Abstract:
A study was undertaken at Sokoine University of Agriculture to investigate the influence of shank colour on egg quality traits and production performance. The study involved green shanked Indigenous (GSI) chickens, yellow shanked Indigenous (YSI) chickens and Rhode Island Red (RIR) genetic groups. The genetic groups were reared under the same environment and management. A total of 240 blood plasma samples were used in assessment of plasma cholesterol content while, 120 egg samples were used to assess egg yolk cholesterol and other egg quality traits. RIR differed significantly (P≤0.05) from GSI and YSI genetic groups in terms of egg number, egg weight, egg mass, laying intensity, yolk ratio and yolk albumin ratio. However, there was no significant difference between the indigenous genetic groups for these parameters as well as fertility, hatchability, growth rate and survival rate. The mean egg weights were 40.1 ± 0.8, 42.3 ± 0.9 and 52.0 ± 0.7 gm while the laying intensities were 46.7 ± 1.76, 46.8 ± 1.7 and 76.7 ± 1.7% for GSI, YSI and RIR genetic groups, respectively. There was no significant difference in egg yolk cholesterol, whilst plasma cholesterol differed significantly between RIR and indigenous types. The mean egg yolk cholesterol were 196.2 ± 7.2, 210.1 ± 7.2 and 201.8 ± 7.2 mg/dl for GSI, YSI and RIR respectively, while the blood plasma cholesterol were 210.4 ± 7.5, 196.5 ± 7.5 and 152.1 ± 7.5 mg/dl for GSI, YSI and RIR, respectively. Furthermore, the study revealed that, egg yolk cholesterol increased gradually with age while plasma cholesterol decreased with age in all genetic groups of this study. Total blood plasma cholesterol level increased when ndigenous types entered into brooding stage resulting in cyclic pattern between laying and brooding.
