Effects of different levels of clove bud (Syzygium aromaticum) on yolk biochemical parameters and fatty acids profile, yolk oxidative stability, and ovarian follicle numbers of laying hens receiving different n-6 to n-3 ratios

•Fish oil and clove bud decreased egg yolk cholesterol, triglyceride and ω-6/ω-3 ratio.•Clove bud could improve n-3-enriched eggs oxidative stability in different conditions.•Fish oil stimulated the impressionability of egg yolk to lipid peroxidation.•Clove bud suppressed egg MDA content and enhanced yolk vitamin E concentration.

The present study was undertaken to investigate the effects of different levels of clove bud (Syzygium aromaticum) powder on yolk biochemical parameters and fatty acids profile, yolk oxidative stability, and ovarian follicle numbers in laying hens receiving different n-6 to n-3 ratios. For this purpose, a total number of 160 laying hens, 43 weeks of age, were assigned 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 also a high vitamin E content (200 mg/kg) in a 2 × 4 factorial arrangement during a 70-d feeding trial. Dietary inclusion of clove bud increased yolk vitamin E concentration (P < 0.05) and resulted in a decline in malondialdehyde level in eggs refrigerated for 30 d (P < 0.05) and 15 d (P = 0.071). Administration of low n-6 to n-3 ratios reduced egg yolk cholesterol (P = 0.058) and vitamin E (P < 0.05) levels and increased the egg yolk malondialdehyde content in both fresh and stored eggs (P < 0.05). Likewise, fish oil and clove bud powder supplementation led to reduced egg yolk n-6 to n-3 ratios (P < 0.001) via fortifying C20:5 (P < 0.001 and P < 0.05) and C22:6 (P < 0.001 and P < 0.001) n-3 fatty acids concentrations, and lowering C18:2 (P < 0.001 and P < 0.01), and C20:4 (P < 0.001 and P < 0.05) n-6 fatty acids contents, respectively. Briefly, dietary inclusion of clove bud powder was found to reduce egg yolk n-6 to n-3 ratio, and to improve its oxidative stability by decreasing malondialdehyde and enhancing vitamin E contents.