As far as a vitamin mix, I really like this one from Stromberg's Poultry. You dissolve in water the first 6-8 weeks: https://www.strombergschickens.com/product/Probiotics-+-w-Electrolytes-&-Vitamins-200-g
It doesn't have Selenium, but using Mazuri Waterfowl Starter (Chewy has it) would help. I also add https://www.amazon.com/AniMed-Vitam...nt,+vit+e+selenium,+zinc,pets,147&sr=1-2&th=1 But only add 1/8 teaspoon, maybe 3 times a week, for a few weeks. Then decrease to twice a week. You CAN overdose on Vitamin E and Selenium! Or I add about 1/4 teaspoon over the feed for the whole flock 2-3x/week. Keep the Vit E/Selenium in a cool place or fridge for best long term potency.
It doesn't have Selenium, but using Mazuri Waterfowl Starter (Chewy has it) would help. I also add https://www.amazon.com/AniMed-Vitam...nt,+vit+e+selenium,+zinc,pets,147&sr=1-2&th=1 But only add 1/8 teaspoon, maybe 3 times a week, for a few weeks. Then decrease to twice a week. You CAN overdose on Vitamin E and Selenium! Or I add about 1/4 teaspoon over the feed for the whole flock 2-3x/week. Keep the Vit E/Selenium in a cool place or fridge for best long term potency.