aurora77 –
Bless you. It is highly commendable that you are looking for ways to show appreciation for something; gratitude is one of the most basic tenets of Judaism. We do have standardized prayers, but we also believe that one can add whatever they feel like in their own words.
The first of the standard morning blessings goes as follows:
Blessed are you LORD, our God, king of the world, who gives the rooster understanding to distinguish between day and night.
If you wish to say a prayer of thanks for your pets, that might be an apt place to insert some of your own thoughts.