Performance, development and use of Romanov in France

Abstract

Abstract. The Romanov (R) breed was imported to France in 1963. In 1987, there were 15 000 purebred and 80 000 FI ewes. The ewes have a high precocity and good adaptability to breeding season changes. Litter size (LS) is about 2.2 at 18 months and over 3 in adults, resulting from a high ovulation rate (OR) and a reduced embryonic mortality (EM). OR is less variable, but LS as variable as in other breeds. There are 0.8 -1.9 % freemartins.In ewe lambs, the heritabilities of OR, EM and LS are 0.39, 0.09 and 0.02, resp. R has a favourable direct effect on lamb viability. Heterosis is high on fertility in ewe lambs, but less on OR and LS, favourable on lamb viability. The lack of performance regression from FI to F 4 in crosses with Berrichon du Cher has allowed the creation of a composite line (INRA 401), used on farms. Ewes suckle a maximum of twins. Lambs grow fast but have a low carcass and meat quality.A good viability of crossbred lambs and a good productivity of FI ewes have been observed both in intensive and extensive conditions. In extensive system, R ewes are relatively susceptible to gastro-intestinal parasitism but are resistant to hepatic or pulmonary parasitism. R lambs seem to be susceptible to caseous lymphadenitis.Favourable results have been obtained with regard to prolificacy of FI or 1/4 R ewes and viability of lambs in six other European countries, but an unfavourable effect of heavy summer heat on male activity and female fertility. Composite lines have been created in Spain and Hungary.

Non-genetic factors affecting litter size, age at first lambing and lambing interval of Romanov sheep in Croatia

“…It is known that ewes exposed to frequent matings may have smaller litters compared to the ewes in the annual lambing system. Ricordeau et al (1988) recorded an LS of Romanov ewes of 3.11 in the annual lambing system and 2.55 in an accelerated lambing system. The coefficient of variation recorded in our research (33.71%) suggests a relatively large variation in LS.…”

Effect of oestrus synchronization with different lengths of progesterone-impregnated sponges and equine chorionic gonadotropin on reproductive efficiency in Romanov ewes during the non-breeding season

“…Embryonic deaths increase especially in oestrus induction during the early postpartum period and are higher in young ewes than mature ones. There is also a positive correlation between the ovulation rate and embryonic deaths (Cornu and Cognié 1985;Ricordeau et al 1988). In our study, embryonic deaths directly decreased lambing rates.…”

“…The lambing rate was 65% after 12-d FGA and 140 to 280 IU eCG treatment during the non-breeding season in Romanov x Pelibuey ewes (Macías-Cruz et al 2013). In addition, embryonic deaths reportedly vary between 17.4% to 19.3% (Ricordeau et al 1988) or 5% to 28% (Cornu and Cognié 1985) in Romanov ewes. In our study, the overall lambing rate was 80% and embryonic death was 20%.…”

“…The mating period, age, and ovulation rate may affect the litter size but the eCG dose does not (Ricordeau et al 1990). In various studies, the litter size in Romanov ewes varied between 1.61 and 3.11 (Ricordeau et al 1988;Đuričić et al 2019). The litter size varied between 2.00 and 2.74 in Romanov ewes after treatment with progesterone and eCG during the non-breeding season (in May) (Cornu and Cognié 1985;Ricordeau et al 1990;Đuričić et al 2019).…”

“…Romanov is a prolific sheep breed of a Russian origin. Romanov ewes have high adaptability and are successfully managed in different breeding systems, with high reproductive performance, lamb yield, and survival rates (Ricordeau et al 1988(Ricordeau et al , 1990Đuričić et al 2019). A large interval between the onset of oestrus and the luteinizing hormone peak is characteristic of Romanov ewes, and the oestradiol concentration in the follicular phase and the progesterone concentration in the luteal phase may be higher than in most sheep breeds.…”