Ivermec is for worms and other internal parasites. It wont do much for other health issues.
Some will give everything an injection of Micotil upon arrival. Nuflor, Naxcel, Exnel, Baytril, are also good for respiratory problems. LA200 or the generics are rated for pneumonia but I have not found it to be as effective...but it is cheap. Penicillin is even cheaper but I dont think it is nearly as effective for "shipping fever" I would watch the calves upon arrival, make sure they have clean water and decent hay and work them 12 to 24 hours after arrival.
The lactic acid buildup from the sale barn and shipping stress can hinder the effectiveness of the vacine...or so I have been told by sources I respect. The wait helps the lactic acid to work out of their system and lets them settle out a bit too. If you have one in obvious distress I would hit it with a round of Micotil and a shot of banamine and B-12 as well to make them feel a little better and hopefully get on feed NOW.
You want them to go to feed and water immediately upon arrival. If they dont...watch them pretty close, maybe even get them up and temp them.
I hope this helps, good luck
Jay