Weekly prevalence of Giardia was increased when calves were left to nurse the dam for 3 d . Mean prevalence of Cryprosporidia ( wk 1 to 4 ) , Eimeria ( wk 4 to 5 ) , Giardia , rotavirus , and coronavirus ( wk 1 to 5 ) were 34 . 7 , 20 . 6 , 27 . 1 , 15 . 8