Response of Thirty Egg-Type Stocks to Four Layer Diets Differing in Protein and Caloric Levels

Abstract

Thirty strains of egg-type pullets hatched in March were fed four rations differing in protein and metabolizable energy. Diet 1 contained 15.1% protein and 2,770 kcal ME/kg of feed; diet 2, 15.1% protein and 3,010 kcal; diet 3, 17.2% protein and 2,770 kcal; and diet 4, 17.2% protein and 3,010 kcal ME/kg of feed. The 2,880 pullets were housed two birds per cage and fed the four diets ad libitum from 150 to 500 days of age. The objectives of the study were to evaluate the four dietary combinations and to search for the presence of genotype by diet interactions for egg production, egg weight, feed efficiency, body weight, and egg mass.Hen-day production for the four ration combinations was 73.40%, 74.38%, 75.61%, and 76.55% for rations 1, 2, 3, and 4, respectively. As protein and caloric level of the diets increased, average egg size, body size, and feed efficiency increased.Highly significant stock differences for egg production, egg size, feed efficiency, egg mass, and body weight were noted; however, diet by stock interactions for these traits were not statistically significant. There were highly significant stock-by-period and ration-by-period interactions for these traits. Despite the lack of statistical significance of the stock-by-ration interaction, there were stocks that deviated considerably from the average for egg production, body weight, and feed efficiency, particularly when fed the low protein-low energy ration, suggesting that some stocks should be fed specific laying diets.