Guinea pigs need calcium in their diet. However, too much calcium can cause problems, like bladder stones or kidney stones. Not enough calcium causes other problems. So how much calcium should a guinea pig eat every day?
Note: The calculations used in this article were updated to reflect more accurate data on March 25, 2018.
Calcium as a Percentage of Daily Calories
I asked my veterinarian friend what the ideal calcium intake should be for a guinea pig to avoid bladder and kidney stones. She just said I should use a diet that was 0.3% calcium.
I’ve also read accounts online where people state that a diet of 0.3% calcium is good for guinea pigs.
However, my question on this method is 0.3% of what? Calories?
When I do the calculations, this method of calculating calcium content does not work out.
A book called Nutrient Requirements of Laboratory Animals: Fourth Revised Edition, 1995. states that a guinea pig should eat around 8 grams (i.e., 8000 mg) of calcium per day per kilogram of pellets. (see Just Count the mg of Calcium, below).
If a guinea pig eats 1/8 cup of pellets per day, that works out to about 130 mg of calcium per day.
Let’s use an example to work out the 0.3% Calcium advice – based on calories. If I feed my guinea pig, let’s say, 100 calories per day, and I want to feed him 0.3% of those calories as milligrams of calcium, that means I am feeding him just 0.3 mg of calcium per day.
But if they’re referring to 0.3% as grams of calcium (not milligrams), that’s 0.3 g of calcium, or 300 mg.
The method (or units) in that advice is not clear.
Here’s an example:So to me, this method of calculating calcium requirements is not useful.
Here is an excerpt from Nutrient Requirements of Laboratory Animals (1995) stating that a normal adult guinea pig should eat around 8g of calcium per day per kg of pellets:
An average adult guinea pig weighs around 900 grams, or 0.9 kg.
To calculate how much calcium your guinea pig is eating, use the spreadsheet method.
Simply open a spreadsheet, list what he eats every day, look up the amount of calcium in that amount of food, and add it up. If you’re using pellets or a food with a label, you can get the info straight from the label. Otherwise, you’ll have to do an Internet search to find the calcium content.
Guinea Pig Pellet Manufacturers
Oxbow has been making quality guinea-pig pellets for a long time, and they have an extensive database of studies on the optimal nutritional requirements for guinea pigs.
They recently mentioned that their Adult Essentials Guinea Pig diet pellets currently have an average of 112 milligrams of calcium per 1/8 cup. Their calcium amount has recently been reformulated from a maximum of 85% calcium to a lower amount of 75% maximum.
They say that “It is important to note that this number can fluctuate due to growing seasons within our natural products. We have worked with leading exotic veterinarians and nutritionists to develop our products, but every animal is different and can have different requirements”.
I think it’s not completely conclusive how much calcium guinea pigs need since they have never done an actual scientific study specifically on that. We can only go by what apparently works for lab animals, but since these animals don’t generally live very long, we can’t be absolutely certain that it’s actually the optimal amount for long-term health.
How Guinea Pigs Absorb Calcium
Guinea pigs absorb more calcium from their food than humans do. On average, guinea pigs absorb about 50% of the calcium they ingest. People, on the other hand, absorb about 30% of the calcium they ingest. Of course, this amount varies based on several factors. For example, excess protein in the diet lessens the amount of calcium that gets absorbed. But it’s a good guide to go by as a general rule.
Vitamin D aids in the absorption of calcium, so giving your guinea pig about 20 minutes of sunlight exposure per day can help him absorb the calcium he eats better. If you can’t take him outside to get some sun, you can purchase a full-spectrum sunlight light bulb and use it for about 20 minutes a day.
If calcium is not absorbed by the body, it goes to the kidneys and bladder to get eliminated through urine. And once there, it can accumulate and create kidney and bladder stones. So it’s better to increase the absorption of the ingested calcium, which again, can be aided by adequate intake of Vitamin D.
How Many Calories Does a Guinea Pig Need per Day?
This question doesn’t have much to do with how much calcium your guinea pig needs, but I wanted to know the answer anyway. I searched the published literature, and there was no one definitive answer (that I could find).
However, there is a law known as Kleiber’s Law. This law was named after Max Kleiber who published his studies in the 1930’s. The law states that, for the vast majority of animals, an animal’s metabolic rate scales to the ¾ power of the animal’s mass.
If q0 is the animal’s metabolic rate, and M the animal’s mass, then Kleiber’s law states that q0 ~ M¾.
Applying this law to humans, we assume the average adult weighs 70 kg (154 pounds). Using Kleiber’s Law, then, the adult human would require about 2200 calories per day.
Applying this law to guinea pigs, we assume the average guinea pig weighs 1 kg, or 1000 grams.
2200 * (1/70)^(3/4) = 91 calories.
The average guinea pig requires 91 calories per day.
That’s the best answer I came up with. If you have different information, please share it in the comments below.
Take Notice of the Calcium to Phosphorus Ratio, too!
The amount of calcium a guinea pig absorbs is interdependent on the amount of phosphorus and magnesium he ingests, as well. For example, a study published by Van Hellemond et al. (1988) observed that guinea pigs fed purified diets that contained 8.4 g Ca/kg with 7.7 g P/kg and 1.0 g Mg/kg retained more calcium than those fed the same concentrations of calcium but with less phosphorus (4.4 g P/kg) and more magnesium (1.9 g Mg/kg).
The ideal calcium to phosphorus ratio for guinea pigs is 1.33 to 1. That means he should have 1.33 times more calcium in his diet than phosphorus.
So when you’re making your spreadsheet (detailed above), you might want to make another column next to calcium (mg), and keep track of the phosphorus content of each food, as well. Then add up all the calcium mg’s he eats in a day as well as all the phosphorus mg’s he eats and divide both by the smallest number (which should be the total mg of phosphorus) to get your ratio.
Other Ratios Matter, Too!
As you can see from the excerpt above, the amount of other minerals also play a role in how much calcium is needed or absorbed. In one study, decreasing the phosphorus and increasing the magnesium content lessened the amount of calcium guinea pigs retained.
You don’t need to sit and stress over the ratios of all the different minerals your guinea pig is eating, but it’s important to be aware. The main point is that you need to make sure your guinea pig is getting a balanced diet of healthy, natural foods.
Just as too much calcium creates problems such as bladder stones (among others), a deficiency of calcium creates problems in guinea pigs, too – especially when they’re young.
The laboratory manual referenced above states:
Signs of calcium deficiency have been produced in young guinea pigs fed a purified diet containing 0.28 g Ca/kg [of pellets, not bodyweight], 0.20 g P/kg, and a low concentration of vitamin D (Howe et al., 1940). Nine of 21 animals fed this diet survived for 60 days. These guinea pigs lost weight and developed rachitic lesions in ribs and long bones. Generally, the younger animals developed more bone abnormalities than the older animals. The teeth of all animals developed extreme enamel hypoplasia.
According to my calculations (and correct me if I’m wrong), a diet with 0.28 g Ca/kg of pellets (using 1/8 cup of pellets per day) means 4.55 mg of Calcium. So, getting approximately 4.55 mg of Calcium per day in these guinea pigs produced the calcium-deficiency symptoms.
This would mean that guinea pigs should never get less than 5 mg of calcium per day, and it appears that around 130 mg Ca per day is ideal.
Table of Calcium Content of Food
You can easily find the calcium content of the different foods that you feed your guinea pig by searching with Google.
Alternatively, you can also check out this handy list published by Guinealynx.
If you’d like to delve a bit deeper, check out page 116 of the 4th revised edition of Nutrient Requirements of Laboratory Animals.