Effect of forage type and forage to concentrate ratio on ruminal fermentation in single-flow continuous-culture and Rusitec fermenters

Abstract

Eight single-flow continuous-culture (SFCC) and 8 Rusitec fermenters were used to compare the ruminal fermentation of 4 diets with forage:concentrate ratios (F:C) of 70:30 or 30:70 and alfalfa or grass hay as forage. Four rumen fistulated goats and 4 rumen fistulated sheep were used as donors for SFCC and Rusitec fermenters, respectively. There were no differences (P>0.05) between fermentation systems (FS) in the daily production of ammonia-N and molar proportions of propionate and isobutyrate, but the other fermentation variables were affected (P<0.05) by the FS. Dilution rate, solids retention time, dry matter digestibility, pH and molar proportions of butyrate, isovalerate and valerate were lower (P¿0.005) in SFCC than in Rusitec fermenters, whereas digestibility of neutral-detergent fibre and acid-detergent fibre, daily production of volatile fatty acids, molar proportion of acetate and acetate:propionate ratio were lower (P<0.001) in Rusitec compared with SFCC fermenters. Interactions (P<0.05) FS x F:C and FS x type of forage were detected for most of the fermentation variables, indicating differences between SFCC and Rusitec fermenters in detecting the effects of F:C ratio and type of forage on ruminal fermentation parameters.