Exegesis:

kai pherete ton moschon ton siteuton ‘and get the fatted calf,’ i.e. the calf fatted for a special occasion.

moschos ‘calf,’ ‘young bull.’

thusate ‘kill (it).’

thuō ‘to sacrifice,’ hence ‘to slaughter,’ ‘to kill.’

kai phagontes euphranthōmen ‘and let us eat and enjoy ourselves, or, celebrate,’ both acts occurring together. For euphrainomai cf. on 12.19.

Translation:

The fatted calf, or, ‘the fattest/best calf,’ “the prize calf” (Good News Translation); An American Translation has an active finite form, “the calf we are fattening” (and in vv. 27 and 30, “the calf he has, resp. you have, been fattening”). Calf, or, ‘young bull,’ cf. on “ox” in 13.15; the generic ‘beast’ is sometimes a sufficient designation, e.g. in East Nyanja, Lomwe, Yao. If the whole concept is foreign to the receptor culture one may say, ‘the very best food I, or, we (inclus.), keep in supply.’

Eat and make merry, or ‘let-us(inclus.)-eat having a feast’ (Tae’), or in a single verb, ‘let-us(inclus.)-be-feasting’ (Toraja-Sa’dan); and cf. 12.19.

Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.