The problem of getting calves onto solid feed at an early stage is made much easier when using the technique of Lollipopping. This process was brought about by farmers experimenting with various methods of getting calves to readily start eating solid feed at an early stage.
Just lean the bag against the side of the pen and cut the bag so you have exposed say 50-75m/m of product and remove any loose plastic. As the product is eaten expose more feed by cutting away the plastic around the top. After 1 – 2 weeks the calves should have accepted the feed and then just continue feeding in a trough as you normally would.