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If a cow or buffalo suddenly gives much less milk, treat the drop as a symptom, not a disease — the animal is telling you something changed. The four most common causes are udder infection (mastitis), heat stress, a feed or water problem, and fever or illness. Check the udder and the animal’s temperature first, look at what changed in feed and weather, and call your veterinarian if there is fever, abnormal milk, red urine or a large unexplained drop.
A small dip at the end of lactation, around heat (oestrus), or with a sudden weather change can be normal. Worry when the fall is sharp (a fifth or more of the yield), lasts more than a day, spreads to several animals, or comes with other signs — off feed, fever, abnormal milk, diarrhoea or laboured breathing. A sudden herd-wide drop usually points to feed, water or an infectious cause; a single-animal drop points to that cow (udder, fever, injury or pain).
Udder infection is the single best-documented cause of milk loss — one case of clinical mastitis can cost 300–400 kg of milk in a lactation. Check each quarter for heat, swelling or pain, and look for clots, flakes, or watery or blood-tinged milk. Sub-clinical cases show no visible change but still cut yield — a CMT test catches these early. See our guides to mastitis prevention and udder health support.
In hot, humid weather cows eat less and milk falls within a day or two. Provide shade, plenty of clean water, ventilation or fans, and feed during cooler hours. Our heat stress guide has the full cooling plan.
A sudden change of fodder, mouldy or spoiled feed, less green fodder, an empty water trough, or a rumen upset (acidosis or simple indigestion) can all cut milk quickly. Check that feed is fresh and unchanged, that minerals are being given, and that clean water is always available. A poor appetite or a cow that stops chewing cud is a warning sign — our note on a cow that stops chewing cud explains first aid. Herbal appetite and rumen support such as Cattle Remedies Ruminova, or a liver tonic like Cattle Remedies Heprich, can help restore intake once the underlying cause is fixed.
Almost any fever cuts milk. Take the temperature (normal is about 38.5–39.5°C). Common culprits in India include tick fevers such as theileriosis and babesiosis, mastitis, and viral fevers. Fever with pale gums or red urine needs a vet the same day.
Around calving, watch for milk fever (weakness, going down), ketosis, and negative energy balance in fresh cows. Oestrus (heat) causes a normal, short one-day dip. A steady low fat or SNF is a different problem — see low milk fat and SNF.
A gradual decline over weeks, with weight loss or a rough coat, often means worms or a mineral deficiency. Follow a deworming schedule and correct minerals with a good mineral mixture.
The most common hidden reasons are sub-clinical mastitis, heat stress, and a feed or water change. Run a CMT test, check the trough and feed, and note the weather before assuming the worst — but if the drop persists, get a vet check.
Yes. Transport, a change of shed or milker, mixing in new animals, noise, or pain (lameness, ticks) can all reduce let-down and yield. Calm, consistent routines and comfortable housing help recovery.
Mild causes (heat, a feed hiccup, oestrus) often recover in a few days. Infections and mastitis take longer, and some yield may be lost for that lactation — which is why early action matters.
A sudden milk drop is a checklist, not a guess: udder, temperature, feed, water, ticks, and what changed. Fix the cause early and most cows bounce back; delay and you can lose milk for the whole lactation. When in doubt — fever, abnormal milk, red urine or a big drop — consult your veterinarian.
Reference: MSD Veterinary Manual — Interactions Between Health and Production in Dairy Cattle.
This article is for general educational purposes and does not replace professional veterinary advice.
