Effects of dietary betaine substitution to a part of methionine on malic enzyme gene expression in laying hens under heat stress using real-time PCR method

This study was conducted to determine the effects of Betaine (Bet) substitution with a part of Methionine (Met) on malic enzyme gene expression in laying hens under heat stress. Ninety six hens (strains of commercial laying 65-wk-old Hy–Line Leghorn in second cycle of production) were performed as a completely randomized design (CRD) with a 2 ×2 factorial arrangement of treatments with three replicate cages and eight hens per cage. There were 4 dietary treatments: two levels of Bet (0 and 13%) substitute to Met combined with two environmental conditions (heat stress (HS) and thermoneutral (TN) conditions). To apply stress, the hens of a salon were exposed under 35 °C, for six hours, daily. Two experimental levels including 100% Met diet as control group and 87% Met + 13% Bet diet as trial group were surveyed. After two month feeding, four hens euthanasia by cervical dislocation and the livers were removed, frozen in liquid N2 and stored at −80 °C. After extracting the total RNA, quality was measured and was used to cDNA synthesis. Finally, mentioned genes expression evaluated by specific promoter and Real- time PCR set. The results indicated that supplementation of the basal diets with Betaine lead to decrease significantly (2.47 unit) in enzyme gene expression in liver tissue (P < 0.01). Also, heat stress decreases significantly (1.96 unit) in the malic enzyme gene expression (P < 0.01). Therefore, Betaine and heat stress could repress malic enzyme gene expression in mRNA level and play important role in decreasing liver fat.