Strutting of the teats is a visible swelling and distension of the teats that occurs when a cow’s udder becomes extremely full, typically in the final 24 hours before calving. The teats appear engorged, firm, and pointed outward rather than hanging in their normal relaxed position. It’s one of several physical signs that ranchers and farmers use to predict when a cow is about to give birth.
What Strutting Looks Like
Under normal conditions, a cow’s teats hang downward in a soft, pliable state. When strutting occurs, the teats become visibly distended and rigid. They may stick out at wider angles from the udder floor, looking almost like they’re being pushed apart by internal pressure. The skin on the teats often appears tight and shiny. The entire udder will look noticeably fuller and more taut than usual.
This happens because of rising intramammary pressure. As the cow’s body prepares for calving, milk and colostrum accumulate rapidly in the udder. That fluid fills the internal reservoirs of each teat (the teat cisterns), causing the tissue to expand outward. The pressure also widens the teat canal, which is the narrow passage at the tip of each teat. When the cistern fills enough, the teat wall thickens with fluid congestion, giving each teat that characteristic swollen, “strutted” appearance.
Timing Before Calving
Strutting of the teats is generally considered one of the immediate signs of calving, placing it in the final 24-hour window alongside relaxation of the pelvic ligaments. It’s distinct from the more gradual changes that happen over the preceding weeks, like udder development (“making bag”), vulvar swelling (“springing”), and loss of the cervical plug.
That said, the timing is not reliable across all cows. Heavy-milking cows may show strutting as much as two or three days before calving, simply because they produce more milk and their udders fill faster. On the other end of the spectrum, a thin or low-producing cow may calve without any noticeable strutting at all. Oklahoma State University and University of Nebraska Lincoln extension resources both note this variability, recommending that ranchers use strutting as just one piece of the puzzle rather than a definitive countdown clock.
Why the Pressure Builds
The core mechanism behind strutting is straightforward: the udder keeps producing milk, but nothing is removing it. In the days before calving, the mammary gland ramps up colostrum production. With no calf yet nursing, that fluid accumulates in the alveoli (tiny milk-producing sacs deep in the udder tissue) and flows down into the teat cisterns. Intramammary pressure climbs steadily.
Research on dairy cows during the dry-off period, when milking stops before the next calving, shows a similar dynamic. Pressure and milk leakage both peak about 24 hours after milking ceases. When pressure exceeds roughly twice the normal physiological range, it begins to reduce blood flow to the mammary tissue, which eventually signals the gland to slow production. But before that feedback kicks in, the udder can become extremely full and tense.
Strutting During the Dry Period
Strutting isn’t limited to the hours before calving. Dairy cows commonly experience it at the start of their dry period, the six-to-eight-week break from milking before the next calf is born. The udder doesn’t stop producing milk immediately when milking ends. For the first two to three days, milk continues to accumulate with nowhere to go, and the resulting pressure can cause the same teat distension seen before calving.
Cows producing more than 15 kilograms of milk per day at dry-off are especially prone to this. In one study, cows that leaked milk after drying off were producing an average of 28.3 kg the day before, compared to 23.4 kg for cows that didn’t leak. About 16.7% of udder quarters showed milk leakage at least once in the 72 hours after drying off, with the peak occurring at the 24-hour mark.
Health Risks of Prolonged Teat Distension
When teats remain strutted for an extended period, the teat canal widens under pressure. This is a concern because the teat canal acts as the udder’s primary barrier against bacteria. A dilated canal makes it easier for environmental pathogens to enter the udder and establish an infection, known as mastitis.
The numbers back this up. Udder quarters that leaked milk 72 hours after drying off had 3.4 times the odds of developing a new infection during the dry period and calving week compared to quarters that didn’t leak. For rear quarters specifically, the odds jumped to 5.8 times higher. Teat shape also plays a role in longer-term mastitis risk: cows with certain teat conformations, like triangular barrels with pointed ends, face about 66% higher risk of clinical mastitis than cows with the most common square-barrel, round-end shape.
Reducing Discomfort and Infection Risk
For dairy operations, the main opportunity to manage strutting comes at dry-off. Gradually reducing milking frequency to about once per day in the week before the dry period helps the udder adjust. This approach lowers intramammary pressure more effectively than abrupt cessation, accelerates the natural process of mammary involution (where the gland shifts out of active milk production), and reduces stress. Research from the University of Helsinki found that gradual cessation improved overall cow welfare compared to sudden dry-off.
Switching to a lower-energy diet in the days before dry-off is another practical strategy, since it naturally decreases milk output. The target is to get daily production down to 15 kg or less before milking stops entirely. Cows dried off above that threshold experience more milk leakage, more infections, and higher mastitis rates in the following lactation.
For beef cows approaching calving, there’s less you can do about strutting itself, since you’re not milking them. The practical value of spotting strutting in a beef herd is simply as a calving predictor. If you see a cow with tight, distended teats alongside relaxed pelvic ligaments and restless behavior, it’s time to keep a close eye on her.