Maintenance of plasma branched-chain amino acid concentrations during glucose infusion directs essential amino acids to extra-mammary tissues in lactating dairy cows

Abstract

The objectives of this study were to investigate the effects of branched-chain AA (BCAA) supplementation when glucose is infused postruminally into lactating dairy cows consuming a diet low in crude protein (CP) and to test the hypothesis that low BCAA concentrations are responsible for the poor stimulation of milk protein yield by glucose. Twelve early-lactation Holstein cows were randomly assigned to 15% and 12% CP diets in a switchback design of 6-wk periods. Cows consuming the 12% CP diet received 96-h continuous jugular infusions of saline and 1 kg/d of glucose with 0, 75, or 150 g/d of BCAA in a Latin square sequence of treatments. Compared with saline, glucose infusion did not affect dry matter intake but increased milk yield by 2.2 kg/d and milk protein and lactose yields by 63 and 151 g/d, respectively. Mammary plasma flow increased 36% during glucose infusion compared with saline infusion, possibly because of a 31% decrease in total acetate plus β-hydroxybutyrate concentrations. Circulating concentrations of total essential AA and BCAA decreased 19 and 31%, respectively, during infusion of glucose, yet net mammary uptakes of AA remained unchanged compared with saline infusion. The addition of 75 and 150 g/d of BCAA to glucose infusions increased arterial concentrations of BCAA to 106 and 149%, respectively, of the concentrations in saline-infused cows, but caused a decrease in concentrations of non-branched-chain essential AA in plasma, as well as their mammary uptakes and milk protein yields. Plasma urea concentration was not affected by BCAA infusion, indicating no change in catabolism of AA. The lack of mammary and catabolic effects leads us to suggest that BCAA exerted their effects on plasma concentrations of the other essential AA by stimulating utilization in skeletal muscle for protein accretion. Results indicate that the glucose effect on milk protein yield was not limited by low BCAA concentrations, and that a stimulation of extra-mammary use of non-branched-chain essential amino acids by BCAA led to a decrease in milk protein yield.

Inhibition of enteric methanogenesis in dairy cows induces changes in plasma metabolome highlighting metabolic shifts and potential markers of emission

“…This can be achieved for instance by exploiting the list of reactions belonging to the sub-network connecting the discriminant metabolites (see supplementary table S5). Nevertheless, it has been reported that increased levels of rumen propionic acid (see below) and glucose, as has been observed in this work, are associated with lower concentrations of branched-chain amino acids in cows plasma 43,44 .…”

Plasma essential amino acid concentrations in response to casein infusion or ration change in dairy cows: A multilevel, mixed-effects meta-analysis

“…These observations are in agreement with studies that reported a decrease in p[BCAA] when dairy cows were fed starchy diets (Cantalapiedra-Hijar et al, 2014), when glucose was infused intravenously (Toerien et al, 2010;Curtis et al, 2014Curtis et al, , 2018 or postruminally (Hurtaud et al, 1998;Lemosquet et al, 2009;Nichols et al, 2016), or when a gluconeogenic substrate was infused in the rumen (propionate; Raggio et al, 2006;Lemosquet et al, 2009) or postruminally (starch; Rius et al, 2010a). The suppressive effect of increased energy supply on p[BCAA] is associated with increased insulin secretion (Rius et al, 2010a;Nichols et al, 2016), an effect well demonstrated during the hyperinsulinemiceuglycemic clamp technique in dairy cows (Laarveld et al, 1981;Griinari et al, 1997;L'Espérance, 2000;Mackle et al, 2000) and other species (Castellino et al, 1990;Tesseraud et al, 1992;Bequette et al, 2001).…”

Energy and nitrogen partitioning in dairy cows at low or high metabolizable protein levels is affected differently by postrumen glucogenic and lipogenic substrates

“…When combined with infusions of casein or AA mixtures, glucose or glucose precursors stimulate milk protein yield in some studies (Raggio et al, 2006;Rius et al, 2010a), but not in all (Clark et al, 1977;Nichols et al, 2016). However, when circulating AA levels are abundant, exogenous glucose appears to have an effect on AA storage in extra-mammary tissues rather than on the stimulation of milk protein synthesis (Clark et al, 1977;Nichols et al, 2016;Curtis et al, 2018), possibly through the anabolic action of insulin on skeletal muscle (Lobley, 1998) and adipose (Griinari et al, 1997). In agreement with this hypothesis, 13% of N intake was retained on HMP-GG, compared with 6% on HMP-C, with no appreciable change in milk N output (1% of N intake) between treatments.…”

“…However, increasing glucogenic energy at low and high levels of protein supply can improve postabsorptive AA transfer efficiency from the gut to milk protein by reducing AA catabolism across the gut and the splanchnic bed, potentially improving mammary gland supply (Rius et al, 2010b). In combination with high circulating AA levels, glucogenic energy may also support N retention by stimulating AA partitioning toward extra-mammary tissues (Clark et al, 1977;Nichols et al, 2016;Curtis et al, 2018).…”