Maybe others already know this but it came as a surprise to me.
I put together a turkey only (meat, bones, heart, liver and gizzards) recipe and was surprised when the nutritional analysis showed the vitamin A content to be very high, a little over the NRC safe upper limit. At first I thought it was a bug in my analysis program. After wasting a lot of time "debugging" my program I realized the problem is that turkey liver has 6.5 times the amount of vitamin A that chicken liver has. I had assumed they would have roughly the same amount.
Vitamin A is one of the fat soluable vitamins meaning that any excess consumed is stored in the body. Very large accumulations of vitamin A are known to cause serious health issues in cats.
Normally vitamin A toxicity is difficult to acheive because it requires very high quantities of vitamin A to be consumed frequently and over a long period of time. The recipe I put together could well result in toxicity if fed frequently. I was planning on feeding it 1 meal out of 4.
The recipe included 0.5 lb liver in a total of 11.5 lb making the liver 4.3% of the whole.
100 grams of turkey liver contains 72,383 IU of vitamin A vs 11,078 IU in chicken liver.
My recipe was 70% water so, my recipe contained 110,040 IU/kg vitamin A including the small amounts present in ingredients other than liver. The NRC recommends 5000 IU/kg and sets a safe upper limit of 100,000 IU/kg. The NRC recommendations are the amount per kg on a dry matter basis.
I don't think turkey liver is readily available to most people but it may be for some as it is with me. Serving it occasionally should not be a concern. But using it frequently as our liver source is probably not a good idea.
============================================================================
100 grams turkey liver => 72383 IU vit A
0.5 lbs turkey liver = 226.8 grams
226.8 grams turkey liver => 164,164 IU vit A
11.5 lbs total recipe = 5216.4 grams = 5.2 kg
recipe total (DMB) = 5.2 kg * .30 = 1.56 kg
164,164 IU/1.56 kg = 105,233 IU/kg
Using chicken liver in place of the turkey liver results in 18,539 IU/kg, well within the safe limit.
