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

Ignacio R Ortolani,Zahia Amanzougarene,Manuel Fondevila

doi:10.5424/sjar/2021192-17653

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.

Highlights

There is an increasing interest for using non-forage fibre sources, often agricultural by-products, in diets for ruminant feeding, as they can contribute to adjust feed costs compared with forages (Bradford & Mullins, 2012).These feeds are generally included as ingredients in the compound feed, and non-forage fibre based diets can maintain or even improve rumen health and performance of dairy cattle under certain conditions (Pereira et al, 1999; Ertl et al, 2015), their use as main sources of fibre is controversial
Propionate proportion was enhanced from BP, barley straw (BS) and soybean hulls (SH), and that of butyrate was higher with palm kernel cake (PK) and oat hulls (OH), whereas no differences among substrates were recorded in acetate proportion
For total gas production and organic matter disappearance (OMd), the experimental unit was the average of the two bottles per treatment incubated for 48 h in the same run, whereas for methane production and volatile fatty acid (VFA) pattern at 12 h the value from a single bottle per run was considered

Summary

Introduction

These feeds are generally included as ingredients in the compound feed, and non-forage fibre based diets can maintain or even improve rumen health and performance of dairy cattle under certain conditions (Pereira et al, 1999; Ertl et al, 2015), their use as main sources of fibre is controversial Their particle size is smaller compared with forages, promoting a limited effect as potentially effective fibre, which is necessary for stimulating rumination and modulating rumen pH in high concentrate feeding conditions (Armentano & Pereira, 1997; Grant, 1997). Composition varies widely in their non-fibrous fraction, with different proportions of protein or even lipids among sources

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