EVALUATION OF EGG PRODUCTION IN HENS ACCORDING TO LAYING TIME IN THE CIRCADIAN RHYTHM

Abstract

The egg production of modern egg-laying lines and crosses reaches 350 eggs in 520 days of life. Therefore, most scientists claim that the egg production of hens has reached a breeding plateau. In order to overcome this plateau, research is being conducted to develop new methods for selecting hens that consider the circadian rhythm as a selection trait. The aim of this research is to study the effect of egg-laying time on the egg production and egg quality of hens with a 24-hour circadian rhythm. The research was conducted at the Department of Farm Animals Breeding and Zootechnologies of the Kuban State Agrarian University. Twenty pullets of the Hisex Brown egg-laying cross were selected for the study. From 120 days of age until the end of the production period (520 days), the pullets were individually housed in a battery cages, where each individual laying hen was monitored 24 hours a day, with the time of egg laying recorded to the nearest minute. Twenty eggs were collected monthly and subjected to morphological analysis, including egg mass, albumen, yolk, and shell weight. The egg components and the albumen/yolk ratio were determined. The study revealed that hens with an egg production exceeding 300 eggs lay eggs within the first 2-3 hours after lights-on, while low-producing hens begin laying eggs after 4-6 hours. High-producing hens typically had 1-2 day laying intervals. Low-producing hens typically had a greater number of longer intervals. Low-producing hens exceeded their high-producing flockmates in the proportion of yolk in their eggs at all age periods. A significant 2,75% advantage in yolk proportion was observed in low-producing hens at 3 months, 1,32% at 5 months, and 1,41% at 6 months. A method for assessing and selecting hens based on egg production intensity as a trait characterizing the synchronicity of egg laying with the circadian rhythm period is proposed.