A beef cow’s energy requirement increases about 30% after calving and her protein needs nearly double, points out Bruce Anderson, University of Nebraska Extension forage specialist.
“Each cow experiences much stress after calving because she is producing milk for her calf and she is preparing her reproductive system to rebreed,” says Anderson. “Underfeeding reduces the amount of milk she provides her calf, and it can delay or even prevent rebreeding.”
Winter grass, cornstalks and other crop residues are low in quality now because they’re weathered and have been pretty well picked over, he says. So hay or silage must provide the needed nutrients. A cow needs 10-12 % crude protein and 60-65 % TDN in her total diet.
Have your forage tested for protein and energy content, determine the nutrient requirements of your cows, then feed them a ration that will meet those requirements. But don't overfeed; that is wasteful and expensive.