Someone shared this prayer with me today, thought I would pass it on to the pet folks here...also useful for expressing condolences to friends or family who have lost a beloved pet (author unknown):
"O God, as we have taken care of (pet's name) in life, we ask that You watch over (him/her) in death. You entrusted (pet's name) to our care; now, we give (him/her) back to You. May (pet's name) find a happy new home in Your loving embrace. As we remember (pet's name), may we love each other more dearly."
