Hay for Preweaned Calves
An interesting article in the Irish Farmers Journal, "Dairy Calf to Beef: Rearing Tips," included some advice regarding providing fiber for preweaned calves.
Recall in this Irish tradition that dairymen have "always" fed straw to preweaned calves. In my experience this traditionally was fed a long straw in a rack in a group pen.
The initial mention is in the context of housing:
"Calves should be housed on a clean, dry bed of straw and they should have access to a good fibre source like hay or straw and also have access to fresh clean water."
The author concludes:
"Hay and straw. A good fibre source like hay or straw should be made available to calves from three days of age. While feeding hay and straw is important, it's also important not to over consume roughage with a resultant decrease in concentrate intake.
Chopped forage 3-4cm (1-1.5 inches) in length is ideal. Quality is also important as poor-quality, stemmy material will result in poor intakes and calves not being able to digest it."
[Emphasis added, ed.]
Reference: Wood, Adam "Dairy Calf to Beef: Rearing Tips" Irish Farmers Journal 28April2018 page 40