Effects of protein-free energy supplementation on blood metabolites, insulin and hepatic PEPCK gene expression in growing lambs offered rice straw-based diet

Abstract

Energy supplementation is important for ruminants consuming low quality forage-based diets to achieve a desired rate of gain (Bowman and Sanson, 1996). Most of the studies concerning energy supplementation to forage-based diet were focused on the associative effects in digestive tracts (Caton and Dhuyvetter, 1997;Bodine and Purvis, 2003;Lardy et al., 2004), while little attention has been paid to the effect of supplemental energy on glucose metabolism and protein status in body tissues. It is well known that the fermentation of readily fermentable energy in the rumen will result in enhanced production of volatile fatty acids and lactate ). These changes in end products of rumen fermentation would consequently influence blood glucose metabolism and endocrine (Sowinska et al., 2001;Sano and Fujita, 2006) ABSTRACT: This study was conducted to investigate the effects of increasing levels of protein-free energy supplementation on blood glucose, urea nitrogen, insulin and gene expression of hepatic phosphoenolpyruvate carboxykinase (PEPCK) in growing lambs offered rice straw-based diet. Thirty-six male Hu lambs (3.5 months old) were divided into four equal groups according to body weight. All animals were fed rice straw ad libitum and supplemented with cornstarch at levels of 0 (control), 60, 120, and 180 g/day, respectively, along with 160 g/day of rapeseed meal. The trial lasted for 60 days with the first 15 days for adaptation. Body weight change and feed intake were recorded. Blood samples were taken at different time points after feeding at the end of the trial, and analyzed for blood glucose, total protein, urea nitrogen and insulin. Liver samples were collected and analysed for the mRNA abundance of hepatic PEPCK. Increasing cornstarch showed a low effect on rice straw intake, but increased average daily gain of lambs significantly (P < 0.05). Blood glucose tended to increase with starch supplementation, but altered within a narrow range. Blood urea nitrogen was decreased significantly (P < 0.05) with increment in supplemental starch. Supplementation of starch at 120 or 180 g/day significantly increased the insulin concentration (P < 0.05) compared with the control. The abundance of cytosolic PEPCK (PEPCK-C) mRNA increased 2.47 times and 3.98 times with 60 and 120 g per day of starch supplementation compared with the control, respectively, while the supplementation of 180 g per day of starch showed a low effect on PEPCK-C gene expression (P > 0.05). Amounts of mitochondrial PEPCK (PEPCK-M) mRNA were not affected by the supplementation of starch at any level (P > 0.05). These results indicate that proper energy supplementation increases the expression of PEPCK-C, and consequently gluconeogenesis and blood glucose increase, while excessive energy may have an inhibitory effect on gluconeogenesis through insulin-involved mechanisms.

Effects of Rice Straw Supplemented with Urea and Molasses on Intermediary Metabolism of Plasma Glucose and Leucine in Sheep

“…Concentration of plasma glucose determined during the last 2 h continuous infusion of isotope dilution did not differ (p = 0.51) between the RSUM-diet and the MH-diet ( Table 5 ). The numerical values of plasma glucose concentration were similar with the data previously reported in sheep fed rice straw supplemented with corn starch as energy source ( Zhang et al, 2009 ). In ruminants gluconeogenesis takes place mainly in liver and rates of plasma glucose turnover (TR) were influenced with several factors such as the type of diet, energy intake and supply of gluconeogenic substrate to the liver ( Ortigues-Marty et al, 2003 ; Sano and Fujita, 2006 ).…”

Inclusion of Kapok Seed Oil in the Diet for Growing of Thin-Tailed Sheep to Reduce Cholesterol and to Improve Omega-Six Fatty Acid Contents of Lamb

“…Increasing of glucose production stimulated insulin hormone secretion that had important role in lipogenesis. Zhang et al (2009) indicated that supplementation of 180 g starch per day to sheep resulted in higher (P<0.05) blood insulin hormone concentration than sheep received 120 g starch per day (0.64 vs 0.53 ng/ml). Faulconnier et al (2007) and Vakili et al (2011) stated that insulin increased lipogenesis by lipolysis inhibition and increased the glucose entry into adipocyte for lipogenesis.…”