What is the position of Jehovah’s Witnesses on giving your pet blood?
YES – The Watchtower, February 15, 1964 p. 127 – Questions From Readers
Would it be a violation of the Scriptures for a Christian to permit a veterinarian to give blood transfusions to a pet? By all means, to do so would be a violation of the Scriptures. … The baptized parent bears the responsibility, for that parent has authority over the child and over the pet and should control the entire matter. That is the parent’s obligation before God.—Eccl. 12:13, 14; Jas. 4:17.
What, then, of animal food? May it be used if there is reason to believe there is blood in it? As far as a Christian is concerned, the answer is No, on the basis of principles already mentioned.