Effect of length of lay of Nigeria indigenous chickens on their egg composition and shell quality
Three hundred and thirty eggs collected from the second to the seventh month of production, from a flock of the Nigeria indigenous (NI) chickens, were analysed to determine the effect of the length of lay on egg composition and shell quality. The weights of the whole egg and its components as well as shell thickness were measured monthly while the proportion of the various components; egg shape index, shell density and shell weight per su..Cace area were calculated. The results showed that egg weight, albumen weight and % albumen increased (P<0.05) with length of lay by 2.6g, 3.Sg, 3.5g and 5.6% respectively between 2nd and 7th months. The change in the weight of the yolk, shell and egg shape index was not significant (P> 0.05) between the 2nd and 7th months while% yolk,% shell, shell thickness and the .shell weight per surface area decreased (P<0.05) by 4.2%, 0.64%, 0.04mm and 0.003g respectively within the same period. Strong phenotypic correlations were observed between the weights of the whole egg and the albumen (r=0.81), shell (r=0.63) and yolk (r=0.46) and also between shell thickness and its weight per surface area (r=0.81). These results indicate tht egg size increased as the NI hen advanced in lay. Eggs laid in the 6th and 7th months contained more albumen than those laid earlier and the shell thickness decreased as the hens advanced in lay thus making them more liable to breakage.
Key words: Nigeria indigenous chicken, length of lay, egg characteristics.