Sudden Drop in Milk Yield — 5 Common Reasons
Did your cow's milk drop from 18L to 10L overnight? A diagnostic guide addressing water blockage, mastitis, and heat waves.
Diagnosing an Overnight Drop
A sudden drop in a cow's daily milk yield (e.g. dropping from 16L to 8L overnight) is a clear alarm. It indicates acute stress, pain, or blockages. Instead of guessing, run a step-by-step diagnostic check to identify the cause immediately before permanent damage occurs.
Check 1: Water Blockage and Dehydration
The single most common reason for an overnight drop is water deprivation. If a water trough was dry, blocked, or contaminated with dung, the cow will refuse to drink. Since milk is 87% water, a lack of drinking water for just 12 hours will cut milk yield in half. Check your water supply and ensure water is clean and fresh.
Check 2: Subclinical or Acute Mastitis
Mastitis causes pain and tissue swelling, redirecting energy to fight infection. Strip a few drops of milk from each quarter onto a black plate or strip cup. Look for clots, flakes, or watery milk. Take the cow's temperature—if she has a fever (>103°F) and a swollen, hard udder, it is acute mastitis requiring immediate veterinary attention.
Check 3: Feed Toxins and Acidosis
Did the cow consume a new batch of feed, moldy silage, or slip into the grain storage? A sudden intake of starch causes acute rumen acidosis, dropping milk instantly. Similarly, mycotoxins in moldy straw or concentrate will depress yield overnight. Remove any suspicious feed and offer dry wheat straw.
Check water access, inspect all four quarters for mastitis, and test for rumen acidosis. Water lock and subclinical infections are the top causes of sudden milk drops.