Effect of sorghum grain supplementation on glucose metabolism in cattle and sheep fed temperate pasture

Abstract

The aim of this work was to evaluate the effect of sorghum grain supplementation on plasma glucose, insulin and glucagon concentrations, and hepatic mRNA concentrations of insulin receptor (INSR), pyruvate carboxylase (PC), and phosphoenolpyruvate carboxykinase (PCK1) mRNA and their association with nutrient intake, digestion and rumen volatile fatty acids (VFA) in cattle and sheep fed a fresh temperate pasture. Twelve Hereford × Aberdeen Angus heifers and 12 Corriedale × Milchschaf wethers in positive energy balance were assigned within each species to one of two treatments (n = 6 per treatment within specie): non-supplemented or supplemented with sorghum grain at 15 g/kg of their body weight (BW). Supplemented cattle had greater plasma glucose concentrations, decreased plasma glucagon concentrations and tended to have greater plasma insulin and insulin-to-glucagon ratio than non-supplemented ones. Hepatic expression of INSR and PC mRNA did not differ between treatments but PCK1 mRNA was less in supplemented than non-supplemented cattle. Supplemented sheep tended to have greater plasma glucagon concentrations than non-supplemented ones. Plasma glucose, insulin, insulin-to-glucagon ratio, and hepatic expression of INSR and PC mRNA did not differ between treatments, but PCK1 mRNA was less in supplemented than non-supplemented sheep. The inclusion of sorghum grain in the diet decreased PCK1 mRNA but did not affect PC mRNA in both species; these effects were associated with changes in glucose and endocrine profiles in cattle but not in sheep. Results would suggest that sorghum grain supplementation of animals in positive energy balance (cattle and sheep) fed a fresh temperate pasture would modify hepatic metabolism to prioritize the use of propionate as a gluconeogenic precursor.

Gluconeogenesis Alteration and p53-SIRT6-Fox01 Signaling Adaptive Regulation in Sheep from Different Grazing Periods

“…Glucose supply plays a crucial role in maintaining adequate cell function of many tissues, including the nervous system, red blood cells, placenta, and mammary gland [ 12 ]. Alterations in glucose metabolism can cause adverse effects [ 9 ].…”

“…In sheep, glucose is mainly synthesized by gluconeogenesis from glucose precursors in their liver [ 12 ]. Forage is fermented by various bacteria and transformed into VFAs (volatile fatty acids) by pivotal enzymes in the rumen [ 25 ].…”

“…It also contributes to the maintenance and function of various cells and tissues of ruminants, including the nervous system, red blood cells, placenta, and mammary gland [ 9 ]. However, the glucose concentration in food has little contribution to the ruminant glucose supply [ 11 ], mainly dependent on gluconeogenesis which predominantly synthesizes glucose by using glucose precursors absorbed following fermentation and digestion of the diet in the liver to meet glucose requirements [ 12 ]. Several enzymes, including PEPCPK (phosphoenolpyruvate carboxykinase), PC (pyruvate carboxylase), G6P (glucose-6-phosphatase), and GLUT2 (Glucose transporter-2), are reported to be involved in controlling of the rate of gluconeogenesis in the liver.…”

Tannic acid supplementation in the diet of Holstein bulls: Impacts on production performance, physiological and immunological characteristics, and ruminal microbiota

“…In addition, we observed the significant reduction of the circulating GC concentration in the cattle of TAM treatment compared with the CON. As a typical mechanism involving gluconeogenesis of ruminants, the secretion of glucagon can be potently activated by the ruminally derived VFA, especially the propionate and butyrate ( 47 – 49 ). For this reason, the decrease in GC level in the TAM treatment might result from the above-mentioned diminishing of ruminal TVFA concentration and butyrate proportion in the same group of this trial.…”