Abstract:
19A Effects of dietary fat and conjugated linoleic acid on metabolic responses to homeostatic signals in pigs E. Ostrowska1,2, M. Muralitharan3, R.F. Cross2, D.E. Bauman4 and F.R. Dunshea1 1 2 3 4 Agriculture Victoria, Victorian Institute of Animal Science, Werribee Vic 3030 Swinburne University, PO Box 218, Hawthorn Vic 3122 Charles Sturt University, PO Box 588, Wagga Wagga, NSW 2650 Cornell University, Ithaca, NY 14853, USA One constraint facing the pig industry is that ad libitum feeding can often result in high levels of body fat. Dietary conjugated linoleic acid (CLA) has been shown to decrease fat deposition and body fat content of pigs (Dunshea and Ostrowska 1999) but the mode of action is unknown. Fatty acids for lipogenesis are derived from either circulating triglycerides of largely dietary origin or can be produced de novo, principally from glucose. The aim of this study was to investigate the effects of dietary CLA and fat on responses to the major regulators of lipid metabolism, insulin and epinephrine. Twenty female cross bred (Lar ge White x Landrace) pigs (65 kg) with venous catheters were fed for eight days either a low fat diet (25 g fat/kg) or a high fat diet (100 g/kg) with either 0 or 10 g/kg of CLA 55. Pigs were offered approximately 90% of ad libitum DE intake and feed was delivered every 3 h to ensure a relatively steady state for measuring plasma metabolites. Plasma glucose and nonesterified fatty acid (NEFA) responses to insulin (3 �g/kg) and epinephrine (3 �g/ kg) were determined on day 8. Plasma NEFA and triglycerides were increased by high fat and CLA feeding whereas plasma glucose was unchanged (Dunshea and Ostrowska 1999). The plasma NEFA response to epinephrine was increased suggesting increased lipolysis with CLA feeding. The plasma glucose response to epinephrine was reduced by high fat feeding and tended to be reduced by dietary CLA. While the antilipolytic effect of insulin was reduced in pigs fed CLA there was no effect of CLA on plasma glucose response to insulin. These data suggest that the responses to homeostatic signals during CLA feeding favour increased lipolysis rather than decreased de novo fat synthesis in adipose tissue. Dunshea, F.R and Ostrowska, E. (1999). Conjugated linoleic acidsnake oil or wonder fat. Recent Advances in Animal Nutrition in Australia 12, 159166. Dunshea, F.R. (1993). Effect of metabolism modifiers on lipid metabolism in the pig. Journal of Animal Science 71, 19661977. Table 1 Effect of dietary fat and CLA on basal metabolite concentrations and responses to insulin and epinephrine. 25 0 10 0 100 10 F Significance C FxC Fat, g/kg (F): CLA_55, g/kg (C): Response to epinephrine Plasma NEFA (�mol.min/L)1 Plasma glucose (mmol.min/L)2 88 81 260 67 135 53 243 39 0.78 0.007 0.018 0.12 0.55 0.98 Response to insulin Plasma NEFA (�mol.min/L)1 Plasma glucose 1 2 _49 _81 40 _76 _43 _73 32 _80 0.98 0.84 0.036 0.86 0.84 0.43 (mmol.min/L)2 Sum of response over first 6 min. Sum of response over first 30 min. Recent Advances in Animal Nutrition in Australia, Volume 12 (1999)