Potency of microbial inocula from bovine faeces and rumen fluid for in vitro digestion of different tropical forage substrates

Abstract

In vitro ruminal fermentation techniques rely on the availability of fistulated ruminants for rumen fluid (RF), a major constraint for resource-poor institutions. An alternative would be to use faecal microbes. This study was therefore designed to compare the potency of fresh bovine faeces against RF as sources of microbial inocula for fermenting six contrasting tropical forages using the Tilley and Terry (Journal of British Grassland Society, 18, 104-111) technique. Faecal inocula were prepared at concentrations of 250 g (Faec250), 300 g (Faec300), 350 g (Faec350), 400 g (Faec400) and 450 g (Faec450) fresh cow faeces per litre bicarbonate buffer. In vitro organic matter digestibility (IVOMD) increased with increasing concentration of faeces at 12-, 24-and 48-h incubation intervals. All faecal inocula except Faec450 had lower potency when compared with RF at all incubation intervals. Digestibility of forage substrates with Faec450 (533 ± 23 g kg )1 DM IVOMD) was comparable to RF (566 ± 5 g kg )1 DM IVOMD) after 48-h incubation. Faec450 showed greater potency on more fibrous and low-protein substrates than RF. The coefficient of determination of the regression models for predicting 12-, 24-and 48-h RF IVOMD from Faec450 were 0AE914, 0AE75 and 0AE756 respectively. It was concluded that inocula prepared from 450 g cow faeces demonstrated great potential as a substitute and predictor for RF in 48-h IVOMD assays of tropical forages.

Comparison of Faecal versus Rumen Inocula for the Estimation of NDF Digestibility

“…For example, Akhter et al [8] obtained significant regression equations between in vitro OMD of eight forages determined with sheep rumen liquor and cow faeces. Another study [6] showed that the OMD of different forages estimated with faecal inoculum was comparable to the OMD determined with cow rumen fluid after 48 h of incubation. Regarding GP, a study [7] showed that in vitro total GP was greater for feeds incubated with cow rumen inoculum as compared to cow faecal inoculum.…”

“…The rumen fluid was collected before the morning meal and was immediately strained through four layers of cheesecloth into a pre-warmed (39 °C) flask with CO 2 and mixed with the buffer solution [10] in a 1:2 ratio. Faecal samples were first mixed with the same buffer solution (at the same 1:2 ratio) and maintained for thirty minutes at 39 °C with CO 2 , and then strained through four layers of cheesecloth [5,6,11].…”

“…The in vitro techniques developed to determine NDFD (for example: [3,4]) involve the use of ruminal inoculum. However, in recent time fresh faeces from ruminants have been investigated as alternative inoculum to replace rumen fluid [5,6,7]. Using a fresh faecal inoculum would have some advantages: it is easier to obtain faeces than rumen liquor and rumen cannulated animals are not needed.…”

“…Using a fresh faecal inoculum would have some advantages: it is easier to obtain faeces than rumen liquor and rumen cannulated animals are not needed. Faecal inocula from cows have been used to evaluate the in vitro organic matter digestibility (OMD) of forages [6,8] and gas production (GP) of different feeds [5,7]. For example, Akhter et al [8] obtained significant regression equations between in vitro OMD of eight forages determined with sheep rumen liquor and cow faeces.…”

Evaluación de métodos nutricionales para reactivar inóculo ruminal preservado analizado a través de cinética de fermentación y digestibilidad de forrajes in vitro

“…One of these sources is ruminant feces; however, results have been inconsistent. For example, fecal inoculum has been demonstrated to be effective for in vitro gas production studies (54) ; nonetheless, fecal inoculum from sheep was not comparable to fresh ruminal fluid when evaluating in vitro dry matter digestibility (55) . In addition, other studies, have revealed that fecal inoculum does not perform as good as ruminal fluid in in vitro fermentation techniques (55,56) , which may be due to differences in the bacterial populations between the rumen and the lower gastrointestinal tract (57) .…”