Vascular Sources of Phenylalanine, Tyrosine, Lysine, and Methionine for Casein Synthesis in Lactating Goats

Bequette, B.J.; Backwell, F.R.C.; Kyle, C.E.; Calder, Andrew A.; Buchan, Vivien; Crompton, L.A.; MacRae, J.C.

doi:10.3168/jds.s0022-0302(99)75243-4

Cited by 55 publications

(46 citation statements)

References 36 publications

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“…delivery from red blood cells [33,45] or from peptide breakdown. The putative contribution from peptides to milk phenylalanine and tyrosine has been shown to increase as the arterial supply of the free amino acids decreased in lactating goats [5]. In the current study, therefore, the peptide contribution to milk methionine and histidine may be a consequence of their low arterial concentrations as a free source.…”

Section: Mammary Metabolismmentioning

confidence: 70%

The effect of jugular or abomasal infusion of amino acids on milk yield in lactating cows fed a protein deficient diet

et al. 2002

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-The influence of first-pass splanchnic metabolism was investigated by comparing the response of 5 lactating cows to an infusion of an amino acid mixture into the abomasum or a jugular vein over 5 d according to a complete block design. The basal diet and the amino acid infusion provided 71% and 14% of crude protein requirements, respectively. The jugular infusion increased (P = 0.01) milk yield by 0.80 kg in comparison to the abomasal infusion, but milk protein yield was not altered. The jugular infusion tended to increase (P = 0.06) the arterial concentration of total essential amino acids by 11% relatively to the abomasal infusion. Mammary plasma flow and net fluxes of amino acids and glucose were not affected by the infusion sites. Variations in essential amino acid concentrations suggest that splanchnic metabolism alters peripheral delivery of amino acids but the recirculation of amino acids within the animal decreased the impact of the first-pass splanchnic metabolism on lactational performances. amino acid / cow / infusion / milk yield / proteinRésumé -Effet d'une perfusion jugulaire ou abomasale d'acides aminés sur la production laitière de vaches en lactation alimentées avec une ration déficiente en protéine. L'influence du premier passage des acides aminés dans le tissu splanchnique a été étudiée en comparant la réponse de 5 vaches laitières à des perfusions abomasale ou jugulaire administrées durant 5 j selon un dispositif en blocs complets. La ration de base et la perfusion d'acides aminés fournissaient 71 % et 14 % des besoins en protéine brute, respectivement. La perfusion jugulaire a augmenté (P = 0,01) la Reprod. Nutr. Dev. 42 (2002)

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Section: Mammary Metabolismmentioning

confidence: 70%

The effect of jugular or abomasal infusion of amino acids on milk yield in lactating cows fed a protein deficient diet

et al. 2002

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“…This suggests that in the high-CP diets, as a result of greater amounts of absorbed CP, larger plasma pools of AA occurred. Larger plasma fluxes of Phe, Met and Lys were observed when Phe or Lys plus Met were infused intravenously into dairy goats at different stages of lactation (Bequette et al, 1999;Mabjeesh et al, 2000). Despite the apparent evidence of more EAA absorbed in the high-CP diets and during LM infusion, milk production was similar among treatments, raising the question of the metabolic fate of these AA at the mammary gland and whole body levels.…”

Section: Discussionmentioning

confidence: 88%

“…Plasma flow measured in this study might be over estimated because certain amount of Phe and Tyr (up to 11% for Phe and 25% for Tyr; Bequette et al, 1999) might be taken up across the mammary gland as plasma-circulating peptides. In order to compare uptake of EAA across the mammary gland, however, it was assumed that the experimental accuracy was similar for all treatment.…”

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

J. Anim. Feed Sci.

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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.

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“…Insufficient uptake of isoleucine and leucine seen in this study suggests that the methionine based blood flow calculations may be underestimating the contribution of the plasma free AA to milk protein output, and that plasma flow was underestimated using this method. Some of this apparent deficit could be reduced by the use of alternative sources of AA, such as erythrocytes and peptides, and there is evidence of AA supply from these sources in studies by Bequette et al (1999) and Pacheco-Rios et al (1999). Pacheco-Rios et al (1999) demonstrated that AA uptake from plasma was insufficient for milk protein output of histidine, lysine, phenylalanine and tyrosine in pasture-fed cows in early lactation.…”

Section: Discussionmentioning

confidence: 99%

“…For histidine, there was a deficit in both plasma and blood, and it appears that for this AA, the blood supply may not be the only precursor pool (Pacheco-Rios et al, 1999). In lactating goats, Bequette et al (1999) showed that between 5% and 25% of the supply of lysine, methionine, phenylalanine and tyrosine for casein synthesis came from circulating peptides. These may be some of the mechanisms that support milk Regulation of mammary amino-acid metabolism by insulin protein output when precursor supply is insufficient, such as in early lactation or with restricted feed.…”

Section: Discussionmentioning

confidence: 99%

Insulin regulation of amino-acid metabolism in the mammary gland of sheep in early lactation and fed fresh forage

Sinclair

Back

Davis

et al. 2009

Animal

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Insulin plays an important role in regulating the partitioning of nutrients to the mammary gland, particularly in lactating ruminants fed concentrate-based diets. There is evidence that the nutritional status of the animals might also affect their response to insulin. This is largely untested in early lactating ruminants fed fresh forage. To investigate nutritional effects on insulin response, 12 lactating sheep, housed indoors, were allocated to one of two treatment groups (hyperinsulinaemic euglycaemic clamp (HEC) or control) in a randomised block design and fed perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) pasture. Mammary amino acid (AA) net uptake from plasma and utilisation for milk protein synthesis was measured during the 4th day of the HEC using arterio-venous concentration differences, and 1-13 C-leucine was used to estimate whole body and mammary gland leucine kinetics. There was no change in feed intake, milk protein output and mammary blood flow during the HEC ( P . 0.1). The HEC decreased ( P , 0.1) the arterial concentrations of all essential AA (EAA) except histidine. The mammary net uptake of some EAA (isoleucine, leucine, methionine and phenylalanine) was reduced by the HEC ( P , 0.1). Leucine oxidation in the mammary gland was not altered during the HEC ( P . 0.1) but mammary protein synthesis was reduced by the HEC ( P , 0.05). These results show that sheep mammary gland can adapt to changing AA precursor supply to maintain milk protein production during early lactation, when fed fresh forage. How this occurs remains unclear, and this area deserves further study.

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Vascular Sources of Phenylalanine, Tyrosine, Lysine, and Methionine for Casein Synthesis in Lactating Goats

Cited by 55 publications

References 36 publications

The effect of jugular or abomasal infusion of amino acids on milk yield in lactating cows fed a protein deficient diet

The effect of jugular or abomasal infusion of amino acids on milk yield in lactating cows fed a protein deficient diet

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

Insulin regulation of amino-acid metabolism in the mammary gland of sheep in early lactation and fed fresh forage

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