You may use the OID .126.96.36.199.188.8.131.52 ( ipNetToMediaTable ) which is defined in RFC1213 to get the Switch's ARP table.
Click "Table View", then the user will see the ARP table.
(The screenshot is from iReasoning MIB Browser which loads RFC1213 MIB)
The following OID names correspond the following ARP parameter:
ipNetToMediaIfIndex = Port
ipNetToMediaPhysAddress = MAC address
ipNetToMediaNetAddress = IP address
ipNetToMediaType = Type