ABSTRACT
Content of p-coumaric (PCA) and ferulic (FA) acid was determined by the HPLC method in fourteen forbs with a potential utilization as forages (range of nutrient content per kg DM: 100 to 244 g CP, 339 to 528 g NDF and 180-369 g ADF. PCA and FA were determined after methanol extraction in four fractions: free phenolic acids extracted into either, ester-bound phenolic acids after alkaline hydrolysis, glycoside-bound phenolic acids after acid hydrolysis, and cell wall-bound phenolic acids after alkaline hydrolysis of the solid residue after the extraction with methanol. Cell wall-bound phenols were quantitatively the most important fraction (50% of total PCA and 47% of total FA, respectively). The differences among plant species in total PCA plus FA control were significant (F-value 775, P < 0.01). The range of total phenol content was 31.3 to 416.3 mg/100 g DM, the overall mean was 84 mg/100 g DM. Content of phenolic acids was correlated neither with ADF, NDF or ADL content (R2 = 1-3%, P > 0.05) nor with CP degradability (R2 = 3% and R2 = 1% for PCA and FA, respectively, P > 0.05). 95.4% and 30.9% of total PCA, and 98.3% and 72.5% of total FA disappeared in the rumen from the sample of Glechoma hederacea (species with the highest phenol content) and from the sample of Galium aparine (species with low phenol content), respectively, within the four hour incubation interval. It is presumed that in comparison with grasses, PCA and FA concentration in tested forbs represents a much lower risk in potential ruminant nutrition.
