steps to get a Mac to report CPU and memory load via SNMP?

My group runs a bunch of Mac Pros and xServes of various flavors, and being a fairly recent hire, I am getting up to speed on how to monitor them properly. We use SolarWinds NPM and SAM, and monitor those Macs via SNMP. Problem: some of them do not report CPU and memory load, and one - volumes. snmp configurations on these are identical. Is this about MIBs? What's the easiest way to get all of our Macs to report CPU and memory load? Say, I have two xServes (OSX 10.6.8 but it doesn't really matter); one is reporting CPU/mem, the other one isn't. snmpd.conf files are identical. What do I need to do to enable CPU/mem polling on the handicapped machine? Is this about copying certain MIBs in /usr/share/snmp from one machine to another? Thanks!