Changing perceptions of the effect of plant phenolics on nutrient supply in the ruminant

Abstract

Mammalian metabolism of plant phenolics, initially studied in monogastric animals, gave an emphasis to their toxic and antinutrient effects. Subsequent studies in tropical ruminants and wild herbivores have highlighted the high levels than can occur in some diets and the extensive microbial modification and degradation that can occur in the tract. This paper reviews aspects of plant phenolics as they relate to ruminant nutrition in tropical or semi-arid environments in which some forage plants contain high levels of phenolic compounds. Effects range from occasional acute toxicity of hydrolysable tannins, to acetate-releasing microbial degradations that apparently enable certain phenolics to act as nutrients. The most important and complex effects are those due to tannin-protein interactions. Although these can clearly reduce feed intake, nutrient digestibilities, and protein availability, many of the interactions are still not understood. The diverse effects of plant phenolics on nutrient flow probably result from the balance between adverse effects on some organisms and the rate at which they are degraded or inactivated by other organisms, and improved animal performance can likely be obtained by manipulation of rumen microbial metabolism.

In vitro antioxidant properties of mangosteen peel extract

“…In contrast, interactions of plant phenolics with proteins may lead to the formation of soluble or insoluble complexes (Shahidi and Naczk 2004). These interactions may have a detrimental effect on the in vivo bioavailability of both phenolics and proteins (Lowry et al 1996;Wollgast and Anklam 2000). Naczk et al (2011) reported that crude extract of phenolics isolated from mangosteen peel displayed a strong protein-precipitating potential.…”

Value Addition of Feed and Fodder by Alleviating the Antinutritional Effects of Tannins

“…These may assist in the detoxification process and also provide additional nutrients to rumen microorganisms, as mulga tannins are known to reduce protein digestibility [91]. The addition of methionine and choline to chick diets alleviated the toxicity of tannic acid and also the toxicity of CTs or possibly the low molecular weight phenolics in sorghum [33], presumably because they functioned as methyl donors in the detoxification process and facilitated the excretion of compounds such as 4-Omethyl gallic acid [35].…”

Browse species from Ethiopia: role in methane reduction and nematode control in goats

“…The effect of tannins on GP is through substrate deprivation or enzyme activity inhibition in rumen microbes. The effect of PA on fermentation is more pronounced with PA containing more PD monomeric units (Huyen et al, 2016;Lowry et al, 1996). All PA-containing browse in the present experiment with the exception of D. angustifolia contained PD, indicating that the GP and CH 4 depressing effect partly originated from PD activity.…”

“…Molecular size, solubility and the number of phenolic groups determine complexation formed by hydrogen bonding between the phenolic protons and the peptide carbonyl groups (Lowry et al, 1996). In general, tannins have higher affinity towards large, porous, proline rich proteins and precipitation of proteins is effective at a neutral pH (Hagerman et al, 1992).…”

“…Phenolic compounds include flavonoids, phenolic acids and tannins and have been found to be the major constituent of some tropical browse species (Mueller-Harvey et al, 1987) with divergent effects on animal nutrition (Lowry et al, 1996). Flavonoids are compounds with a low molecular weight and consist of flavonols, flavones, flavanols and isoflavones.…”