Genetics of Growth and Reproduction in the Turkey: 5. Selection for Increased Body Weight Alone and in Combination with Increased Egg Production

Abstract

Selection for increased 16-week body weight alone resulted in a large increase in body weight and a major reduction in egg production over nine generations of selection. The realized heritability estimates for 16-week body weight were .31 ± .04 and .30 ± .03, respectively, for males and females. The realized genetic correlation between female 16-week body weight and egg production was −.4 2 ± .12. Large negative realized genetic correlations (−.50 to −.63) were observed between female 16-week body weight and intensity of lay traits (average clutch length, maximum clutch length and rate of lay), while generally only small non-significant positive correlations were found between body weight and broodiness traits (number of broody periods, length of broody period, and total days lost from broodiness). No significant correlations with egg weight, percent fertility or hatchability of fertile eggs were observed.Gains in 16-week body weight of from approximately 1/4 to 1/2 of those observed when selecting for body weight alone were achieved in another line without any reduction in egg production by the use of a selection index which gave three times the emphasis on 16-week body weight as on 180-day egg production. The realized heritability of 16-week body weight and the realized genetic correlations with egg production, intensity of lay traits and broodiness traits were similar in this line to those estimated in the line selected only for increased 16-week body weight.