In France, the first real experiments with sheep crossbreeding began in 1963 at the INRA Domain of Bourges, using Cotentin, Border Leicester and Romanov (RO) rams on Berrichon du Cher (BC) ewes and production of crossbreds from two and three breeds. On account of the higher productivity of RO crossbreds as well as the good adaptation of RO ewes to sheep-fold management, the experiments were directed towards a more analytical study of the performances of the parental BC and RO ewes, possessing complementary qualities, and of their crossbreds (F1 and F2 and the 2 back-crosses). This study summarizes the main results obtained by the different research teams of INRA on fertility, prolificacy and its components, ovulation rate and embryonic losses, adaptability to breeding season changes (fertility at out of season lambings, or at accelerated rhythm of reproduction), endocrinological criteria, milk production of the dams, viability of lambs, and carcass quality as well as the productivity of four schemes using Romanov in crossbreeding. The introduction of Finnish ewes and rams was made in private farms as far back as 1966, but this breeding was ceased in 1970 for sanitary reasons. The remaining no culling breeding ewes are compared with the Romanov ones in the INRA Domain of Bourges. The results obtained with Finnish ewes are comparable with those of the Romanov as regards precocity and length of the breeding season, but the prolificacy of ewes and particularly the viability of lambs seem to be lower. However, these results are based on small numbers of observations and must be checked by the current studies taking place in several experimental farms.
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