Effects of hydroxycinnamic acids (Ferulic and p-Coumaric acids) in barley cultivars on cell wall components degradability in rumen

Barley grain contains hydroxycinnamic acids especially Ferulic (FA) and p-Coumaric acid (pCA) become cross-linked to cell wall polysaccharides as lignification commences that are the major inhibiting factors of biodegradability of plant cell walls in the rumen. Chemical characteristics, FA and pCA content of 11 Iranian barley cultivars determined. Using 3 fistulated ewes, the effects of FA and pCA content on ruminal degradation of dry matter (DM), neutral and acid detergent fiber (NDF and ADF) and lignin were studied. In barley cultivars, DM varied from 82.52 to 90.90 %; NDF varied from 9.64 to 27.34 % DM; ADF varied from 2.03 to 8.13 % DM and lignin varied from 0.87 to 3.03 % DM. The FA content ranged from 151.2 to 354.2 μg/g; and pCA content ranged from 114.5 to 444.4 μg/g of DM. Ruminal degradation parameters for DM, NDF, ADF and lignin were different between barley cultivars. The soluble fraction, slowly degradable, potential degradable, and undegradable fraction of DM were 2.92 to 56.33%; 42.64 to 91.45%; 65.68 to 98.97%, and 1.02 to 34.31%, respectively. The rate of ruminal degradation for DM varied among barley cultivars from 3.64 to 27.81% h-1. The FA was related to rumen indigestible DM, NDF, ADF and lignin, while pCA correlated with ADF. Using multi-regression, FA and pCA were inhibiting factors of ruminal degradability for DM and cell wall components; and FA was the most effective factor to predict DM degradability, while both FA and pCA affected NDF and ADF ruminal degradability