Long-Term Dietary Supplementation with Betaine Improves Growth Performance, Meat Quality and Intramuscular Fat Deposition in Growing-Finishing Pigs

This study was designed to investigate the effects of dietary betaine supplementation on growth performance, meat quality and muscle lipid metabolism of growing-finishing pigs. Thirty-six crossbred pigs weighing 24.68 ± 0.97 kg were randomly allotted into two treatments consisting of a basal diet supplemented with 0 or 1200 mg/kg betaine. Each treatment included six replications of three pigs per pen. Following 119 days of feeding trial, dietary betaine supplementation significantly enhanced average daily gain (ADG) (p < 0.05) and tended to improve average daily feed intake (ADFI) (p = 0.08) and decreased the feed intake to gain ratio (F/G) (p = 0.09) in pigs during 100~125 kg. Furthermore, a tendency to increase ADG (p = 0.09) and finial body weight (p = 0.09) of pigs over the whole period was observed in the betaine diet group. Betaine supplementation significantly increased a*(45 min) and marbling and decreased b*(24 h) and cooking loss in longissimus lumborum (p < 0.05), tended to increase intramuscular fat (IMF) content (p = 0.08), however had no significant influence on carcass characteristics (p > 0.05). Betaine supplementation influenced the lipid metabolism of pigs, evidenced by a lower serum concentration of low-density lipoprotein cholesterol (p < 0.05), an up-regulation of mRNA abundance of fatty acid synthase and acetyl-CoA carboxylase (p < 0.05), and a down-regulation of mRNA abundance of lipolysis-related genes, including the silent information regulators of transcription 1 (p = 0.08), peroxisome proliferator-activated receptorα (p < 0.05), peroxisome proliferator-activated receptor gamma coactivator-1α (p = 0.07) and carnitine palmitoyl transferase 1 (p < 0.05) in longissimus lumborum. Moreover, betaine markedly improved the expression of microRNA-181a (miR-181a) (p < 0.05) and tended to enhance miR-370 (p = 0.08). Overall, betaine supplementation at 1200 mg/kg could increase the growth performance of growing-finishing pigs. Furthermore, betaine had a trend to improve meat quality and IMF content via increasing lipogenesis and down-regulating the abundance of genes associated with lipolysis, respectively, which was associated with the regulation of miR-181a and miR-370 expression by betaine.