Plasma Levels of Energy Metabolites and Pancreatic Hormones in Relation to the Level of Intake and Intraruminal Infusions of Volatile Fatty Acids in Fed Wether Sheep

Abstract

Abstract The effect of feeding level and intraruminal infusion of volatile fatty acids (VFA) on the jugular plasma concentrations of energy metabolites and insulin and glucagon was studied in wether sheep. Three animals (42 kg ± 0.5 of body weight) of the Swedish Landrace breed were fed a grass hay and barley diet (70:30 on a dry matter basis) at three levels of intake (L1, L2, L3) in a change-over design. In addition to the diet, 3 different VFA mixtures and water (control) were continuously infused into the rumen during 16 days (one mixture during 4 consecutive days). The energy content of the VFA mixtures infused was equivalent to 17% of the calculated metabolizable energy intake per day. Plasma levels of non-esterified fatty acids and citrate decreased, and plasma insulin increased with increasing energy intake. When propionate was absent from the VFA infusion mixtures, plasma citrate tended to increase with increasing energy intake. The plasma citrate levels were negatively correlated to the concentrations of glucose and insulin in plasma. The concentrations of glucose and insulin in plasma were increased by the infusion of propionate in animals fed at L3. There was a high correlation between plasma glucose and insulin. Plasma glucagon levels were not affected either by level of intake or by VFA infusions. No evidence was found to support the concept that propionate is a major regulator of insulin and glucagon secretion in fed sheep.