Switching for formula

Cara
I was exclusively breastfeeding but we are weaning to be a formula fed baby. She gets 5 formula bottles and only 1 nursing session. 
The last day or two she has been getting feisty later in the afternoon and when being held, she's kicking her legs straight out and lifting her belly into the air. 
What is this? She normally doesn't have issues passing gas, but it seems that she isn't tooting that much anymore. 
I thought maybe the breast milk made her toot...
Suggestions?!?