Selection for Increased Egg Production Based on Annual Record in Three Strains of White Leghorns.

Abstract

Three strains (L3, L5 and L8) of White Leghorns reproduced by random mating in a closed population for over 20 yr were subjected to family selection for annual egg production. The annual egg production period was divided into various part period segments with their corresponding residual egg production records. Combined estimates of heritabilities and genetic correlations were calculated for each segment of the production curve. Relative efficiency of the genetic progress expected in the annual and residual records using part record vis-a-vis complete part record was estimated.For each part period segment heritabilities were the same -whether they were estimated from egg number or from percent production -and showed very high values when estimated from a segment that includes the 21 st wk. Heritabilities of the residual records were low for the L3 and moderate for the L5 and L8 strains. Percent production or egg number of the complete part record showed a very high genetic correlation with annual egg production in all strains, a high genetic correlation with residual record in the L8 strain, and a low genetic correlation with residual record in the L3 and L5 strains. A very high annual relative selection efficiency could be obtained by using for selection the percent production of complete part record, but the persistency of layers could be increased by using for selection the percent production of other partial records. (

Genetic Parameter Estimation of Partial Egg Production Traits in Layers

“…Heritability of annual egg production is low or moderate. On the contrary, the estimates obtained from partial records are higher than the estimates from annual production (Boukila et al, 1987;Besbes et al, 1993). Bohren et al (1970) recommended the indirect selection on partial records to improve the annual egg production.…”

“…They and others used partial records as a selection criterion due t,o the high relationship between part and annual production. According to Foster (1981), there are many advantages of selection based on partial records due to shortening of the generation interval and the appropriate time of caging, selection, mating and hatching always occurs a t the same time of year and also this kind of records are less affected by environmental variation (Boukila et al, 1987). Heritability of annual egg production is low or moderate.…”

Genetic parameters for egg production in meat quails through partial periods

“…Egg production in poultry depends on age when first egg is laid, egg-laying rate and laying persistence, being these the main factors for selection in laying birds (BOUKILA et al, 1987). In Brazil, laying quail peak of egg production ranges between 93 to 95%, whereas meat quail reaches 80 to 85%.…”

Influência das coletas sistemáticas e parciais na seleção de codornas por meio de curvas de probabilidade de postura

“…Entre as mais importantes características de produção em codornas está o número de ovos, influenciando diretamente no lucro. A escolha do melhor critério de seleção para a produção de ovos deve levar em consideração três fatores conjuntamente: a idade ao primeiro ovo (maturidade sexual), a taxa e a persistência de postura (Boukila et al, 1987).…”

“…Porém, a utilização da seleção indireta, tomando-se como critério de seleção a produção acumulada durante a fase inicial da postura, pode ser uma alternativa para solucionar problemas de aumento do intervalo de geração, no entanto, animais selecionados nesta idade apresentam menores taxas de postura e fertilidade, implicando em maior esforço para multiplicação do material selecionado. Boukila et al (1987) citam que observações parciais da produção são vantajosas nesses casos, visto serem menos afetadas pelas variações ambientais. Santos (2003), ao trabalhar com codornas de postura, analisou produções parciais acumuladas e totais, e observou um aumento do ganho genético na produção total quando a seleção foi praticada com base na produção parcial.…”