Plasma essential amino acid concentration and profile are associated with performance of lactating dairy cows as revealed through meta-analysis and hierarchical clustering

Authors: LETELIER, PAULINA - University Of Wisconsin; Zanton, Geoffrey; DOREA, JOAO - University Of Wisconsin; WATTIAUX, MICHEL - University Of Wisconsin

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/16/2022
Publication Date: 5/4/2022
Citation: Letelier, P., Zanton, G.I., Dorea, J.R., Wattiaux, M.A. 2022. Plasma essential amino acid concentration and profile are associated with performance of lactating dairy cows as revealed through meta-analysis and hierarchical clustering. Journal of Dairy Science. 105(6):5044-5061. https://doi.org/10.3168/jds.2021-21028.
DOI: https://doi.org/10.3168/jds.2021-21028

Interpretive Summary: A meta-analysis was conducted to determine the association between plasma essential amino acid (EAA) profile, cow performance, and plasma urea nitrogen (PUN). A subsequent analysis revealed two plasma EAA clusters. Cows in cluster 1 had lower proportion of leucine, valine and branched-chain amino acids and greater proportion of phenylalanine, lysine, isoleucine, and threonine in total plasma EAA, greater milk, protein and fat yield and numerically lower PUN than cows in cluster 2. Our findings suggested the existence of an association between the plasma EAA profile and productive performance.

Technical Abstract: This meta-analysis was designed to identify and describe potential associations between plasma essential amino acid (EAA) profile, performance, and indicators of N utilization in lactating dairy cows. We hypothesized that plasma EAA profile may serve as an indicator of (im)balances of EAA supply to the mammary gland. The dataset of this study included 22 feeding trials and 96 dietary treatments. A mixed-model analysis was conducted on EAA plasma concentration ([EAA]p) in response to the fixed-effect of the categorical covariate EAA, continuous covariate of National Research Council (NRC) predicted metabolizable protein (MP) supply, continuous covariate of body weight (BW), the categorical covariate EAA and MP supply interaction, the [EAA]p and BW interaction, and the random effect of study. The residuals of the mixed model were standardized based on Z-score and clustered using the hierarchical method (Euclidean distance and Ward’s minimum variance method) resulting in two clusters. The plasma EAA profiles were determined for each cluster as the proportion of individual [EAA]p relative to the total [EAA]p. A fixed-effect model specifying heterogeneity in the covariance structure was used to evaluate the effect of cluster on plasma EAA profile and cow performance, feed and N efficiencies, and plasma urea-N (PUN). Cluster 1 had lower individual and total [EAA]p compared to cluster 2. Due to the use of residual [EAA]p in the mixed-effect model, no difference in MP supply, energy supply and BW was found between clusters. There was no difference between clusters for Arg, His, and Met. However, cows in cluster 1 had lower proportions of Leu, Val and branched-chain amino acids (AA) and greater proportion of Ile, Lys, Phe and Thr compared to cows in cluster 2. Cows in cluster 1 had higher milk energy output (+3.2 Mcal/d), true protein yield (+87 g/d) and fat yield (+236 g/d), milk Mcal: dry matter intake (+8% units), and numerically lower PUN (-1.2 mg/dL) than cows in cluster 2, suggesting greater utilization of AA for milk protein and less hepatic catabolism of AA-N. The mechanism remains unclear, but our findings suggested that plasma EAA profile reflects the balance of coordinated metabolic activities between the liver and the mammary gland. Although the concept of an ideal plasma EAA profile should be evaluated experimentally under various feeding strategies, the relative proportions of [EAA]p reported here may serve as indictors of (im)balances as related to distinct levels of productivity and feed efficiency.