shi 950-21 2) C . Itoh Feedmills Co., LTD., To investigate the effect of phase feeding of amino acids for laying hens during laying period, the laying period from 20 to 80 weeks of age was divided into 3 phases as 20-30, 30-60 and 60-80 weeks of age, and the hens were fed with 8 feeding programs. Five dietary amino acids (lysine, methionine, threonine, isoleucine and tryptophan) levels were adjusted to 100, 115 and 130% of the NRC requirement. The hens in non phase feeding groups were fed 130,

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... 15, 100% (groups 1, 2, 3) and commercial diet as a reference (group 9). The hens in phase feeding groups were fed with following programs: 130-115 -115 (group 4) , 130-115-100 (5), 130-100-130 (6), 115-115-100 (7) or 100-130-130% (8) for phase I-II-III. The oviposition was recorded every day and egg weight was measured every Monday, Wednesday and Friday throughout the experimental period. And the eggshell strength, eggshell weight and Haugh unit were estimated every 10 weeks after 30 weeks of age. The first egg age and egg weight were not different among dietary amino acid levels. However the hens in 100% diet groups decreased their body weight considerably after the start of laying. Their performance was also inferior to other groups. When the dietary amino acid level was decreased from 130 to 115 to 100% gradually (group 5), there was no difference in the performance throughout the experimental period compared with 130% diet (group 1). However, the length of laying peak in experimental groups was shorter than that in reference group. The egg weight of hens fed 130% diet was the largest. The eggshell strength and Haugh unit were decreased with age. But the effective phase feeding program to maintain the egg quality was not determined.