Frequent lambing of sheep flocks in Spain: productivity and management consequences

The first part of this paper reviews the Spanish literature dealing with the possibility of increased lambing frequency in Spanish flocks. Seasonal anoestrus occurs in all the Spanish breeds considered, although even in the most unfavourable month some sexual activity is observed, such as in Aragonesa flocks, where it reaches up to 80% in some years. The percentage of cyclical ewes in spring is favourably influenced by good feeding levels and by the introduction of males previously removed from the flock for a few months. In the second part we deal with the results obtained in several commercial farms in Aragon differing in mating management. No hormone treatments are used in these farms. In the farms where orderly and short matings are practised more lambings (1.39 vs. 1.29) and more lambs/ewe/year (1.76 vs. 1.40) are obtained than in those with continuous or nearly continuous mating periods. They can also choose the most favourable dates to obtain their lambs with regard to sale prices and ewe supplementary feed costs. In these conditions, Romanov × Aragonesa ewes give 40% more lambs/ewe than Aragonesa ewes without decreasing the number of lambings per year.