Effect of tannin-containing hays on enteric methane emissions and nitrogen partitioning in beef cattle1

Impact of growth implants and low-level tannin supplementation on enteric emissions and nitrogen excretion in grazing steers

The primary objective of this experiment was to evaluate the effects of a growth-hormone implant (Revalor-G, Merck Animal Health., Rahway, NJ, USA) and tannin supplementation (Silvafeed BX, Silva Team, San Michele Mondovi CN, Italy) on enteric methane (CH4) emissions and estimated nitrogen (N) excretion in grazing steers. Steers (n = 20; initial body weight [IBW] = 343 ± 14 kg) were acclimated to use a portable automated head-chamber system (AHCS) to measure CH4 and a SmartFeed Pro automated feeder for dietary supplementation (C-Lock Inc., Rapid City, SD, USA). After the training period, steers were randomly assigned to a 2 × 2 factorial arrangements of treatments, with 2 levels of growth-hormone implants, no-implant (NO-IMP) or implanted (IMP), and 2 levels of tannin supplementation, no tannin supplementation (NO-TAN) or tannin supplementation (TAN). This created 4 treatment groups: (1) NO-TAN and NO-IMP, (2) TAN and NO-IMP, (3) IMP and NO-TAN, and (4) TAN and IMP. Tannin was offered daily at 0.30% dry matter intake (DMI) through 0.5 kg/hd/d sweetfeed supplement (Sweetfeed Mix, AgFinity., Eaton, CO, USA) with a targeted tannin intake at 48 g/hd/d. No (P ≥ 0.05) implant × tannin interaction was detected for any dependent variable, so only the main effects of implant (NO-IMP vs. IMP) and tannin supplementation (NO-TAN vs. TAN) are discussed. Implant status did not affect (P ≥ 0.56) final body weight (FBW) or average daily gain (ADG) during the 90 d grazing period. There was no effect (P ≥ 0.15) of growth implant on CH4 production or emission intensity (EI; g CH4/kg gain). Additionally, IMP steers tended (P ≤ 0.08) to have less CH4 yield (MY; g CH4/g DMI) and higher blood urea nitrogen (BUN) than NO-IMP steers. Tannin supplementation did not impact (P ≥ 0.26) FBW or ADG. However, NO-TAN steers tended (P = 0.06) to have a greater total DMI than steers supplemented with tannin. No effect (P ≥ 0.22) of tannin supplementation was observed for CH4 production and EI. Nitrogen utilization as measured through BUN, urine N, fecal N, or fecal P was similar (P ≥ 0.12) between TAN and NO-TAN animals. The findings indicate that low-level dietary supplementation to reduce enteric emissions is difficult in grazing systems due to inconsistent animal intake and that growth implants could be used as a strategy to improve growth performance and reduce EI of steers grazing improved pasture.

Investigating the efficacy of purified tannin extracts from underutilized temperate forages in reducing enteric methane emissions in vitro

The study investigated how the concentration and composition of purified tannin extracts, at various inclusion rates, affect the ruminal in vitro fermentation parameters. Tannin extracts were isolated from four different forage species: birdsfoot trefoil (Lotus corniculatus), sulla (Hedysarum coronarium), big trefoil (Lotus pedunculatus), and salad burnet (Sanguisorba minor). Plants extracts were purified by Sephadex LH-20 gel chromatography and analyzed by UPLC-ESI-MS/MS. The results showed a large variation among the extracts from different species in terms of tannin composition and structural features. The extracts from salad burnet were dominated by hydrolysable tannins, comprising mainly ellagitannins. The extracts derived from sulla and big trefoil contained predominantly proanthocyanidins (PA), primarily composed of prodelphinidins with high mean degree of polymerisation (mDP). Birdsfoot trefoil extracts comprised procyanidin-rich PAs with low mDP. To determine whether the combined presence of tannins and flavonoid together lead to synergistic or antagonistic effects, the tannin extracts were incubated both with or without rutin at concentrations of 10, 20, and 30 g/kg DM, using a base substrate of perennial ryegrass (Lolium perenne, control). In general, all the tannin extracts decreased methane (CH4) production compared to the control, while no significant effect of rutin was observed on both gas (GP) and CH4 production, neither pure, nor in the simultaneous presence of tannins. The highest CH4 reduction (15%, at 30 g/kg DM) was observed from sulla and big trefoil extracts compared to control, but this was also supplemented with a concomitant reduction in GP (11%) indicating a reduction in feed digestibility. The extracts from birdsfoot trefoil and salad burnet reduced CH4 by up to 12% without significantly reducing GP, indicating the importance of tannin composition on ruminal fermentation.

Quantifying the Impact of Different Dietary Rumen Modulating Strategies on Enteric Methane Emission and Productivity in Ruminant Livestock: A Meta-Analysis

A meta-analysis was conducted with an aim to quantify the beneficial effects of nine different dietary rumen modulating strategies which includes: the use of plant-based bioactive compounds (saponin, tannins, oils, and ether extract), feed additives (nitrate, biochar, seaweed, and 3-nitroxy propanol), and diet manipulation (concentrate feeding) on rumen fermentation, enteric methane (CH4) production (g/day), CH4 yield (g/kg dry matter intake) and CH4 emission intensity (g/kg meat or milk), and production performance parameters (the average daily gain, milk yield and milk quality) of ruminant livestock. The dataset was constructed by compiling global data from 110 refereed publications on in vivo studies conducted in ruminants from 2005 to 2023 and anlayzed using a meta-analytical approach.. Of these dietary rumen manipulation strategies, saponin and biochar reduced CH4 production on average by 21%. Equally, CH4 yield was reduced by 15% on average in response to nitrate, oils, and 3-nitroxy propanol (3-NOP). In dairy ruminants, nitrate, oils, and 3-NOP reduced the intensity of CH4 emission (CH4 in g/kg milk) on average by 28.7%. Tannins and 3-NOP increased on average ruminal propionate and butyrate while reducing the acetate:propionate (A:P) ratio by 12%, 13.5% and 13%, respectively. Oils increased propionate by 2% while reducing butyrate and the A:P ratio by 2.9% and 3.8%, respectively. Use of 3-NOP increased the production of milk fat (g/kg DMI) by 15% whereas oils improved the yield of milk fat and protein (kg/d) by 16% and 20%, respectively. On the other hand, concentrate feeding improved dry matter intake and milk yield (g/kg DMI) by 23.4% and 19%, respectively. However, feed efficiency was not affected by any of the dietary rumen modulating strategies. Generally, the use of nitrate, saponin, oils, biochar and 3-NOP were effective as CH4 mitigating strategies, and specifically oils and 3-NOP provided a co-benefit of improving production parameters in ruminant livestock. Equally concentrate feeding improved production parameters in ruminant livestock without any significant effect on enteric methane emission. Therefore, it is advisable to refine further these strategies through life cycle assessment or modelling approaches to accurately capture their influence on farm-scale production, profitability and net greenhouse gas emissions. The adoption of the most viable, region-specific strategies should be based on factors such as the availability and cost of the strategy in the region, the specific goals to be achieved, and the cost-benefit ratio associated with implementing these strategies in ruminant livestock production systems.

Trade-offs between selection of crude protein and tannins in growing lambs

Tannins are phenolic compounds that provide benefits to ruminants due to their protein-binding affinities and antioxidant properties. However, tannins may also have negative orosensorial and postingestive effects that decrease feed intake. This study explored how lambs trade off the ingestion of crude protein (CP) with the ingestion of potentially beneficial and toxic condensed and hydrolyzable tannins, and the ensuing impacts on diet digestibility, animal performance, and blood parameters. Thirty-two lambs were housed in individual pens for 8 wk and had access to 2 isoenergetic diets that varied in the concentration of CP (High-high in protein [HP] or Low-least preferred [LP]) and the presence of a mix of condensed and hydrolyzable tannins (4% DM). Animals were assigned to 4 treatment groups (N = 8 lambs/group) and received a simultaneous offer of: HP and LP (Control); HP and LP + tannins (HP - LP+); HP+ tannins and LP (HP + LP-); and both HP and LP with tannins (HP + LP+). All lambs preferred HP over LP and they avoided tannins in the diets (P < 0.001). Dry matter and CP intake were the lowest in HP + LP- (P < 0.0001), and DMD did not differ between Control and the other groups (P > 0.05), but it was greater for HP - LP + (P < 0.0001). CP digestibility was greater for groups without tannins in HP (P < 0.0001), but average daily gain (ADG) did not differ among treatments (P > 0.05). No differences between Control and HP + LP + were found in plasma antioxidant activity, total phenolic concentration, or haptoglobin concentration (P > 0.05). Intake of tannins was HP + LP+ > HP + LP- > HP - LP + (P < 0.0001), and fecal excretion of nitrogen (N) was HP + LP+ > HP - LP+ = HP + LP- > Control (P < 0.05). In addition, intake of tannins with both diets reduced blood urea nitrogen (BUN) concentration relative to Control (P < 0.05), thus suggesting a shift in the partitioning of N excretion from urine to feces. In summary, lambs prioritized the selection of HP over LP, regardless of the presence of a tannin extract in either or both diets. Nevertheless, lambs modulated their tannin consumption as a function of the specific diet where the tannin extract was added, with increasing levels of intake as tannins were present in just LP, then in just HP, and finally in both diets. Dietary tannins did not constrain ADG and resulted in a shift in the partitioning of N excretion from urine to feces. Such shifts have been found to result in reduced production of environmental pollutants such as ammonia, nitrous oxide, and nitrates.

Could natural phytochemicals be used to reduce nitrogen excretion and excreta-derived N2O emissions from ruminants?

Ruminants play a critical role in our food system by converting plant biomass that humans cannot or choose not to consume into edible high-quality food. However, ruminant excreta is a significant source of nitrous oxide (N2O), a potent greenhouse gas with a long-term global warming potential 298 times that of carbon dioxide. Natural phytochemicals or forages containing phytochemicals have shown the potential to improve the efficiency of nitrogen (N) utilization and decrease N2O emissions from the excreta of ruminants. Dietary inclusion of tannins can shift more of the excreted N to the feces, alter the urinary N composition and consequently reduce N2O emissions from excreta. Essential oils or saponins could inhibit rumen ammonia production and decrease urinary N excretion. In grazed pastures, large amounts of glucosinolates or aucubin can be introduced into pasture soils when animals consume plants rich in these compounds and then excrete them or their metabolites in the urine or feces. If inhibitory compounds are excreted in the urine, they would be directly applied to the urine patch to reduce nitrification and subsequent N2O emissions. The phytochemicals' role in sustainable ruminant production is undeniable, but much uncertainty remains. Inconsistency, transient effects, and adverse effects limit the effectiveness of these phytochemicals for reducing N losses. In this review, we will identify some current phytochemicals found in feed that have the potential to manipulate ruminant N excretion or mitigate N2O production and deliberate the challenges and opportunities associated with using phytochemicals or forages rich in phytochemicals as dietary strategies for reducing N excretion and excreta-derived N2O emissions.

Effects of Acacia mearnsii added to silages differing in nutrient composition and condensed tannins on ruminal and manure-derived methane emissions of dairy cows

This study investigated the effects of acacia (extract of Acacia mearnsii) and sainfoin (Onobrychis viciifolia) as condensed tannin (CT)-rich sources on ruminal and manure methane (CH4) emissions in comparison with non-CT silages characterized by different contents of the cell wall and water-soluble carbohydrates. In a 3 × 6 incomplete Latin square design, 30 Holstein cows (63 ± 23 d in milk; mean ± SD; 33.8 ± 7.6 kg of milk per day, body weight 642 ± 81 kg) were provided with ad libitum access to 1 of 6 total mixed rations comprising 790 g of silage and 210 g of concentrate per kilogram of dry matter (DM). The silages were either rich in sainfoin [neutral detergent fiber (NDF): 349 g/kg of DM], perennial ryegrass (NDF: 420 g/kg of DM), or red clover (NDF: 357 g/kg of DM). Each silage was supplemented with 20 g/kg (of total diet DM) of acacia or straw meal. Feed intake and milk yield were recorded daily. Milk composition and ruminal fluid characteristics and microbiota were analyzed. The individual ruminal CH4 production was determined using the GreenFeed system, and CH4 emissions from the manure of cows fed the same diets were measured in a parallel experiment over 30 d at 25°C using a dynamic flux chamber. The CT sources did not reduce CH4 yield or emission intensity. Acacia reduced milk production (from 26.3 to 23.2 kg/d) and DM intake (from 19.7 to 16.7 kg/d) when supplemented with ryegrass, and both CT sources reduced the milk protein content and yield. Acacia supplementation and ryegrass silage reduced the ruminal acetate:propionate ratio. Furthermore, during acacia treatment, the abundance of Methanobrevibacter archaea tended to be lower and that of Thermoplasmata was higher. Acacia reduced the CH4 emissions from manure for the ryegrass group by 17% but not for the sainfoin and clover groups. Feeding sainfoin silage resulted in the lowest manure-derived CH4 emissions (-47% compared with ryegrass). In conclusion, acacia reduced ruminal CH4 production by 10%, but not emission intensity, and the mitigation effect of sainfoin depended on the silage to which it was compared. Because mitigation was partially associated with animal productivity losses, careful evaluation is required before the implementation of tanniferous feeds in farm practice.

The Impact of Mineral and Energy Supplementation and Phytogenic Compounds on Rumen Microbial Diversity and Nitrogen Utilization in Grazing Beef Cattle

The objective of this study was to evaluate the effect of the addition of a phytogenic compound blend (PHA) containing hydrolyzable tannins, carvacrol, and cinnamaldehyde oil to mineral salt or energy supplementation on the rumen microbiota and nitrogen metabolism of grazing Nellore cattle. Eight castrated Nellore steers were distributed in a double-Latin-square 4 × 4 design, with a 2 × 2 factorial arrangement (two types of supplements with or without the addition of the PHA), as follows: energy supplement without the PHA addition (EW); energy supplement with the PHA addition (EPHA); mineral supplement without the addition of the PHA (MW); mineral supplement with the PHA addition (MPHA). Steers that received supplements with the PHA have a lower ruminal proportion of valerate (with the PHA, 1.06%; without the PHA, 1.15%), a lower ruminal abundance of Verrucomicrobia, and a tendency for lower DM digestibility (with the PHA, 62.8%; without the PHA, 64.8%). Energy supplements allowed for higher ammonia concentrations (+2.28 mg of NH₃-N/dL), increased the propionate proportion (+0.29% of total VFA), and had a higher ruminal abundance of Proteobacteria and Spirochaetae phyla in the rumen. The PHA addition in the supplement did not improve nitrogen retention, reduced the ruminal proportion of valerate, and had a negative impact on both the total dry-matter digestibility and the abundance of several ruminal bacterial groups belonging to the Firmicutes and Verrucomicrobia phyla.

In vitro ruminal fermentation, methane production and nutrient degradability as affected by fruit and vegetable pomaces in differing concentrations

Pomaces are food industry by-products and may serve as animal feed to increase sustainability of meat and milk production. The aim of the present study was to evaluate fermentation characteristics of dried fruit and vegetable pomaces in a short-term in vitro experiment using the Hohenheim Gas Test. A selection of six fruit (apple, aronia, orange, pomegranate, red, white grape) and three vegetable (beetroot, carrot, tomato) pomaces was tested in three concentrations (150, 300, 500 g kg-1 of dry matter (DM)) as supplement to the basal diet (hay, used as control). Three runs were performed, using rumen fluid from one of three different rumen-cannulated cows in each run. Per run, each compound was tested in duplicate. After 24 h incubation, total gas production, methane and CO2 concentration, short-chain fatty acids, in vitro organic matter digestibility as well as microbial counts were determined. In addition, the pomaces' polyphenol content including the fractions non-tannin phenols, condensed tannins and hydrolysable tannins were analysed. Most pomaces did not significantly affect rumen fermentation characteristics in any of the tested dosages and may thus be applied in ruminant nutrition without adverse effects. Aronia significantly decreased (-14.5%) the organic matter digestibility in the highest concentration whereas apple (+12%), carrot (+10%) and beetroot (+8%) increased gas formation related to digestible organic matter. The 500 g kg-1 dosage of pomegranate significantly decreased methane formation by about 28% without impairing digestibility. Pomegranate was the only pomace of those high in total tannins that contained exceptionally high amounts of hydrolysable (90% of total tannins) and proportionally low amounts of condensed tannins (10% of total tannins), indicating that the hydrolysable tannins most likely reduced the methane production. Therefore, pomegranate pomace may be an interesting option for a methane mitigating feed supplement in ruminants and should be considered for following in vivo testing.

Effects of replacing Brachiaria hay with either Desmodium intortum or dairy concentrate on animal performance and enteric methane emissions of low-yielding dairy cows

In Africa, cattle are often fed low quality tropical roughages resulting in low-yielding animals with high methane (CH4) emission intensity (EI, g CH4/per unit of product). Supplementation with protein is known to improve the nutritive value of the otherwise low-quality diets. However, animal nutrition studies in East Africa that are accompanied by CH4 emission measurements are lacking. Thus, an animal experiment was conducted to quantify the effect of supplementing cattle fed mainly on low-quality Urochloa brizantha hay (control diet; CON; crude protein (CP) = 7.4%) or supplemented with either a tannin-rich leguminous fodder, Desmodium intortum hay (DES) or a commercial dairy concentrate (CUBES) on voluntary dry matter intake (DMI), nutrient apparent total tract digestibility, nitrogen (N) retention, enteric CH4 production and animal performance (milk and average daily gain). Twelve mid-lactating crossbred (Friesian × Boran) cows (initial liveweight = 335 kg) were used in a 3×3 (Period × Diet) Latin square design with each period running for four weeks. Compared to CON, DES decreased nutrient (DM, OM, CP) intake, apparent total tract digestibility and daily milk yield. In contrast, CUBES increased nutrient intake and animal performance compared to CON, while nutrients’ apparent total tract digestibility was not different, except for CP digestibility that increased. Compared to CON, DES and CUBES improved overall N retention by the animals as a proportion of N intake. The DES diet compared with CON and CUBES, shifted the proportion of N excretion via urine to the fecal route, likely because of its tannin content. Both DES and CUBES, compared to CON, reduced methane yield (MY, g CH4/kg DMI) by 15% and 9%, respectively. The DES diet reduced absolute enteric CH4 emissions by 26% while CUBES increased emissions by 11% compared to CON. Based on the present findings, high supplementation levels (&gt;50%) of Desmodium intortum hay is not recommended especially when the basal diet is low in CP content. Supplementation with lower levels of better managed Desmodium intortum forage however, need to be investigated to establish optimal inclusion levels that will improve animal productivity and reduce environmental impact of livestock in smallholder tropical contexts.

Effects of Dietary Inclusion of Sericea Lespedeza Hay on Feed Intake, Digestion, Nutrient Utilization, Growth Performance, and Ruminal Fermentation and Methane Emission of Alpine Doelings and Katahdin Ewe Lambs

Twenty-four Alpine doelings, initial 25.3 ± 0.55 kg body weight (BW) and 10.4 ± 0.11 mo of age, and 24 Katahdin ewe lambs, 28.3 ± 1.02 kg BW and 9.6 ± 0.04 mo of age, were used to determine effects of dietary inclusion of Sericea lespedeza (Lespedeza cuneata) hay on feed intake, digestion, growth performance, energy metabolism, and ruminal fermentation and methane emission. There were four periods, the first three 42 days in length and the fourth 47 days. Diets consumed ad libitum contained 75% coarsely ground hay with alfalfa (ALF), a 1:1 mixture of ALF and LES (ALF+LES), and LES (10.0% condensed tannins; CT). The intake of dry matter (DM) tended to be greater (p = 0.063) for Katahdin than for Alpine (4.14 vs. 3.84% BW; SEM = 0.110). The dry matter intake was similar among the diets (3.97, 4.10, and 3.89% BW for ALF, ALF+LES, and LES, respectively; SEM = 0.134). The digestion of organic matter (75.3, 69.3, and 65.5%; SEM = 0.86), neutral detergent fiber (61.7, 50.5, and 41.4%; SEM = 1.49), and nitrogen (78.8, 66.9, and 50.8% for ALF, ALF+LES, and LES, respectively; SEM = 0.92) decreased as the dietary concentration of lespedeza increased (p < 0.05). However, there was an interaction (p < 0.05) between the breed and diet in nitrogen digestion, with a greater value for goats vs. sheep with LES (54.4 vs. 47.3%; SEM = 1.30). The digested nitrogen intake decreased markedly with the increasing quantity of lespedeza (38.0, 27.5, and 15.7 g/day for ALF, ALF+LES, and LES, respectively; SEM = 1.26). The average daily gain was greater for Katahdin than for Alpine (p < 0.001; 180 vs. 88 g, SEM = 5.0) and ranked (p < 0.05) ALF > ALF+LES > LES (159, 132, and 111 g, respectively; SEM = 6.1). The ruminal methane emission differed (p < 0.05) between animal types in MJ/day (1.17 and 1.44), kJ/g DM intake (1.39 and 1.23), and kJ/g ADG (18.1 and 9.8 for Alpine and Katahdin, respectively). Regardless of the period and animal type, diet did not impact methane emission in MJ/day or relative to DM intake, BW, or ADG (p > 0.05). The digestible and metabolizable energy intakes, heat production, and retained energy were not affected by diet (p > 0.05). In conclusion, future research should consider the marked potential effect of CT of forages such as lespedeza on nitrogen digestion and associated effects on protein status and other conditions that may be impacted.

Response of Phytogenic Additives on Enteric Methane Emissions and Animal Performance of Nellore Bulls Raised in Grassland

The objective of this study was to evaluate the intake and digestibility of nutrients, emission of enteric CH4, and productive performance of Nellore bulls grazing Urochloa brizantha cv. Marandu palisade grass pastures during the rainy season, receiving an energy supplement or mineral supplement, with or without the inclusion of phytogenic additives. Forty-eight Nellore bulls were treated with: (1) energy supplement without the inclusion of phytogenic additives; (2) energy supplement with the inclusion of phytogenic additives; (3) mineral supplement without the inclusion of phytogenic additives; and (4) mineral supplement with the inclusion of phytogenic additives. Consumption of total dry matter (DM), crude protein (CP), apNDF, and energy; digestibility of DM, CP, and energy; average daily gain; stocking rate; and gain per area were higher in animals consuming energy supplements than those consuming mineral supplements. Digestibility of DM, NDF, and energy levels were lower in animals that consumed phytogenic additives. Compared with mineral supplements, the supply of energy supplements provides higher nutrient intake, increases enteric CH4 emission, and improves nutrient digestibility, providing a greater productive performance. The inclusion of phytogenic additives negatively affected nutrient intake and digestibility, did not reduce enteric CH4 emission, and influenced productive performance.

Beef Steer Performance on Irrigated Monoculture Legume Pastures Compared with Grass- and Concentrate-Fed Steers

Fall- or spring-born steers grazed monoculture irrigated birdsfoot trefoil (BFT; Lotus corniculatus L.) or cicer milkvetch (CMV; Astragalus cicer L.) pastures for approximately 12 weeks for 3 years and were compared with steers on concentrate diets. In the 3rd year, an irrigated meadow bromegrass (MBG; Bromus biebersteinii Roem. and Schult.) pasture treatment was added for further comparison. Steer average daily gain (ADG) was 1.31, 0.94, 0.83 and 0.69 kg d−1 on concentrate, ‘Norcen’ BFT, ‘Oberhaunstadter’ BFT, and ‘Monarch’ CMV diets, respectively; ADG on grass pastures was 0.43 kg d−1. The ADG on the concentrate diet was greater than ADG on legume or grass pastures, ADG was greater on BFT than CMV in every year (p < 0.03), and ADG on BFT was greater than ADG on grass (p < 0.03). The rate constant of gas production of an in vitro rumen fermentation demonstrated a slower rate of microbial digestion for CMV than for BFT. The elevated ADG on BFT pastures may be due to greater non-fiber carbohydrate (NFC) concentration and reduced neutral detergent fiber (NDF) concentration combined with condensed tannins that protect proteins in the rumen but do not impede protein digestion in the abomasum and intestines.

Adding polyethylene glycol to steer ration containing sorghum tannins increases crude protein digestibility and shifts nitrogen excretion from feces to urine

The objectives of the experiment were to study the effects of adding polyethylene glycol (PEG) to steer ration containing high sorghum tannins on rumen fermentation, nutrient digestion, nitrogen (N) balance and plasma biochemical parameters. Eight growing steers at 16 months of age were allotted to a replicated 4 × 4 Latin square design with 4 treatments and 4 periods (19 d each). Polyethylene glycol at 0, 1.75, 3.50 and 7.00 g/kg dry matter (DM) were added to a basal ration containing 27.82% DM of sorghum grain (total tannins 3.3 g/kg DM) as the treatments. The results indicated that adding PEG quadratically increased the ruminal pH (P = 0.049), tended to linearly increase the ruminal concentration of total volatile fatty acids (P = 0.070), increased the molar proportion of acetate (P = 0.016), linearly decreased the molar proportion of butyrate (P = 0.015), and tended to increase the molar proportion of iso-valerate (P = 0.061) and the ruminal concentration of ammonia N (P = 0.092). Adding PEG tended to quadratically decrease the relative abundance of methanogenic archaea (P = 0.082), linearly decreased the relative abundance of Fibrobacter succinogenes (P = 0.008) and decreased the relative abundance of Butyrivibrio fibrisolvens (P = 0.048) at 7.00 g/kg DM. Dietary addition with PEG increased the crude protein (CP) digestibility (P < 0.001) and tended to increase the neutral detergent fiber digestibility (P = 0.066) in a linear manner. Adding PEG to basal ration also increased the plasma globulin concentration (P = 0.029) and tended to linearly increase the plasma total protein concentration (P = 0.069). Adding PEG linearly decreased the fecal N excretion (P < 0.001) and the fecal N-to-total N excretion ratio (P = 0.004) and increased the urinary N-to-total N excretion ratio (P = 0.004) and urinary urea excretion (P = 0.010) without affecting the urinary N and total N excretions (P > 0.05). It was concluded that adding PEG effectively improved the CP digestibility of the ration containing high sorghum tannins but increased the urinary urea excretion without improving the N retention and N retention rate in steers.

Nitrogen Balance of Dairy Cows Divergent for Milk Urea Nitrogen Breeding Values Consuming Either Plantain or Perennial Ryegrass

Simple Summary

We studied the nitrogen excretion patterns of cows selected for divergent nitrogen excretion consuming either ryegrass or plantain. Both the use of a plantain diet as well as the use of low milk urea nitrogen breeding values were found to reduce the concentration of urinary urea nitrogen per urination event compared to cows with a high milk urea nitrogen breeding value and cows consuming a ryegrass-based diet. These results indicate that both the use of cows with low milk urea nitrogen breeding values and the use of a plantain diet are tools that temperate pastoral dairy production systems can use to reduce nitrogen loses.

Abstract

Inefficient nitrogen (N) use from pastoral dairy production systems has resulted in environmental degradation, as a result of excessive concentrations of urinary N excretion leaching into waterways and N₂O emissions from urination events into the atmosphere. The objectives of this study were to measure and evaluate the total N balance of lactating dairy cows selected for milk urea N concentration breeding values (MUNBVs) consuming either a 100% perennial ryegrass (Lolium perenne L.) or 100% plantain (Plantago lanceolata L.) diet. Sixteen multiparous lactating Holstein-Friesian × Jersey cows divergent for MUNBV were housed in metabolism crates for 72 h, where intake and excretions were collected and measured. No effect of MUNBV was detected for total N excretion; however, different excretion characteristics were detected, per urination event. Low MUNBV cows had a 28% reduction in the concentration of urinary urea nitrogen (g/event) compared to high MUNBV cows when consuming a ryegrass diet. Cows consuming plantain regardless of their MUNBV value had a 62% and 48% reduction in urinary urea nitrogen (g/event) compared to high and low MUNBV cows consuming ryegrass, respectively. Cows consuming plantain also partitioned more N into faeces. These results suggest that breeding for low MUNBV cows on ryegrass diets and the use of a plantain diet will reduce urinary urea nitrogen loading rates and therefore estimated nitrate leaching values, thus reducing the environmental impact of pastoral dairy production systems.

Impact of condensed tannin-containing legumes on ruminal fermentation, nutrition, and performance in ruminants: a review

Legume forages, such as sainfoin (Onobrychis viciifolia Scop.) and birdsfoot trefoil (Lotus corniculatus L.), can increase the forage quality and quantity of Western Canadian pastures, thus increasing producer profitability due to increased gains in grazing ruminants, while also reducing risk of bloat in legume pastures due to the presence of proanthocyanidins. Proanthocyanidins or condensed tannins (CT) are secondary plant polyphenol compounds that have been regarded as anti-nutritional due to their ability to bind protein in feeds, enzymes, and microbial cells, therefore disrupting microbial digestion and slowing ruminal protein and dry matter (DM) digestion. Research has shown that at high concentrations (>50 g·kg−1 DM), CT can disrupt microbial digestion. However, at low dietary inclusion rates (5–10 g·kg−1 DM), they reduce bloat risk, increase ruminal undegradable protein, reduce enteric methane production, and benefit anthelmintic activity. Yet, research gaps still exist regarding grazing persistence and forage yield of novel CT-containing forages and their biological activity due to their vast differences in CT stereochemistry, polymer size, and intermolecular linkages. The objectives of this review are to summarize information regarding the impact of CT on ruminal fermentation, carbohydrate and protein metabolism, and the potential to identify and select for forages that contain CT for ruminant production.

Non-fiber Carbohydrates in Forages and Their Influence on Beef Production Systems

Forages can provide a complete diet for ruminant animals, increasing the sustainability of beef production systems worldwide while reducing competition with humans for agricultural land or grain crops. Much of the emphasis on the nutritional characteristics of forages has been on the fiber, sugars, starch, and protein they supply to the rumen, despite the fact that other less-explored constituents, i.e., neutral detergent soluble fiber (NDSF) and other non-structural or non-fiber carbohydrates (NFC) also play a key role in the nutrition of ruminants. This paper explores the less investigated potential of temperate legumes to accumulate levels of NFC comparable to corn silage or beet pulp in cool, dry environments under irrigation, and its implications for forage-based beef production systems. We conclude that genetic or managerial interventions (i.e., breeding programs, defoliation frequency) or ecological conditions (i.e., climate, elevation) that increase concentrations of NFC in legumes can enhance beef production, meat quality, and the efficiency of nitrogen utilization by ruminants while reducing environmental impacts.

In vitro digestibility of mountain-grown irrigated perennial legume, grass and forb forages is influenced by elevated non-fibrous carbohydrates and plant secondary compounds

BACKGROUND

Perennial legumes cultivated under irrigation in the Mountain West USA have non-fibrous carbohydrate (NFC) concentrations exceeding 400 g kg^-1 , a level commonly found in concentrate-based ruminant diets. Our objective was to determine the influence of NFC concentration and plant secondary compounds on in vitro rumen digestion of grass, legume and forb forages compared with digestion of their isolated neutral detergent fiber (NDF) fraction. Forages were composited from ungrazed paddocks of rotationally stocked, irrigated monoculture pastures between May and August 2016, frozen in the field, freeze-dried, and ground.

RESULTS

The maximum rate (R_Max ) of gas production was greater for the legumes alfalfa (ALF; Medicago sativa L.) and birdsfoot trefoil (BFT; Lotus corniculatus L.) than for the legume cicer milkvetch (CMV; Astragalus cicer L.) the grass meadow brome (MBG; Bromus riparius Rehm.) and the non-legume forb small burnet (SMB; Sanguisorba minor Scop.), and intermediate for the legume sainfoin (SNF; Onobrychis viciifolia Scop.). The R_Max of isolated NDF was greatest for BFT and CMV, intermediate for ALF, SNF and SMB and least for MBG.

CONCLUSIONS

More than 900 g of organic matter kg^-1 dry matter of legumes was digested after 96 h. Across forages, the extent of whole-plant digestion increased with NFC and crude protein concentrations, decreased with NDF concentrations, and was modulated by secondary compounds. The extent of digestion of isolated NDF decreased with concentration of lignin and residual tannins. © 2020 Society of Chemical Industry.

Mature herbs as supplements to ruminant diets: effects on in vitro ruminal fermentation and ammonia production

Context High concentrations of crude protein in ruminant diets may lead to excessive production of ruminal ammonia, which may stress the animal’s metabolism and impact nitrogen efficiency. This may become a problem in zero-concentrate feeding systems when pasture grass is rich in crude protein. Polyphenols such as tannins may protect part of dietary protein from ruminal degradation and thus inhibit ammonia formation. Aims The present study screened mature herbs for their potential to mitigate ruminal ammonia formation in cattle, when provided as a supplement to a forage diet. Methods Thirty-five temperate-climate, herbaceous meadow plant species (including three legumes) that appear in biodiverse natural and sown pastures were investigated for their effects on ruminal ammonia production. Aboveground material was harvested during ripening of the seeds and analysed for nutrient and phenol concentrations. Net energy and protein absorbable at the duodenum were calculated. Incubations (24 h) with cattle rumen fluid following the in vitro Hohenheim Gas Test protocol were performed to compare the effects of the test plants on ruminal gas and ammonia formation. Test plants replaced one-third of a basal mixture consisting of 57% Lolium perenne L. and 43% Medicago sativa L. (air-dry-matter basis). Results were compared with those obtained with the basal mixture alone. Key results According to regression analysis, ammonia concentration after incubation was negatively related to concentrations of total extractable phenols and total tannins in feed mixtures, whereas the relationship was weakly positive with dietary crude protein. In 23 and 19 of the test diets, respectively, in vitro gas production (indicating ruminal organic matter digestibility) and ammonia concentrations in the incubation medium after 24 h were significantly lower than with the basal mixture alone. Incubations containing Galium verum L., Leontodon hispidus L., Lotus corniculatus L., Onobrychis viciifolia Scop., Plantago lanceolata L., Sanguisorba minor Scop. and Scabiosa columbaria L. maintained gas production and estimated in vitro organic matter digestibility while at the same time lowering ammonia concentrations. Conclusions Seven mature herbs of a screening of 35 proved to have potential for positive effects on ruminal protein utilisation without impairing fermentation. Implications These herbs are of particular interest as dietary supplements for dairy cows grazing protein-rich pastures.

Effect of Leucaena leucocephala and corn oil on ruminal fermentation, methane production and fatty acid profile: an in vitro study

Aims This in vitro study aimed to examine the effect of proportions of Leucaena (Leucaena leucocephala (Lam.) de Wit) to Napier grass (Pennisetum purpureum Schumach) or levels of corn oil (CO) and their interaction on ruminal fermentation, methane (CH4) production and fatty acid profile. Methods The experiment was conducted as a 4 × 3 factorial arrangement following a completely randomised design with two factors. The treatments were according to the proportion of Leucaena and Napier grass (in g/kg DM, Treatment (T)1 = 0:750 (control), T2 = 250:500, T3 = 500:250, T4 = 750:0). Three levels of CO (in mg rumen fluid, CO1 = 0, CO2 = 10, CO3 = 20 respectively) were added to each of the diet, giving a total 12 dietary treatments. Key results Replacing Napier grass with Leucaena at 500 g/kg (T3) and 750 g/kg (T4) levels increased the molar volatile fatty acid concentration, microbial protein synthesis (P &lt; 0.001) and ammonia nitrogen concentration (P = 0.003), whereas ruminal protozoa concomitantly decreased (P &lt; 0.05). The addition of CO at 10 mg also reduced the number of ruminal protozoa compared with the control (P &lt; 0.001). A significant Leucaena × CO interaction was observed on the increase of ammonia nitrogen and microbial protein synthesis, and CH4 production was simultaneously suppressed (P &lt; 0.001). There was also a significant Leucaena × CO interaction on increasing concentration of C18:1 cis-9, C18:2 cis-10 cis-12 and α-linolenic acid, which thus contributed to the increase of n-3 polyunsaturated fatty acids accumulation in the culture (P &lt; 0.001). However, the concentration of C18:0 was not influenced by the treatments (P &gt; 0.05). Conclusion This study demonstrated that the inclusion of Leucaena into a Napier grass-based diet at 500 g/kg and 750 g/kg DM positively affected rumen fermentation, reduced CH4 formation and increased beneficial fatty acids in the rumen. Although CO had similar positive effects on CH4 production and targeted beneficial fatty acids, it reduced the microbial protein synthesis at inclusion of 20 mg/mL DM. Overall, there were synergistic interactions between Leucaena and CO in reducing CH4 production and improving the fatty acid profile in the rumen. Implications It is possible to improve animal productivity while reducing the environmental impact of livestock production through inclusion of tannin-containing Leucaena and CO in ruminant diets in tropical regions where C4 grasses typically have low nutritive value.

Grazing diverse combinations of tanniferous and non-tanniferous legumes: Implications for beef cattle performance and environmental impact

We tested the effect of increasingly diverse combinations of tanniferous legumes (birdsfoot trefoil-BFT, sainfoin-SF) and alfalfa (ALF) on cattle performance, methane (CH₄) emissions and nitrogen (N) balance. Pairs of heifers (401 ± 49.6 kg) grazed three spatial replications of 7 treatments (n = 3/treatment): monocultures (BFT, SF, ALF) and all possible 2- and 3-way choices among strips of these legumes in a completely randomized block design of two 15-d periods during 2 consecutive years. Average daily gains (ADG) of heifers grazing the tanniferous legumes (1.05 kg/d) were 40% greater (p < 0.10) than of heifers grazing ALF (0.74 kg/d) during the first year. Heifers grazing the 3-way choice had greater intakes (10.4 vs 7.8 kg/d; p = 0.064) and ADG (1.21 vs. 0.95 kg/d, p = 0.054) than those grazing monocultures, suggesting a nutritional synergism among legumes. The average CH₄ emissions for legume monocultures vs. 2- and 3- way choices was 222 vs. 202 and 162 g/kg BW gain (p > 0.10), respectively. For heifers grazing SF and BFT compared with ALF, blood urea N was less (14.3 and 16.8 vs 20.8 mg/dL; p < 0.05) as were urinary N concentrations (3.7 and 3.5 vs 6.0 g/L; p < 0.05), but fecal N concentrations were greater (34.5 and 35.5 vs 30.5 g/kg, respectively; p < 0.05). Combining both tanniferous legumes (SF-BFT) led to the greatest declines in urinary N (2.24 g/L) and urea-N (1.71 g/L) concentration, suggesting that different types of tannins in different legumes result in associative effects that enhance N economy. In addition, heifers grazing 3-way choices partitioned less N into urine (40.7 vs 50.6%; p = 0.037) and retained more N (36.1 vs 25.2%, p = 0.046) than heifers grazing monocultures. In summary, combinations of tanniferous legumes with alfalfa improved animal performance and reduced environmental impacts relative to monocultures, resulting in a more sustainable approach to beef production in pasture-based finishing systems.

Phytogenic Additives Can Modulate Rumen Microbiome to Mediate Fermentation Kinetics and Methanogenesis Through Exploiting Diet-Microbe Interaction

Ruminants inhabit the consortia of gut microbes that play a critical functional role in their maintenance and nourishment by enabling them to use cellulosic and non-cellulosic feed material. These gut microbes perform major physiological activities, including digestion and metabolism of dietary components, to derive energy to meet major protein (65-85%) and energy (ca 80%) requirements of the host. Owing to their contribution to digestive physiology, rumen microbes are considered one of the crucial factors affecting feed conversion efficiency in ruminants. Any change in the rumen microbiome has an imperative effect on animal physiology. Ruminal microbes are fundamentally anaerobic and produce various compounds during rumen fermentation, which are directly used by the host or other microbes. Methane (CH4) is produced by methanogens through utilizing metabolic hydrogen during rumen fermentation. Maximizing the flow of metabolic hydrogen in the rumen away from CH4 and toward volatile fatty acids (VFA) would increase the efficiency of ruminant production and decrease its environmental impact. Understanding of microbial diversity and rumen dynamics is not only crucial for the optimization of host efficiency but also required to mediate emission of greenhouse gases (GHGs) from ruminants. There are various strategies to modulate the rumen microbiome, mainly including dietary interventions and the use of different feed additives. Phytogenic feed additives, mainly plant secondary compounds, have been shown to modulate rumen microflora and change rumen fermentation dynamics leading to enhanced animal performance. Many in vitro and in vivo studies aimed to evaluate the use of plant secondary metabolites in ruminants have been conducted using different plants or their extract or essential oils. This review specifically aims to provide insights into dietary interactions of rumen microbes and their subsequent consequences on rumen fermentation. Moreover, a comprehensive overview of the modulation of rumen microbiome by using phytogenic compounds (essential oils, saponins, and tannins) for manipulating rumen dynamics to mediate CH4 emanation from livestock is presented. We have also discussed the pros and cons of each strategy along with future prospective of dietary modulation of rumen microbiome to improve the performance of ruminants while decreasing GHG emissions.

Milk production, nitrogen utilization, and methane emissions of dairy cows grazing grass, forb, and legume-based pastures

Achieving high animal productivity without degrading the environment is the primary target in pasture-based dairy farming. This study investigated the effects of changing the forage base in spring from grass-clover pastures to forb or legume-based pastures on milk yield, N utilization, and methane emissions of Jersey cows in Western Oregon. Twenty-seven mid-lactation dairy cows were randomly assigned to one of three pasture treatments: grass-clover-based pasture composed of festulolium, tall fescue, orchardgrass, and white clover (Grass); forb-based pasture composed of chicory, plantain, and white clover (Forb); and legume-based pasture composed of red clover, bird's-foot trefoil, berseem clover, and balansa clover (Legume). Pastures were arranged in a randomized complete block design with three replicates (i.e., blocks) with each replicate grazed by a group of three cows. Production and nutritive quality of the forages, animal performance, milk components, nitrogen partitioning, and methane emissions were measured. Feed quality and dry matter intake (DMI) of cows were greater (P ≤ 0.05) for Legume and Forb vs. Grass, with consequent greater milk and milk solids yields (P < 0.01). Cows grazing Forb also had more (P < 0.01) lactose and linoleic acid in milk compared with cows grazing the other pastures, and less (P = 0.04) somatic cell counts compared with Grass. Cows grazing Forb had substantially less (P < 0.01) N in urine, milk, and blood compared with cows grazing the other pastures, with not only a greater (P < 0.01) efficiency of N utilization for milk synthesis calculated using milk urea nitrogen but also a larger (P < 0.01) fecal N content, indicating a shift of N from urine to feces. Both Forb and Legume had a diuretic effect on cows, as indicated by the lower (P < 0.01) creatinine concentration in urine compared with Grass. Methane emissions tended to be less (P = 0.07) in cows grazed on Forb vs. the other pastures. The results indicate that Forb pasture can support animal performance, milk quality, and health comparable to Legume pasture; however, Forb pasture provides the additional benefit of reduced environmental impact of pasture-based dairy production.

Ruminal Fermentation, Growth Rate and Methane Production in Sheep Fed Diets Including White Clover, Soybean Meal or Porphyra sp

Simple Summary

In ruminant feeding, the use of diets containing seaweeds could be a valuable alternative to conventional diets. The objective of this work was to investigate the ruminal fermentation, growth rate and methane production in sheep fed a diet including Porphyra sp. compared with diets including clover silage or soybean meal. Including Porphyra sp. had little impact on ruminal fermentation and methane production both in vitro and in vivo. Lambs fed Porphyra sp. had a similar growth rate to those fed a diet including soybean meal, confirming previous in vitro and in situ observations on the high-quality protein of Porphyra sp. in ruminant feed.

Abstract

The aim of the present work was to investigate the potential of Porphyra sp. as an alternative source of protein to soybean meal in diets for sheep. Our experimental treatments included a control diet (CON) based on grass silage and crushed oats and three diets containing protein supplements, clover silage (CLO), soybean meal (SOY) or Porphyra sp. (POR) to increase dietary crude protein concentrations. We studied its effects on rumen fermentation, growth rate and methane emissions. Ruminal fermentation characteristics, kinetics of gas production and methane production were studied in vitro by using batch cultures inoculated with rumen inoculum from sheep. There were no differences among diets in total volatile fatty acids (VFA) production or in the VFA profile in vitro. Across treatments, we measured no differences in methane production either in vitro or in vivo, and we saw no noticeable antimethanogenic effect of Porphyra sp. The present in vivo trial with lambs showed no differences in average daily weight gain when fed diets including Porphyra sp. or soybean meal diets (250 and 254 g/d, respectively). We conclude that Porphyra sp. has a protein value similar to high-quality protein sources like soybean meal.

Effect of Lipid-Encapsulated Acacia Tannin Extract on Feed Intake, Nutrient Digestibility and Methane Emission in Sheep

Simple Summary

Enteric methane is not just a contributor to anthropogenic greenhouse gas emission, it also represents a loss of potential feed energy. The use of Acacia tannin extracts as a dietary additive effectively reduced methane production while also modulating nitrogen loss. The reduction in methane output in sheep receiving the encapsulated-Acacia tannin extract (ATE), as compared to the crude-ATE diet, suggests the potential use of encapsulation to improve tannin inclusion in ruminant diets, by enabling the sustained release of the tannin to the rumen environment.

Abstract

Tannins have become important phytochemicals in ruminant production, due to their wide range of biological activities. The use of a crude extract often comes with limitations, such as reduced feed intake and fibre digestibility, which could be overcome by the use of encapsulated tannin extract. In this study, four rumen-cannulated Merino wethers were used in a 4 × 4 Latin square design to determine the effect of encapsulating Acacia mearnsii tannin extract on intake, nutrient digestibility, and methane emission. The animals were placed on one of the following diets: control diet only, diet + silvafeed (Silvafeed ByPro, 10 g/kg feed), diet + Acacia tannin extract (ATE), 40 g/kg feed), and, diet + lipid-encapsulated-ATE (palm oil encapsulated ATE, 50 g/kg feed) in 4 cycles. Wethers were offered an Eragrotis and Lucerne hay-based total mixed ration diet above maintenance requirement with forage: concentrate ratio 50:50. Silvafeed, a commercial tannin additive, was used as a positive control. Nutrient intake was not different across the treatments, but nutrient digestibility was affected by dietary additives (p < 0.05). Compared to the control, and unlike the crude extract, encapsulated-ATE and silvafeed did not reduce dry matter, organic matter, and neutral detergent fibre digestibility. While the overall N-retention and total N-excretion (g/d) were not affected by dietary additives, ATE and encapsulated-ATE diets reduced urine-N excretion (g/d) and only a slight reduction was observed in silvafeed diet. The faecal-N proportion was highest in the ATE diet (388 g/kg N-intake), followed by encapsulated-ATE (317 g/kg), and silvafeed (267 g/kg), with the control diet having the lowest proportion (230 g/kg). The acetate:propionate (A:P) ratio reduced as a result of the inclusion of dietary additives with crude ATE and silvafeed having lower A:P ratio compared to the control diet. Methane production expressed in g/kg dry matter (DM) intake was reduced by 12%, 30% and 19% in the silvafeed, crude ATE and encapsulated-ATE diets, respectively (p < 0.05). The reduced methane production with higher neutral detergent fibre (NDF) digestibility in the encapsulated-ATE, compared to the crude-ATE, confirms that encapsulated-tannin can be used as an additive in ruminant diets.

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.