Gluconeogenesis in Ruminants: Glucose Kinetic Parameters in Calves under Standardized Conditions

Young, J.W.; Trott, David; Berger, P.J.; Schmidt, Stephen P.; Smith, Jennifer A.

doi:10.1093/jn/104.8.1049

Cited by 23 publications

(11 citation statements)

References 27 publications

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“…It can be calculated that even if all skeletal muscle in the body was taking up glucose at the maximum mean rate of the hind leg in the present study, it would account for about 1x5 mmol min-'. It has recently been reported that in resting fed steers, of similar body-weight to our own, total glucose entry rate exceeds 5.5 mmol min-' [Young, Trott, Berger, Schmidt and Smith, 1974], and it is likely that this rate is increased during cold exposure.…”

supporting

confidence: 67%

Changes in the Metabolism of the Shivering Hind Leg of the Young Ox During Several Days of Continuous Cold Exposure

1975

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The effect of 4 days of continuous exposure to a cold environment on blood flow in, and oxygen and energy substrate uptake by the shivering hind leg has been studied in young steers. The animals shivered throughout the period of cold exposure and total oxygen consumption (total V0o) remained 40-50% greater than Vo, during thermoneutrality. Leg blood flow (leg 0) and oxygen uptake (leg Vo,) increased two-and four-fold respectively on the first day of cold. Both had declined significantly by the final day, leg Q to a level 37% greater than, and leg Vo, to about double, pre-cold levels. The change in the relationships of leg 0 and leg Vo2 to total V0r was examined by linear regression analysis, which suggested that the changing contribution of leg V01 to total Vo2 was entirely due to changes in leg Q, rather than in the arteriovenous difference in blood oxyhaemoglobin saturation across the leg. The net uptakes by the leg of free fatty acids (FFA), acetate, glucose and lactate all increased on the first day of cold. Both glucose and acetate uptakes were greater on day 4 than on day 1 in the cold, in spite of the lower leg Vo , but net uptakes of FFA and lactate were considerably lower. The decrease in net uptake of FFA is attributed mainly to an increase in the rate of lipolysis and release of FFA from fat depots in the leg, because of the associated progressive increase in the release of glycerol and oleic acid from the leg. The molar ratios of net carbohydrate substrate, acetate and FFA uptakes to leg Vo, are compared.The results suggest that tissues other than the leg muscles become increasingly important as sites of heat production, and that there are changes in the utilization of glucose, acetate and FFA by shivering muscle, during prolonged cold exposure.When the young steer is exposed to cold for several hours, vigorous shivering in the muscles of the hind legs is associated with substantial increases in leg blood flow (leg 0) and oxygen uptake (leg Vo,) [Bell, Thompson and Findlay, 1974]. This increase in leg metabolism is supported by increases in the net leg uptake of plasma volatile fatty acids (VFA) [Bell, Gardner and Thompson, 1974] and free fatty acids (FFA) and blood glucose and lactate [Bell, Gardner, Manson and Thompson, 1975], the relative importance of these substrates depending on time after feeding. However, under natural conditions, cattle can be subjected to cold for periods much longer than several hours. It has been reported that ex'posure of mature non-lactating, non-pregnant cows to sub-zero temperatures for 3 days results in continuous shivering, which is most vigorous after 1 day in the cold, and in elevated peripheral plasma FFA and glucose levels on all 3 days [Olsen and Trenkle, 1973]. However, little is known about the metabolism of shivering muscle during other than acute cold exposure in cattle or any other species.The present experiments were therefore done to measure any changes which might occur in oxygen uptake and the pattern of energy substrate utilization by the leg during ...

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confidence: 67%

Changes in the Metabolism of the Shivering Hind Leg of the Young Ox During Several Days of Continuous Cold Exposure

1975

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“…Specific ob jectives for this study were: (a) to study the eifects of feeding two different amounts of a high-grain diet upon production of propionate in the bovine rumen; (b) to investigate the reproducibility of measure ments of propionate pool size and produc tion rate; and (c) to obtain propionate production rates relating to gluconeogene sis in cattle on a highly controlled feeding regime fed one specific diet. Glucose kinetics and glucose absorption already have been studied in steers under similar conditions (7,16).…”

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confidence: 99%

Gluconeogenesis in Ruminants: Propionic Acid Production from a High-Grain Diet Fed to Cattle

Yost

Young

Schmidt

et al. 1977

The Journal of Nutrition

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Effects of amount of feed intake on in vivo remen propionate production and the reproducibility of measurements of propionate production rates were investigated in five dairy steers weighing 142 to 228 kg. Each steer received 275 g of an 80%-grain diet every 2 hours, and three of the five steers later received 500 g/2 hours. Rumen propionate pool sizes and production rates were determined at both intakes by administering a single dose of [1-14C] propionate via rumen fistula and observing decreasing specific activity of rumen propionate for 4 hours. A linear regression equation was calculated from the natural logs of decreasing specific activity. Propionate pool sizes averaged 30.6 and 47.4 g, and production rates averaged 579 and 1032 g/day at feed intakes of 275 and 500 g/2 hours. Thus, propionate production changed in almost direct proportion to feed intake. Acetate to propionate ratios were about 3:1 in rumen fluid. Considerable variability in estimates of propionate pool sizes and production rates was found both within and among steers. The results indicate propionate production is nearly equivalent to blood glucose turnover determined previously; all propionate produced in the rumen, however, is not used for glucose synthesis.

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“…Rumen fermentation rapidly converts plant carbohydrates into VFA allowing little soluble carbohydrate to reach the small intestine. Therefore, the adult ruminant relies heavily on gluconeogensis to provide the necessary glucose (Young et al, 1974).…”

Section: Gluconeogenesismentioning

confidence: 99%

“…Gluconeogenic capability of these animals increases with age allowing for a successful transition (Young et al, 1974). However, solid feed must be offered to produce rumen VFA.…”

Section: Gluconeogenesismentioning

confidence: 99%

Effect of forage addition to the diet on rumen development in calves

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Gluconeogenesis in Ruminants: Glucose Kinetic Parameters in Calves under Standardized Conditions

Cited by 23 publications

References 27 publications

Changes in the Metabolism of the Shivering Hind Leg of the Young Ox During Several Days of Continuous Cold Exposure

Changes in the Metabolism of the Shivering Hind Leg of the Young Ox During Several Days of Continuous Cold Exposure

Gluconeogenesis in Ruminants: Propionic Acid Production from a High-Grain Diet Fed to Cattle

Effect of forage addition to the diet on rumen development in calves

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