If you’ve been milking goats for any length of time, you’ve likely dealt with mastitis, plugged ducts, or flaky milk at some point—but what if you feel something hard inside the teat that doesn’t seem to be attached to anything? You could be dealing with a rare condition known as a milk stone.
Milk stones, also called lactoliths or milk calculi, are solid masses that can form inside the mammary system of a goat, typically within the teat or gland cistern. Though not common, understanding how and why they form can help you avoid misdiagnosing or mistreating a blocked teat. Let’s look at what causes milk stones in goats, how to recognize them, and what you can do about them.
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What Are Milk Stones?
Milk stones are firm, stone-like masses composed primarily of casein (a milk protein), calcium salts, and occasionally cellular debris. These masses usually develop in the teat cistern or gland cistern and may obstruct milk flow to varying degrees. While they can sometimes be confused with clumps caused by mastitis, they are not the result of infection or inflammation. Instead, milk stones are a mechanical issue: something physical is in the way of the milk exiting the teat.
You may first notice a milk stone when your normally easy-to-milk doe suddenly becomes slow to let down, or when the milk stream starts and stops unexpectedly. She might also get upset when you try to milk that teat. Some goat owners can feel a small, hard lump inside the teat while milking, while others may only suspect an issue when one side of the udder isn’t producing normally but shows no signs of mastitis.
How Common Are Milk Stones?
Milk stones are relatively rare in goats, especially compared to more well-known udder issues like mastitis or udder edema. We only had one doe get milk stones after 21 years of milking 10-20 goats per year.
Most veterinary research on lactoliths comes from studies on cows, but occasional case reports do appear in the goat-specific literature. Because hand-milking allows for more tactile feedback, owners who milk by hand may be more likely to notice a milk stone than someone using a machine. We discovered our goat had a problem when her triplets stopped nursing on one side.
In many cases, milk stones go undetected until they partially or completely block the teat canal, leading to visible changes in milk flow or udder pressure. Since they don’t usually cause inflammation, infection, or systemic illness, they can be easy to miss until they become problematic.
Symptoms of Milk Stones
One of the first signs of a milk stone is an intermittent or weak milk stream despite normal udder fullness. The milk may start flowing and then stop abruptly, or you may feel resistance when squeezing the teat. You might also feel a hard object inside the teat while milking, especially if the stone is large.
Unlike mastitis, milk stones typically don’t cause fever, udder heat, or pain. The goat may appear completely healthy, and the affected half of the udder may look normal aside from the reduced milk flow. In short, a goat with a milk stone will generally act normal, and the udder won’t feel hot, hard, or swollen.
What Causes Milk Stones?
The precise cause of milk stone formation isn’t fully understood or documented, but it’s believed to involve a combination of milk chemistry, diet, and udder management. One leading theory is that milk stasis—when milk sits in the udder for extended periods—allows minerals and proteins to settle and crystallize. This can happen if a doe’s kids are suddenly weaned, she is milked irregularly, or has a damaged teat that prevents full emptying.
Dietary factors may also play a role. High levels of calcium or protein in the diet could contribute to stone formation, especially if the goat’s mineral balance is off. A sudden drop in milk production or abrupt drying off may also change the pH and mineral content of the remaining milk, creating ideal conditions for a stone to form.
Injury or scarring inside the teat canal could also provide a spot for minerals to start accumulating. Inflammation, even without infection, might trigger the body to deposit protective material that later calcifies.
Diagnosing Milk Stones
Milk stones are usually diagnosed based on clinical signs and physical examination. If you feel something hard inside the teat or notice inconsistent milk flow without other symptoms of mastitis, it’s worth considering a milk stone. In more advanced settings, veterinarians can confirm the diagnosis with ultrasound, particularly if the stone is higher up in the udder and not easily felt.
It’s important to differentiate a milk stone from mastitis. In mastitis, you’ll often see thick or discolored milk, swelling, and signs of pain or illness. A California Mastitis Test (CMT) may show high somatic cell counts in mastitis cases, but usually not with a milk stone—unless the stone is irritating the tissue enough to trigger inflammation.
Removing a Milk Stone
If you suspect a milk stone, the goal is to remove it as gently as possible. Sometimes, the stone will dislodge on its own during milking and exit with the milk. You might see a small, white or yellowish object — often the size of a grain of rice — come out into the milk pail. They are firm to the touch and may resemble small pebbles or bits of chalk.
You can try massaging the teat gently or changing your milking technique to help the stone work its way down. However, if the stone is lodged tightly or causing a full blockage, do not force it out. This could injure the teat or lead to infection. In those cases, veterinary intervention may be required. A vet may use a sterile catheter to retrieve the stone or, in rare cases, surgically remove it under sedation.
After the stone is removed, monitor the goat’s udder closely for signs of swelling, pain, or infection. Most goats recover without complications, though some may have scarring or develop recurring issues in the same teat.
Can a Goat Still Be Milked with a Milk Stone?
You should continue milking a goat if you think it has a milk stone, assuming milk is still coming out of the teat. If milk is still flowing, you may be able to keep milking the goat while gently monitoring the stone’s position. However, partial blockages can reduce overall production and lead to backup of milk, which increases the risk of mastitis.
If the stone is fully blocking the teat, you’ll need to remove it before resuming milking on that side. In most cases of complete blockage, you’ll need to see a vet. In some cases, scar tissue or chronic obstruction may make that teat permanently nonfunctional.
Milk stones themselves are not dangerous unless they cause complications like blocked ducts, mastitis, or udder damage. That said, it’s always best to treat them early to avoid worsening the situation.
In our doe’s case, we were able to clear the blockage, and she never had another problem in the two years since that happened.
Prevention: How to Reduce the Risk of Milk Stones
While there’s no guaranteed way to prevent milk stones, a few management strategies can lower the risk. Regular and consistent milking is key—avoid abrupt weaning, especially during peak lactation, or long gaps between milkings.
Diet matters, too. Be sure your goats have a balanced mineral intake, especially a proper calcium-to-phosphorus ratio of 1:1 to 2:1. Avoid excessive calcium supplementation. Also, ensure good udder hygiene to prevent any minor injuries or inflammation that could serve as a starting point for stone formation.
Finally, knowing what’s normal for each goat makes it easier to catch changes early. If a previously high-producing teat suddenly slows down without any signs of illness, don’t assume it’s just a fluke—check for obstructions, including the possibility of a milk stone.
Final Thoughts
Milk stones in goats may be rare, but they’re not unheard of—and they can be surprisingly tricky to identify. While they usually aren’t dangerous on their own, they can interfere with milk flow and potentially lead to more serious issues if not addressed.
The good news is that most milk stones can be resolved with careful observation, gentle handling, and veterinary support when needed. And by following good milking practices and ensuring your goats are nutritionally balanced, you can significantly reduce the chances of ever seeing one.
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