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Production Performance and Egg Quality of Hy-Line W36 Laying Hens Fed Reduced-Protein Diets at a Constant Total Sulfur Amino Acid:Lysine Ratio

F. Khajali^*, E. A. Khoshouie^*, S. K. Dehkordi^,1 and M. Hematian^*

^* Department of Animal Science, Faculty of Agriculture, Shahrekord University, Shahrekord, Iran, 88186-34141; and Laboratory for Animal Nutrition, Department of Animal Production, University of Ghent, 9090 Ghent, Belgium

¹ Corresponding author: Saeid.KarimiDehkordi{at}UGent.be

Two hundred eight 20-wk-old Hy-Line W36 hens at a 5% production rate were assigned to 2 dietary treatments varying in CP content. Each treatment consisted of 13 replicates of 8 hens. Dietary CP levels of the control diet were 17.8, 19.9, 18.5, and 15.5% during the periods of 1) a 5 to 50% production rate, 2) a 50% production rate until mo 7, 3) mo 8 to 10 of the production cycle, and 4) mo 10 to 12 of the production cycle, respectively. The respective CP levels of the reduced-CP diet fed during these phases were 16.3, 18.4, 17.0, and 13.9%. The reduced-CP diets had dietary CP levels approximately 1.5 percentage units lower than their control counterparts. Dietary treatments met the minimal requirements for amino acids recommended by NRC (1994). Hen-day egg production, egg mass, and FCR were maintained well on the low-protein diet during the first 8 mo of production but tended to be impaired thereafter. In mo 10 and 11 of the laying period, egg mass was significantly (P < 0.05) reduced and FCR was significantly (P < 0.05) impaired on the reduced-CP diet compared with the control diet. Egg weight, eggshell thickness, eggshell breaking strength, and albumen height were not significantly affected by feeding the reduced-CP diet. In conclusion, layer performance can remain satisfactory on reduced-CP diets for short periods, but long-term feeding of reduced-CP diets may not be advisable because it will reduce performance in the late stage of production.

Key Words: egg quality • laying hen • performance • protein