Katahdin is a breed of domestic sheep developed in Maine, United States and named after Mount Katahdin - the state’s highest peak. This breed was developed by crossing selected St. Croix sheep from the Virgin Islands with various other breeds, including the Suffolk. Thus, it has wide adaptability and good for many areas. They are also significantly tolerant of internal and external parasites. Katahdin is the largest size of sheep in National Breeding Center. The average Katahdin ewe weight is 120 to 160 pounds and the ram's weight is 180 to 250. The carcass rate of this breed is good. Overall, it will be a good choice to improve the body size of the original flock.

Barbados Black Belly has obvious brown and black colors. This breed is more sensitive than the other two breeds. However, they are very disease resistant and parasite tolerant. Besides, these sheep can be raised with very little grain, and don't require intensive management. Therefore, it is suitable for someone who just starts sheep business. Barbados Black Belly has high reproductive efficiency. On average these sheep can have 2 lambs per litters. The body size of this breed is comparatively small and slower growing than most other sheep. Thus, Barbados Black Belly is not a good choice for commercial production.

Dorper was developed in 1930's by crossing Dorset Horn and Blackhead Persian sheep. Dorper has special characteristics of its black head and white body. This breed is one of the most fertile breeds of sheep with good body length and shape. The rams can reach a live weight to 198-264 pounds and the ewes 110-176 pounds. Dorper carcass has a good conformation and fat distribution.