Heritablity Estimates of Some Clutch Traits in the Laying Hen.

Abstract

Oviposition time of 419 hens from a White Leghorn population of two lines divergently selected for high and low yolk-albumen ratio was observed at four stages of egg production period for a duration of about 30 days in each stage. A total of 1, 498 records were used in the analyses of this study. The clutch traits for heritability estimation include; intra-clutch mean lag of oviposition time (LAG), mean delay of pause day between clutches (DELAY), the rate of internal laying (IP), the number of clutches (CN), the average length of clutches (CL), and the average size of clutches (CS). LAG and DELAY were estimated by the multiphasic model (LUC et al., 1995). Heritabilities of these clutch traits were estimated by a sire-dam nested model and intra-sire regression of daughter on dam.Means of LAG were 1.04 hours and 1.32 hours for high and low lines, respectively. Corresponding heritability estimates were 0.41, 0.32, 0.62, and 0.55, 0.51, 0.62 for sire component and combined components of sire and dam, and intra-sire regression coefficient of daughter on dam, respectively. Heritability estimates of DELAY were not different from zero in both lines using the two methods. Medium and high heritability estimates of CN, CL and CS were found for both high and low lines in the two methods, except for regression estimates in the high line. Heritability estimates in the low line were higher than that in the high line for most traits, except for DELAY and IP.