In vitro characterisation of the rumen fermentation pattern of the cell wall fraction from several fibrous sources

Abstract

Aim of study: To isolate fibre effect from other factors when comparing fibrous sources, the rumen fermentation pattern of extracted cell walls was studied.Material and methods: Cell wall fractions from soybean hulls (SH), sugarbeet pulp (BP), palm kernel cake (PK), oat hulls (OH), dehydrated alfalfa meal (DA) and barley straw (BS) were incubated in four 48 h series.Main results: Cell wall extraction efficiency was ± 0.07 units over the neutral detergent fibre content, except for PK, which recovery was 0.20. Gas produced from BP and SH was higher (p<0.05) from 6 h. PK behaved similarly to SH from 6 to 24 h but maintained constant thereafter, whereas gas volume from OH was the lowest from 24 to 48 h (p<0.05). All substrates recorded a maximum rate of gas production at 12 h, except OH, for which fermentation was constant on time. The organic matter disappearance after 48 h incubation agreed with these results, being higher with BP and SH, whereas OH was the lowest (p<0.05). The proportion of methanein total gasproduced was higher in OH than BP at 36 and 48 h (p<0.05). The highest total VFA concentration was recorded with BP (p<0.05). Propionate proportion was enhanced from BP, BS and SH, and that of butyrate was higher with PK and OH, whereas no differences among substrates were recorded in acetate proportion.Research highlights: Fermentation of the cell wall fraction of fibrous feeds is not directly linked to its chemical composition, not even to its lignin proportion.