Pegasus looks like it's a simple molassed chaff so to be honest you will be better off changing it anyway. Low sugar/starch chaff is better for natives & better at preventing ulcers.
On a small amount you could change straight away but you might find they turn their nose up at it as they are used to the sugar content.
Any feed store will do a cheap molassed chaff so if they don't eat the new chaff you could try mixing with a molassed chaff at first then reducing it.
There's essentially 2 types of chaff - straightforward chaff eg mollichaff light, Dengie meadow light, honey chop lite & healthy, top chop lite etc which would all be suitable. Then there are complete feeds which have added vitamins, minerals etc examples are happy hoof molasses free, Dengie hi-fi etc.
If you are feeding a complete feed you need to feed the recommend quantity daily to get the right quantity of vitamins etc. if you only feed a scoop a day you need to add a balancer so it doesn't make sense buying the more expensive complete feed.
I think you are best feeding a low sugar/starch chaff & then a balancer on top.
I change mine between honey chop lite, Dengie meadow lite & mollichaff lite depending on what shop I use. Some ponies are fussier than others when it comes to 'light' feeds. The only one I found they wouldn't touch was Top chop zero.