I have made the mash without the oats, but theyLOVE the oats! Those are always the first things they pick out of any thing I make them. They eat those down and then pick over the rest. The sourdough starter isn’t for “nutritional content” per se, but it is for a boost of fermentation bacteria  for their gut & crop health (similar to how a pre/probiotic would be). They seem to enjoy the mash more with the sourdough starter than without it, so I just add it when I have it on hand.
They always have free access to feed in the run, (in multiple gravity feeders or bowls) as well as a bowl in the coop if they are hungry before we let them out in the morning; but the breakfast snack is just sometbing “extra” we have always done for them since they were babies- it’s not a meal replacement,  It’s just a “good morning” snack for them.
 It is USUALLY a protein rich snack (yes, eggs and ham are legit something they get

 I buy diced ham and make a scrambled egg for them- yes my husband thinks I’m nuts but 


.  but sometimes it’s shredded chicken, or some solider worms, but there is always some protein rich item as the base of the snack.  I always mixed it with other items to balance it (some fresh kale and dry oat for instance for a veggi/carb component). But it’s usually about 1/4-1/3 a cup total of food. They don’t hork it down either, they each eat a few bites and then wander off to get a drink of water and eat some crumbles. They return to bowl throughout the morning and finish it off by 10 or so.
They are picky, but very ladylike when it comes to eating. Nobody glutton eats or hogs the bowl. They eat a few bites at a time and wander off for other things (usually they come to hop in my lap for morning cuddles before wandering off to go “chicken” For the day.
 I’ve tried tossing some pellets around on the ground multiple times before and they ignore it. They end up molding after a few days (foggy mornings get them damp) or they are attracting ants, so I stopped that. This afternoon I placed a handful of pellets into a “treat bowl” and left it in the run. They pecked at it once and walked away and hours later it’s still untouched; we will see if they become more interested.