We had a rabbit wither up and almost die on us the other day. Since detecting a severe malnutrition problem which explains why she did not get bred when she was supposed to, we have moved her out to pasture and started feeding 100% alflafa to supplement the pasture she is getting. In just a day or two she has recovered remarkably well.
Come to find out, the feed we were buying for her - and for all of our rabbits - was killing her. We examined the label and researched what all of the chemical terms really meant. The feed was labelled as the only feed for rabbits of any age and the only thing they would ever need.
We quickly realized that this was reductionist science at its worst and, in my opinion, it is not limited to just animal feeds. People "feed" is going, or has already gone, in this direction.
The feed turned out to be bits and pieces of the individual nutrients added to fillers like alfalfa meal (the stuff left over from pellet production, corn, and fiber (the chaff, shells, etc a byproduct of wheat, oats, and barley processing), and other chemicals that obstensibly were added because rabbits need them.
The link below shows what was in our feed and why we stopped using it immediately and switched to pasture and alfalfa for a supplement.
Rabbit Food Ingredients