Malate, citrate, and amino acids in tall fescue cultivars: Relationship toanimal preference

Grazing animals depend on little-understood chemical and physical rues when selecting forage diets. This study determined malate, citrate, and amino a cid concentrations in endophyte-free tall fescue (Festuca arundinacea Schre b.) and related those concentrations to cultivar, harvest time, and grazing -animal preference. 'Barcel','Kenhy', 'Kentucky-31', 'Missouri-96', 'Mozark ', 'Stargrazer', and the two accessions C1 and HiMag were established in th ree replicates within each of three pastures. Organic acids were determined on regrowth within each plot during four seasons and two years; amino acid s were determined on regrowth of four cultivars across three replicates dur ing both spring and fall seasons in one year. Malate and citrate were extra cted with boiling water and quantified by high-performance liquid chromatog raphy (HPLC) with an organic acid column. Amino acids were hydrolyzed, sepa rated by ion-exchange HPLC, and quantified as their ninhydrin derivatives. Both malate and citrate concentrations differed between years. During one y ear only, malate concentrations were higher in Kenhy (68 g kg(-1) dry matte r [DM], most preferred) than in Mozark (54 g kg(-1) DM, least preferred). C itrate concentrations (13 g kg(-1) DM) were not different among cultivars. Eighteen amino acids (including tryptophan) accounted for 75% of total N. T hus, tissue N data were used as covariates to amino acid data in the ANOVA. Kenhy contained higher concentrations of eight amino acids than did other cultivars. These differences may reflect presence of Lolium genes in Kenhy. Cattle (Bos taurus L.) grazing preference (0 = not eaten; 10 = completely eaten) was not related to malate, citrate, or amino acid concentrations amo ng cultivars.