Christine, I mix the Mazuri waterfowl with purina omega 3 layer pellet, boss, whole oats. I have noticed the newest pair (McGraw & Peaches from CottageRose) will pick all of the boss and waterfowl out first then eat the other. 

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I've been starting my goslings on the Mazuri Starter the past couple years. Then I switch over to Purina Flock Raiser once a day (evenings) when they are big enough to be outside and eat grass all day.
The adult birds and bigger goslings get flock raiser and oats during the summer. In the fall, the birds get lots of apples off my two apple trees in their pen and I cut the oats. When winter rolls around, I give flock raiser and when it gets below 25 degrees I add a little bit of corn. The first of February until the end of breeding season I start the birds on Gamebird Breeder and add some red wheat. Instead of putting red cell in their water, I am putting it in their grains this year.
Christine
IMO I would be more worried about that dog-gone soy in commercial rations than animal products protein.
Geese maybe prefer grass but in the wild I'm sure they eat snails and little fishies.
Soy has a precursor to estrogen which can mess with hormones.