Effect of dietary betaine supplementation on lipogenic enzyme activities and fatty acid synthase mRNA expression in finishing pigs

An experiment was conducted to investigate the effect of dietary betaine supplementation on growth performance, carcass characteristics, lipogenic enzyme activities in subcutaneous adipose tissue and mRNA expression of fatty acid synthase (FAS) in finishing pigs. Forty-eight crossbred barrows and gilts (Duroc × Seghers 15 line × Seghers 12/36 line) with a body weight of 55.7 ± 0.48 kg were divided into two groups, and three replicates of eight pigs (four barrows and four gilts) were assigned to each group. Pigs were fed a maize–soybean meal basal diet supplemented with either 0 or 1250 mg betaine/kg feed for 42 days. At the end of the trial, two pigs (one barrow and one gilt) weighing around 90 kg were selected from each replicate and slaughtered. Average daily gain increased by 5.5% (P<0.05) with betaine supplementation, but average daily feed intake and feed conversion ratio were not affected. Adding betaine to diet increased carcass lean proportion and loin muscle area (P<0.01) and decreased carcass fat proportion (P<0.01) and average backfat thickness (P<0.05). Betaine did not influence dressing proportion, proportion of skin and bone of the carcass or leaf fat weight. Betaine supplementation decreased the activities of acetyl-CoA carboxylase, FAS and malic enzyme in subcutaneous adipose tissue by 18.0% (P<0.01), 18.8% (P<0.05) and 14.5% (P<0.05), respectively, but the activities of glucose-6-phosphate dehydrogenase and isocitrate dehydrogenase were not affected (P>0.10). Semi-quantitative reverse transcription polymerase chain reaction analysis revealed a 25% decrease in FAS mRNA expression in pigs fed betaine (P<0.05). A significant correlation between mRNA expression level and potential enzyme activity for FAS was found (r = 0.93; P<0.01). The study suggests that the reduction in adipose tissue observed in pigs fed additional betaine might result from diminished rates of lipogenesis that is a consequence of decreased activities and gene expression of lipogenic enzymes, as evidenced by the decrease in FAS mRNA expression.