If you just want to show day and month, use a different formatting for the layout field object.
You can do this as a script or calculation or preset presentation of data.
The script line would look something like this:
Day ( yourtable::yourdateofbirthfield ) & " " & MonthName ( yourtable::yourdateofbirthfield )
Alternatively and, much easier is to simply change the data formating for the field presentation as shown below.
What you describe as a script line is really a calculation. To be a script line it would need an action instruction, such as Set Field.
Nevertheless, the calc is correct—it will isolate day and month, separated by a space, from the DOB field. Make sure the result of the calc is Text, not Date.