Buttons and Yohji are big time alfalfa junkies They get 1 handful of alfalfa hay each, twice a week. It all gets wolfed down very quickly!
Alfalfa hay is regarded as high in calcium and generally, the advice is to limit intake of high calcium food in adult rabbits. Calcium content in rabbit food is a much discussed issue and I sometimes get queries about it as well.
This is briefly what I know about calcium metabolism in rabbits (based solely on my own understanding of the articles which I’ve come across):
- The concentration of plasma/blood calcium in rabbits is higher than that of most mammals. Rabbits require calcium in their diet to maintain this concentration level.
- When calcium levels are low, the rabbit’s system will attempt to raise calcium levels by re-absorbing calcium firstly from the kidneys, then the intestines and lastly, from the skeleton.
- An excess of calcium will also cause health problems in rabbits. Calcium is absorbed by the gastrointestinal tract and any excess is excreted via the urinary tract. Excessive excretion of calcium in the urine may lead to urinary tract calculi (urinary stone) and/or bladder sludge (thickening of the urine with calcium salts, without forming any stones).
- Calcium content in food should not be looked at in isolation. The presence of other organic compounds may affect calcium absorption e.g. oxalate bonds with calcium to form calcium oxalate which is insoluble and indigestible – it will not be absorbed by the body.
- A large percentage of calcium in alfalfa hay is in the form of calcium oxalate (some articles say ~20-30%).
- Calcium in vegetables appear to be less of a concern than calcium in alfalfa hay. This is because calcium level in vegetables is usually quoted as a ‘dry weight’ percentage, which does not take into account the high water content of vegetables (~90%). The actual amount of calcium consumed would be a very much ‘diluted’ amount compared to the quoted percentage. Additionally, many vegetables which are high in calcium also contain high levels of oxalate.
Please correct me if I got anything wrong above..
So what does all that mean?
My personal, non-expert take is this: Food need not be eliminated completely from a rabbit’s diet simply because it has higher calcium content. Rabbits still require calcium in their diet to maintain the right concentration of plasma/blood calcium. Higher-calcium food can be fed in limited or moderate amounts. Each rabbit is different so always keep an eye out for signs indicating that a particular food isn’t suitable for a particular rabbit.
It’s funny how my rabbits have got me searching for all sorts of rabbit-related articles. Frankly, I don’t even pay half as much attention to myself or my diet.. I’m really living in a ‘rabbit centered universe’, as D. Moll puts it! 😀