I don't think there is much problem even in this weather after a few days or a week. I have week old calves running and playing in the snow like southern kids at a Christmas snow.

It's getting them hatched successfully that I am most concerned about.  This is an unusual winter - cold winter seems to be leading to large calves. Not too bad but big.  I may just shift back two weeks next spring - then watch, it will be 60 degrees and sunny all March! 

Last year my neighbor could not make maple syrup after February because we did not get the freeze/thaw cycles. This year he'll likely have sap running until April!  Figures. I move calving and nature moves the seasons!

Jim at Dawn