Especially, Dorset sheep have had infusions of other white-faced breeds to increase their size, so short sighted breeders can win ribbons at shows. There are some genuine, pure Dorsets left in the United States, but, they are getting more difficult to find. Breeds known for high prolificacy are Finnsheep, Booroola Merino and Romanous. These breeds actually have from two to five lambs in a litter. Most sheep producers are unable or unwilling to deal with ewes giving birth to three or more lambs.
Healthy sheep are more reproductively useful than diseased sheep.
Footrot, internal parasites, abortive diseases, lack of thrift, nutritional diseases, etc., can all affect reproduction in sheep. Certainly, a ram or ewe free of disease will more closely approach an ideal individual. Three stages of the production cycle can be managed nutritionally to optimize reproduction. The pre-breeding period can positively influence production by flushing both the rams and ewes with increased energy. Increasing energy to ewes should increase body weight and number of eggs ovulated, thus, increasing lambing rate.