Avoiding asynchronous loading lag

Hi, I have an animation where at the beginning I show the first part of a Guitexture and at the end the second part of the Guitexture (like a swipe effect). This is probably not the best way. Initially I used the "drawtexture" (consumes much less space texture then GUI) and I was moving the rect but it is not a fluid motion. If have any tips about this is welcome. However, the real problem is that if I start the asynchronous loading before or during the animation, it lags. So I have to call the loading at the end of the animation wasting time. Is there any way to increase the priority of the animation?

The loading is invoked by a Coroutine.