An alternative to weaning by age, which is common
in our industry, is the traditional concentrate- or starter-dependent
weaning strategy. Optimal preweaning
starter intake before step down (>0.5 kg/d) is essential
for postweaning intake and gain and is influenced
by the nutrient content of the milk replacer and calf
starter (Stamey et al., 2012; Kertz and Loften, 2013).
Greenwood et al. (1997) demonstrated that calves fed
low planes of nutrition could be successfully weaned
when starter intake reaches 1% of BW. It was also
determined that postweaning growth did not differ
between calves that were weaned when starter intake
reached 1.5 and 2.0% of BW (Greenwood et al., 1997).
In the current study, weaning was based on age, and
reduction of milk resulted in an increase in starter intake.
This finding opposes the concentrate-dependent
method, in which the level of starter intake prompts the
milk reduction. In the current trial, calves weighed 66.5
kg when weaned at 6 wk and 83.5 kg when weaned at
8 wk, thereby requiring starter intakes of 0.67 and 0.84
kg/d, respectively, to reach 1% of BW. This target was
easily achieved for 8WW calves, which consumed 1.38%
of BW the week before weaning. However, this target
was not met for 6WW calves, which consumed only
0.6% of BW the week before weaning. Ultimately, this
finding indicates that when feeding 1.2 kg/d of MR,
weaning at 6 wk is too early when calves are weaned
according to the concentrate intake as a percentage of
BW (Greenwood et al., 1997). Calves weaned at 6 wk
could not achieve optimal starter intake during stepdown
and weaning, which had a longstanding effect
on gastrointestinal development and growth. However,
calves weaned at 8 wk had higher starter intake preweaning
and were more able to maintain adequate ME
intake postweaning, possibly due to gastrointestinal
and metabolic development from higher levels of solid
feed intake preweaning