This is done to take advantage of early pasture growth following the break of the season. Rams are usually joined during December and January, although specialist lamb producers and stud breeders often use an earlier joining period. However, if an early joining period is used, many ewes will not be 'cycling' unless their sexual activity has been stimulated to bring them into oestrus early. Generally, the introduction of entire rams into flocks induces ewes to ovulate about 48 hours later. This occurs if the ewes have not seen or smelt rams or male goats for at least one month.
Some ewes then have a short oestrous cycle and ovulate six days later.
In many ewes, neither of these ovulations is accompanied by oestrus. Joining teasers before the entire rams are introduced is the best way to induce ewes to cycle. If the teasers are run with the ewes for 14 days, most of the ewes will be served early in the joining period after the entire rams are introduced on day 15. Where rams are joined with ewes before mid to late January for a six week or shorter period, then using teasers before the entire rams are joined will increase the percentage of lambs born as well as concentrate the lamb drop. A survey in the Darkan area showed that 4 per cent more ewes lambed after being teased before a six week joining in the middle of the breeding season.