I have just received a bulletin from my breed society in France that is worth sharing. There has been an agreement to standardise tariffs upon a regional basis.
The information on the costs of disposing of a dead horse can be found at www.angee.fr
and click on documents and tarifs.
As an indication the costs for a horse (sang) more than two years old varies from €180 in the north west to €450 in the very south east and more for a trait but less for pony or donkey.