I trust Holderread and Metzger's findings - HOWEVER - there is good reason to be concerned about thiamine deficiency in waterfowl. Ducks and geese require twice as much thiamine as do chickens [1]. Medicated chick feed given as the ONLY food risks thiamine deficiency two ways.
1) unmedicated chick feed and layer pellets have lower levels of thiamine than duck/waterfowl feeds [so low it's not reported on the feed tag, compared to Purina duck thiamine 27.27 mg/lb] feeds.
2) adding a THIAMINE BLOCKER to low-thiamine feed makes it even less available.
Turns out this is a problem even with chickens!
Hens feed an amprolium-medicated layer feed produced eggs with low yolk thiamine levels and resultant high late-incubation embryo mortality and high numbers of weak/dead chicks in the hatching trays [2].
I looked into this because I feed my ducks/geese unmedicated layer pellets. It's no problem because they also eat fish, frogs, worms and some cat food when molting.
[1] Nutrient Requirements of Poultry: Ninth Revised Edition, 1994 (1994)
[2] Estimation of Thiamine Requirement for Optimum Hatchability from the Relationship Between Dietary and Yolk Levels of the Vitamin.
https://www.semanticscholar.org/pap...-Ott/ac50510ede562d8ae63591c7ffe3744bf264ca88