It is a well known industry target that cows should be a minimum of 4.5 at dry off at the end of May - preferably 4.7, so the cows only have to gain 0.5 of a BCS over winter, to reach the desired target of 5.0 to 5.5 condition score at the point of calving. Cows at BCS of 3.5 should be dried off now. Cows less than 3.5 are unlikely to get to BCS 5.0 by calving even if maximally fed. Remember some supplementary feeds are better at partitioning to BCS than other - maize, barley (cereals) and as we see on a lot of farms now, fodderbeet.
Ideally cow wintering groups would be made up according to calving date - however if your herd BCS is wide, as is commonly the case, it is suggested to winter the bottom portion of the herd separately and feed these preferentially. You may wish to consider making up wintering groups based on a combination of both BCS and calving date. Our practice can offer a service where we can individually BCS cows and match these with their predicted calving dates. Cows are then split into early calving skinnies, early calving fats, late calving fats etc. Sheds fitted with Protrak makes drafting simple! Also with the current wet weather, the number of lame cows on some farms is increasing, so decisions on dry off and BCS may be brought forward to allow for developing lameness issues.