Changes in mammary metabolism in response to the provision of an ideal amino acid profile at 2 levels of metabolizable protein supply in dairy cows: Consequences on efficiency

Abstract

The aim of this study was to compare the modifications in mammary gland metabolism by supplying an ideal versus an imbalanced essential AA (EAA) profile at low and high metabolizable protein (or PDIE, its equivalent in the INRA feeding system). Four lactating, multiparous Holstein cows received 4 treatments composed of 2 basal diets containing 2 levels of PDIE (LP or HP) and 2 different infusions of AA mixtures (AA- or AA+) in the duodenum. The AA+ mixture contained Lys, Met, Leu, His, Ile, Val, Phe, Arg, Trp, and Glu, whereas the AA- mixture contained Glu, Pro, and Ser. The infusion mixtures were iso-PDIE. The diet plus infusions provided 13.9 versus 15.8% of crude protein that corresponded to 102 versus 118g/kg of dry matter of PDIE in LP and HP treatments, respectively. The treatments were designed as a 2×2 crossover design of 2 levels of PDIE supply (LP vs. HP) with 28-d periods. Infusions of AA in the duodenum (AA- vs. AA+) were superimposed to diet within each 28-d period according to 2×2 crossover designs with 14-d subperiods. Increasing the PDIE supply tended to increase milk protein yield; however, the efficiency of PDIE utilization decreased and the plasma urea concentration increased, indicating a higher catabolism of AA. The AA+ treatments increased milk protein yield and content similarly at both levels of protein supply. This was explained by an increase in the mammary uptake of all EAA except His and Trp. The mammary uptake of non-EAA (NEAA) was altered to the increase in EAA uptake so that the total AA uptake was almost equal to milk protein output on a nitrogen basis. The ratio between NEAA to total AA uptake decreased from 46% in LPAA- to 40% in LPAA+, HPAA-, and HPAA+ treatments. The PDIE efficiency tended to increase in the AA+ versus the AA- treatments because the NEAA supply and the amount of NEAA not used by the mammary both decreased. Nevertheless, our AA+ treatments seemed not to be the ideal profile: the mammary uptake-to-output ratio for Thr was higher than 1 in LPAA-, but it decreased to 1 in all the other treatments, suggesting that Thr was deficient in these treatments. Conversely, an excess of His was indicated because its uptake was similar in AA+ and AA- treatments. In conclusion, balancing the EAA profile increased milk protein yield and metabolizable protein efficiency at both levels of protein supply by increasing the mammary uptake of EAA and altering the NEAA uptake, leading to less AA available for catabolism.

Mammary gland utilization of amino acids and energy metabolites differs when dairy cow rations are isoenergetically supplemented with protein and fat

“…Factors such as lack of steady-state feeding, fewer blood samples taken over the milking interval, and larger cow variation are limitations of the current study and place a limit of accuracy on the U:O measurements that should be accepted. Although the absolute values for U:O for the group 1 AA and for total AA indicate some discrepancy on the whole, the relative differences in response to PT 5 (no effect on the total group 1 AA, increased group 2 AA) align with other studies performing mammary AA net balance under conditions of supplemental MP (Raggio et al, 2006;Haque et al, 2015). Previous mammary balance studies have produced total AA balances greater than or equal to unity (Raggio et al, 2006;Doepel and Lapierre, 2010), but some studies present values near 0.90 (Larsen et al, 2014(Larsen et al, , 2015, with values ranging from 0.83 to 0.96 within a study (Larsen et al, 2014).…”

Diets rich in starch improve the efficiency of amino acids use by the mammary gland in lactating Jersey cows

“…However, when the power analysis was carried out for the 2 most important metabolic measurements to be analyzed in the present study (AA and glucose mammary net fluxes of AA and glucose), taking into account residual variances from published data (Lemosquet et al, 2009;Haque et al, 2015), reasonable effect size (20%; Rulquin et al, 2004;Rius et al, 2010), and sample size equal to 10 individuals per CHO level, the resulting statistical power ranged from 0.5 to 0.6. A linear mixed model using the LME procedure within the nlme package (Pinheiro et al, 2008) in R software (R Development Core Team, 2009) and including a random intercept term for each cow was used.…”

“…One of the most effective ways in dairy cattle to increase MNE (Huhtanen and Hristov, 2009), and then to reduce the manure N output (Yan et al, 2006), is to reduce the dietary CP content. However, low-protein diets may dramatically affect milk protein yield unless other dietary components, such as dietary energy content (Hanigan et al, 1998a) or AA profile (Haque et al, 2015), are concurrently modified.…”

Essential amino acid ratios and mTOR affect lipogenic gene networks and miRNA expression in bovine mammary epithelial cells

“…Despite the lack of effect on milk fat yield, the higher ratio of Lys to Val used in the present study was to mimic the lowest level of Val recommended in the literature [ 20 ]. Similarly, the chosen ratio of Thr to Phe was to maintain it as close as possible to the theoretical optimal (~1.0:1.0) as discussed in Haque et al [ 1 ]. The Lys to Thr ratios were chosen based on data from Prizant and Barash [ 9 ].…”

“…Previous research has underscored that provision of adequate levels of essential AA (EAA) is critical for improving N utilization efficiency as well as maximizing bovine milk protein synthesis [ 1 ]. Rulquin et al [ 2 ] proposed “ideal” values for intestinal absorption of EAA in dairy cows; however, after absorption, AA flow first to the liver where substantial and differential net removal occurs leading to marked alterations in the pattern of AA that can be supplied to the mammary gland [ 3 ].…”