Whole Blood and Plasma Amino Acid Uptakes by Lactating Bovine Mammary Glands

The response in dairy cows fed high-concentrate diets to abomasal infusion of lysine (Lys) and methionine (Met) at two levels of dietary CP was examined. Four multiparous Israeli Holstein cows (day in milk=l 80±30, means ± SE) were utilized in a 4x4 Latin square design experiment that included a 2x2 factorial arrangement with 18-d periods. Cows were surgically prepared with abomasal cannulae and catheters implanted in the costoabdominal artery. Two diets were composed to contain high and low crude protein (CP) content (152 vs 132 g/kg dry matter). Abomasal infusion of either water or Lys (38 g/d) plus Met (14 g/d) was performed with each diet. On the last day of the experimental period the metabolism of amino acids (AA) across the mammary gland was monitored. Dry matter intakes and milk and protein yields were not affected by either dietary CP level or postruminal infusion of Lys plus Met and averaged 15.9, 21.4, and 0.694 kg/d, respectively. Milk fat content and yield were not affected by dietary CP concentration, but did increase with abomasal infusion of Lys plus Met (33.3 vs 37.2 g/kg; PO.04, and 0.703 vs 0.762 kg/d; PO.05, respectively). Arterial plasma concentration of Lys and Met increased by 2.4-and 3.5-fold, respectively, when these AA were infused abomasally.

Section: Discussionmentioning

confidence: 99%

Responses of cows to abomasal infusion of lysine and methionine at two levels of dietary protein

Mabjeesh¹,

Smoler²,

Abramson³

et al. 2002

“…Moreover, the difference in flux of glutamate and glutamine in the red blood cells of the fed compared to unfed pigs suggests that this blood pool has a specific counter current role to that of plasma in transporting amino acids destine for deamination to a-ketoglutarate and subsequent glucose synthesis in the liver. Hanigan et al (1991) discussed the counter current role of red blood cells for transporting amino acids in the opposite direction of the plasma free amino acid pool in dairy cows. Red blood cells may also have an ancillary function in the renal-intestinal transport and exchange of urea cycle intermediates based on the concentrations of citrulline and ornithine in the arterial red blood cells of the fed pigs.…”

Section: Plasmamentioning

confidence: 99%

“…On the other hand, total concentration of amino acids in the arterial red blood cells of fed compared to unfed pigs suggest that this blood pool also has a role in the transport of free amino acids that has been reported for other animals. For instance, transport of amino acids in red blood cells have been reported in cattle (Hanigan et al, 1991;Koeln et al, 1993), dogs (Elwyn, 1966;Elwyn et al, 1968), sheep (Young and Ellory, 1977;Heitmann and Bergman, 1980) and humans (Felig et al, 1973). Moreover, the difference in flux of glutamate and glutamine in the red blood cells of the fed compared to unfed pigs suggests that this blood pool has a specific counter current role to that of plasma in transporting amino acids destine for deamination to a-ketoglutarate and subsequent glucose synthesis in the liver.…”

Section: Plasmamentioning

confidence: 99%

“…Arginine is not an indispensable amino acid in older pigs because of it's de novo synthesis in the kidneys using citrulline as a precursor (Wu et al, 1994). Hanigan et al (1991) classified the red blood cell transport of citrulline and ornithine as being counter current and equal with the plasma free amino acid pool, respectively, based on arterial-venous differences in dairy cows. The red blood cells of pigs may have a similar role.…”

Section: Plasmamentioning

confidence: 99%

See 1 more Smart Citation

Flux of amino acids and peptides across the portal vein-drained tissue of pigs

Caine¹,

Verstegen²,

Sauer³

et al. 1999

An experiment was carried out to determine the flux of amino acids across the portal veindrained tissue into and out of the plasma and red blood cell free amino acid pools and the plasma peptide pool of the portal vein blood of growing pigs. Four pigs, fitted with catheters in a carotid artery and the portal and mesenteric veins, were fed a maize starch-based diet with wheat gluten as protein source. The feed was given daily at the level of 2% body weight as a wet mash (1:2, w/v water) in two equal meals at 08.00 and 16.00 h. After 5-d adaptation to diet, the pigs received their 08.00 h meal and, subsequently, were not fed again for 28 h. At 4 (fed) and 28 (unfed) h after receiving the meal, simultaneous 8 mL blood samples were taken from the portal vein and carotid artery of each pig. The flow of whole blood and plasma were determined by the indicator-dilution method, using continuous infusion of /?-aminohippuric acid into the mesenteric vein. Blood sampling and flow measurements were repeated 5 d later. Total flux of amino acids were higher (P=0.02) in the plasma (55.7 vs 1.9 mmol/h) and plasma peptide (123.2 vs -1.2 mmol/h) pools of portal vein blood of fed compared to unfed pigs, respectively. Corresponding total flux in the red blood cell pool (77.5 vs 5.9 mmol/h) was not statistically significant (P=0.29) because of a large standard error 4 Corresponding author 28 FLUX OF AMINO ACIDS ACROSS PORTAL VEIN WALL due to inconsistency between the pigs and accumulated analytical variation. A substantial proportion of the amino acids in the plasma peptide pool of portal vein blood of fed pigs were of dietary origin based on a similar amino acid profile to that of wheat gluten. In conclusion, the plasma free amino acid and plasma peptide pools, and probably the red blood cell free amino acid pool, of portal vein blood are involved in the flux of amino acids across the portal vein-drained tissue of pigs.

“…The Fick method is still widely used (Hanigan et al, 1991;Hanigan et al, 1992;Cant et al 1993), though several of the necessary assumptions are often invalid over short time periods. Blood flow to any organ is usually variable over time (Mepham, 1982), and arterial concentration of most metabolites varies with time, influenced largely by stage of lactation and the cows feeding regime.…”

Section: Blood Flowmentioning

confidence: 99%

Towards a mechanistic model of amino acid uptake and metabolism by the mammary gland of the lactating dairy cow: A literature review

Mass¹,

France²,

McBride³

1998

A,review is given of information available to produce a dynamic mechanistic model of amino acid uptake and subsequent intracellular metabolism including milk and tissue protein synthesis within the lactating bovine mammary gland. To be a truly mechanistic representation of actual biology the model must address each AA individually, uptake via transporters must be described bidirectionally as has been observed in vitro and in vivo, and the requirements for all mammary origin milk proteins including oc-lactalbumin and B-lactoglobulin must be addressed. A conceptual framework for such a model is advanced.