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

Abstract

Simple SummaryThe evaluation of fibre digestibility is very important for the formulation of ruminant diets. Fibre digestibility is usually determined in lab with rumen inoculum obtained from cannulated cows. The research of alternative and less invasive inoculum sources is a critical issue that should be addressed. The present study evaluated the potential of faecal inocula, obtained from cows fed different diets, to assess fibre digestibility of different substrates at different incubation times (48, 240 and 360 h). At short incubation time, fibre digestibility obtained with rumen fluid was always higher than those obtained with faecal inocula, confirming a lower activity of the faecal inocula compared with rumen fluid. However, the type of diets fed to the donor animals had a significant effect on fibre digestibility, with a more active faecal inoculum for cows fed a diet based on maize silage. Despite the differences obtained at the short incubation time, the digestibility values at longer intervals showed that faecal inoculum could replace rumen inoculum. As a consequence, faeces may replace rumen fluid as inoculum for end-point measures, avoiding the use of cannulated animals and decreasing the analytical costs.AbstractCow faeces have been investigated as alternative inoculum to replace rumen fluid to determine neutral detergent fibre (NDF) digestibility (NDFD). Aims of this study were to estimate: (1) the NDFD (48 h) of feed ingredients using a rumen inoculum in comparison with faecal inocula from cows fed diets with different forage basis; (2) the undigestible NDF (uNDF) at 240 and 360 h with ruminal fluid and faecal inocula from lactating cows fed two different diets. At 48 h incubation, the NDFD was affected both by feed and type of inoculum (p < 0.01) and by their interaction (p = 0.03). Overall, the mean NDFD was higher for rumen inoculum than for faecal inocula (585 vs. 389 g/kg NDF, p < 0.05), and faecal inoculum obtained from cows fed hay-based diets gave lower NDFD than those from cows fed maize silage (367 vs. 440 g/kg, p < 0.05). At long incubation times, the average uNDF was affected by substrate, inoculum and incubation time (p < 0.01), but not by their interactions. For each inoculum, significantly lower values were obtained at 360 than at 240 h. Regressions between uNDF with rumen and with the tested faecal inocula resulted in r2 ≥ 0.98. Despite the differences at 48 h, the uNDF showed that faecal inoculum could replace rumen fluid at longer incubation times.

Rumen Content from Slaughterhouse as an Alternative Inoculum Source for In Vitro Analysis of Feeds: A Multivariate Approach

“…However, a prior adaptation of ruminal microorganisms to this compound is possible, so its degradability is significant. As observed in Chiaravalli et al [43] and Kilama et al [56], lignin is the most important component of NDF or non-degradable NDF that can affect the digestibility of the dry matter or organic matter of foods used in feeding ruminants.…”

“…The quality and source of the ruminal inoculum directly influence the in vitro evaluation of feed for cattle. The inoculum can be significantly affected by the feed offered to the animals, which can result in differences in the populations of microorganisms in the rumen [18,[42][43][44]. This variation affects the digestibility of the nutritional components of the diet.…”

Forages and pastures symposium: an update on in vitro and in situ experimental techniques for approximation of ruminal fiber degradation

“… Hughes et al (2012) determined that bovine feces included at a rate of 450 g/L of bicarbonate buffer was similar to rumen fluid in the estimate of organic matter digestibility coefficients for tropical forages. Chiaravalli et al (2019) , found that fecal inoculum from dairy cows underpredicted NDF disappearance, primarily when incubations were carried out beyond 288 h for the determination of iNDF. It should be noted, however, that the fecal inoculum to buffer ratio was 1:2 in that instance, well under the 45% recommended by Hughes et al (2012) .…”

In Vitro Techniques Using the DaisyII Incubator for the Assessment of Digestibility: A Review

“…Bovine FF may be used to replace bovine RF for incubation times no lower than 48 h [59]. Chiaravalli et al [60] utilised an AD II incubator to estimate the undigestible NDF of seven substrates using three different inocula (one rumen and two faeces) and considering two incubation times (240 and 360 h). The undigestible NDF results showed that faecal inoculum could be used to replace RF for long incubation times and that faeces can be used as an inoculum for end-point measurements.…”