Metabolism of Propionate, Glucose, and Carbon Dioxide as Affected by Exogenous Glucose in Dairy Cows at Energy Equilibrium

Abstract

In vivo kinetic techniques were used to quantify changes in metabolism of propionate, glucose, and blood CO2 when glucose was infused intravenously at 0, 342, or 737 g/d into four lactating cows. Neither production of milk or milk fat nor composition of milk was changed. Production of milk protein increased for the high glucose treatment. Isotope dilution data were used to calculate irreversible losses of rumen propionate, plasma glucose, and blood CO2 and to determine a unique solution for flux of C in this three-pool system. Irreversible losses of propionate and CO2 were not changed. Infusions of glucose increased irreversible loss of glucose in proportion to amounts infused, thus indicating there was no change in endogenous production of glucose. For the control, 52% of the C flux of blood glucose was derived directly from rumen propionate and another 26% came from other gluconeogenic substrates. Flux of C into glucose from exogenous sources increased in proportion to amounts of glucose infused. Flux of C from rumen propionate remained constant. The rate of C leaving the glucose pool, other than as CO2, tended to increase with infusion of glucose, and oxidation of glucose tended to increase for the high glucose treatment. High producing cows adjusted to increased exogenous glucose by increasing glucose utilization and without decreasing endogenous glucose production.

Precursors for liver gluconeogenesis in periparturient dairy cows

“…In the study by Casse et al (1994), liver uptake of glucogenic VFA could account for about 100% of the liver glucose release; however, the net liver VFA fluxes were relatively higher compared with the other studies and there was no obvious explanation for the discrepancy. The estimates for the contribution of propionate to glucose calculated from net liver uptake of glucogenic VFA are similar to estimates obtained with the isotope technique in steers (Veenhuizen et al, 1988), lactating dairy cows (Amaral et al, 1990) and goats (Danfaer et al, 1995). As outlined previously, the liver net uptake of propionate increases from pre partum to post partum and continues to increase as feed intake increases (Reynolds et al, 2003;Kristensen, 2009a and2012;Raun and Kristensen, 2011).…”

Milk production and concentrations of blood metabolites as influenced by the level of wet distiller’s solubles in dairy cows receiving grass silage-based diet

“…The blood concentration of ketones decreased slightly with increasing amount of WDS in the diet. This suggests that either BHB was cleared more rapidly or that ketogenesis decreased when glucose availability increased in relation to energy requirements (Amaral et al 1990). Similarly, Orskov and MacLeod (1990) reported that an increase in blood glucose concentration with decreased blood BHB concentration.…”

Effect of dietary energy source on energy balance, production, metabolic disorders and reproduction in lactating dairy cattle

“…In general, the negative effect of extra lipogenic sources on dry matter intake is higher when the degree of saturation of fatty acids is lower, probably because of the more pronounced negative effects of unsaturated fatty acids on rumen carbohydrate fermentation. As a result, 73% of the studies on feeding extra lipogenic nutrients [15,61,63,65,75,100,101,104,106] and also 73% of the studies on increasing dietary glycogenic nutrients [61,[69][70][71][72]117] obtained a higher net energy (NE) intake in the treatment group compared to the control group, illustrated by Figure 4 shows an overview of studies that reported milk yield and composition after feeding either more glycogenic nutrients or lipogenic nutrients. Both feeding extra lipogenic nutrients or glycogenic nutrients had similar effects on kg of milk produced per day [8, 15, 60-72, 75, 77, 78, 82, 99-104, 106, 107, 110, 111, 115-122] …”