Genetic evaluation of feed efficiency traits and thermoregulation in different strains of egg laying chicken

Evaluation of feed efficiency traits was conducted in four different strains of egg laying chicken viz; single comb white leghorn PL 2, Rhode Island Red, Dahlem Red and Naked Neck. Rhode Island Red, a dual purpose breed, had significantly higher body weights at 20 and 40 weeks of age, ratio of body weights, egg production and egg production derived traits of rate of lay, egg mass, egg mass per functional day, better thermoregulatory ability but lower egg weight %. Egg type strains (White Leghorn and Naked Neck) had higher egg weight as compared to dual purpose strains (Dahlem Red and Rhode Island Red). Rhode Island Red had higher egg number except during 29–32 weeks when Dahlem Red had higher egg number. Actual feed consumed per day (g), feed efficiency per day and feed efficiency per kg of egg mass first increased with age and then showed declining trend. The actual feed consumed per day was higher in Naked Neck strain except during 29–32 weeks when Rhode Island Red was having higher consumption. Feed efficiency per day and per kg egg mass was higher in White Leghorn and Naked Neck strain indicating that the egg type strains have better feed utilization than the dual purpose strains. Expected feed consumption per day was lower than actual feed consumption per day in the egg type strains and was higher than actual feed consumption per day for the dual purpose strains. Expected feed consumption per day was higher in Rhode Island Red strain except during 29–32 weeks periods when both egg type strains were having higher consumption. Residual feed consumption which refers to the unexplained fraction of variance of feed consumption between individual hens showed fluctuating trend with age. Residual feed consumption was higher in Naked Neck strain and lower in Dahlem Red.