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
This report describes expression of heritable reticuloendotheliosis virus (REV) vector ME111 in 20 independent lines of transgenic chickens. The results are strikingly different from studies of Moloney virus in transgenic mice, where restricted expression of inherited proviruses has led to their use primarily as insertional mutagens rather than general agents for gene transfer. In contrast, the REV ME111 provirus is actively transcribed in a variety of tissues from transgenic chickens, is expressed from transcriptional control elements present in the long terminal repeat of the provirus, and codes for active neomycin phosphotransferase II. The REV vector system as applied to the chicken represents a departure from the long-established paradigm of retroviral transgenes in mice and provides a new approach to the study of avian biology.
Asunto(s)
Virus de la Reticuloendoteliosis/genética , Animales , Animales Modificados Genéticamente , Northern Blotting , Embrión de Pollo , Pollos , Vectores Genéticos , Kanamicina Quinasa , Hígado/enzimología , Hibridación de Ácido Nucleico , Fosfotransferasas/genética , Fosfotransferasas/metabolismo , ARN/genética , ARN/aislamiento & purificación , ARN Viral/genética , ARN Viral/aislamiento & purificación , Secuencias Repetitivas de Ácidos Nucleicos , Bazo/enzimología , Tubulina (Proteína)/genéticaRESUMEN
Injection of infectious non-replicating REV vector directly beneath the chicken blastoderm leads to infection of embryonic stem cells. Vector sequences are present in a variety of specialized tissues of embryos and mature birds derived from infected blastoderms. Breeding studies show that replication-defective REV vectors can transfer heritable, non-viral genetic information into the chicken germ line.
Asunto(s)
Pollos/genética , Genes rev , Transfección , Animales , Animales Modificados Genéticamente , Vectores GenéticosRESUMEN
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.