My apologies Bam, but with all due respect that statement is a little misleading. According to the well recognized resource The House Rabbit Society, foods containing oxalic acids are perfectly safe when fed properly (please see below or click the link at the bottom of this note.) . If that is the only problem with sorrel than it should be safe.
Sighted from rabbit.org:
“Many plants contain a naturally occurring chemicals called an alkaloids, which are mild toxins that protect plant in the wild. The one most talked about
with rabbits is oxalic acid and it is completely harmless to animals or humans when consumed in small amounts. The amount of oxalic acid within each plant
can vary significantly due to several factors including the composition of the soil the plant grew in, the time of year and the age of the plant. Most
of the fresh vegetables we feed rabbits have a low to zero level of oxalic acid, but a few, most notably parsley, mustard greens and spinach have relatively
high levels. (Note that kale, which is often implicated as a high oxalate food is actually very low in oxalates). The toxicity of oxalic acid comes with
feeding large quantities of foods high in this chemical and can result in tingling of the skin, the mouth and damage to the kidneys over time. These foods
are nutritious and do not need to be excluded from the diet if you feed them appropriately. I recommend feeding a minimum of at least 3 types of leafy
greens a day (and only one of them should be from the group listed above) Don’t feed the same greens all the time from week to week if possible, mix it
up. For instance if you feed parsley this week, then leave it out of the diet for next week and use something else. Rotating the greens will also give
your bunny variety in taste, texture and general nutrition!
LIST OF POSSIBLE FOODS TO FEED
Leafy Greens I (need to be rotated due to oxalic acid content and only 1 out of three varieties of greens a day should be from this list)
• Parsley
• Spinach
• Mustard greens
• Beet greens
• Swiss chard
• Radish tops
• Sprouts (from 1 to 6 days after sprouting, sprouts have higher levels of alkaloids)…”
http://rabbit.org/suggested-vegetables-and-fruits-for-a-rabbit-diet/
.
