Variation in egg quality characteristics of selected indigenous chicken ecotypes of Uganda reared under intensive production system
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Eggs are among the cheapest accessible source of high-quality animal protein especially for the rural poor. Although egg quality has been widely emphasised, there is a shortage of published information on the quality of eggs from the indigenous chickens of Uganda. This study therefore aimed at assessing of variation in external and internal egg quality parameters and establishing the relationships between external and internal egg quality parameters of indigenous chickens. The hens were sourced from households in Apac, Gulu, Lira, Katakwi and others from the chicken flock at NaSARRI as part of an on-going indigenous chicken improvement project by the National Livestock Resources Research Institute (NaLIRRI) under the National Agricultural Research Organization (NARO). These chickens were assembled and maintained at Mukono Zonal Agricultural Research and Development Institute (MUZARDI) and formed the foundation stock. The chickens were allocated to pens according to their origin/ ecotype in a completely randomised design in groups of 10 hens. The birds were raised under a deep litter system, fed a uniform layer diet and clean drinking water at all times. At their second egg laying cycle, three (3) eggs were randomly selected from each pen thrice a week. For each egg, external quality parameters that were measured included egg weight (EW), egg length (EL), middle-breadth (MB), shell weight (SW), shape index (SHI), shell thickness (ST), shell ratio (SR), shell index (SI) while the internal quality characteristics determined included yolk depth (YD), yolk diameter (YDia), yolk weight (YW), yolk ratio (YR), yolk index (YI), albumen depth (AD), albumen weight (AW), Haugh unit (HU), and egg yolk colour score (YCS). Data collected was subjected to Analysis of variance using SAS software to compare differences between means of different ecotypes and relationships between the internal and external quality parameters established using Spearman’s correlation coefficient. All graphs were produced using the R software. Results revealed variations in external and internal egg quality parameters across the ecotypes. Eggs laid by hens from Apac were significantly (P<0.05) heavier and longer than those of other ecotypes. Significant (P<0.05) difference was also observed in egg breadth and in shape index. Eggs laid by hens from Gulu had significantly thicker shells whereas eggs laid by hens from Katakwi were significantly (P<0.05) higher in SW, SI and SR. Eggs laid by hens from Katakwi still had higher YD, YI and YR. YCS was only significantly (P<0.05) different for eggs laid by hens from Gulu. Eggs laid by hens from Apac and lira had significantly (P<0.05) higher AD, HU and AW. Egg weight had positive significant correlations with most external and all internal egg quality parameters but with differences in intensities. Stronger correlations were observed with middle breadth, albumen weight, egg length and yolk weight. The variations observed across the ecotypes influence preference choices, marketing, egg handling and breeding. Furthermore, egg weight is a good indicator of internal egg quality.