Sheep convert low quality vegetation into useful products and thus provide livelihoods. Deccani sheep are reared on the Deccan plateau in Western India, having a dry, monsoonal climate. They are reared for lamb production and have only single lambs. The number of lambs weaned by a ewe per year is the key determinant of profit. It is necessary to increase the productivity of sheep to ensure sustainability of this enterprise. This PhD thesis identifies the traits of economic importance in the Deccani sheep production system. It then investigates critically the early results of the FecB gene introduction program to improve reproductive rate. This program is about the only example in a developing country context, of the successful use of an identified mutation influencing livestock production. Reproductive, weight, survival and worm resistance traits of FecB carrier sheep are analyzed and the use of a mate selection approach is investigated for integrating several complex issues. It will be useful to students and teachers of animal genetics, scientists, extension workers, aid agencies, policy makers and anyone interested in using livestock genetic improvement as a means of development.