Animal Reproduction Science 42 ( 19%) 205-214 Genetic improvement through technology F.W. Nicholas reproductive Department of Animal Science, Universiry of Sydney, Sydney, N.S.W . 2006, Australia Abstract Reproductive technologies can increase the rate of genetic improvement, but they have the potential to cause an even greater increase in the rate of inbreeding. Determining how to gain genetic advantage from these technologies, while at the same time minimising their genetic disadvantages, has provided a major challenge for geneticists. The overall conclusions are that artificial insemination (AI), multiple ovulation and embryo transfer (MOET), and in vitro embryo production (IVEP) can produce substantial increases in the rate of genetic improvement, with acceptable rates of inbreeding. In contrast, semen sexing, embryo sexing and embryo cloning can produce only limited increases in the rate of genetic improvement. However, embryo cloning can produce a once-only substantial boost in the average genetic merit of commercial stock, and can revolutionize breed structure. Reproductive technologies also have a major role to play in the important task of conserving animal genetic resources: in particular, there is an urgent need for methods of gamete cryopreservation that can be applied in isolated field conditions, for all of the major domesticated species. Keywords: AI; Cryopreservation; Embryo cloning; Embryo sexing; IVEP; MOET; Semen sexing 1. Introduction Reproductive technologies have many potential uses. The aim of this paper is to review the ways in which these technologies can be used to achieve genetic improve- ment in domesticated animal species. For the most part, the review will concentrate on sheep and cattle improvement programmes being conducted within a closed population, and on the transfer of this improvement to the commercial sector. 2. The genetic effects of reproductive technologies In essence, the most basic effect of reproductive technologies is to increase reproduc- tive potential. This means that fewer parents are required to produce a given number of 0378-4320/%/$15.00 Q 1996 Elsevier Science B.V. All rights reserved PII SO378-4320(96)01511-4