Carcass traits:Data presented in Table 4 showed that, absolute weight of carcass, giblets and total edible part was significantly (P<0.05) increased by dietary Spirulina groups compared with the control group. While, relative weight of carcass traits studied was not significantly affected by dietary treatment. It must be mentioned that the dietary Spirulina platensis–additives (0.1,0.2 and 0.3 g Spirulina/kg diet had heavier (P<0.05) carcass weight and total edible part by 5.8%, 11.4% and 16.4% and5.6%, 11.1% and15.7% compared with the control group, respectively. The significant (P < 0.05) improvement of carcass weight and total edible part may be related to increasing live body weight. In line with the present results, several authors reported that body weights, weight gain, carcass yield percentage, and feed conversion ratio were significantly (P>0.05) increased by dietary inclusion of Spirulina platensis as compared to the control diet (Ross and Dominy, 1990; Nikodémusz et al., 2010; Kaoud, 2012; Kharde et al., 2012).It is of interest to note that absolute or relative abdominal fat weight Table 4, it was significantly (P<0.05) reduced by increasing dietary treatments level. This reduction may be attributed to the reduction in plasma total lipids and cholesterol. In this respect, khan et al., (2005) reported that Spirulina have shown regulatory role on lipid and carbohydrate metabolism by exhibiting glucose and lipid profile correcting activity in animals.Average weights of lymphoid organs (organs that are mostly responsible for the immunological response in birds) as absolute and relative weights are recorded in Table 5. Results showed that absolute and relative weights of bursa and thymus significantly (P<0.05) increased for all treatment groups compared with the control one. While,weight of spleen had a significant increase only in absolute weight. In accordance with the present results, Kaoud, (2012) reported that the absolute and relative weights of bursa and thymus was increased for all groups fed dietary Spirulina compared with the control group. These results may be as an indicator of good healthy status of chicks fed dietary spirulina. In this respect Bennett and Stephens (2006) reported that the bursa functions are half of the bird's immune system and the size of the bursa reflects the bird's overall health status. Sick or stressed birds have small bursa while, healthy, productive birds have large bursa. Bursa size is a biological measure of how well flocks are managed and protected from disease.Also, liver weight (Table 4) may indicate that anti-nutritional factors presented in spirulina platensis were not effective. These results were supported by the findings of several scientists (Belay,1993; Baojiang, 1994), who reported that Spirulina-polysaccharide acts similarly to phycocayanin. It improves the immune system's ability to detect and destroy foreign microbes or eliminate toxins. It also enhances T-cells and improves thymus gland function. In agreement with the present results, Qureshi et al, (1994) reported that dietary Spirulina could increase size of thymus glands for greater T-cell production of broiler chocks. Also, Kaoud, (2012) reported that, the absolute and relative weights of bursa and thymus was increased for all groups fed dietary Spirulina compared with the control group.
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