Hi Anthony Lawrence! The scientists explained it to me that, unlike other systems like lung, heart, etc, the reproductive system in newly born mammals is still developing. So, it is relatively easily to introduce new tissue into a young animals reproductive system and have it develop as they do. As far as your second question, I don’t think I asked that one! (maybe you should do my job! Lol). But, I believe they have studied it in mice for quite a while so expectation is it will stick around for a while. But frankly, even a single season with a surrogate sire could have a large impact on changing genetic potential in a herd.