Abstract
Breeding practice and experimental trials with swine breeding during the last 50 years, are sketched briefly. Advances in genetics in respect to the topics included in the review are mentioned. Results show that; breed averages differ in important characters; emphasis on meat type hogs has increased; effort is being exerted to improve hogs in economically important traits through selection and breeding practice; variations in most of the important traits are sufficiently heritable to permit additional improvement; inbreeding tends to reduce litter size farrowed and weaned, and growth rate, but inbreeding can be used to hold together a stock containing unusually good genes so that extensive use can be made of such stock; characters affected adversely by inbreeding show heterosis in crosses. Progeny testing of pigs in Denmark and Canada is reviewed. Results indicate that progeny testing can be effective in changing carcass traits, economy of gain and growth rate of pigs. New developments in pig testing, and certifying litters appear to be constructive steps. Copyright © . .