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| The study was carried out to investigate the effects of methionine source and level on hepatic methionine and lipid metabolism of commercial laying hens fed with low nutrient level (LN) or moderate nutrient level (MN) diets under restricted feeding. A completely randomized design was used. Within each nutrient level, there were 2 methionine sources (DL-methionine, DLM; DL-2-hydroxyl-4-methylthio-butiric acid, HMTBA) and 3 supplementation levels (LN: 0, 0.091 and 1%; MN: 0, 0.113 and 1%). A total of 2000 layers was allocated to 10 dietary treatments with 10 replicates for each. For hens fed LN diets: regardless of nutrient level, methionine source and level had no effects on concentration of Hcy in liver or plasma; hens treated with DLM had higher plasma Met and Tau concentration than those treated with HMTBA; when compared with the control group, adding methionine (HMTBA source) at 0.091% or 1% markedly increased the expression of GNMT; adding methionine (DLM source) at 1% significantly increased the expression of BHMT. Under the condition of feeding MN diets: plasma Met concentration significantly increased with methionine supplementation. Adding methionine (HMTBA source) at 0.113% or 1% significantly increased the expression of ADA and adding methionine (HMTBA source) at 0.113% significantly increased the expression of MS. When control diet was fed, hens fed LN diets had higher expression of BHMT and MS. When adding methionine (HMTBA source) at 1%, hens fed LN diets had higher expression of SAHH, MTHFR, CEBPβ, AdipoR2, INF-α and IL-1β. When adding methionine (DLM source) at 1%, feeding LN diet significantly increased the expression of TNF-α. In conclusion, methionine deficiency may increase the methionine regeneration by up-regulating the expression of genes involved in hepatic methionine metabolism. Under the condition of adding excess HMTBA, feeding low-nutrient diet may increase the folate-dependent pathway of methionine regeneration, SAMe-dependent transmethylation, fat synthesis and inflammatory cytokines in liver, and increase the potential risk of liver diseases. |
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| Keywords:laying hens, methionine, methionine hydroxyl analogue, lipids, plasma free amino acid |
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