There's a lot of ALS (all life stages), it should be fine to switch. Not sure if Acana changed their kibble size, but I used to feed my guys Grasslands a couple of years ago & the kibble was pretty big. I had to cut it for them bc it was so dense & hard. Momo had a hard time chewing it, he has really small teeth & mouth. I got so sick of cutting them w/scissors, we switched.
Here's a great thread about kibble sizes & pics.
http://www.yorkietalk.com/forums/yor...ce-thread.html