slip under the rumen to the left. Large, deep-bodied breeds such as Holstein-Friesian are most at risk.
• Types: in LDA the abomasum moves from the right ventral abdomen to lie between the rumen and the left abdominal wall. In right displacement (RDA) it dilates and moves dorsally on the right, and it may twist on its mesenteric axis (abomasal volvulus), which cuts off blood supply and is an emergency.

Clinical signs

• LDA: partial anorexia (refuses concentrate but eats some roughage), sudden drop in milk yield, secondary ketosis (ketone smell, ketonuria), scanty soft faeces, reduced rumen sounds, and sometimes a bulge behind the left last ribs; temperature, pulse and respiration are usually normal.
• RDA and volvulus: more severe and faster, with anorexia, colic, distension of the right flank, dehydration, tachycardia (over 100 per minute is a bad sign), scanty dark faeces and, in volvulus, shock and death within 48–96 hours if untreated.

Diagnosis

• Simultaneous auscultation and percussion: a high-pitched "ping" over an area between the 9th and 13th ribs on the left in LDA, or the 10th–13th ribs on the right in RDA, extending further back in volvulus. It must be distinguished from pings of rumen gas, pneumoperitoneum and caecal dilatation.
• Succussion: a splashing sound on ballottement.
• Ultrasonography: shows abomasal folds and fluid lateral to the rumen.
• Abomasocentesis: fluid from the ping area has pH below about 4 and no protozoa, which confirms it is abomasal.
• Rectal examination: a distended viscus in the right caudal abdomen can be felt in RDA or volvulus.
• Blood and urine: hypochloraemic, hypokalaemic metabolic alkalosis, and ketones in urine or milk.

Treatment

• LDA, rolling (closed method): the cow is cast on her right side, rolled onto her back and rocked so the gas-filled abomasum floats back to the ventral midline, then rolled onto her left side and stood up. It is cheap, but relapse is common, so it is often combined with blind toggle-pin fixation or laparoscopic abomasopexy.
• LDA, surgery: right-flank pyloro-omentopexy (Hannover method), left-flank abomasopexy (Utrecht method) or right paramedian abomasopexy, which fix the abomasum permanently.
• RDA and volvulus: immediate right-flank laparotomy with decompression, derotation and omentopexy.
• Medical support: intravenous fluids with potassium chloride (and oral KCl), calcium borogluconate for hypocalcaemia, propylene glycol or dextrose for ketosis, treatment of metritis or mastitis, and a return to good-quality roughage.

Prevention: transition-cow management: adequate effective fibre and gradual introduction of concentrates after calving, a correct body condition score at calving (about 3–3.5), prevention of milk fever (for example, anionic salts before calving), and prompt treatment of ketosis and uterine disease.

(b) Hypomagnesaemic Tetany Causes: magnesium is not stored in a readily available form in the body, so blood levels depend on daily absorption, mainly from the rumen. Tetany develops when intake or absorption falls short of the losses in milk and other secretions.

• Lush pasture tetany (grass or lactation tetany): in lactating cows grazing young, rapidly growing grass or cereal fodder (such as wheat or oats) that is low in magnesium and high in potassium and nitrogen, often after heavy potash or nitrogen fertiliser. Potassium reduces magnesium absorption across the rumen wall, and low sodium makes it worse.
• Winter tetany: in cattle on poor roughage.
• Transport tetany: after stress, fasting or transport.
• Calf tetany: in calves of 2–4 months kept on milk alone.
• Other factors: cold, wet, windy weather and fasting precipitate attacks.

Clinical signs: normal serum magnesium is about 1.8–2.4 mg/dL (0.75–1.0 mmol/L). Clinical signs usually appear below about 1.0 mg/dL, and CSF magnesium below about 1.0 mg/dL.

• Peracute: the animal is found dead or goes down suddenly in convulsions.
• Acute: hyperaesthesia, nervousness, twitching of the face and ears, grinding of teeth, frothing, a stiff gait and staggering, then falling with tonic-clonic convulsions, paddling, opisthotonus, nystagmus, a pounding heart and death within hours if untreated.
• Subacute: excitability and tremors, progressing over days.

Diagnosis: history of lush pasture and lactation, signs, response to treatment, and low serum magnesium (often with low calcium). After death, magnesium in the vitreous humour below about 0.75 mmol/L (for up to 48 hours) or in CSF confirms it. It is differentiated from milk fever (flaccid, not excitable), nervous ketosis, rabies, lead poisoning and polioencephalomalacia.

Treatment: handle the animal quietly, since excitement can precipitate a fatal convulsion.

• Give calcium-magnesium borogluconate solution (for example, 400 mL of a solution with 25% calcium borogluconate and 5% magnesium hypophosphite) slowly intravenously while monitoring the heart.
• Give 200 mL of 50% magnesium sulphate subcutaneously at several sites to provide a sustained supply. Magnesium sulphate must not be given rapidly intravenously, as it can cause heart block and respiratory arrest.
• Sedate violent convulsions (for example with xylazine), then give oral magnesium for several days, since relapse is common.

Prevention

• Feed about 50–60 g of calcined magnesite (MgO) per cow daily in concentrate or mineral mixture during risk periods, or use magnesium bullets or boluses, magnesium in drinking water, or pasture dusting with MgO.
• Avoid heavy potash on grazing pastures in spring and provide common salt.
• Offer hay or straw before turning cattle onto lush pasture, and protect them from cold, wet weather.
• Feed calves on milk some concentrate and hay from early age.

(c) Enhanced acceptability of indigenous livestock breeds in a changing climate Climate change brings more heat waves, erratic rainfall, fodder scarcity and new disease patterns. Indigenous breeds, shaped by centuries of natural and farmer selection in these conditions, cope better:

• Heat tolerance: zebu cattle such as Tharparkar, Kankrej, Gir, Sahiwal and Red Sindhi have more and larger sweat glands, loose skin with a large dewlap and more surface area per unit mass, short, glossy, light-coloured coats that reflect radiation, and pigmented skin. At the cellular level they show better heat shock protein responses. Their milk yield falls less than that of Holstein-Friesian crossbreds when the temperature-humidity index rises above about 72, and their fertility is less affected by heat.
• Disease and parasite resistance: zebu cattle are more resistant to ticks and tick-borne diseases (theileriosis, babesiosis), and indigenous poultry such as Aseel and Kadaknath, and goats such as Black Bengal, survive better with little veterinary care.
• Low-input feeding: smaller body size and lower maintenance needs let breeds such as Vechur and Punganur, the Rathi and Tharparkar of the Thar, and Deccani and Changthangi sheep, thrive on crop residues, grazing and browse, and survive droughts that crossbreds cannot.
• Water economy: desert breeds such as Rathi and Tharparkar cattle, Magra and Marwari sheep and camels need less water.
• Multiple uses: draught (Kangayam, Hallikar, Amritmahal), manure and dung-fuel make them valuable in rain-fed, low-carbon farming systems.
• Genetic diversity: as insurance against future climates and diseases, local breeds carry adaptive genes, and zebu genetics have been used abroad; for example Ongole cattle became the Nelore of Brazil, and Gir underlies the Girolando.

Balanced view: indigenous cattle usually yield less milk per animal, so their methane emissions per litre of milk can be higher unless productivity is improved; exotic crossbreds remain important where feed and management are good.

Policy: the Rashtriya Gokul Mission (Gokul Grams, sex-sorted semen of indigenous breeds, IVF), breed registration by ICAR-NBAGR, and the National Livestock Mission reflect this shift, aiming to improve indigenous breeds' productivity through selection while keeping their resilience.