Issues emerged after Muller declared that his horse D'Avie supported an harm ahead of breeding season - something which the animal rights association contend was 'preventable and unnecessary'.
Nearby his spouse Lisa, who may be a horse coach and competes in occasions, the couple have been running a horse cultivate in Germany - where they offer the solidified horse semen for €200 (£167.55).
In a explanation this week, Muller clarified: 'Tragically, we have terrible news. Our D'Avie will not be accessible within the another few months. Shockingly, he slipped amid a test endeavor to plan for breeding season and fell significantly on his side.
'He maintained an damage to the foot range and will require total rest for the following few months. He's a intense fellow, and he may have been more regrettable.'
That in turn caused PETA spokesperson Jana Hoger to talk out and brandish the hones that driven to the harm as 'unnecessary'.
The articulation said: 'It is unpleasant that self-broadcasted horse significant others drive creatures in their care to perform unnatural sexual acts to benefit from it.
'The wounds D'Avie endured beneath the supervision of Lisa and Thomas Müller were preventable and unnecessary.'
There's no proposal of wrongdoing by Thomas Muller or his spouse. Sportsmail have contacted Bayern Munich for comment but are as of however gotten no comment.