Planning and organisation pf improvement programmes; Definition of the breeding objective; Genetic basis of sheep improvement programmes; Selection criteria; Performance recording, data processig and adjustment of records; Adjustment of records; Calculation, presentation and use of the information; Industry structure and dissemination of genetic gain; Populations size and genetic improvement; Techniques for increasing the rate of genetic gain; Final remarks: the future.

Perhaps less than 10 percent of the world's sheep have hair coats instead of wool fleeces, but as an animal resource, these sheep are important far out of proportion to their numbers. Hair coats provide an advantage in the face of the heat, humidity, and other stresses of the tropics. Small in body size, early to mature, and often highly prolific,

The place and potential for sheep em tropical and subtropical regions; Available genetic resources: the origin and classification of the world's sheep; Improvement programs; Nutrient requirement of hair sheep in tropical and subtropical regions; Forage resources in northeast Brazil: their value and management; Supplemental feed resources and their utilization by hair sheep; Reproduction in sheep; Herd health management of sheep in the semiarid tropics; Facilities and installations for hair sheep production; Products and marketing; Tropical sheep production systems; Some suggestions for improved productivity through management; Recommendations for further research.

The objectives of this study are: (1) to obtain estimates of genetical and environmental parameters for growth and reproduction characters of three tropical breeds of sheep Morada Nova, Brazilian Somali and Santa Ines; (2) to examine genotype by environmental interactions in order to optimally match these three genotypes with different environments by assessing the effect of different levels of nutrition on productivity of sheep in a semi-arid environment.