Depends on when tupping is. Sheep are short day ovulators. Traditionally they start tupping on Guy Falkes (5th Nov) to lamb on 1st April (148 days gestation). They usually time tupping so that lambing occurs in the Easter hols, so late March depending on when the full moon falls etc. Some systems lamb earlier so that they can sell their lambs at Easter as the meat gets a better price (everyone wants a lamb roast on Easter Sunday) compared to in August/September when fat lambs flood the market. Now that I've bored you all silly, I'll go and start learning the intricacies of ruminant digestion.