RESUMO
This study was carried out to investigate the effects of different levels of clove bud (Syzygium aromaticum) powder and vitamin E on serum lipid profile, enzyme activities and antioxidant indices, as well as hepatic biochemical and histological alterations in laying hens receiving different n-6 to n-3 ratios. A total of 160 laying hens, 43 weeks of age, were allotted to 8 experimental diets with 5 cages of 4 birds each. Dietary treatments consisted of two ratios of n-6 to n-3 (16.71 and 2.35), three levels of clove bud (0.0, 2.0 and 4.0 g/kg) and a high vitamin E level (200 mg/kg, as a positive control in each level of n-6 to n-3 ratio) in a 2 × 4 factorial arrangement during 70 days of the experiment. Results showed that a decline in the n-6 to n-3 ratio led to a reduction in serum cholesterol concentration (p < 0.05) and an increase in serum HDL content (p < 0.05). Additionally, decreasing n-6 to n-3 ratio and increasing clove bud level caused a remarkable decline in serum aspartate aminotransferase (p < 0.05 and p < 0.001) and alanine aminotransferase (p < 0.05 and p < 0.05) enzyme activities. Furthermore, total antioxidant capacity (p < 0.05 and p < 0.001) as well as serum vitamin E concentration (p < 0.05 and p < 0.001) was decreased and enhanced by low n-6 to n-3 ratio diets (LRD) and clove bud powder respectively. Decreasing the n-6 to n-3 ratio lowered hepatic lipid (p < 0.05) and glycogen contents (p < 0.01) as well as tissue integrity (p < 0.05), and raised liver MDA concentration (p < 0.001), markedly. Nevertheless, increments in clove bud content led to a reduction (p < 0.01) in liver relative weight (p < 0.05) and hepatic fat vacuole numbers. In general, the best synergistic responses on modulating of blood lipids and serum enzyme activities were observed when the highest level of clove bud was supplemented in the diets with low n-6 to n-3 ratio. Likewise, antioxidant indices were improved by administration of dietary clove bud powder although feeding fish oil was observed to elevate the susceptibility of blood and hepatocytes to lipid peroxidation.
