Abstract
Female reproductive traits were studied in four pure breeds (the Finnsheep, Suffolk, Targhee and Minnesota 100), the F1 crosses between Finnsheep rams and females of the other three breeds and F2 and backcross ewes. Precocity of sexual development, defined as the percentage of ewe lambs lambing at 12 months of age, was measured in 709 ewe lambs in 4 years. Lambing and weaning rates were measured for a total of 1,030 parturitions of 1- to 3-year-old ewes over 3 years. Purebred Finnsheep ranked highest of all pure breeds and crosses for all three traits, with a single exception: backcross F × (F×S) ewe lambs ranked first in percentage ewe lambs lambing. For ewe lamb precocity, the ranking of the standard breeds, in decreasing order, was Suffolk, Minnesota 100 and Targhee. For number of lambs born, the ranking was Suffolk, Targhee, Minnesota 100, and, for number weaned, it was Targhee, Suffolk, Minnesota 100. The F1 crosses were highly fertile, as ewe lambs and ewes of all three ages produced and weaned considerably more lambs than did standards. Finnsheep backcrosses, in most cases, were as fertile as the F1 and purebred Finnsheep and, in terms of prolificacy, were intermediate to those groups. One-quarter Finnsheep ewes were more fertile and prolific than standard pure-breds. On average, F2 ewes were inferior to the F1 in all traits, and were similar to the ¼ Finnsheep ewes. Finnsheep lambs had moderate perinatal mortality, but lambs that were born alive had an excellent survival rate to weaning (97.5%), superior to that of Targhee (85.2%), Minnesota 100 (78.9%) or Suffolk (76.8%) lambs. Copyright © 1981. American Society of Animal Science . Copyright 1981 by American Society of Animal Science.