Diet type, apparent metabolisable energy and digesta viscosity in laying hens of two different ages

Diets based on wheat, barley or sorghum were fed to younger and older laying hens for a period of 12 weeks. Production and weekly egg mass were higher for the younger birds and feed intake and feed conversion efficiency were higher for the older hens, with no effect of diet. Egg shell quality and egg internal quality were better for the younger hens. The sorghum diet resulted in eggs with better shell quality but lighter shell colour and lower albumen quality. AME was higher for the older birds and differed among diets, with sorghum the highest and barley the lowest. Excreta moisture was higher for the wheat and barley diets than the sorghum diet, and higher for the older birds. The digesta viscosities of the jejunum and ileum were higher for the wheat and barley diets than for the sorghum diet and not different between the younger and older hens.