LAUSR

Abstract The effects of dietary methionine (Met) and betaine (Bet) on slaughter performance, serum biochemical parameters, and liver betaine-homocysteine methyltransferase (BHMT) were investigated in geese. Six Met-deficient diets were prepared according to a 2 × 3 factorial design that included two levels of Bet (0 and 600 mg/kg) and three levels of Met (0, 600, and 1200 mg/kg). Three hundred 21-d-old healthy male Yangzhou geese with similar body weight were randomly distributed into 6 groups with 5 replicates per treatment and 10 geese per replicate. All geese had free access to diets and water for 49 d. slaughter performance were recorded at 70 d of age. Results showed that increasing dietary levels of methionine gave a linear ( P  P  > 0.05). Geese that received 600 mg/kg Bet had a higher percentage of eviscerated yield than those that did not ( P   0.05). There were significant interaction effects between Met and Bet in dressing percentage, half-eviscerated yield, and eviscerated yield ( P   0.05). Increasing supplemental Met led to linear increases in serum concentrations of total protein (TP), albumin (ALB), and globulin (GLOB) and hepatic crude protein levels ( P   0.05). Bet supplementation also increased TP and ALB plus high- and low-density lipoprotein in serum and the mRNA level of BHMT ( P   0.05) in livers. In contrast, triglyceride and homocysteine were higher in geese that did not receive additional Bet than those in the Bet supplementation group ( P   0.05). The hepatic crude fat contents in the Bet supplementation group also decreased ( P   0.05). Significant interactions between Met and Bet supplementation ( P   0.05) were detected in several amino acids. In conclusion, optimal Met dietary supplementation could increase growth performance, serum TP, ALB, and GLOB and hepatic protein synthesis in growing goslings. Furthermore, dietary supplementation with Bet could possibly replace Met for slaughter performance through upregulation of BHMT gene expression.