That's an issue that honestly had never occurred to me. I did a quick google search and found an article called 'Ethical Issues of Transplanting Organs from Transgenic Animals into Human Beings' which present deontological and consequentialist critiques.

Here's an excerpt of the conclusion regaring animal-based ethical considerations.

From the animal-based side, the supporters of animal welfare school believe that starting this treatment process will destroy animal welfare from broad dimensions. This happens because its genetic structure is modified and therefore, the animal will not have the chance to live its instinct and will be deprived of the least factors necessary to live like being safe from pain and suffering. Therefore, even from the viewpoint of these philosophers who believe in the use of animals when necessary, this method at its present level is neither justified nor verified from the ethical point of view, but if its benefit and safety is proved, compromising the animal welfare to save a human life is justifiable.

And the final conclusion taking all considerations

Consequently, considering the above mentioned facts, we can conclude that within the current situation, transgenic animals’ organ transplantation into to human is not ethically justified; therefore, it needs to develop further .

Just some food for thought.