title: Data on the reduction in improving effect of A.I. Bulls in relation to the genetic trend of the population.
abstract: In order to clarify the question of the reduction in improving effect of A.I.bulls in relation to the genetic trend of the population, the authors have carried out two model calculations: a) This one assumed different genetic progress as well as different improving effects of bulls. The duration and extent of improving effect have been examined. b) The data on an US-Holstein-Friesian elite population was processed to determine changes in improving effect during a period of 10 years, assuming 1 per cent genetic gain per year. Ten per cent of this elite population were chosen and examined as a 'nucleus population'.Conclusions are as follows: 1. In female populations representing continuous and considerable genetic progress, even bulls of excellent genetic merit can assure improvement for only a few years. 2. The improving effect may be referred to a definite population only if the progeny test results are directly related to the average of the population, or if these can be adjusted properly. 3. A 'nucleus population', selected and maintained by high selection pressure, could have such a great genetic superiority that progress is assured for a long time in the 'population with high breeding value'. 4. A significant genetic advance has to be achieved, maintained and utilized in the sire-producing mating category. This requires reasonable rationalization of selection and mating, utilizing international gene-resources and continuous control of the breeding value of sires in the populations.
authors.affiliation: Agricultural College, Kaposvár, Hungary.
authors.forename: J
authors.initials: J
authors.lastname: Dohy
authors.forename: I
authors.initials: I
authors.lastname: Boda
authors.forename: A
authors.initials: A
authors.lastname: Kovách