I am having issues with this batch of calves and haven't hit this kind of situation before so I'm hoping you guys can help me out. We've got 6 10-15 day old calves left out of 11 that we got 9 days ago. Unfortunately the temp dropped below 20F a day or two after we got them, which I wasn't expecting, I thought we'd have them a little older before the real cold hit. They don't have a cough or scours. Two died with zero notice, looked good at last check, dead when we got there for the next. The other 3 stopped nursing the cow and then the bottle and then didn't respond to tube feeding. My assumption based on their appearance is starvation from the standpoint of needing more calories to stay warm than they can get in them rather than lack of calories in. We have them in with 2 good nurse cows, heat lamps and starter feed which some are nibbling and are bottle feeding (or tube feeding if they won't suck a bottle) in the evenings too. I plan to add a morning and mid-day bottle during my days off today and this weekend but then it's back to work and that's not an option. We are using a good milk replacer but I am tempted to add some vegetable oil to add more calories to burn. Any ideas or suggestions?