All B12 sources are non-plant. For curled under toes or walking on hocks, the treatment should include riboflavin (vitamin B 2.) Good food sources of B 2 are beef, liver, egg yolk, crushed almonds, plain yogurt, and nutritional yeasts can be used. The easiest source is B complex tablets that have all B vitamins.
a few years ago I had a chick hatched on day 24, assisted and she had curly toes. it happened on sunday. I searched on line to get some help and found that she needed vitamin b 12 and among other sources I found sesame seeds. that was the only thing I had at home. I gave her some seeds, she loved them and the next morning her toes were perfect. she is still with me, a nice chunky hen about 4 years old.