Laying Performances and Genetic Parameters in Some Breeds of Chickens

Abstract

The present study was performed to analyse the data from three years' records of White Leghorns consisting of two strains (WL-D, WL-E), Barred Plymouth Rocks (BPR), New Hampshires (NH) and Rhode Island Reds (RIR), which had been bred at the former Omiya Livestock Breeding Station of Ministry of Agriculture and Forestry.Laying performance was recorded every day throughout the pullet year using the trapnest, and eggs were also weighed individually every day. Heritabilities of some economical traits and genetic correlations among laying performances were estimated.1. Age at the first egg ranged from 170 to 199 days, i.e. Barred Rocks matured earlier about 30 days than D strain of White Leghorns. Average body weight at the first egg in the three dual-purpose breeds was above 2, 000g, but that in the White Leghorns was around 1, 550g. Average egg weight in pullet year was generally small, ranging from 51.3 (WL-D) to 56.8g (RIR). Time interval from the first egg to average egg weight was the shortest in Rhode Island Reds (66.8 days), and was the longest in Barred Rocks (89.4 days). Survivors' egg production for 365 days showed a fairly good record in all breeds. Among them, that of Barred Rocks and Rhode Island Reds averaged 279.7 and 276.4 eggs, respectively. Total weight of eggs produced for pullet year was the highest in Rhode Island Reds (15, 699.8g), and was the lowest in New Hampshires (12, 561.2g) (Table 1).2. Heritability estimates for age at the first egg, body weight at the first egg and average egg weight in pullet year were considerably high, being above 0.3. It was noticeable that heritabilities of time interval from the fist egg to average egg weight were high (0.40-0.65) in all breeds except for New Hampshires showing a low value of 0.17. The estimates for laying performance substantially agreed with that reported by previous workers (Table 2).3. Genetic and phenotypic correlations of body weight and age at the first egg, average egg weight to the annual production record were of considerably high and negative. There appeared a higher correlation coefficients above -0.5 between age at the first egg and time interval from the first egg to average egg weight (Table 3 and 4).