Absorption and metabolism of glucose by the mesenteric-drained viscera of sheep fed on dried-grass or ground, maize-based diets

Abstract

1. Sheep fitted with re-entrant canulas in the proximal duodenum and terminal ileum were used to determine the amount of a-glucoside entering, and apparently disappearing from, the small intestine when either dried-grass or ground maize-based diets were fed. The fate of any a-glucoside entering the small intestine was studied by comparing the net disappearance of such a-glucoside from the small intestine with the absorption of glucose into the mesenteric venous blood.2. Glucose absorption from the small intestine was measured in sheep equipped with catheters in the mesenteric vein and carotid artery. A continuous infusion of [6-3H]glucose was used to determine glucose utilization by the mesenteric-drained viscera and the whole-body glucose turnover rate (GTR).3. The amounts of a-glucoside entering the small intestine when the dried-grass and maize-based diets were given were 13.9 (SE 1.5) and 95.4 (SE 16.2) g/24 h respectively; apparent digestibilities of such a-glucoside in the small intestine were 60 and 90% respectively.4. The net absorption of glucose into the mesenteric venous blood was -2.03 (SE 1-20) and 19.28 (SE 0.75) mmol/h for the dried-grass and maize-based diets respectively. Similarly, total glucose absorption amounted to 1.52 (SE 1.35) and 23.33 (SE 1.86) mmol/h (equivalent to 7 and 101 g/24 h respectively). These values represented 83 and 11 1 % of the a-glucoside apparently disappearing from the small intestine, determined using the re-entrant cannulated sheep.5. Total glucose absorption represented 8 and 61 % of the whole-body GTR for the dried-grass and maize-based diets respectively. Endogenous glucose production was significantly lower when the sheep were fed on the maizebased diet compared with the dried-grass diet.6. The mesenteric-drained viscera metabolized a small amount of glucose, equivalent to 234 and 17% of the total glucose absorbed for the dried-grass and maize-based diets respectively. 7. It is concluded that a large proportion of the starch entering the small intestine of sheep given a maize-based diet is digested and absorbed as glucose, and thus contributes to the whole-body GTR.

Intestinal amino acid absorption in lambs fed fresh Lucerne (Medicago sativa) during an established Trichostrongylus colubriformis infection

“…The net flux of AA across the MDV in the current study (1 to 5 g/day) is similar to the 4 to 6 g/day reported by MacRae et al (1997b) at similar intakes, but the similar net fluxes of AA across the MDV between control and parasitised lambs contrast with the observations for leucine by Yu et al (2000). While mesenteric plasma flows are within the ranges in the literature for sheep at a similar age and DM intake (700 to 1000 ml/min; Janes et al, 1985;MacRae et al, 1997b;Yu et al, 2000;Bermingham et al, 2007b), they are highly variable (CV of 28% to 40% in the control and parasitised lambs, respectively), and this variability may have masked any effects of infection on MDV AA fluxes. High variability (.25%) in blood flow across the MDV has been observed previously (MacRae et al, 1997b;Yu et al, 2000), and might be attributed to either incomplete mixing of the dye in those blood vessels or movement of the catheter due to peristaltic intestinal contractions (MacRae et al, 1997b).…”

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

“…In these cases, the endogenous hepatic glucose production was significantly reduced but not on a 1:1 basis, such that the rise in glucose absorption was accompanied by a rise in whole body glucose turnover. Similarly, exogenous glucose supply, either via intraduodenal or intrajugular infusions, increases glucose turnover in sheep [11,23] despite some reduction in endogenous glucose synthesis (noted by 59 only). The degree of inhibition of endogenous glucose synthesis is dose dependent with intrajugular infusions of glucose up to 0.5 mmol·min -1 [26].…”

“…The previous survey of the literature specifically indicated that the inclusion of maize in the diet improves glucose turnover. With maize based diets, rich in bypass starch, absorbed glucose may contribute to glucose turnover to a variable but sometimes to a considerable extent (up to 60% [23,27,31]). In beef steers fed dry-rolled sorghum, it was evaluated that glucose absorption from starch intestinal digestion could account on average for a third of the glucose metabolism [6].…”

Effect of supplemental calcium propionate on insulin action to blood glucose metabolism in adult sheep

“…The inconsistency of effects of supplemental propionate on blood glucose metabolism may be involved in the dose, duration or method of propionate supplementation, the stage of animals, or feeding managements. Although basal blood GTR was within the ranges of blood GTR as determined by the isotope dilution methods using stable and radio isotopes, blood GTR for the Prop diet seemed to be near the upper margin [12,18,28,29]. Because blood GTR is influenced by the type of diet, energy intake and physiological status [28][29][30], these factors may be related.…”

“…Although basal blood GTR was within the ranges of blood GTR as determined by the isotope dilution methods using stable and radio isotopes, blood GTR for the Prop diet seemed to be near the upper margin [12,18,28,29]. Because blood GTR is influenced by the type of diet, energy intake and physiological status [28][29][30], these factors may be related. OrtiguesMarty et al [29] reviewed the relationship between glucose turnover rate and ME intake in growing ovines, growing bovines and adult ovines, and suggested that growth stage on glucose turnover rate is probably as important as the effect of animal species.…”