Enrichment efficiency of lutein in eggs and its function in improving fatty liver hemorrhagic syndrome in aged laying hens

Abstract

In this study, we evaluated the enrichment efficiency of lutein in eggs and its function in preventing fatty liver hemorrhagic syndrome (FLHS) in aged laying hens. Five groups of laying hens (65 wk old) were fed basal diets supplemented with 0, 30, 60, 90, or 120 mg/kg of lutein. The supplementation period lasted 12 wk followed by 2 wk of lutein depletion in feed. The results revealed that lutein efficiently enriched the egg yolks and improved their color with a significant increase in relative redness (P < 0.001). Lutein accumulation increased in the egg yolk until day 10, then depletion reached a minimum level after 14 d. Overall, zeaxanthin content in all the groups was similar throughout the experimental period. However, triglycerides and total cholesterol were significantly decreased in the liver (P < 0.05) but not significantly different in the serum (P > 0.05). In the serum, the lipid metabolism enzyme acetyl-CoA synthetase was significantly reduced (P < 0.05), whereas dipeptidyl-peptidase 4 was not significantly different (P > 0.05), and there was no statistical difference of either enzyme in the liver (P > 0.05). Regarding oxidation and inflammation-related indexes, malondialdehyde, tumor necrosis factors alpha, interleukin-6, and interleukin-1 beta were decreased, whereas superoxide dismutase and total antioxidant capacity increased in the liver (P < 0.001). The function of lutein for the same indexes in serum was limited. It was concluded that lutein efficiently enriched the egg yolk of old laying hens to improve their color and reached the highest level on day 10 without being subject to a significant conversion into zeaxanthin. At the same time, lutein prevented liver steatosis in aged laying hens by exerting strong antioxidant and anti-inflammatory functions, but also through the modulation of lipid metabolism, which may contribute to reducing the incidence of FLHS in poultry.

Keywords: egg; enrichment efficiency; fatty liver hemorrhagic syndrome; lutein; old laying hen.

Figure 1

Egg yolk color scores on weeks 6 and 12. L0: control diet; L1, L2, L3, and L4: control diet supplemented with lutein at 30, 60, 90, and 120 mg/kg feed, respectively. L*: relative lightness; a*: relative redness; b*: relative yellowness. Data are presented as means ± standard deviation (n = 8); different superscript letters within a time of test indicate significant differences between groups (P < 0.05). Analysis of variance (ANOVA) was conducted for each time point separately.

Figure 2

Lutein and zeaxanthin concentration in egg yolks on weeks 0, 6, and 12. L0: control diet; L1, L2, L3, and L4: control diet supplemented with lutein at 30, 60, 90, and 120 mg/kg feed, respectively. Data are presented as means ± standard deviation (n = 8); different superscript letters within a time of the test indicate significant differences between groups (P < 0.05). Analysis of variance (ANOVA) was conducted for each time point separately.

Figure 3

Efficiency rate of lutein in egg yolks on weeks 6 and 12. L0: control diet; L1, L2, L3, and L4: control diet supplemented with lutein at 30, 60, 90, and 120 mg/kg feed, respectively. Data are presented as means ± standard deviation (n = 8); different superscript letters within a time of the test indicate significant differences between groups (P < 0.05). Lutein efficiency rate = (lutein concentration in yolk × yolk weight × egg production)/(average feed intake × lutein concentration in the diet) × 100. The measured lutein contents in diets were used. Analysis of variance (ANOVA) was conducted for each time point separately.

Figure 4

Lutein accumulation and depletion trend in eggs (A) and egg yolk color trend (B). L1: control diet supplemented with lutein at 30 mg/kg feed; L4: control diet supplemented with lutein at 120 mg/kg feed. A0, A2, A4, A6, A8, A10, A12, A14: lutein content in egg yolks tested on days 0, 2, 4, 6, 8, 10, 12, and 14 of supplementation, respectively; w6, w12: lutein content in egg yolks tested on weeks 6 and 12 of supplementation, respectively; D2, D4, D6, D8, D10, D12, and D14: lutein content in egg yolks tested on days 2, 4, 6, 8, 10, 12, and 14 after supplementation period, respectively. Bars correspond to standard deviation.

Figure 5

Lipid-related indexes in serum and liver on week 12. L0: control diet; L1, L2, L3, and L4: control diet supplemented with lutein at 30, 60, 90, and 120 mg/kg feed, respectively. Data are presented as means ± standard deviation (n = 8); different superscript letters indicate a significant difference between groups (P < 0.05). Abbreviations: TG, triglycerides; TC, total cholesterol; DPP4, dipeptidyl-peptidase 4; AACS, acetyl-CoA synthetase.

Figure 6

Oxidation and inflammation-related indexes in serum and liver on week 12. L0: control diet; L1, L2, L3, and L4: control diet supplemented with lutein at 30, 60, 90, and 120 mg/kg feed, respectively. Data are presented as means ± standard deviation (n = 8); different superscript letters indicate a significant difference between groups (P < 0.05). Abbreviations: MDA, malondialdehyde; GSH-Px, glutathione peroxidase; SOD, superoxide dismutase; AST, aspartate aminotransferase; ALT, alanine aminotransferase; T-AOC, total antioxidant capacity; TNF-α, tumors necrosis factors alpha; IL-6, interleukin-6; IL-1β, interleukin-1 beta.

Figure 7

Oil Red O (ORO) staining of the liver samples on week 12. Magnification: 200 × . Red arrow: indicates nuclei in blue; blue arrow: indicates fats in red. L0: control diet; L2 and L4: control diet supplemented with lutein at 60 and 120 mg/kg feed, respectively.

Figure 8

Liver hematoxylin and eosin (H&E) staining on week 12. Magnification: 200 × . Yellow arrow: fat vacuoles in the cytoplasm; red arrow: inflammatory cell infiltration in liver parenchyma; blue arrow: mild edema in cells. L0: control diet; L2 and L4: control diet supplemented with lutein at 60 and 120 mg/kg feed, respectively.