Rumen fermentation and nitrogen balance of lambs fed diets containing plant extracts rich in tannins and saponins, and associated emissions of nitrogen and methane

Effects of cassava chips (Manihot esculenta Crantz) and rain tree pods (Samanea saman) fermented with traditional fermentation starter (loog-pang kaomark) on growth performance, rumen fermentation, and microbial population in goats

To obtain guidelines for improving the quality of animal feed on production performance, rumen fermentation, and microbial population in goats. A total of 16 native-bore crossbred goats were used. A randomized complete block design (RCBD) was planned to compare four supplementation forms. There were four different loog-pang kaomark fermented cassava chips and rain tree pods (CRFLK) at proportions 100:0, 60:40, 50:50, and 40:60, respectively. The results of this study found that rice straw intake in terms of kg was higher in goats fed CRFLK 50:50, 60:40, and 40:60. While CP, NDF, and ADF digestibility were increased in goat fed CRFLK 50:50 and 40:60. The concentration of acetic acid was decreased by supplementation of CRFLK (p < 0.05) whereas NH3-N and propionic acid were increased (p < 0.05) by goat fed CRFLK. However, CH4 was decreased (p < 0.05) as a result of supplementation of CRFLK. The goat fed CRFLK decreased the protozoal population (p < 0.05). Moreover, the bacteria population was increased by fed with CRFLK (p < 0.05). This study concluded that feeding concentrate inclusion with CRFLK 50:50 and 40:60 resulted in higher propionic acid, CP digestibility, and lowest CH4 production.

Rumen protozoa population and carbohydrate-digesting enzymes in sheep fed a diet supplemented with hydrolysable tannins

The aim of the study was to compare the effect of adding different sources of hydrolysable tannins to the sheep diet on protozoa population and carbohydrate digestion in the rumen. The study was performed in 3 Polish Lowland ewes fistulated to the rumen in a 3 × 3 Latin -square design. Control sheep (CON) received (g/d): meadow hay (600), barley meal (300), soybean meal (100) and vitamin-mineral premix (20). Sheep from the experimental groups were additionally administered 12.6 g/kg DM oak bark extract (OAK) and 3.91 g/kg DM tannic acid (TAN). The net consumption of tannins was approx. 0.4% DM for both additives. Regarding the count of protozoa, a significant interaction between diet and sampling time was documented for all ciliates (P<0.01), with a significant effect of both factors when considered separately. Experimental diets reduced the number of total protozoa and Entodinium spp. (before, 2 and 4 h after feeding; P<0.01), while increasing the abundance of Isotricha spp. population (4 h after feeding; P<0.01) in the rumen. Interestingly, the count of Ophryoscolex spp. after feeding the TAN diet increased before feeding and 2 h after feeding in comparison to the CON and OAK groups, respectively, and subsequently decreased compared to the CON diet (4 and 8 h after feeding, P<0.01). A significant interaction between the diet and sampling time was observed for xylanolytic activity (P<0.01) in the rumen, with a significant effect of sampling time, which decreased its activity in CON (after feeding) and OAK sheep (2 h after feeding; P<0.01). For amylolytic activity (P<0.10), there was a trend towards a significant interaction between experimental factors, with a significant effect on both diet and sampling time. Detailed analysis showed that the TAN diet significantly reduced amylolytic activity 2 h after feeding compared to the CON group (P<0.05). In conclusion, the TAN diet significantly reduced the number of total protozoa and Entodinium spp., which consequently reduced amylolytic activity in the rumen, without any significant effect on pH and carbohydrate fermentation in the rumen.

The Utilisation of Tannin Extract as a Dietary Additive in Ruminant Nutrition: A Meta-Analysis

Simple Summary

Tannin has been extensively assessed for its potential and utilisation as a ruminant feed additive in recent years and is becoming important due to its beneficial effects on modulating ruminant performance and health and mitigating methane emissions. However, evidence concerning the effect of tannin in extracted forms on ruminants appears to be inconclusive on whether it can genuinely provide either beneficial or detrimental effects for ruminants. Moreover, the effects of various sources, types of tannin extract, or appropriate levels of supplementation on ruminants remain unclear. Therefore, there is a need for a systematic evaluation concerning the effects of tannin extract on rumen fermentation, digestibility, performance, methane emissions, and metabolism of ruminants.

Abstract

The objective of this meta-analysis was to elucidate whether there are general underlying effects of dietary tannin extract supplementation on rumen fermentation, digestibility, methane production, performance, as well as N utilisation in ruminants. A total of 70 papers comprised of 348 dietary treatments (from both in vivo and in situ studies) were included in the study. The database was then statistically analysed by the mixed model methodology, in which different experiments were considered as random effects and tannin-related factors were treated as fixed effects. The results revealed that an increased level of tannin extract inclusion in the diet lowered ruminant intake, digestibility, and production performance. Furthermore, the evidence also showed that an increased level of tannin extract decreased animal N utilisation where most of rumen by-pass protein was not absorbed well in the small intestine and directly excreted in the faeces. Due to the type of tannin extract, HT is more favourable to maintain nutrient intake, digestibility, and production performance and to mitigate methane production instead of CT, particularly when supplemented at low (<1%) to moderate (~3%) levels.

Supplementation with Yucca schidigera improves antioxidant capability and immune function and decreases fecal score of dairy calves before weaning

Yucca schidigera (YS) is a species of plant rich in antimicrobials, antioxidants, and immunomodulators. It has been used as feed additive to improve animal performance and decrease methane emissions in cattle. However, few studies have evaluated YS in dairy calves. In this study, we evaluated the effects of YS on the growth performance, antioxidant capacity, and immune function in dairy calves before weaning. We randomly assigned 40 newborn female Holstein calves (4 d old; 40 ± 5 kg of body weight) to 1 of 4 treatments (n = 10 per treatment), which were fed 0, 3, 6, or 9 g/d of YS powder. The YS allowance was mixed into milk or milk replacer and fed twice daily. Dry matter intake (both liquid and starter feed) and fecal score were recorded daily, and body weight, withers height, body length, and heart girth were measured at 4, 14, 28, 42, and 60 d of age. Blood was sampled from the jugular vein at 14, 42, and 60 d of age after the afternoon feeding for analysis of serum antioxidant capacity and immune function. Feeding YS did not affect dry matter intake, but decreased the feed-to-gain ratio with a quadratic dose effect. Over the whole study period, the average daily gain tended to linearly increase with the increasing YS doses, and it was 6.8% higher in diets supplemented with 9 g/d of YS than in the basal control diet without YS. The YS supplementation linearly decreased fecal score in a dose-dependent manner, and the frequency of diarrhea was significantly decreased as the YS supplementation increased throughout the whole study period. The YS supplementation also linearly decreased maleic dialdehyde concentration in the serum compared with the control group. The activity of catalase tended to linearly and quadratically increase, and that of glutathione peroxidase increased linearly with the increased YS supplementation. Serum concentrations of IgA and IgG increased linearly with the increased YS supplementation, and that of IgG tended to increase quadratically. To the best of our knowledge, this is the first study that demonstrated that feeding YS to young calves could improve growth, feed efficiency, and immunity, and decrease fecal score and diarrhea. The results of this study indicated that feeding YS at 9 g/d may be recommended to benefit dairy calves before weaning.

Potential of Molecular Weight and Structure of Tannins to Reduce Methane Emissions from Ruminants: A Review

Simple Summary

Regardless of the production system adopted, ruminant livestock contribute to greenhouse emissions that are associated with climate change. Among the greenhouse gases, enteric methane produced from the rumen is of the greatest concern because it is the largest single source of livestock emissions. Among the different dietary strategies examined to decrease methanogenesis in ruminants, the use of tannins shows promise, but has received only moderate attention. However, tannins are abundant in both tropical and temperate plants and so are widely available globally and may be an economical approach for livestock producers to mitigate enteric methane emissions. This review explores the challenges and opportunities of using dietary tannins to reduce enteric methane emissions from ruminants.

Abstract

There is a need to reduce enteric methane (CH₄) to ensure the environmental sustainability of ruminant production systems. Tannins are naturally found in both tropical and temperate plants, and have been shown to consistently decrease urinary nitrogen (N) excretion when consumed by ruminants. However, the limited number of in vivo studies conducted indicates that the effects of tannins on intake, digestibility, rumen fermentation, CH₄ production and animal performance vary depending on source, type, dose, and molecular weight (MW). There are two main types of tannin in terrestrial plants: condensed tannin (CT; high MW) and hydrolysable tannin (HT; low MW). Consumption of CT and HT by ruminants can reduce N excretion without negatively affecting animal performance. High MW tannins bind to dietary protein, while low MW tannins affect rumen microbes, and thus, irrespective of type of tannin, N excretion is affected. The structure of high MW tannin is more diverse compared with that of low MW tannin, which may partly explain the inconsistent effects of CT on CH₄ production reported in in vivo studies. In contrast, the limited number of in vivo studies with low MW HT potentially shows a consistent decrease in CH₄ production, possibly attributed to the gallic acid subunit. Further in vivo studies are needed to determine the effects of tannins, characterized by MW and structural composition, on reducing CH₄ emissions and improving animal performance in ruminants.

Are dietary strategies to mitigate enteric methane emission equally effective across dairy cattle, beef cattle, and sheep?

The digestive physiology of ruminants is sufficiently different (e.g., with respect to mean retention time of digesta, digestibility of the feed offered, digestion, and fermentation characteristics) that caution is needed before extrapolating results from one type of ruminant to another. The objectives of the present study were (1) to provide an overview of some essential differences in rumen physiology between dairy cattle, beef cattle, and sheep that are related to methane (CH₄) emission; and (2) to evaluate whether dietary strategies to mitigate CH₄ emission with various modes of action are equally effective in dairy cattle, beef cattle, and sheep. A literature search was performed using Web of Science and Scopus, and 94 studies were selected from the literature. Per study, the effect size of the dietary strategies was expressed as a proportion (%) of the control level of CH₄ emission, as this enabled a comparison across ruminant types. Evaluation of the literature indicated that the effectiveness of forage-related CH₄ mitigation strategies, including feeding more highly digestible grass (herbage or silage) or replacing different forage types with corn silage, differs across ruminant types. These strategies are most effective for dairy cattle, are effective for beef cattle to a certain extent, but seem to have minor or no effects in sheep. In general, the effectiveness of other dietary mitigation strategies, including increased concentrate feeding and feed additives (e.g., nitrate), appeared to be similar for dairy cattle, beef cattle, and sheep. We concluded that if the mode of action of a dietary CH₄ mitigation strategy is related to ruminant-specific factors, such as feed intake or rumen physiology, the effectiveness of the strategy differs across ruminant types, whereas if the mode of action is associated with methanogenesis-related fermentation pathways, the strategy is effective across ruminant types. Hence, caution is needed when translating effectiveness of dietary CH₄ mitigation strategies across different ruminant types or production systems.

Invited review: Nitrogen in ruminant nutrition: A review of measurement techniques

Nitrogen is a component of essential nutrients critical for the productivity of ruminants. If excreted in excess, N is also an important environmental pollutant contributing to acid deposition, eutrophication, human respiratory problems, and climate change. The complex microbial metabolic activity in the rumen and the effect on subsequent processes in the intestines and body tissues make the study of N metabolism in ruminants challenging compared with nonruminants. Therefore, using accurate and precise measurement techniques is imperative for obtaining reliable experimental results on N utilization by ruminants and evaluating the environmental impacts of N emission mitigation techniques. Changeover design experiments are as suitable as continuous ones for studying protein metabolism in ruminant animals, except when changes in body weight or carryover effects due to treatment are expected. Adaptation following a dietary change should be allowed for at least 2 (preferably 3) wk, and extended adaptation periods may be required if body pools can temporarily supply the nutrients studied. Dietary protein degradability in the rumen and intestines are feed characteristics determining the primary AA available to the host animal. They can be estimated using in situ, in vitro, or in vivo techniques with each having inherent advantages and disadvantages. Accurate, precise, and inexpensive laboratory assays for feed protein availability are still needed. Techniques used for direct determination of rumen microbial protein synthesis are laborious and expensive, and data variability can be unacceptably large; indirect approaches have not shown the level of accuracy required for widespread adoption. Techniques for studying postruminal digestion and absorption of nitrogenous compounds, urea recycling, and mammary AA metabolism are also laborious, expensive (especially the methods that use isotopes), and results can be variable, especially the methods based on measurements of digesta or blood flow. Volatile loss of N from feces and particularly urine can be substantial during collection, processing, and analysis of excreta, compromising the accuracy of measurements of total-tract N digestion and body N balance. In studying ruminant N metabolism, nutritionists should consider the longer term fate of manure N as well. Various techniques used to determine the effects of animal nutrition on total N, ammonia- or nitrous oxide-emitting potentials, as well as plant fertilizer value, of manure are available. Overall, methods to study ruminant N metabolism have been developed over 150 yr of animal nutrition research, but many of them are laborious and impractical for application on a large number of animals. The increasing environmental concerns associated with livestock production systems necessitate more accurate and reliable methods to determine manure N emissions in the context of feed composition and ruminant N metabolism.

In vitro evaluations of pellets containing Delonix regia seed meal for ruminants

The objective of the present research was to determine the influence of various doses of the pellets containing DR seed meal (PEDEM) on in vitro CH₄ gas production, in vitro digestibility, protozoal count, and ruminal fermentation characteristics. The study was designed as a completely randomized design with eight levels of PEDEM supplementation at 0, 2, 4, 6, 8, 10, 12, and 14 mg DM. Gas production rate constants for the insoluble fraction (c) and cumulative gas production at 96 h were quadratically increased when PEDEM was supplemented (P < 0.05). The concentration of NH₃-N was linearly increased when the PEDEM concentration (P < 0.05) was increased, whereas the population of protozoa was linearly decreased when the level of PEDEM supplementation (P < 0.05) was increased. The supplementation of PEDEM in substrate quadratically affected the mean values of in vitro dry matter digestibility (IVDMD), in vitro organic matter digestibility (IVOMD), and in vitro NDF digestibility (P < 0.05). TVFA, acetic acid (C2), and butyric acid (C4) were not altered by different doses of PEDEM supplementation (P > 0.05). In contrast, the concentration of propionic acid (C3) was quadratically affected with the supplementation of PEDEM (P = 0.05). The inclusion of PEDEM did not change the CH₄ concentration at 6 h of incubation (P > 0.05), whereas the CH₄ concentration at 24 h of incubation and the mean values were linearly reduced with additional doses of PEDEM (P < 0.05). Compared with the control group, the mean CH₄ concentration was reduced at 51.1% with 12 mg PEDEM, whereas 59.6% was reduced with 14 mg PEDEM supplementations. The supplementation of PEDEM at 12 mg has the potential to manipulate rumen fermentation, to manipulate in vitro digestibility and to reduce protozoa and CH₄ production.

Saponin-Induced Shifts in the Rumen Microbiome and Metabolome of Young Cattle

The aim of this study was to explore the effects of saponins on the rumen microbiota and the ruminal metabolome. Alfalfa hay (AH) and soybean hulls (SH) were used as fiber sources for the control diets. The AH and SH diets were supplemented with tea saponins resulting in two additional diets named AHS and SHS, respectively. These 4 diets were fed to 24 young male Holstein cattle (n = 6 per diet). After 28 days of feeding, the rumen fluid from these cattle was collected using an oral stomach tube. Illumina MiSeq sequencing and ultrahigh-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (UHPLC-QTOF/MS) were used to investigate the changes in the ruminal microbes and their metabolites. The relative abundance of Prevotellaceae_YAB2003 increased, while Ruminococcaceae_NK4A214 and Lachnospiraceae_NK3A20 decreased in SHS and AHS compared to SH and AHS, respectively. Feeding SHS resulted in higher ruminal concentrations of squalene, lanosterol, 3-phenylpropanoic acid, and citrulline compared to SH. The different microbial genes predicted by Tax4Fun were involved in amino sugar and nucleotide sugar metabolism. The pathways of arginine and proline metabolism, purine metabolism, and pyrimidine metabolism were enriched by different metabolites. Moreover, in the SH group, a positive correlation was observed between Prevotella_1 (Bacteroidetes), Prevotellaceae_YAB2003 (Bacteroidetes), and Christensenellaceae_R.7 (Firmicutes), and the metabolites, including citrulline, lanosterol, and squalene. The increased abundances of Prevotella_1, Ruminococcaceae_UCG.002, and Prevotellaceae_YAB2003 might result in increased fiber digestion and nutrient utilization but nutrient digestion was not measured in the current study. In summary, saponins have the ability to modulate the ruminal microbial community and ruminal metabolites and thus affect the rumen environment. However, the response seems to be dependent on the composition of the basal diet. This study provides a comprehensive overview of the microbial and biochemical changes in the rumen of cattle fed saponins.

Manipulation of ruminal fermentation and methane production by dietary saponins and tannins from mangosteen peel and soapberry fruit

Four fistulated Holstein Friesian heifers were used in a 4 × 4 Latin square design with a 2 × 2 factorial arrangement. The main factors were two roughage-to-concentrate ratios (R:C, 70:30 and 30:70) and two supplementation levels of soapberry fruit-mangosteen peel (SM) pellets (0 and 4% tannins-saponins of total diets). Rice straw was used as a roughage source. The diet was fed ad libitum as a total mixed ration. SM pellets contained crude tannins and saponins at 12.1 and 15.7% of DM, respectively. It was found that at R:C 30:70 the DM intake and the digestibility of DM, CP and NDF were increased (p < 0.05), while SM pellet supplementation reduced the DM digestibility (p < 0.05). Ruminal pH was decreased at R:C 30:70. Total VFA and propionate was increased at high concentrate level and after SM pellet supplementation (p < 0.05); simultaneously, the acetate concentration and the acetate-to-propionate ratios were decreased (p < 0.05). Methane production was decreased at R:C 30:70 and additionally when SM pellets were supplemented (p < 0.05). This was in agreement with the percentage of methanogens in total ruminal DNA. Furthermore, the number of fungal zoospores were reduced at a higher concentrate proportion (R:C 30:70) and by SM-pellet supplementation (p < 0.05). Protozoal populations were diminished when SM pellets were supplemented (p < 0.05). In this study, it was shown that the roughage-to-concentrate ratio, as well as the supplementation of SM pellets containing condensed tannins and saponins, caused changes in ruminal microorganisms and their fermentation end-products.

Nutrient intake, digestibility and performance of Gaddi kids supplemented with tea seed or tea seed saponin extract

Objective

An experiment was conducted to determine the nutrient intake, digestibility, microbial protein synthesis, haemato-biochemical attributes, immune response and growth performance of Gaddi kids fed with oat fodder based basal diet supplemented with either tea seed or tea seed saponin (TSS) extract.

Methods

Eighteen male kids, 7.03±0.16 months of age and 19.72±0.64 kg body weight, were distributed into three groups, T₀ (control), T₁, and T₂, consisting of 6 animals each in a completely randomized design. The kids were fed a basal diet consisting of concentrate mixture and oat fodder (50:50). Animals in group III (T₂) were supplemented with TSS at 0.4% of dry matter intake (DMI), and group II (T₁) were supplemented with tea seed at 2.6% of DMI to provide equivalent dose of TSS as in T₂. Two metabolism trials were conducted, 1st after 21 days and 2nd after 90 days of feeding to evaluate the short term and long term effects of supplementation.

Results

The tea seed (T₁) or TSS (T₂) supplementation did not affect DMI as well as the digestibility of dry matter, organic matter, crude protein, neutral detergent fibre, and acid detergent fibre. Nutritive value of diet and plane of nutrition were also comparable for both the periods. However, the average daily gain and feed conversion ratio (FCR) were improved (p<0.05) for T₁ and T₂ as compared to T₀. The microbial protein supply was also higher (p<0.05) for T₁ and T₂ for both the periods. There was no effect of supplementation on most blood parameters. However, the triglyceride and low density lipoprotein cholesterol levels decreased (p<0.05) and high density lipoprotein-cholesterol level increased (p<0.05) in T₂ as compared with T₀ and T₁. Supplementation also did not affect the cell mediated and humoral immune response in goats.

Conclusion

Tea seed at 2.6% of DMI and TSS at 0.4% DMI can be fed to Gaddi goats to improve growth rate, FCR and microbial protein synthesis.

Effects of Protein Level and Mangosteen Peel Pellets (Mago-pel) in Concentrate Diets on Rumen Fermentation and Milk Production in Lactating Dairy Crossbreds

Four, lactating dairy crossbreds (50%×50% Holstein Friesian×Native Zebu cattle) were randomly assigned according to a 2×2 factorial arrangement (two protein levels and two levels of mangosteen peel pellets (Mago-pel)) in a 4×4 Latin square design to receive four dietary treatments. All cows received concentrate at a proportion of 1 kg concentrate per 2 kg of milk yield, and urea-treated 5% rice straw (UTRS) was given ad libitum. It was found that total dry matter intakes, nutrient digestibility, ruminal pH and NH₃-N concentrations were not affected (p>0.05) by treatments. Concentrations of ruminal pH and NH₃-N were not affected by dietary treatments although the concentration of BUN varied significantly (p<0.05) between protein levels (p<0.05). The populations of rumen bacteria and fungal zoospores did not differ among treatments (p>0.05); however, the population of protozoa was decreased (p<0.05) when cows received Mago-pel supplementation. The composition of the population of bacteria, identified by real-time PCR technique, including total bacteria, methanogens, Fibrobacter succinogenes and Ruminococcus albus was similar (p>0.05) among dietary treatments (p>0.05); however, copy numbers of Ruminococcus flavefaciens was increased when protein level increased (p<0.05). Microbial protein synthesis, in terms of both quantity and efficiency, was enriched by Mago-pel supplementation. Milk yield was greatest in cows fed UTRS based diets with concentrate containing protein at 16% CP with Mago-pel, but were lowest without Mago-pel (p<0.05). In addition, protein level and supplementation of Mago-pel did not affect (p>0.05) milk composition except solids-not-fat which was higher in cows fed the diet with 19% CP. Therefore, feeding a concentrate containing 16% CP together with 300 g/hd/d Mago-pel supplementation results in changes in rumen fermentation and microbial population and improvements in milk production in lactating dairy crossbreds fed on UTRS.

Bioactivity of phytochemicals in some lesser-known plants and their effects and potential applications in livestock and aquaculture production systems

Livestock and aquaculture production is under political and social pressure, especially in the European Union (EU), to decrease pollution and environmental damage arising due to animal agriculture. The EU has banned the use of antibiotics and other chemicals, which have been shown to be effective in promoting growth and reducing environment pollutants because of the risk caused to humans by chemical residues in food and by antibiotic resistance being passed on to human pathogens. As a result of this, scientists have intensified efforts in exploiting plants, plant extracts or natural plant compounds as potential natural alternatives for enhancing the livestock productivity. This paper discusses work on the effects of various phytochemicals and plant secondary metabolites in ruminant and fish species. The focus is on (i) plants such as Ananas comosus (pine apple), Momordica charantia (bitter gourd) and Azadirachta indica (neem) containing anthelmintic compounds and for their use for controlling internal parasites; (ii) plants containing polyphenols and their applications for protecting proteins from degradation in the rumen, increasing efficiency of microbial protein synthesis in rumen and decreasing methane emission; for using as antioxidants, antibacterial and antihelmintic agents; and for changing meat colour and for increasing n-3 fatty acids and conjugated linoleic acid in meat; (iii) saponin-rich plants such as quillaja, yucca and Sapindus saponaria for increasing the efficiency of rumen fermentation, decreasing methane emission and enhancing growth; for producing desired nutritional attributes such as lowering of cholesterol in monogastric animals; for increasing growth of fish (common carp and Nile tilapia) and for changing male to female ratio in tilapia; and for use as molluscicidal agents; (iv) Moringa oleifera leaves as a source of plant growth factor(s), antioxidants, beta-carotene, vitamin C, and various glucosinolates and their degraded products for possible use as antibacterial, antioxidant, anticarcinogenic and antipest agents; (v) Jatropha curcas toxic variety with high levels of various phytochemicals such as trypsin inhibitor, lectin, phytate and phorbol esters in seeds limiting the use of seed meal in fish and livestock diets; and the use of phorbol esters as bio-pesticidal agent; and (vi) lesser-known legumes such as Entada phaseoloides seeds containing high levels of trypsin inhibitor and saponins, Sesbania aculeate seeds rich in non-starch polysaccharides and Mucuna pruriens var. utilis seeds rich in l-3,4-dihydroxyphenylalanine and their potential as fish feed; Cassia fistula seeds as a source of antioxidants; and the use of Canavalia ensiformis, C. gladiata and C. virosa seeds containing high levels of trypsin inhinitor, lectins and canavanine. The paper also presents some challenges and future areas of work in this field.

Prevention of rotavirus infections in vitro with aqueous extracts of Quillaja Saponaria Molina

BACKGROUND

Rotavirus is the leading cause of severe diarrhea disease in newborns and young children worldwide, estimated to be responsible for over 300,000 childhood deaths every year, mostly in developing countries. Rotavirus-related deaths represent approximately 5% of all deaths in children younger than 5 years of age worldwide. Saponins are readily soluble in water and are approved by the US FDA for inclusion in beverages intended for human consumption. The addition of saponins to existing water supplies offers a new form of intervention into the cycle of rotavirus infection. We believe that saponins will 'coat' the epithelium of the host's small intestine and prevent attachment of rotavirus.

DISCUSSION

This experiment provides in vitro data for the possibility of including saponin in drinking water to prevent infections of rotavirus. We demonstrate that microgram amounts of extract, while exhibiting no cell cytotoxicity or direct virucidal activity, prevent rotavirus from infecting its host cells. In addition, the presence of residual amounts of extract continue to block viral infection and render cells resistant to infection for at least 16 h after the removal of the extract from the cell culture media.

CONCLUSION

We demonstrate that two Quillaja extracts possess strong antiviral activity at concentrations more than 1000-fold lower than concentrations exhibiting cell cytotoxicity. Extract concentrations as high as 1000 μg/ml are not cytotoxic, but concentrations as low as 1.0 μg/ml are able to block rotavirus and reovirus attachment and infection.

The influence of dietary tannin supplementation on digestive performance in captive black rhinoceros (Diceros bicornis)

Free-ranging browsers such as the black rhinoceros (Diceros bicornis) consume a diet that contains tannins, whereas the diets offered to them in captivity consist mostly of items known to contain hardly any such secondary plant compounds. Tannins could have potentially beneficial effects, including the chelation of dietary iron (iron storage disease is a common problem in black rhinos). Here, we tested the acceptance, and the consequences on digestion variables, of a low-dose tannin supplementation in captive animals. Eight black rhinoceroses from three zoological institutions were used. Faecal output was quantified by total faecal collection. Diets fed were regular zoo diets supplemented with either tannic acid (T, hydrolysable tannin) or quebracho (Q, condensed tannins); overall tannin source intake increased at 5-15 g/kg dry matter (DM) in relation to regular zoo diets. Adaptation periods to the new diets were >2 months. Additional data were taken from one hitherto unpublished study. Data were compared to measurements in the same animals on their regular zoo diets. All animals accepted the new diets without hesitation. There was no influence of tannin supplementation on digestion coefficients of DM and its constituents, or faecal concentrations of short-chain fatty acids or lactate. Water intake did not increase during tannin supplementation. Should the inclusion of dietary tannin sources be an objective in the development of diets for captive rhinoceroses, moderate doses such as used in this study are unlikely to cause relevant depressions of digestive efficiency and will not interfere with bacterial fermentation in a relevant way.

Plant bioactives for ruminant health and productivity

Plants have been used throughout history for their medicinal properties. This use has often focused on human health but plants have also been, and still are, applied in ethnoveterinary practice and animal health management. In recent times, the use of synthetic chemicals has become prevalent. Public awareness of the potential environmental and health risks associated with heavy chemical use has also increased. This has put pressure on regulatory bodies to reduce the use of chemicals in agriculture. The most striking example is the 2006 banning of antibiotics in animal feed by the European Union. Moves such as this have increased the drive to find alternatives to synthetic chemicals and research has again turned to the use of plant bioactives as a means of improving animal health. Current scientific evidence suggests there is significant potential to use plants to enhance animal health in general and that of ruminants (cattle, deer, sheep, etc.) in particular. Active areas of research for plant bioactives (particularly saponin and tannin containing plants) include reproductive efficiency, milk and meat quality improvement, foam production/bloat control and methane production. Nematode control is also a significant area of research and the evidence suggests a much broader range of phytochemicals may be effective. This review presents a summary of the literature and examines international research efforts towards the development of plant bioactives for animal health.