Morag, M., Negev Institute for Arid Zone Research, Beer-Sheva, Israel
Eyal, E., Volcani Institute of Agricultural Research, Rehovot, Israel

Two attempts were made to increase the number of lamb crops in intensively managed dairy sheep flocks. Rams were introduced into the flocks for the first 100 days after lambing. The ewes were milked twice daily from parturition. In the first flock of 188 ewes, the lambs were weaned at birth. Half the ewes received a course of progesterone and PMS in the third week post partum. 49 % of the treated ewes conceived at average of 49 days post partum, and 59 % of the non-treated ewes at an average of 53 days postpartum. The hormone treatment reduced milk yield by 17 % in the ewes which conceived and by 26 % in those which did not conceive. Milk yield was 7 % lower in those ewes which conceived a second time. Yield in the subsequent lactation was very low. In the second flock, the lambs of 83 ewes were weaned 40 days after lambing. 89 % of the sheep conceived at an average of 64 days after lambing. The pregnant ewes yielded 6 % less milk than those ewes which did not conceive. Yield in the following lactation was satisfactory. The practical implications of the results in terms of the possibilities of future production in dairy flocks are discussed. © 1971, Cambridge University Press. All rights reserved.