Absorption, Plasma Flux and Oxidation of L-Leucine in Heifers at Two Levels of Intake1

Ac, Hammond; Gb, Huntington; Pj, Reynolds; Hf, Tyrrell; Jh, Eisemann

doi:10.2527/jas1987.642420x

Cited by 16 publications

(18 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For all AA, dietary restriction resulted in a numerical decrease in ILR irrespective of the type of sample (whole blood or plasma) analysed. Similar effects of feed intake on Leu ILR have been reported in beef cattle (Hammond et al 1987;Lobley et al 1987;Lapierre et al 1996Lapierre et al , 1999, sheep (Liu et al 1995) and dairy goats (Riis, 1988). The only exception to this finding was Glu, for which the ILR in restricted animals was numerically higher.…”

Section: Discussionsupporting

confidence: 74%

“…One way to measure the total body flux of an AA in animals is by quantifying the dilution of a tracer substance (Reeds, 1992;Lobley, 1993). Both radioactive (Hammond et al 1987;Lobley et al 1987;Crompton & Lomax, 1993) and stable isotopes (Bequette et al 1994;Liu et al 1995;Lapierre et al 1996Lapierre et al , 1999 have been used to label AA for this purpose. A technique using the infusion of a mixture of 13 C-universally labelled AA of algal origin has allowed the simultaneous estimation of the whole-body fluxes of an array of AA.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Whole-body fluxes and partitioning of amino acids to the mammary gland of cows fed fresh pasture at two levels of intake during early lactation

et al. 2003

View full text Add to dashboard Cite

The utilisation of essential amino acids (EAA) by the mammary gland of lactating dairy cows fed fresh forages was studied to provide basic information useful in designing strategies to increase the production of milk protein from pasture-fed dairy cows. The relationship between the flux of EAA in the whole body and their uptake by the mammary gland was determined in four cows in early lactation (length of time in milk 44 (SD 14·5) d) producing 21 (SD 4·0) kg milk/d. The cows were maintained in metabolism stalls and fed fresh perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) pasture ad libitum or restricted to 75 % ad libitum intake. The whole-body fluxes of amino acids (AA) were measured using an arterio-venous infusion of universally 13 C-labelled AA. Whole-body fluxes of fourteen AA were estimated. Isotope dilution indicated that mammary utilisation accounted for one-third of the whole-body flux of EAA, with individual AA ranging between 17 and 35 %. Isoleucine, leucine, valine and lysine were the EAA with the greatest partitioning towards the mammary gland (up to 36 % of the whole-body flux), which could reflect a potentially limiting effect on milk protein synthesis. In the case of AA with low partitioning to the mammary gland (for example, histidine), it is suggested that non-mammary tissues may have priority over the mammary gland and therefore the supply of this AA may also limit milk protein synthesis.

show abstract

Section: Discussionsupporting

confidence: 74%

mentioning

confidence: 99%

Whole-body fluxes and partitioning of amino acids to the mammary gland of cows fed fresh pasture at two levels of intake during early lactation

et al. 2003

View full text Add to dashboard Cite

show abstract

“…03 of plasma LeuTR, the isotope infused would not influence plasma LeuTR. Plasma LeuTR was comparable with those reported in growing cows (Hammond et al 1987;Dawson et al 1998;Lapierre et al 1999). Lobley et al (1987) studied the effect of progressive reduction in food intake on WBPS with the [1-14 C]Leu method in finishing beef steers and found that food intake influenced overall protein metabolism.…”

Section: Discussionsupporting

confidence: 70%

Effect of metabolizable protein intake on rates of plasma leucine turnover and protein synthesis in heifers

et al. 2007

View full text Add to dashboard Cite

SUMMARYAn isotope dilution method using [1-13C]leucine (Leu) infusion together with open-circuit calorimetry was applied to determine the effect of metabolizable protein (MP) intake on rates of plasma Leu turnover and whole body protein synthesis (WBPS) in six heifers. WBPS rate was estimated from rate of plasma Leu turnover and Leu oxidation to carbon dioxide. The experiment consisted of three levels of MP intake and was conducted in a two 3×3 Latin square designs of three 21-day periods. The experimental diet consisted of mixed hay, maize and soybean meal. Dietary MP intake of each dietary treatment was 4·3, 4·5 and 4·9 g/kg BW0·75/day by changing maize and soybean meal weights. Metabolizable energy (ME) intake was similar for all dietary treatments. When plasma α-[1-13C]keto-isocaproic acid enrichments were used as markers indicating intracellular Leu enrichments, plasma Leu turnover rate (LeuTR) increased (P=0·012) and WBPS tended to increase (P=0·091) as MP intake increased. In contrast, plasma LeuTR and WBPS were not influenced if plasma [1-13C]Leu was taken to indicate intracellular Leu enrichments. Total and plasma Leu oxidation rates did not change but intracellular Leu oxidation increased (P=0·044) with increasing MP intake. In heifers, it is suggested that rates of plasma Leu turnover and WBPS are influenced by dietary MP intake, independent of ME intake, although the change in MP intake was relatively small.

show abstract

“…Based on the lack of a dietary difference in the rate of whole-body protein synthesis, it might therefore be concluded that in the present experiment duodenal flows of amino acids were similar for the two diets. This is unlikely though, as the greater leucine entry and oxidation rates, and greater plasma leucine concentrations of animals fed dried grass (Table 5), are indicative of greater leucine absorption on this diet, as these parameters have been shown to be a function of intake (Meguid et al 1986;Hammond et al 1987;Lapierre et al 2002;Savary-Auzeloux et al 2003). This is supported by the effect of MEI, and thus protein intake as the relative composition of the diets remained unchanged, on these parameters associated with whole-body protein metabolism.…”

Section: Protein Metabolismmentioning

confidence: 90%

Fat and protein metabolism in growing steers fed either grass silage or dried grass

et al. 2006

View full text Add to dashboard Cite

Cattle fed grass silage diets have been reported to have high carcass fat:protein ratios. The effect of grass silage and dried grass diets, fed at different levels of intake to ensure a range of equivalent metabolisable energy intakes (MEI) from 1 ·1 £ metabolisable energy requirement for maintenance to ad libitum, on fat and protein metabolism in twenty-four Hereford £ Friesian steers was investigated. After about 84 d of dietary treatment rates of whole-body fat and protein metabolism were measured, as were rates of lipogenesis in omental, perirenal and subcutaneous adipose tissue. Carcass composition was determined. Animals fed silage had greater (P,0 ·001) carcass fat:protein ratios than animals fed dried grass at equivalent levels of MEI. Animals fed silage had lower (P,0 ·001) rates of protein gain. Rates of leucine entry and oxidation were lower (P,0 ·001) in animals fed silage, but there was no dietary difference in the rate of whole-body protein synthesis. There was no dietary difference in the rate of carcass fat gain, but rates of lipogenesis in perirenal adipose tissue were significantly (P¼ 0 ·007) higher in animals fed silage. There was no dietary difference in the rate of palmitate and glycerol entry or palmitate oxidation. There were no interactions between MEI and diet, indicating that increments of energy were utilised with the same efficiency from both diets. It was concluded that the high carcass fat: protein ratios of young growing steers was due to limited rates of protein accretion and not to elevated rates of carcass fat accretion. Grass silage forms the basis of many winter diets fed to beef cattle in the UK. The performance of animals fed silage is variable and often disappointing in terms of feed intake and the overall efficiency of energy (Thomas & Chamberlain, 1990) and amino acid (Beever et al. 1992;MacRae et al. 1995) utilisation. It has been reported that animals fed silage have a high carcass fat:protein ratio (Lonsdale, 1976;Moore & Steen, 1983;Baker et al. 1985Baker et al. , 1992Steen & Moore, 1988Steen, 1991). That protein deposition is limited in animals fed grass silage is now well established (Gill et al. 1987). Whether or not fat deposition is increased in these animals is unclear.With continuing pressures to increase the utilisation of grass in ruminant production systems, a greater understanding of the partition of nutrients between fat and protein deposition in animals fed grass silage is required if useful models to predict animal performance are to be developed. The objective of the present study was to determine whether or not an increased fat deposition contributes to the high carcass fat:protein ratio of animals fed grass silage by simultaneously investigating fat and protein metabolism, using isotope dilution and incorporation techniques, and carcass composition of young, growing steers fed either grass silage or dried grass. As both the quantity and form of metabolisable energy (ME) are considered to be important determinants of animal performance (Beever et al. ...

show abstract

Absorption, Plasma Flux and Oxidation of L-Leucine in Heifers at Two Levels of Intake1

Cited by 16 publications

References 10 publications

Whole-body fluxes and partitioning of amino acids to the mammary gland of cows fed fresh pasture at two levels of intake during early lactation

Whole-body fluxes and partitioning of amino acids to the mammary gland of cows fed fresh pasture at two levels of intake during early lactation

Effect of metabolizable protein intake on rates of plasma leucine turnover and protein synthesis in heifers

Fat and protein metabolism in growing steers fed either grass silage or dried grass

Contact Info

Product

Resources

About