Weight to send to market and slaughter are completely different. Sending them to market they prefer lighter lambs, whereas if you are slaughtering for your own consumption most people like them heavier (but not fatter, there is a thin line). Ours were slaughtered at about 6 1/2 months last year and were heavy but not fatty, killed out at about 21-26kg, if they were going to market they would have been too heavy and wouldn't have made a good price compared to a 35kg live lamb.