Linux MemAvailable via SNMP

Hi,

I am using SNMP via Zenoss 5.1.x to monitor Linux memory usage. 

As far as I can tell from my research I can not monitor "available memory" using only SNMP provided OIDs as is.

Is there a way to calculate and display available memory as opposed to showing free memory?

# free -k
                   total            used            free            shared  buff/cache   available
Mem:        7231552     3593476     1625732         696     2012344     3339784

# snmpwalk -v 3  localhost iso.3.6.1.4.1.2021.4.6.0

UCD-SNMP-MIB::memAvailReal.0 = INTEGER: 1623968 kB

Thanks