The 200mmf/2.8 was a typo and I meant to type 80-200mmf/2.8.
Because of the low lighting and the lack of flash, I do not photograph Dog Agility indoors. To stop the action, you need a shutter speed of between 1/250 to 1/1000 depending on the angle of the dog and how fast it is going. I also photograph Basketball indoors and the brightest gymnasium in Alaska I have to shoot iso 800, 1/250, f/2.8. So if your indoor Dog Agility is as bright as this gymnasium, then you will have to shoot at iso 3200, 1/250, f/5.6. Your lens is too slow for this kind of work. You are going to have underexposed and lots of digital noise in your photos because you can not get the exposure correct. The last Dog Agility Trial I did indoors was so dark that I had to go into the roof and hang 4 1000 watt White Lightning Strobes just to be able to shoot at 1/250, iso 400, f/2.8. With the storbes in the ceiling, the judges ruled that it was not a safety concern for the dogs because the flash was overhead, instead of in the eyes. Still, some dogs froze when the strobes went off, so even this is not a viable solution. Until Nikon or Canon comes out with a camera that will go 6400 noise free, the inside Dog Agility trials just won't be covered much.

If you limited yourself to some of the closer obstacles, you could get by with an 85mmf/1.4 lens. that would give your 4 stops more light than what you have and 2 stops more light than what I am using. that lens is around $1000.00