Egg quality improvement by using Spirulina platensis was conducted in 320 Roman brown hens 17 weeks of ages. The laying hens were randomly assigned to 4 experimental groups (Completely Randomized Design; CRD), 4 replicates of 20 laying hens. Group 1, the chickens were fed control diet without S. platensis (0%). Group 2 and 3 the chickens were fed the 0.10 and 0.15% S S. platensis diets respectively. Group 4, the chickens were fed commercial laying hen diet. The egg production performance and egg quality were observed for 12 weeks. The nutritional content in boiled whole egg, amino acid profile in boiled white egg, fatty acid profile in boiler egg yolk and antioxidant activity in raw egg yolk were observed at the end of the experimental period. The overall results of the 1-12 weeks showed that the feed intake and egg production were not different (P > 0.05). The feed conversion ratio of commercial group was not different from control group (P >0.05) but higher than the S. platensis groups (P < 0.05). The egg weight, yolk index, egg shell thickness, strength and color and Hough unit of the experimental groups were not different (P > 0.05). The egg yolk color in the
S. platensis groups was higher than the control group but lower than the commercial group (P < 0.05).
The moisture, crude protein, nitrogen free extract (NFE), crude fat, crude fibre, calcium and phosphorus of whole boiled egg were not different (P > 0.05). The raw egg yolk of the 0.10% S. platensis group showed the DPPH radical-scavenging activity as 25.95% and was not different from control group (P > 0.05) but the using Spirulina platensis at 0.15% decreased the DPPH radical-scavenging activity to 6.49% (P < 0.05). The antioxidant activity was not found in the commercial diet group. The boiled egg yolk fatty acid profile in the control and 0.15% S. platensis groups were not different (P > 0.05) excepted that the tricosylic acid was detected in S. platensis group, the myristic acid of Spirulina platensis group was higher than control and the steric acid and docosahexaenoic acid in S. platensis group was lower than control (P < 0.05). The boiled white egg amino acid profile in the control and 0.15% S. platensis groups were not different (P > 0.05) excepted that the isoleucine and valine of the 0.15% S. platensis group tended to be higher than control group (P = 0.098 and P = 0.091). Therefore, the 0.15% S. platensis can be use in safety laying hen diet to improved egg yolk colour and increased mysristic acid in egg yolk and increased isoleucine and valine in white egg although the egg yolk color was lower than the using of commercial diet which the synthesis colour was added.