Egg Shell Quality: 1. Effect of Dietary Manipulations of Protein, Amino Acids, Energy, and Calcium in Aged Hens on Egg Weight, Shell Weight, Shell Quality, and Egg Production

Abstract

Sixteen dietary treatments (including four protein, four energy, and eight calcium levels) were fed to 560 aged hens for 8 weeks in an attempt to improve shell quality by reducing egg weight without reducing shell deposition. Decreasing the dietary protein from 20 to 11.5% in isocaloric diets resulted in a decrease in egg weight, shell weight, and serum calcium. No improvement in egg specific gravity and no adverse effect on egg production and feed consumption were noted. The response of hens to the 16 or 13.5% protein diet was similar to that of the hens fed the 20% protein diet. Increasing the dietary calcium level from 3 to 4.25% did not prevent the decline in shell weight. Exaggerating the protein deficiency by increasing the dietary energy level from 2.42 to 3.30 kcal ME/g in graded increments and calcium from 2.56 to 4.94%, respectively, also did not prevent the decline in shell weight as egg weight decreased. Body weight decreased as the protein level decreased. Percent yolk increased while percent shell and albumin decreased as egg size decreased. Within 3 weeks after returning the hens to the control feed (16% protein), there was no significant difference in egg weight, shell weight, or feed consumption.It was concluded that reducing egg size by dietary manipulation of protein, amino acids, energy, and calcium also reduced shell deposition, thus preventing any improvement in shell quality; and that the dietary protein level can be reduced to as low as 11.5% in old hens for at least 1 to 2 months prior to hen disposal without any adverse affect on production.