Comparison of Egg Quality among Three Local Chicken Breeds in Yunnan Province

Purpose To compare the egg quality differences of Wuding chicken (WDC), Yanjin black-bone chicken (YJC) and YN chicken (YNC) endemic to Yunnan, and to explore the laying performance of Yunnan local chicken.

Methods A total of 30 eggs of each of three chicken breeds at 24 weeks and 30 weeks of age under the same management conditions were randomly selected (indicated W₂₄ and W₃₀, respectively), and their egg quality indexes were measured and compared.

Results 1) Among different breeds, there was an extremely significant differences in egg weight of W₂₄ and W₃₀ among three chicken breeds, showing YJC>YNC>WDC; the egg shape index of W₃₀ of YJC and WDC was extremely significantly higher than that of YNC, but there was no significant difference among the W₃₀ of three breeds; the Haugh unit of W₂₄ of WDC was extremely significant higher than that of YJC and YNC; the eggshell strength of W₂₄ of YNC was highest (P<0.01), but there was no significant difference among W₂₄ of three breeds; the eggshell thickness of W₂₄ of YNC and YJC was extremely significantly higher than that of WDC, and the eggshell thickness of W₃₀ of YNC was significantly higher than that of YJC and WDC; the eggshell ratio of YJC was lowest (P<0.01); the yolk ratio of W₂₄ of YNC and YJC was extremely significantly higher than that of WDC, but there was no significant difference among the W₃₀ of three breeds; the albumen ratio of W₂₄ of WDC was extremely significantly higher than that of YNC. The average coefficient of variation of egg quality traits of the three chicken breeds was less than 10%, of which YNC was the smallest (8.29%), and the overall uniformity of the traits was the best; the YJC was the highest (9.66%). The coefficient of variation was minimum (3.40%) for egg shape index and maximum (19.73%) for eggshell strength. (2) Between different weeks age, from 24 to 30 weeks of age, the egg weight of the three chicken breeds showed an upward trend, but the eggshell thickness showed a downward trend; the yolk color and Haugh unit of YJC and YNC showed a downward trend, but that of WDC showed an upward trend.

Conclusion The egg weight of three Yunnan local chicken breeds is between 35.48-47.66 g, of which YJC is the heaviest, WDC is the lightest, and egg weight increases with the increase of chicken week age; the eggshell quality of YNC is the best, followed by WDC, YJC is the worst; the albumen quality of WDC is the best, followed by YNC, and YJC is the worst; the eggshell thickness decreases with the increase of chicken week age.