Ractopamine increases glucose turnover without affecting lipogenesis in the pig

Abstract

The β-agonist ractopamine (RAC) promotes protein deposition with little effect on fat deposition in the pig. The present study was conducted to assess whether the lack of effect on fat deposition was due to a lack of effect of ractopamine on lipogenesis. Twenty crossbred pigs (initial liveweight 80 kg) surgically prepared with cephalic vein catheters were used in a 2×2 factorial experiment with the respective factors being sex (boar or gilt) and dietary RAC (0 or 20 mg/kg of ractopamine.HCl). Pigs were offered 3·0 kg/day of their respective diets for 24 days. On Day 4 and 23 of the experiment, pigs were injected with [U- ¹⁴C]-glucose and serial blood samples taken to determine glucose turnover. Adipose tissue biopsies were taken 240 min after injection of labelled glucose and lipogenesis was estimated from the incorporation of ¹⁴C into adipose tissue lipid. Dietary RAC increased average daily gain (P < 0·050), and average growth rate was greater in boars than in gilts (P < 0·050). Dietary RAC increased glucose turnover by 24%, presumably to support the increased skeletal muscle protein deposition that occurs during dietary RAC treatment. There was no effect of dietary RAC on the rate of lipogenesis in adipose tissue, which is consistent with the lack of effect of dietary RAC on the rate of fat deposition.

β-agonist, adipose tissue.