Safe fertilizers to use on grass where our pet rabbits graze

Question
Hello Dana,

The cold winter here in the UK has left us with a slow grass growth rate,so we were wondering if there are any organic grass fertilizers that you could recommend/have used on a lawn used for rabbits to graze on?

Sorry this is such a random question (!!), but we use grass as one of the main components of our rabbits diets, so we have quite a high demand for it.
We have heard that you can put calcified seaweed on your lawn to increase growth rate, but we aren't sure if this is safe for our buns to graze on after???

Any help greatly appreciated! Thank you in advance!!!
Katie :-)

Answer
Dear Katie,

Sorry for the delay.  I meant to stay on "vacation" during student advising and registration time here at UM, but forgot to update!  :(  But I hope it's not too late to answer your question.

The only fertilizer I'd consider safe for a lawn where bunnies graze would be treated/sterilized commercial manure mixes.  The higher the nitrogen content, the more vegetative growth the lawn will do.  It won't be as quick as applying 20-20-20 inorganic fertilizers, but manure and compost are much safer (and will last a lot longer).

Hope that helps!

Dana