Blood flow and nutrient exchange across the liver and gut of the dairy cow

Abstract

1. The rate of blood flow in the portal and hepatic veins, and the net exchange across the gut and liver of volatile fatty acids (VFA), glucose, lactate, pyruvate, amino acids, ketone bodies, glycerol, non-esterified fatty acids (NEFA) and oxygen, were measured in lactating and non-lactating cows (a) in the normal, fed state and (b) before, during and after 6 d of fasting.2. Blood flow rate through the liver was 52% higher in normal, fed, lactating cows as compared with non-lactating cows, and was decreased by fasting in both groups of cows. Portal blood flow rate increased with an increase in metabolizable energy (ME) intake.3. Lactating, as compared with non-lactating, cows exhibited lower arterial concentrations of glucose and lactate, higher net portal outputs of VFA and ketone bodies, a higher net hepatic output of glucose, and higher net hepatic uptakes of propionate and lactate. The splanchnic outputs of acetate, glucose and hydroxybutyrate were all apparently greater in the lactating cows.4. Fasting caused a rapid decrease in the blood concentrations of the VFA and an increase in those of glycerol and NEFA. The portal, i.e. gut, outputs of VFA, lactate, ketone bodies, alanine and (serine+ threonine), and the portal uptake of 0,, were all decreased by fasting. Fasting for 6 h also decreased the hepatic output of glucose and acetate by 77 and 95% respectively, increased the hepatic uptake of pyruvate, glycerol and NEFA, and doubled hepatic ketone-body output. The splanchnic output of acetate and glucose and the splanchnic uptake of 0, were also decreased by fasting. 5.The net portal outputs of VFA, lactate and hydroxybutyrate, and the net hepatic output of glucose, were all correlated with ME intake in fed and fasted cows. Hepatic glucose output was also correlated with milk yield. 6. The net hepatic uptake of gluconeogenic precursors measured in this study could account for net hepatic glucose output in the fasted cows, but not in the fed cows. The net hepatic uptake of the ketogenic precursors butyrate and NEFA was sufficient to account for the hepatic output of ketone bodies in both fed and fasted cows, but it is unlikely that the hepatic uptake of ketogenic precursors could also account for the observed hepatic output of acetate.The gut and liver of the dairy cow can be considered to operate together as a functional unit, termed the splanchnic bed, that supplies nutrients to the remainder of the body. During lactation the splanchnic bed plays a major role in supplying precursors required for milk synthesis. Therefore, changes in metabolite flux across the splanchnic bed will be expected to have major effects on milk synthesis and on the metabolic status of the animal. Alterations in splanchnic metabolism could arise as a result of variation in feed intake or of metabolic events associated with milk production.In the present study the effects of differences in feed intake were monitored by comparing fed and fasted cows, while the effects of differences in productive demand were monitored by comparing la...

Responses of hepatic blood flows to changes in intake in sheep: a meta-analysis

“…In Below Maintenance and Below 1 Above The Maintenance metabolisable energy requirement was set at 150 kJ MEI/kg BW per day for the present study (INRA, 1988 The relationship of Webster et al (1975) between portal blood flow (PBF; l/min) and MEI (MJ/24 h) was: PBF 5 1.326 1 0.554 e (0.0978 3 MEI) . c The relationship of Lomax and Baird (1983) between portal blood flow (PBF; l/kg BW 0.75 per hour) and MEI (MJ/kg BW 0.75 per day) was: PBF 5 4.745 e (0.813 3 MEI) .…”

Revue bibliographique : Variations quantitatives et métabolisme des lipides dans les tissus adipeux et le foie au cours du cycle gestation-lactation 2e partie : chez la brebis et la vache

“…Chez les ruminants, la néoglucogenèse dépend en premier lieu des entrées de précurseurs exogènes, c'est-à-dire des quantités d'aliments ingérées (Elliot, 1980 ;Lomax et Baird, 1983 (Oldham et Lindsay, 1983 ;Journet et al, 1983 ;Rémésy et al, 1984Rémésy et al, , 1986 (Ford, 1959 ;Reid, 1980 ;Mazur et al, 1986b) qui peut être fortement accentuée par le jeûne (Brumby et al, 1975 ;Reid et al, 19791. La Gerloff et al, 1986a ;Rayssiguier et al, 1986b) mais pas systématiquement (Perkins et al, 1983 ;Reid et al, 1986).…”

Quantitative aspects of blood and amino acid flows in cattle

“…Blood flow through the splanchnic tissues Observations were taken from 28 publications concerning growing steers, heifers or cows to build a file of 120 observations (Baird et al, 1975;Casse et al, 1994;Early et al, 1987;Eisemann and Huntington, 1994;Eisemann and Nienaber, 1990;Gross et al, 1988;Guerino et al, 1991;Hammond et al, 1987;Harmon et al, 1988Harmon et al, , 1993Huntington, 1982Huntington, , 1984Huntington, , 1987Huntington and Prior, 1983;Huntington et al, 1983Huntington et al, , 1990Krehbiel et al, 1992;Kreikemeier et al, 1991;Lomax and Baird, 1983;McGuire et al, 1989;Prior ual (1986). Interestingly, these flows could also be fitted with S-shaped curves (Moore, 1985 (Sauvant, 1994), the level of energy intake which increased hepatic and portal blood flows.…”