I have some calves just weaned recently and after reading your post looked up some information on H somnus -

This is a short and informative sheet if anyone is interested:

http://edis.ifas.ufl.edu/VM066   or pdf version prints out nicely: http://edis.ifas.ufl.edu/pdffiles/VM/VM06600.pdf

Jim at Dawn

Thinking about your plan to take them to the sale barn - it is in everyone's best interests to get that disease REALLY taken care of before going back to the sale barn! Or we are just passing it around to everyone - which may be related to the rendering truck being busy nearby. Looks like the thing to do is to get them ALL in for shots then a second round 21 days later. Spread by urine and breeding as I read it. Calves in tight quarters certainly exposed to each others urine.

Thank you for the posts and alert.