Hassan , S. and Al Aqil, A. (2015) “Effect of Adding Dietary Date (Phoenix dactylifera) Pits Meal With/or Without β -mannanase on Productive Performance and Eggshell Quality Parameters of Layer Hens”, International Journal of Poultry Science, 14(11), pp. 595–601. doi:10.3923/ijps.2015.595.601.