Milk yield and fat drop in a Murrah buffalo herd during the July heat wave
Ramkishan keeps 12 Murrah buffaloes in Jhajjar district. In the first week of July the maximum temperature touches 44°C. His shed is 40 ft × 20 ft with an asbestos roof at 8 ft, no fans or foggers, and the only water trough stands outside in the full sun. He ties the buffaloes outside for about four hours each afternoon while he cleans. Two second-lactation buffaloes that were giving 9.0 L and 8.5 L of milk a day have fallen to 6.5 L and 6.0 L within a week. The society fat test for the same animals dropped from 7.2% to 5.4%. Both show respiration of 44–48 per minute, rectal temperature of 39.7°C, reduced feed intake and slower rumination. There is no history of a hot, hard udder or clots in the milk. The farmer has started oxytetracycline injections and wants to double the concentrate to recover the yield.
1. Is infection the most likely explanation for the fall in yield and fat? Give your reasoning and list the first six actions you would take in the next 48 hours.
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Assessment. Infection is not the first explanation. A buffalo's normal rectal temperature is roughly 38.0–39.5°C, so 39.7°C is marginal and cannot by itself explain a herd-level fall. There is no hot, hard udder, no clots and no report of foul discharge. Respiration of 44–48 per minute, reduced intake and sluggish rumination in July, with the water trough in the sun and an asbestos roof, point to heat stress; high yielders suffer most because their heat production is higher. Still, rule out mastitis with a strip cup and CMT on all quarters, and metritis by vaginal examination, before ignoring infection.
Next 48 hours. (1) Move the water trough inside and give cool, clean water at all times. (2) Provide air movement with 2–3 fans and foggers, or wet the floor and walls in the afternoon. (3) Stop tying the animals outside during the hot hours; clean the shed early morning or evening. (4) Shift most of the feeding to 5–7 am and after 7 pm. (5) Give 40–50 g salt plus an electrolyte mixture and 2–3 kg green fodder per animal. (6) Record rectal temperature, respiration and milk yield twice daily for a week. Do not continue oxytetracycline without a diagnosis; it does not correct heat stress and leaves residues in milk.
2. Explain why milk fat fell from 7.2% to 5.4% in these buffaloes and how you would restore it.
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Heat stress reduces dry-matter intake. With less roughage eaten, the concentrate-to-roughage ratio rises, rumen pH falls and the fermentation pattern shifts towards propionate at the cost of acetate. Acetate and beta-hydroxybutyrate are the main precursors of milk fat, so fat percentage drops. Buffalo milk fat is naturally 6.5–7.5%, so 5.4% indicates a real diet-induced depression, not a breed effect.
To restore fat: keep roughage at 60–65% of dry matter and do not chop straw very fine; feed 2–3 kg green fodder daily; where concentrate exceeds 3 kg per animal, add 100–150 g sodium bicarbonate and split the concentrate into 3–4 feeds; add 100–150 g protected or bypass fat for high yielders; supply cool water continuously; avoid any sudden increase in concentrate. Recheck the society fat test after 10–14 days. If fat remains low, check for subclinical mastitis and confirm that the sample was drawn properly and tested before the milk was mixed.
3. The farmer proposes doubling the concentrate from about 2 kg to 4 kg per animal per day. Explain the risks and what you would advise instead, using numbers.
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A 7 L buffalo already needs roughly 1.5–2 kg of concentrate; doubling to 4 kg adds about 24 kg of concentrate per day across 12 animals. A sudden rise of that size lowers rumen pH, causes subacute ruminal acidosis, depresses fibre digestion and can push milk fat down further rather than up. It also increases the heat of digestion, worsening heat stress, and can trigger laminitis and poor fertility.
Advice: cap concentrate at about 2.5 kg per head per day, increasing by only 250–300 g every 3–4 days; keep long wheat straw and green fodder in the ration; spend the extra money on shade, fans, a second water trough, bypass fat and a mineral mixture instead of more concentrate. Watch the dung: loose, acidic dung with undigested grain indicates acidosis. If possible, check rumen pH; below 5.8 in a clinically normal animal indicates subacute acidosis and the concentrate must be reduced and roughage increased.