Feeding supplements to rams grazing poor pastures before the start of joining can increase the size of the testes. A ewe must receive between 50 and 100 million sperm deposited in her vagina to have a good chance of conception. Rams are very active at the start of joining and mate frequently. There is a marked drop in the number of sperm in each ejaculate soon after the start of joining. Ewes which receive more than one service during an oestrus have a better chance of conceiving than ewes which receive only one service, because they will be inseminated with more sperm.
Rams have a large capacity to produce sperm and a strong desire to mate continually with ewes.
With flocks grazing highly oestrogenic subterranean clover pastures, it is suggested that a higher percentage of rams be joined with the ewes, that is, at least 2 per cent of mature rams. In the agricultural areas, mature rams often dominate younger rams and prevent them from mating ewes. Therefore, do not join two-tooth rams with the same flock as older rams. In the pastoral areas, large paddocks and low stocking rates reduce the opportunity for mature rams to dominate inexperienced rams and young rams need not be segregated during joining. Previous mating experience improves the efficiency of rams.