according to urban dictionary
Service
1.To fuck.
(Originating from the horse breeding industry where "service" is a
euphemism for bringing the
stud to
mount the
mare. Same as
tupping in sheep breeding.)
2. To have sex with a
mardy bitch to keep her happy, as in a mechanic servicing a car to keep it running smoothly.
happy birthday! i wish you much service today, and always.