I have 8 cows that I currently feed good hay, a trace mineral block, and the occasional protein/mineral tub. Calving right now and I haven't had trouble with fertility in the past, just a cow that had a retained placenta. I've been told I need to provide them a loose mineral/granular mineral. I looked into the soil mineral content in NW Iowa and there is sufficient selenium in our soil. Should I I get a mineral without selenium? and if so will it be an additional cost?