The study was a 3 × 2 × 2 complete factorial design
with roughage supplement source: wheat straw (STR)
versus MS versus maize cob silage (MC), amount: 250
versus 500 g of DM/d, and particle size: chopped (4 to
5 cm) versus ground (1 cm) as factors. Composition
of roughage used is shown in Table 3. Dried MS and
MC were used to improve the quality of the grinding
process. Maize silage and MC were dried in a dryer
at 350°C for 6 min. Three control treatments were included:
MR only, MR plus an iron supplement diluted
in the milk (MR+), and a diet of MR plus ad libitum
HY. The factorial design involved a total of 300 animals
(240 treated and 60 control) in 15 groups of 4 pens
each. The MR+ calves received 58 mg of Fe/kg of DM
in the starter milk, and 116 mg of Fe/kg of DM in the
fattening milk (Table 2).