I.N.R.A. research on the Romanov sheep breed in France: A review

Abstract

The Romanov, a prolific breed of sheep from the Soviet Union, has been widely studied at the Institut National de la Recherche Agronomique (I.N.R.A.), in pure breeding, crossbreeding and even as a support for the Booroola gene. Physio-genetic studies concern testis parameters, ovarian follicle population at birth and follicle population dynamics (a greater number of “recruitable” pre-ovulatory follicles), levels of gonadotrophins and response to pregnant mare's serum gonadotrophin (PMSG). Ewes exhibit a high precocity. Their litter size (LS) is the result of a high ovulation rate (OR) and a reduced embryonic mortality (EM). Freemartins range from 0.8 to 1.9%. In ewe lambs, heritability is 0.39 for OR, 0.09 for EM and 0.02 for LS. The direct effect of the breed is favourable on lamb viability. The heterosis effect is high for fertility in ewe lambs, not significant for OR and LS, and favourable for lamb viability. Lambs have a high growth rate, but a low carcass and meat quality. The Romanov shows a higher susceptibility to gastrointestinal parasitism and caseous lymphadenitis. The F1 ewes have a high productivity, whatever the conditions (intensive or extensive) or the reproductive system (one lambing per year or three in 2 years). The absence of regression of performance from F1 to F4 has led to the creation of a composite line, the I.N.R.A. 401. In 1987, there were 15 000 purebred, 80 000 F1 and 21 000 I.N.R.A. 401 ewes. The Romanov breed has been introduced into northern and southern Mediterranean countries. Favourable results have been obtained, however there is a depressive effect of heavy summer heat on male activity and female fertility. Composite lines have been created in Spain and Hungary.