We use Calcivet or D-Nutrical for our girls who have started laying some thin shelled and soft shelled eggs. We pour a little splosh onto something tasty (grape, piece of apple, piece of cucumber, cake crumbs etc) and feed to them. You mustn't give it more than 5 days out of 7.
Contains Vitamin D3 to maximise calcium absorption in the bird's gut. It also supports shell formation and normal bone development in birds. It can also be used as an oral calcium supplement for egg bound birds like the egg laying hybrids that can become calcium deficient over time.
Add to water at 5ml per 200ml or pour 5ml over soaked seed.
Direct dose is 0.2ml per 100g body weight.