Extended Weaning Time Needed
Many dairies have adopted some form of intensive milk/milk replacer feeding programs for their calves. [Intensive feeding is used here to refer to any program that feeds more than 1# of m.r. daily.]
Research findings are emerging that emphasize the need for extending weaning times for intensive-fed calves in order to provide for adequate rumen development when they are fully weaned.
Recently published research (Hill and others, 2016) fed three intensive-feeding preweaned rations:
(weights are as-fed milk replacer powder, 28-20 and it was reconstituted at 14% solids)
- Lowest = 1.45#(0,66kg) for 39 days, 0.7#(0.33kg) for 3 days (2x feeding at 6:30AM and 2:00PM)
- Middle = 1.9#(0.88kg) for 5 days, 2.4#(1.1kg) for 23 days, 1.45#(0.66kg) for 18 days, 0.7#(0.33kg) for 7 days
- Highest = 1.9#(0.88kg) for 5 days, 2.4#(1.1kg) for 37 days, 1.2#(0.56kg) for 7 days
Note that they fed a 28-20 milk replacer - this provides a very high energy input at feeding levels of 2.4#(1.1kg) daily and depending on environmental challenges (cold weather) the energy:protein ratio may over feed energy. The authors suggest that lower fat levels might be considered - and, I would add, "depending on cold weather challenges."
Note that the feeding interval was 7.5 hours (6:30 and 2:00PM). When calves were fed 2.4#(1.1kg) daily that was 4 quarts twice daily. I wonder if the study results (efficiency of m.r. digestion) might have been different if the feeding interval had been stretched out to 9 to 10 hours? Or, even 3x feeding?
Note that for the "Middle" ration how the "step-down" period starts at 28 days of age (4 weeks) providing a 25 day-long step-down. This is in contrast to the 7 day-long "step-down" for the highest treatment group.
So, was the milk replacer ration (Lowest, Middle, Highest) related to rumen maturity at 11 and 16 weeks of age?
Number One: If we compare the Lowest m.r. feeding rate (i.e., 1.45#(0.66kg) daily) to the Middle ration with the extended step-down protocol they found similar levels of rumen maturity as measured by ADF and NDF at both 11 and 16 weeks of age.
Number Two: The heifers fed with the Highest m.r. feeding protocol had less rumen maturity than either the Lowest or Middle rations.
If "step-down" interval has to be uniform for all calves (in contrast to weaning based on calf starter grain intake) longer intervals work better than shorter ones in achieving higher levels of rumen maturity.
Reference: T.M. Hill and Others, "Effect of milk replacer program on calf performance and digestion on nutrients in dairy calves to 4 months of age." Journal of Dairy Science 99:8103-8110 October 2016.