Overmilking and Teat Damage: How Milking Duration Affects Udder Health

What Is Overmilking?

Overmilking occurs when the milking cluster remains on the cow's udder after milk flow has effectively stopped. In modern milking equipment, automatic cluster removal (ACR) systems detect when milk flow drops below a threshold and remove the cluster automatically. Operations without ACR — or with poorly calibrated thresholds — may routinely overmilk cows.

Overmilking is one of the leading equipment-related causes of teat damage and, through teat damage, one of the major preventable contributors to mastitis.

The Mechanism of Teat Damage

During milking, the vacuum applied through the liner alternates between milking phase (liner open, vacuum draws milk from the teat canal) and rest phase (liner closes against the teat, creating a massage phase that maintains blood flow). This pulsation cycle is designed to work with milk flow — when milk is present, the vacuum is doing useful work; when it is not, the vacuum pulls on teat tissue without the cushioning effect of the milk column.

When milk flow stops and the cluster remains on the teat:

• Congestion: blood and lymphatic fluid accumulate in the teat end and teat skin from the continued vacuum stimulus without milk flow to relieve pressure
• Hyperkeratosis: repeated over-exposure to vacuum without milk causes callosity and roughening of the teat orifice and surrounding skin — the teat end changes shown in teat end scoring as scores 3 and 4
• Teat canal inflammation: teat canal tissues become edematous (swollen), affecting the sphincter muscle's ability to close the teat orifice completely between milkings

These teat changes directly increase susceptibility to mastitis: a roughened, congested teat orifice is harder to disinfect with post-milking teat dip and provides better bacterial adhesion conditions.

Prevention and Response

Calibrate ACR thresholds: milk flow thresholds for cluster removal should be set at the manufacturer's recommended level — typically 200–300 mL/min. A threshold set too low to try to "empty the udder" causes significant overmilking.

Check milking time distribution: in a well-managed parlor, most cows should finish milking within 5–8 minutes. Cows that consistently take 12+ minutes may have flow issues or be overmilked.

Teat end scoring program: quarterly teat end scoring of the whole herd identifies whether teat damage is becoming a herd-level problem.

Emollient teat dips for recovery: where teat damage is already present, post-milking dips with high emollient content support teat skin recovery. Vilnus LA includes conditioning additives suitable for teat skin rehabilitation alongside post-milking disinfection.

Contact AgroLyne for post-milking dip selection for herds with teat condition issues.