Bone broth is a topper, not a meal, and it is safe only when it is built to three numbers: an 8-hour simmer, 30 mL per serving, and no more than 2 servings a week. Homemade unsalted broth usually lands under 100 mg of sodium per 100 mL; carton stock and every bouillon cube push past that line by 4 to 8 times. Feed it for flavor and for water intake, never as a protein or joint supplement.
Two rules sit above the numbers. No bone goes into the bowl the cat eats from, and no onion, garlic, leek, chive, or scallion goes into the pot at any stage. Both appear in ordinary human recipes, and both send cats to a clinic.
What 30 mL actually delivers
Unsalted broth from chicken or beef bones is thin food: 5 to 15 kcal and 1 to 3 g of protein per 100 mL, so 30 mL is 2 to 5 kcal and under 1 g of protein. For a 4 kg cat eating 200 to 250 kcal a day, that is 1 to 2 percent of daily calories. It will not restart a cat that has stopped eating.
What it does well is add water. A cat that laps 120 mL a day from a bowl will often take another 30 to 60 mL when the bowl smells of chicken. If you already track moisture through wet food, that number is the one to move; the two food types are compared in wet versus dry food.
The 8-hour simmer, step by step
Use 1 kg of raw bones to 2 L of cold water. Bring it to a bare simmer at 85 to 95 C and hold that range for 8 hours. A hard boil emulsifies fat, clouds the broth, and makes the skim harder to lift; anything under 80 C for the first hour is warming bones, not extracting from them.
Eight hours pulls gelatin out of collagen and some minerals out of the bone matrix, but it does not turn bones into a calcium supplement. A 100 mL serving typically carries well under 50 mg of calcium, and the figure swings with bone type, animal age, and how much water went in. Any claim that broth rebuilds cartilage or reverses arthritis has no controlled evidence behind it in cats.
Water loss matters more than time. Two liters reduced to 1.2 L concentrates sodium by roughly 40 percent, so salt added at the start doubles by the time the pot comes off the heat. Add none and let the reduction work in your favor.
Why the bones come out before the cat arrives
Cooked bone splits into fragments 3 to 10 mm long with sharp edges. A cat working on a cooked chicken neck or a marrow bone can perforate the palate, wedge a piece between the molars, or swallow a splinter that reaches the stomach. The risk is not limited to large bones.
Strain twice: first through a 3 to 4 mm kitchen sieve, then through 1 mm mesh or a double layer of cheesecloth. Run a finger around the inside of the strainer after the second pass, because grit means a third pass. Chill the pot for 4 to 6 hours so the fat sets, then lift the cap off; skimming cuts calories by 30 to 50 percent.
Onion, garlic, and the 3-ingredient rule
Allium plants damage feline red blood cells and the effect accumulates across meals. No safe dose of onion powder has been established for cats, and a stock cube or soup base often lists onion and garlic as the second and third ingredients. Signs of Heinz body anemia appear 1 to 5 days after exposure: pale gums, weakness, fast breathing, dark urine, so call a vet the same day.
Keep the pot to 3 ingredients: bones, water, and one aromatic the cat can have, such as a 2 cm piece of carrot or a pinch of parsley. No salt, no bouillon, no wine, no xylitol-sweetened anything, no onion family, and no bay leaf left in for 8 hours.
Sodium: the 100 mg per 100 mL line
| Liquid | Sodium, mg per 100 mL | Serving allowed | Times per week |
|---|---|---|---|
| Homemade, no salt | 20-60 | 30 mL | 2 |
| Homemade, salted to taste | 250-400 | none | 0 |
| Carton stock, low sodium | 120-200 | 15 mL | 1 |
| Regular chicken stock | 300-500 | none | 0 |
| 1 bouillon cube in 250 mL | 800-1000 | none | 0 |
Read the label as sodium per 100 mL, not per serving. A carton at 190 mg per 100 mL is not automatically out: 30 mL delivers 57 mg, which is fine once a week. Poured twice a day, the same carton adds 114 mg of sodium a day to a cat whose whole diet should stay near 100 to 200 mg.
Fitting 30 mL into the week
Warm the portion to 37 to 38 C, close to body temperature, and offer it in a saucer instead of mixing it through the whole meal. A cat that dislikes the smell then walks away and still eats dinner; if it laps, stir 10 to 15 mL into 20 to 30 g of wet food.
Two servings a week is the ceiling, spaced at least 72 hours apart. Daily broth is how sodium and fat creep in, and how a cat learns to refuse plain food. If the goal is water, raise the wet food share; see the wet food ratio guide.
When broth is the wrong idea
Skip it for a cat with heart disease on a sodium limit, chronic kidney disease at stage 3 or 4, a history of pancreatitis, or uncontrolled hyperthyroidism. Skip it for kittens under 6 months, whose growth needs a complete diet, and for any cat on a prescription formula that 30 mL of fat can unbalance.
Stop and call a vet if vomiting starts within 24 hours of a serving, if diarrhea runs past 24 hours, if the cat refuses food for 12 hours, or if the gums look pale. After a bone batch, any of those signs needs the batch reviewed too.
Batch, freeze, and label
Make 2 L, strain, chill, and freeze in 30 mL portions in an ice cube tray, then bag the cubes. A 2 L batch gives about 40 servings, or 20 weeks at 2 a week. Hold cubes 3 months at minus 18 C; in the fridge, broth keeps 3 days.
Write the date and every ingredient on the bag. A batch that went in with onion cannot be rescued by boiling, and the label is the only thing that keeps it out of a bowl 6 weeks later.
Run it in this order: simmer 8 hours at 85 to 95 C with 3 ingredients, strain through 4 mm and 1 mm, chill 4 to 6 hours and skim, portion 30 mL and freeze, then feed twice a week at 37 to 38 C. Check stool for 24 hours after the first serving; loose stool means the next batch waits a month, and a second reaction means it stops.
Terms mentioned in this article
Frequently asked
Can I give bone broth to my cat every day?
No. Two servings of 30 mL a week is the working ceiling, spaced at least 72 hours apart. Daily servings add sodium and fat faster than most owners expect, and a cat fed broth on top of every meal often starts refusing plain food. If the goal is water intake, raise the wet food share instead and keep broth as an occasional topper.
Is store-bought stock safe if I boil it first?
Boiling does not remove salt or onion. A carton at 300 to 500 mg of sodium per 100 mL and a bouillon cube at 800 to 1000 mg stay over the line after any amount of cooking, and allium toxins are not destroyed by heat. Use only unsalted homemade broth, or skip broth and add plain warm water to the food.
How do I know the broth caused a problem?
Feed one 30 mL serving at 37 to 38 C on a day when nothing else changes, then watch stool for 24 hours. Loose stool or vomiting inside that window points at the broth. Stop it, wait 7 days, and if a second single serving triggers the same signs, leave broth out of the diet and mention it at the next vet visit.