Glucose and L‐lactate metabolism in pregnant and in lactating ewes fed barley‐ or ground maize‐based diets

Abstract

SUMMARYThe contribution of glucose absorbed from the small intestine to whole-body glucose metabolism was examined in ewes during late pregnancy and early lactation, using diets based on ground barley or ground maize. Glucose and L-lactate turnover in the whole body and the mesenteric-drained viscera were investigated in these ewes using isotope dilution techniques. The net absorption of glucose by the mesenteric-drained viscera and whole-body glucose turnover were unaffected by diet or reproductive status. Arterial and mesenteric venous blood glucose concentrations, arterial and mesenteric venous L-lactate concentrations and wholebody lactate turnover were all significantly higher in lactation than in pregnancy. The wholebody rates of lactate conversion to glucose and to other products were significantly higher in lactation than in pregnancy. Using a two-pool model of whole-body glucose and lactate metabolism, a relatively high percentage of glucose was converted to lactate (64-84%), accounting for 60-80% of whole-body lactate turnover. A model of glucose and lactate metabolism by the mesenteric-drained viscera was constructed. Both the calculated endogenous glucose production and the visceral conversion of glucose to lactate were greater in lactation than in pregnancy when barley was fed. Calculated total glucose absorption was relatively constant, contributing between 26 and 59% of whole-body glucose turnover. Diet had little effect on glucose and lactate metabolism in either the mesenteric-drained viscera or the wholebody of breeding ewes.

Effects of monensin on glucose metabolism in transition dairy cows

“…Another potential area that affects the estimations of gluconeogenesis from propionate is its oxidation within the rumen wall. Unlike sheep, where an extensive (60-80%) incorporation of C from propionate to lactate occurs before conversion to glucose (Perry et al, 1994), a negligible (about 3-5%) oxidation of propionate occurs within the rumen epithelium of cows (Bergman, 1990). This is in agreement with the results of Brockman (2005), who indicated that in the movement of C label from glucose to pyruvate or lactate and back to glucose, the exit of the C label was not detected.…”

Propionate supplementation did not increase whole body glucose turnover in growing lambs fed rye grass

“…On the other hand, Veenhuizen et al [8] fed steers at similar MEI and still reported a 59% increase in glucose turnover following propionate supplementation, at the same level as in this present study (30 mmol·d -1 ·kg BW -1 ). However, the steers presented a lower basal glucose turnover (42 mmol·d -1 ·kg BW -0.75 ) than that measured in the present study (60 mmol·d -1 ·kg BW -0.75 ), or by [14] and [48].…”

Whole body glucose turnover in growing and non-productive adult ruminants: meta-analysis and review

“…In lactating or pregnant ruminants, glucose turnover is clearly affected by changes in glucose requirements [12,[74][75][76]. In adult sheep, glucose turnover was better correlated with energy balance than with intake level, suggesting that the nutritional status of the animal had at least as much influence as the supply of glucose precursors [32].…”