First of all, let me mention that there are some differences between modern "bowling" and "Kegeln" (e.g. number of pins), but in the following I will use the translation "bowling" for "Kegeln". Maybe a more appropriate is "skittles" or "ninepins" according to dict.leo.org.
Gut Holz
Literally "good wood". "Holz" is a bowling term for the pins. "Gut Holz" is a bowlers greeting. It uses the non-inflected version of the adjective "gut". One would expect an inflected form ("Gutes Holz") but non-inflected forms are sometimes found in idiomatic expressions.
Ein Hoch dem Kegelsport
"Hoch" literally means "high". As a noun it means "a cheer", "cheers". The dative-construction "dem Kegelsport" can be translated as "to bowling sports".
Halt ihn!
Literally "hold it" (ihn=male=der Kegelsport; it=neuter=bowling sports); the meaning is "preserve/conserve bowling".
Zum Wohle sei unser Wort
"Zum Wohle" literally means "to/for the good"; it is a drinking toast like "Cheers!". "sei unser Wort" is "Konjunktiv I" and can be translated as "be our word". The whole phrase: "Our word be for the good."