Weaning Age and Intensive Milk Feeding Programs
Field experience and research trials have demonstrated the effect of intensive milk feeding programs for dairy replacement heifer calves on the timing of calf starter grain intake. As milk intake goes up the starter grain intake is delayed.
The research reported here looked at delaying weaning of intensively milk fed calves from 60 to 75 days. The intensive program for calves weaned at 60 days was 4 liters/day on days 3-10, 6 liters/day on days 11-20, 8.5 liters/day on days 21-55, decreased to 4/25 liters/day on days 56-60 (total of 411 liters).
The intensive program for calves weaned at 75 days was 4 liters/day on days 3-10, increased to 6 liters/day on days 11-70, decreased to 3 liters/day on days 71/75 (total 407 liters).
They compared these groups using these measures at 90 days:
Average daily gain
Final body weight
The 75-day weaned heifers when compared to the the 60-day weaned heifers were higher on all three comparison measures.
In my reading of these results I see the advantage of getting more adequate rumen development in the 75-day heifers. This is one of the first studies I can recall that compared feed efficiency. However, few dairies will wait to wean at 75 days.
A practical alternative would be to modify their 60-day protocol to look like this:
4 L/day on days 3-10
6 L/day on days 11-14
8 L/day on days 15-35
4 L/day on days 36-60
In order to save labor I fed the 4 L/day on days 36-60 once a day, with free choice water and calf starter grain.
My experience with this protocol regarding starter grain intake was initial grain intake greater than 1 cup (110-115g) daily did not start until about 21 days. With high milk feeding the grain intake stayed low until I dropped the milk back to 4 L/d at 36 days - then the calves had a steady upward trend on grain intake until they were eating 4-5 pounds (2-2.25kg) a day by 60 days.
Reference: M. Mirzael and Others, "Effects of preweaning total plane of milk intake and weaning age on intake, growth performance, and blood metabolites of dairy calves." Journal of Dairy Science 101:4212-4220 May 2018