RESUMEN
This paper is a review of selection methods that have been used in commercial breeding of table egg stocks, broilers, and turkeys, based on the author's experience. In addition, a number of historic developments that have shaped or influenced the selection process are listed and the significance of each is discussed. The merits of mass selection are noted and compared with the multiple forms of family selection, e.g., full or half sibs, progeny testing, and recurrent methods. Each of these methods is believed to have nearly universal application in applied breeding programs being practiced today. This review concludes that a combination of individual and family selection practices aimed at improving multiple traits simultaneously is required to remain a successful supplier of breeding stock to the current commercial industry.
Asunto(s)
Crianza de Animales Domésticos/historia , Cruzamiento/historia , Selección Genética , Crianza de Animales Domésticos/economía , Crianza de Animales Domésticos/tendencias , Animales , Femenino , Historia del Siglo XX , Masculino , Modelos Económicos , Modelos Genéticos , Aves de Corral/genéticaRESUMEN
The influence of the B locus blood group on adult viability and egg production was studied in two White Leghorn populations (S1 and S2) synthesized from inbred line crosses. Each line segregated for four B alleles. Four homozygotes and six heterozygotes were produced in each line over a five-year period, and for an additional three years tests on certain blood-group combinations were continued. A total of 4371 birds were included in the study. Greatest differences in blood groups were found in the S1 line, with the B(2) and B(21) alleles seemingly having favorable effects and with B(1) having unfavorable effects. The B(1) homozygote was consistently the lowest in egg production (53.2%) and highest adult mortality (40.4%). The relative spread in standard deviation units between the B(1) and B(2) homozygotes was more than three times greater in adult mortality than in egg production; B(2) was incompletely dominant to B(1). Within the S1 line, the superiority of the heterozygotes was mainly a consequence of the poor fitness of the B(1) homozygote, suggesting that in a random-mated population B(1) would be maintained only by mutation and not by a polymorphic mechanism.-Over the eight years of the experiment, adult viability of the B(1) homozygote improved 4.4% per year (P<0.05). Assuming this regression results from natural selection, either of two hypotheses can account for the results: (1) The B locus is pleiotropic with natural selection for many B modifiers, and (2) the B locus is neutral but linked to a major fitness locus.