Hello!
The very existence of “personal” guardian angels (ie, one angel per person) is not a formal doctrine of the Church, but has been widely taught and upheld by many theologians and ancient scholars. And the concept has been expanded to include the idea that individual people gain additional “personal” guardian angels when they assume some particular important office, such as a priest, Bishop, or Christian King. And furthermore that guardian angels may be assigned to groups such as Christian nations. A greater angelic protection of such persons/groups is deemed necessary to counter the forces of the devil acting in opposition, who would find such persons/groups a target of opportunity. Again, none of this is defined Catholic Doctrine, but it is widely held by many respected Catholic theologians, drawing heavily upon Jewish understanding of the Angelic Choirs.
Animals, however, while possessing a life-giving soul, do not possess an eternal spirit. These act according to their own nature. They can be trained somewhat, but are still inherently governed by their animal nature. They are thus not subject to the corruption of demonic influences (despite what some owners of hound dogs and Siamese cats might think) and thus have no need of heavenly angelic countermeasures.
So, while I can assure you that the Catholic Church has never taken a definitive doctrinal position on the question, I have no doubt that the majority of Catholic theologians would agree that animals have no need of personal guardian angels, and thus do not have them.