A pound/head/day is not going to affect anything. What most are talking about is heavy feeding during the last 60 days of pregnancy as this is where the most growth of the fetus is naturally occurring and if heavy fed, the calves can get big. Personally we have fall calving cows, and during the winter we feed about 5#s/head per day until April, and we have found it slows down hay consumption, and is not that much more than hay, in fact probably saves us money in the long run.