The Watchtower teaches that Jehovah's Witnesses do not celebrate birthdays in part due to a couple of tragedies during two of them, which therefore places them under a negative light in God's eyes.
If such select reasoning from the Bible places birthdays in unfavorable light, how about pets? Specifically, let's consider dogs.
We will see how dogs are often viewed, whom they are associated with and are they appropriate then for Jehovah's Witnesses?
Straight from their 2013 revision of the Bible provided by the Watchtower Society:
Isaiah 56:10 - His watchmen are blind, none of them have taken note. All of them are speechless dogs, unable to bark. They are panting and lying down; they love to slumber.
Psalms 22:16-21 - For dogs surround me; They close in on me like a pack of evildoers, Like a lion they are at my hands and feet. I can count all my bones. They look on and stare at me. They divide my garments among themselves, And they cast lots for my clothing. But you, O Jehovah, do not remain far away. You are my strength; hurry to help me. Save me from the sword, My precious life from the paws of dogs; Save me from the mouth of the lion and the horns of wild bulls; Answer and save me.
Proverbs 26:11 - Like a dog that returns to its vomit, The stupid one repeats his foolishness.
Philippians 3:2 - Look out for the dogs; look out for those who cause injury; look out for those who mutilate the flesh.
Revelation 22:15 - Outside are the dogs and those who practice spiritism and those who are sexually immoral and the murderers and the idolaters and everyone who loves and practices lying.
From their own Bible, dogs are often placed in a negative light with unfavorable connotations and associated with those who are liars, idolaters, murderers, sexually immoral and practice spiritism.
From the Watchtower's own version of the Bible using their reasoning, Jehovah's Witnesses should be more concerned with avoiding or having dogs as pets, if they are drawing any sort of conclusion to avoid birthdays from the Bible.