The effect of epigallocatechin gallate on laying performance, egg quality, immune status, antioxidant capacity, and hepatic metabolome of laying ducks reared in high temperature condition

Abstract

Epigallocatechin gallate (EGCG) is a main component in green tea extract, which possesses multiple bioactivities. The present research studied the effects of EGCG on the laying performance, egg quality, immune status, antioxidant capacity, and hepatic metabolome of Linwu laying ducks reared under high temperature. A total of 180 42-w-old healthy Linwu laying ducks were allocated into control or EGCG-treated groups. Each treatment had 6 replicates with 15 ducks in each replicate. Diets for the two groups were basal diets supplemented with 0 or 300 mg/kg EGCG, respectively. All ducks were raised in the high temperature condition (35 ± 2 °C for 6 h from 10:00 to 16:00, and 28 ± 2 °C for the other 18 h from 16:00 to 10:00 the next day) for 21 days. Results showed that EGCG increased the egg production rate (p = 0.014) and enhanced the immunocompetence by improving serum levels of immunoglobulin A (p = 0.008) and immunoglobulin G (p = 0.006). EGCG also fortified the antioxidant capacity by activating superoxide dismutase (p = 0.012), catalase (p = 0.009), and glutathione peroxidase (p = 0.021), and increasing the level of heat-shock protein 70 (p = 0.003) in laying ducks' liver. At the same time, hepatic metabolomics result suggested that EGCG increased the concentration of several key metabolites, such as spermidine (p = 0.031), tetramethylenediamine (p = 0.009), hyoscyamine (p = 0.026), β-nicotinamide adenine dinucleotide phosphate (p = 0.038), and pantothenic acid (p = 0.010), which were involved in the metabolic pathways of glutathione metabolism, arginine and proline metabolism, β-alanine metabolism, and tropane, piperidine, and pyridine alkaloid biosynthesis. In conclusion, 300 mg/kg dietary EGCG showed protection effects on the laying ducks reared in high temperature by improving the immune and antioxidant capacities, which contributed to the increase of laying performance of ducks. The potential mechanism could be that EGCG modulate the synthesis of key metabolites and associated metabolic pathways.

Keywords: Epigallocatechin gallate; antioxidant; hepatic metabolomics; high temperature; laying ducks; production performance.

Figure 1.

Plots of multivariate statistical comparison of hepatic metabolome data in ducks between CON and EGCG groups. (a) OPLS-DA score plot in negative ion mode; (b) permutation test on OPLS-DA plot in negative ion model; (c) OPLS-DA score plot in positive ion mode; (d) permutation test on OPLS-DA plot in positive ion model.

Figure 2.

Hierarchical clustering of differential hepatic metabolites in ducks between CON and EGCG groups.

Figure 3.

KEGG pathway analysis overview of altered hepatic metabolic pathways in ducks between CON and EGCG. Lg10 (P) indicates log operation on the ion abundance of metabolites identified by mass spectrometry. Each dot represents a pathway and the color indicates the p-value of the enrichment. A larger circle indicates that there are more metabolites annotated to this pathway. E is environmental information processing. H is human diseases. M is metabolism. O is organismal systems.

Figure 4.

Relative abundances of metabolites involved in the 4 significantly altered metabolic pathways. (a) Spermidine; (b) tetramethylenediamine; (c) hyoscyamine; (d) β-nicotinamide adenine dinucleotide phosphate (NADPH); (e) pantothenic acid.

Figure 5.

Schematic diagram of the modulated metabolites and potential disturbed metabolic pathways. Up-regulated metabolites detected are shown in the red background; blank background means no statistically significant change or undetected. NADPH, β-nicotinamide adenine dinucleotide phosphate.