Amlan Kumar Patra

Exploitation of dietary tannins to improve rumen metabolism and ruminant nutrition

Tannins (hydrolysable and condensed tannin) are polyphenolic polymers of relatively high molecular weight with the capacity to form complexes mainly with proteins due to the presence of a large number of phenolic hydroxyl groups. They are widely distributed in nutritionally important forage trees, shrubs and legumes, cereals and grains, which are considered as anti-nutritional compounds due to their adverse effects on intake and animal performance. However, tannins have been recognised to modulate rumen fermentation favourably such as reducing protein degradation in the rumen, prevention of bloat, inhibition of methanogenesis and increasing conjugated linoleic acid concentrations in ruminant-derived foods. The inclusion of tannins in diets has been shown to improve body weight and wool growth, milk yields and reproductive performance. However, the beneficial effects on rumen modulation and animal performance have not been consistently observed. This review discusses the effects of tannins on nitrogen metabolism in the rumen and intestine, and microbial populations (bacteria, protozoa, fungi and archaea), metabolism of tannins, microbial tolerance mechanisms to tannins, inhibition of methanogenesis, ruminal biohydrogenation processes and performance of animals. The discrepancies of responses of tannins among different studies are attributed to the different chemical structures (degree of polymerisation, procyanidins to propdelphinidins, stereochemistry and C-C bonding) and concentrations of tannins, and type of diets. An establishment of structure-activity relationship would be required to explain differences among studies and obtain consistent beneficial tannin effects.

A new perspective on the use of plant secondary metabolites to inhibit methanogenesis in the rumen

Recently, greenhouse gas emissions have been of great concern globally. Ruminant livestock due to production of methane during normal fermentation in the rumen contributes substantially to the greenhouse effects. During the recent decade, a paradigm shift has been initiated whether plant secondary metabolites (PSM) could be exploited as natural safe feed additives alternative to chemical additives to inhibit enteric methanogenesis. More than 200,000 defined structures of PSM have been known. Some plants or their extracts with high concentrations of bioactive PSM such as saponins, tannins, essential oils, organosulphur compounds, flavonoids and many other metabolites appear to have potential to inhibit methane production in the rumen. The possible mechanisms and effects of many PSM on rumen methanogenesis are not clearly understood. Saponins may decrease methanogenesis through the inhibition of rumen protozoa and in turn may suppress the numbers and activity of methanogens. Although the direct effect of saponins on methanogens has not been demonstrated, saponins might inhibit methanogens at high doses. Tannins may inhibit the methanogenesis directly and also via inhibition of protozoal growth. Essential oils, organosulphur compounds and flavonoids appear to have direct effects against methanogens, and a reduction of protozoa associated methanogenesis probably plays a minor role for these metabolites. The chemical structure and molecular weight of the PSM and chemical composition of diets dependent upon the different feeding regimes may influence the effects of PSM on methane production. Although PSM may negatively affect nutrient utilization, there is evidence that methanogenesis could be suppressed without adversely affecting rumen fermentation, which could be exploited to mitigate methane emission in ruminants.

Dietary phytochemicals as rumen modifiers: a review of the effects on microbial populations

In the recent years, the exploration of bioactive phytochemicals as natural feed additives has been of great interest among nutritionists and rumen microbiologists to modify the rumen fermentation favorably such as defaunation, inhibition of methanogenesis, improvement in protein metabolism, and increasing conjugated linoleic acid content in ruminant derived foods. Many phytochemicals such as saponins, essential oils, tannins and flavonoids from a wide range of plants have been identified, which have potential values for rumen manipulation and enhancing animal productivity as alternatives to chemical feed additives. However, their effectiveness in ruminant production has not been proved to be consistent and conclusive. This review discusses the effects of phytochemicals such as saponins, tannins and essential oils on the rumen microbial populations, i.e., bacteria, protozoa, fungi and archaea with highlighting molecular diversity of microbial community in the rumen. There are contrasting reports of the effects of these phytoadditives on the rumen fermentation and rumen microbes probably depending upon the interactions among the chemical structures and levels of phytochemicals used, nutrient composition of diets and microbial components in the rumen. The study of chemical structure–activity relationships is required to exploit the phytochemicals for obtaining target responses without adversely affecting beneficial microbial populations. A greater understanding of the modulatory effects of phytochemicals on the rumen microbial populations together with fermentation will allow a better management of the rumen ecosystem and a practical application of this feed additive technology in livestock production.

Enteric methane mitigation technologies for ruminant livestock: a synthesis of current research and future directions

Enteric methane (CH4) emission in ruminants, which is produced via fermentation of feeds in the rumen and lower digestive tract by methanogenic archaea, represents a loss of 2% to 12% of gross energy of feeds and contributes to global greenhouse effects. Globally, about 80 million tonnes of CH4 is produced annually from enteric fermentation mainly from ruminants. Therefore, CH4 mitigation strategies in ruminants have focused to obtain economic as well as environmental benefits. Some mitigation options such as chemical inhibitors, defaunation, and ionophores inhibit methanogenesis directly or indirectly in the rumen, but they have not confirmed consistent effects for practical use. A variety of nutritional amendments such as increasing the amount of grains, inclusion of some leguminous forages containing condensed tannins and ionophore compounds in diets, supplementation of low-quality roughages with protein and readily fermentable carbohydrates, and addition of fats show promise for CH4 mitigation. These nutritional amendments also increase the efficiency of feed utilization and, therefore, are most likely to be adopted by farmers. Several new potential technologies such as use of plant secondary metabolites, probiotics and propionate enhancers, stimulation of acetogens, immunization, CH4 oxidation by methylotrophs, and genetic selection of low CH4-producing animals have emerged to decrease CH4 production, but these require extensive research before they can be recommended to livestock producers. The use of bacteriocins, bacteriophages, and development of recombinant vaccines targeting archaeal-specific genes and cell surface proteins may be areas worthy of investigation for CH4 mitigation as well. A combination of different CH4 mitigation strategies should be adopted in farm levels to substantially decrease methane emission from ruminants. Evidently, comprehensive research is needed to explore proven and reliable CH4 mitigation technologies that would be practically feasible and economically viable while improving ruminant production.

Meta-analyses of effects of phytochemicals on digestibility and rumen fermentation characteristics associated with methanogenesis

BACKGROUND A meta-analysis study was conducted to investigate the changes in rumen fermentation characteristics when methane inhibition by phytochemicals is employed. The whole database containing 185 treatment means from 36 published studies was divided into four subsets according to the major phytochemicals used in the studies, i.e. saponins, tannins, essential oils (EO) and organosulfur compounds (OS). RESULTS Changes in protozoal numbers showed linear relationships with changes in methane production by saponins (R(2) = 0.48), tannins (R(2) = 0.30) and EO (R(2) = 0.20) but not OS. Concentrations of total volatile fatty acids (VFA) and acetate did not show any relationship (P > 0.1) with changes in methane due to saponins. However, propionate production increased linearly with increasing inhibition of methane (R(2) = 0.31), which resulted in a linear (R(2) = 0.26) decrease in acetate/propionate ratio (A/P) with decreasing methane production. Concentrations of total VFA, acetate and propionate did not change with changes in methane production by tannins. However, A/P showed a significant linear relationship (R(2) = 0.27) with decreasing methane formation. Concentrations of total VFA (R(2) = 0.44) and propionate (R(2) = 0.15) changed linearly and positively with changes in methane production by EO. However, acetate production (R(2) = 0.22) and A/P (R(2) = 0.17) increased linearly with increasing inhibition of methane by EO. Changes in concentrations of total VFA (R(2) = 0.60) and acetate (R(2) = 0.35) decreased linearly while those of propionate increased linearly (R(2) = 0.23) with increasing inhibition of methane by OS. Consequently, A/P decreased linearly (R(2) = 0.30) with decreasing methane production by OS. Digestibilities of organic matter (OM) and neutral detergent fibre were not affected by inhibition of methane production by saponins, EO and OS, but digestibility of OM decreased with decreasing methane production by tannins. CONCLUSION The inhibition of methane production by phytochemicals results in changes in rumen fermentation that differ depending on the types of phytochemicals.

Effects of extracts of spices on rumen methanogenesis, enzyme activities and fermentation of feeds in vitro

BACKGROUND An experiment was conducted to study the effects of boiling water, methanol and ethanol extracts (0, 0.25 and 0.50 mL) of seeds of Foeniculum vulgare (fennel), flower buds of Syzygium aromaticum (clove), bulbs of Allium sativum (garlic), bulbs of Allium cepa (onion) and roots of Zingiber officinalis (ginger) on rumen methanogenesis, fibrolytic enzyme activities and fermentation characteristics in vitro. RESULTS Ethanol and methanol extracts of fennel, clove and garlic at 0.50 mL and clove at 0.25 mL inhibited (P < 0.05) methane production. Carboxymethylcellulase activity was reduced (P < 0.05) by ethanol and methanol extracts (0.50 mL) of fennel and clove (0.25 and 0.50 mL). The extracts of clove reduced (0.25 and 0.50 mL) xylanase and acetylesterase activities, and the fennel extract (0.50 mL) reduced (P < 0.05) xylanase activity. However, the extracts of garlic (0.50 mL) increased (P < 0.05) acetylesterase activity. Concentrations of volatile fatty acids were reduced (P < 0.05) by the extracts of garlic and onion. The extracts of garlic caused a decrease (P < 0.05) in acetate:propionate ratio (A:P) at 0.50 mL, whereas A:P was increased (P < 0.05) by the inclusion of 0.50 mL extracts of clove. Methanol and ethanol extracts of clove decreased (P < 0.05) in vitro organic matter degradability. Extracts (0.50 mL) of clove decreased (P < 0.05) the numbers of total protozoa, small entodiniomorphs and holotrichs, whereas extracts of onion, ginger and garlic enhanced (P < 0.05) protozoal numbers (both entodiniomorphs and holotrichs). CONCLUSION Ethanol and methanol extracts of fennel and garlic have potential to inhibit rumen methanogenesis without adversely affecting rumen fermentation.

Estimation of methane and nitrous oxide emissions from Indian livestock

Greenhouse gas (GHG; methane and nitrous oxide) emissions from enteric fermentation and manure management of Indian livestock were estimated from the last two Indian livestock census datasets (2003 and 2007) using IPCC Tier 2 (2006) guidelines. The total annual GHG emissions from Indian livestock increased in 2007 compared to the year 2003 with an annual growth rate of 1.52% over this period. The contributions of GHG by dairy cattle, non-dairy cattle, buffaloes, goats, sheep and other animals (yak, mithun, horse, donkeys, pigs and poultry) were 30.52, 24.0, 37.7, 4.34, 2.09 and 3.52%, respectively, in 2007. Enteric fermentation was the major source of methane, accounting for 89.2% of the total GHG emissions, followed by manure methane (9.49%). Nitrous oxide emissions accounted for 1.34%. GHG emissions (CO(2)-eq. per kg of fat and protein corrected milk (FPCM)) by female animals were considerably lower for crossbred cows (1161 g), followed by buffaloes (1332 g) and goats (2699 g), and were the highest for indigenous cattle (3261 g) in 2007. There was a decreasing trend in GHG emissions (-1.82% annual growth rate) in relation to milk production from 2003 to 2007 (1818 g and 1689 g CO(2)-eq. per kg FPCM in 2003 and 2007, respectively). This study revealed that GHG emissions (total as well as per unit of products) from dairy and other categories of livestock populations could be reduced substantially through proper dairy herd management without compromising animal production. In conclusion, although the total GHG emissions from Indian livestock increased in 2007, there was a decreasing trend in GHG production per kg of milk production or animal products.

Effects of supplementing low‐quality roughages with tree foliages on digestibility, nitrogen utilization and rumen characteristics in sheep: a meta‐analysis

Thirty-six published studies containing 219 treatment means and 1069 sheep were included in the dataset for meta-analysis to elucidate responses of foliage supplementation on digestibility, nitrogen balance and rumen parameters. Major predictive variables were percentages of foliages in diets (FL), crude protein (CP) in foliages (FCP), NDF in foliages (FNDF), NDF in basal forages (BNDF), CP in basal forages (BCP), CP in total diets (DCP) and foliage CP intake (FCPI). Organic matter digestibility increased linearly (p = 0.10) with increasing FL, but responded quadratically to DCP (p = 0.021) and BCP (p < 0.001), with maximal OM digestibility occurred at 14.6% of CP in diets (R(2) = 0.12). The digestibility of CP was affected by FL (p = 0.01), FCPI (p < 0.026), FCP (p < 0.001), FNDF (p < 0.001) and DCP (p < 0.032) positively and quadratically, and maximal response was at 14.1% DCP (p < 0.001), 51% FL (p < 0.001), 29% FCP (p < 0.001) and FCPI of 122 g/day (p < 0.001). The digestibility of NDF increased quadratically (p = 0.09) with increasing FL, peaking at 16% foliage levels, decreased quadratically (p = 0.001) with increasing FNDF and decreased linearly (p = 0.048) with increasing FCPI. Digestible OM and CP intakes were the highest at 37.2% and 42.1% FL, respectively. Fecal N excretion increased linearly with increasing FL (p < 0.001) and DCP (p < 0.001, R(2) = 0.66). However, FCPI (p = 0.082), FCP (p = 0.003) and BCP (p < 0.001) affected fecal N excretion positively and quadratically. Urinary N excretion increased linearly (p < 0.001) with increasing FL (R(2) = 0.45), FCPI (R(2) = 0.79), FCP (R(2) = 0.51), BCP (R(2) = 0.72) and DCP (R(2) = 0.77). Rumen NH(3) concentration was affected positively and quadratically (p = 0.023) by FL with a peak rumen NH(3) level of 160 mg/l at 17.3% FL. However, rumen NH(3) concentration (mg/l) increased linearly with increasing FCP (p = 0.001), FCPI (p = 0.01) and DCP (p < 0.001). In conclusion, catalytic foliage supplementation at low levels, preferably, at 16% may enhance nutrient utilization, while foliage levels up to 42% may result greater performance of sheep fed on low-quality roughages.

An Overview of Antimicrobial Properties of Different Classes of Phytochemicals

Plants produce a great diversity of phytochemicals, the beneficial properties of which have been used by humans for centuries since the advent of human civilization. With the discovery of effective and potent antimicrobial compounds, these synthetic antimicrobial compounds are widely used to prevent and cure microbial diseases. However, the development of antibiotic resistant strains of bacteria, reduced efficacy and safety of antimicrobials and the search of new antimicrobials against emerging incurable diseases by conventional antimicrobial agents have revived to explore phytochemicals as an alternative to synthetic antimicrobial compounds. Although numerous studies have been conducted in vitro and in vivo in the recent years on the efficacy of plant phytochemicals as antimicrobial agents, this chapter provides an overview of the antimicrobial properties of some major group of phytochemicals, namely, different phenolic compounds, alkaloids, saponins, iridoids and secoiridoids, polyacetylenes, glucosinolates, terpenoids, sulfinate, limonoids (tetranortepenoids) and anthranoids against pathogenic bacteria, fungi, viruses and commensal bacteria in the intestinal tracts of humans and animals. This chapter also discusses their antimicrobial mechanisms of action, the efficiency of different groups of phytochemicals against multiple-drug resistant bacteria, the effect of active dietary phytometabolites on the beneficial and pathogenic microbes of the gastrointestinal tracts and the outcomes of combination of phytofactors and drugs interactions.

Aspects of nitrogen metabolism in sheep-fed mixed diets containing tree and shrub foliages

Data on N utilisation by sheep-fed diets containing foliages were analysed to develop prediction equations for N excretion in faeces (FN) and urine (UN), and to determine endogenous N excretion. Overall, 218 dietary treatments from forty-four publications were compiled in the database. This database was split into three subsets: without foliage in the diets (FL-0); foliage levels (FL) in between 0 and 310 g/kg (FL-L); FL in between 310 and 800 g/kg diets (FL-H) to study the effects of foliages on metabolic faecal N (MFN) and endogenous urinary N (EUN). Nitrogen intake (NI) as single independent factor was the best predictor of FN (R2 0.75), UN (R2 0.81) and total N excretion (R2 0.86). Addition of dietary N concentration and FL for FN (R2 0.82), dietary N concentration and foliage NI for UN (R2 0.85), and FL and foliage NI for total N excretion (R2 0.92) as supporting predictors to this relationship slightly increased R2 values. The monomolecular and exponential models slightly improved the prediction of N excretion with NI as a predictor compared with the linear model. The excretion of MFN was greater for FL-H compared with FL-0, but was similar between FL-0 and FL-L, and FL-L and FL-H. However, EUN decreased in FL-H compared with FL-0 and FL-L, but was similar between FL-0 and FL-L. In conclusion, using NI as the primary predictor produced an accurate prediction of N excretion. Inclusion of foliages in the diets may shift N excretion from urine to faeces and increase the excretion of MFN and EUN.