Diet Cascade (IDC) is a theory by bird veterinarian Greg
J. Harrison, DVM
that links a wide variety of illnesses, behaviors, etc. to problems in
the diet. It is similar to proposals made about human and other
animal diets as we find that more and more issues are interconnected.
over-simplified version is ‘you are what you eat’. If we offer foods
that are too high or too low in nutrients- even ‘micro- nutrients’ like selenium- or foods that have lost nutritional
values or gone ‘bad’ due to poor handling or storage, etc. then it
will have real effects on whatever eats it. The effects may start
small- pH imbalances, cellular issues, etc. but the ‘cascade’ part kicks in as things snowball and little
things start building into major problems.
We already know
that the foods we offer tortoises in captivity are nothing like what
they get in the wild- most wild foods are much higher in available
calcium and fiber for example. We try to make up for
this with additional variety or pelleted diets, and yet we still see many issues that
can be traced to diet- soft shells, pyramiding,
illnesses, listlessness, unusual growth patterns, reproductive
The visible symptoms of IDC do not show upry, flaky skin; loss of color; loose scales; excess
until things have been going wrong on a cellular level for some
time.The first signs often show up in the feathers in birds, so
probably show up on the skin on tortoises- although we probably cannot
easily see it- things like d
shedding; overgrown scute edges, long nails, and beak overgrowth. Unusual feces are another early sign that something is
not right- pale, wet, loose; or dark, dry, hard, or otherwise ‘unusual’. The next signs would show up
in the slower-growing tissues- issues like soft bones, soft shells,
IDC is fatal in severe cases, but would more likely cause long-term problems, like shorter
lifespans, increased susceptibility to disease or parasites, reduced
reproduction, increased medical problems, and so on.
is no single, quick fix to IDC, the original article
makes several suggestions that we can adapt for use with
tortoises. While many of these are mentioned elsewhere on this site,
here are the main ideas:
- Make sure fresh water is always available.
appropriate, fresh, wholesome foods with prepared diets formulated
for your species of tortoise. (We would suggest that this also include as
much natural grazing on ‘good stuff’ as possible.)
- Supplement as needed, especially calcium, vitamins A,
D, and E, fiber, iron, etc.- but do not overdo it. See ‘Vitamins and Nutrients‘.
- Do not overfeed, especially things like proteins,
fats, sugars, salts, dairy, raw grains, and chemicals and preservatives.
- Store all foods correctly. Follow expiration dates and store
prepared foods in air-tight, air-free containers or bags at cool temps to avoid rancidity.
- Handle all foods properly to prevent contamination.
- Consider adding grit. Wild
tortoises routinely eat sand and may need this to help process tough
plants. Small amounts of ‘calcium sand’, bird grit, or clean fine
sand in the food should work.
- Offer ‘enrichments‘ that help offer natural opportunities-
bones or cuttlebone to gnaw on, hard-rind fruits to work at biting, hanging bunches of greens from a hook, etc.
balanced with consistency. Feed at about the same time every day, in
about the same place, but vary what is offered and toss in some
surprises occasionally, like hiding mushrooms or strawberries in the
- Keep doing your homework to learn the best practices.