The amount of grass that would provide the recommended daily allowance (RDA) of calcium also contains 350mls water, which is an important consideration, especially for rabbits with urinary tract disease.
AMOUNT OF FOOD THAT PROVIDES RDA OF CALCIUM
63g of nuggets. These contain 0.9% calcium. If the nuggets were 'low in calcium' i.e. 0.45% then twice the amount shown would provide 500mg calcium. It would be easy for a rabbit to eat that amount. It could eat more.
The bag holds 463g grass, which is approximately the amount that a rabbit would need to eat to meet the recommended daily allowance of calcium. It is a large volume so it is unlikely that a rabbit could eat so much grass that its calcium intake would be excessive
Approximately 463g of grass provides 500mg calcium. In the digestive tract of a rabbit the water would be extracted from the grass and it would be separated into large and small particle in the colon. In this photos, 463g of grass has been dried and separated into large and small particles to show the volume, which approximates the amount of food that can pass through a rabbit's digestive tract. The large particles would be expelled as hard faecal pellets and the small particles would fill the caecum so it is reasonable to think that 463g might be close to the amount of grass that a rabbit would eat in a day.
The amount of calcium in hay is variable. It depends on the type of soil it was grown on and the species of grass. The amount of water in hay also varies. This image shows 113g grams of hay- the amount that would contain 500g if it was 15% water with a calcium content of 0.52%. This is a typical analysis.
Although the calcium content of dandelions is high (1.87%0, they are 85% water. Two large plants (178g) will provide 500mg calcium.
Kale sometimes has a bad reputation for rabbits because of its calcium content (approximately 1.3%). However it is 85% water, which means that a rabbit can eat a lot of it without eating a lot of calcium. This picture shows 265g kale, which is the amount that would provide 500mg. It is more than most rabbits would eat in a day. A typical bag of kale from the supermarket contains 200g. A big bag contains 400g.
Approximately 1kg of broccoli (2 large florets) provides 500mg calcium. A rabbit might eat that amount but it is unlikely
Watercress is often considered to be a high calcium food. The calcium content is 1.2% but 95% of watercress is water. so a rabbit would have to eat approximately 830g to to ingest the recommended daily allowance of 500g. This equates to just 11 bags of watercress from the supermarket.
Mineral blocks can provide an alarmingly high amount of calcium to rabbits that chew large amounts. The calcium content is approximately 19% and there is very little water. A rabbit would only need to eat a nineteenth of one of the bars shown in this image to meet the Recommended Daily Allowance of 500mg. If the rabbit chews large amounts, it places a high burden on the kidneys and bladder to excrete the large amount of calcium. This would be alright in a rabbit with a healthy urinary tract but could easily cause problems in a rabbit with compromised kidney or bladder function. Another problem with mineral blocks is the small particle size of the powder. These particles will be moved into the caecum by the motility of the hindgut and could add to impaction problems in rabbits that are dehydrated or have consumed large amounts of the block. They also have a very low phosphorus content and a highly inverse calcium to phosphorus ratio.
Carrots are 88% water and are low in calcium (0.37%). A rabbit would need to eat about 1.13g to ingest 500g calcium. This equates to about 10 carrots. Carrot tops are high in calcium (1.94) but are not heavy. The tops from about 1.5 bunces would provide 500g calcium.
A rabbit would need to eat approximately 15 apples to obtain 500mg calcium. This is too much for a rabbit to eat in a day
Maize has a very low calcium content. Despite its low water content, a rabbit would have to eat about 5kg to get its recommended daily allowance of 500mg of calcium. This would fill about 10 cereal boxes. It is impossible for a rabbit to eat that much food in one day.
Although spinach is rich in calcium, it is also mostly water. A rabbit would have to eat about 630g i.e 2-3 bags of spinach from the supermarket to ingest 500mg calcium.
Bananas have a very low calcium content (0.06%). A rabbit would have to eat about 17 bananas to ingest 500mg calcium. Bananas are also rich in soluble fibre that is easily converted into fat by rabbits. A diet that is rich in banana will lead to obesity.
Although spring cabbage is rich in calcium, it also has a high moisture content. A rabbit would need to eat about 150g to meet the recommended daily allowance of 500g calcium. Most supermarket bags contain 500g spring greens.