as said before, you need the seed to tiller and emerge before the frosts so even though its still growing here and unseasonably mild, usually grass needs sowing from end of april onwards, once the frost has finished.
if the pigs have made a mess i would plough it up now (if you can get on it) if not leave it till spring too, if ploughed up let the frosts work it down and reseed once the frosts have gone and when soils have warmed up again say april / may.