The Utilization of Prairie-Based Blend Pellet Products Combined with Newly Commercial Phytochemicals (Feed Additives) to Mitigate Ruminant Methane Emission and Improve Animal Performance

Abstract

The objective of this review is to comprehensively upbring the development potency of value-added pellet products from prairie industry by-products or co-products in combination with newly developed hydrolysable tannins (HT) and saponin to mitigate ruminant methane emission and improve the productivity of ruminant animals. The prairie region often produced plentiful amount of co-products and by-products that still have nutritional properties and can be utilized as ruminant feed to keep the sustainability in the agriculture sector. In ruminants, rumen microbial fermentation produces methane (CH4) as one of the outputs that can cause energy loss and act as a potent greenhouse gas (GHG) in the open atmosphere. Recently, the newly developed HT extracted from nutgall (Gallae chinensis) and saponin extracted from tea (Camellia sinensis) products are commercially available at affordable prices and are able to reduce methane emissions. Reducing methane emissions is vital to aid and support carbon reduction goals, but it must be accomplished while preserving and increasing business, maximizing profit, and providing economic return and benefit to pulse, cereal, and oil-crop growers. In conclusion, the prairie unused product combined with the aforementioned phytochemicals can be developed as a new pellet product. However, further research may be needed to determine the most effective additive levels of both saponin and HT products due to their anti-nutritional abilities while maintaining and improving livestock productivity.

1. Introduction

1.1 Canadian prairies pothole region (CPPR)

Saskatchewan (SK), Alberta (AB), and Manitoba (MB) are three Canadian Prairies with expansive areas, partially covered by grasslands, plains, and lowlands stretching from Alberta’s Rocky Mountain foothills to Manitoba’s Red River Valley. The Canadian section of the prairie region is the country’s largest and most intensive grain crop production area, which spans 312,746 km² and accounts for about 83% of Canada’s total agricultural land area and about 5% of Canada’s total land [36, 100, 140]. Based on The Canada Guide [146], the economy of prairie land in Canada is significantly increasing led by the growth of industries followed by jobs and population in the mid-twentieth century with its main industries of services, oil, agriculture [livestock industries (dairy cattle, beef cattle, and sheep), and crop cultivation (canola, wheat, oats, and barley)]. A Recent report released by Canada Agriculture Census [20] also showed that Canadian Prairies (Manitoba, Alberta, and Saskatchewan) accounted for 83% of total Canada’s farms, nearly all of Canada’s canola (99,2%), spring wheat (97,6%), barley (96,2%), and 72,7% of Canada’s cattle industry.

1.2 Canadian prairies feed source potential

Being one of the world’s top producers and exporters of agricultural goods, Canada has the potential to play a significant role in the development of the cellulosic biorefinery industry supported by its abundant supply of cellulosic biomass produced by the agricultural sector [97, 114, 133]. Canadian Prairie Region produces various types of unused goods that can still be utilized as animal feed due to its high energy and starch contents [102]. The Pulse industry often produces low grade peas (Pisum sativum) or lentil screenings as by-products. Peas are processed in various ways such as frozen, raw, or canned, and expelled without using the pod (peas exterior component) and make up around 35–40% of the total peas’ weight [99]. With 254.2 g/kg CP, 869.0 g/kg DM, 31.4 g/kg ash, 8.5 g/kg ether extract, and 12.8 MJ/kg EM making peas (Pisum sativum) one of the most valuable feed sources either for ruminants or poultry [118]. In bio-oil processing, canola or carinata meals are also produced as co-products. Canola meals are considered as a proper ruminant feed because it is highly palatable to ruminants, inexpensive, it has a well-balanced amino acid (AA) profile and has no direct food value for humans [50, 53, 132]. Its protein content has also been proven to be highly degradable in the rumen [106], making it less effective as a post-ruminal AA source (44.3–74%) [161]. However, it is not recommended for livestock to directly consume it without pre-processing due to its poor quality, lack of phytonutrients, and incomplete nutrient content. Nevertheless, supplementing it with a multi-nutrient additive can produce high-quality feed that is able to successfully satisfy the livestock’s daily need for nutrients [6]. Additionally, plant-based meal (e.g., soy protein, pea protein, and starches) utilization for animal feed is environmentally friendly because every kilogram of their production releases approximately 1 kg of carbon dioxide into the atmosphere [123].

1.3 Benefit of prairies co-product and by-product utilization

Development of international and domestic markets for prairie pulse, cereal, and oil-crop producers, and feeds and livestock industries is a key to maintain and increase business, maximize profit, and provide economic return and benefit to pulse, cereal, and oil-crop producers. The utilization of both agricultural co-product and by-product based on prairie co-products from bio-oil processing (canola or carinata meal), pulse screenings (damaged peas/lentil, a non-food grade of peas/lentil/faba) can keep the sustainability in the agriculture sector. Moreover, the environmental impact of feed and animal production, as well as the economic value of innovative feeds in alternate applications, is critical [45]. The viability of utilizing alternative feeds for grazing animals is determined by factors such as feed value of novel feeds, animal production responses, and feed costs in comparison with standard diets. Many studies have proven that improper utilization of agricultural waste can cause severe environmental issues such as groundwater pollution, pathogen proliferation, and greenhouse gas emission [25, 155, 157]. To improve the competitive market (both domestic and international), it is necessary to establish a new suitable product that is environment-friendly and capable of reducing Greenhouse Gas (GHG) emission by mitigating ruminants (dairy, beef cattle, or sheep) methane, but also these new products have high feed milk/meat value (FMV) and are easily transported/shipped. High production ruminants (dairy and beef cattle) need to have an optimized nutrient supply for optimized high milk/meat production from newly developed feed products without causing severe GHG pollution by mitigating ruminant (dairy, beef cattle, or sheep) methane.

2. Feed additive utilization in ruminant daily feed

2.1 Feed additives on nutrition and performance

Feed additives are chemicals, microorganisms, or preparations that are purposely added to feed or water in order to carry out one or more of the activities mentioned above, besides feed material and premixtures. There are various functions of feed additives including to positively influence the properties of feed, the properties of animal products, and color, fulfil the nutritional needs of animals, influence the environmental effects of animal production, influence animal performance or welfare, particularly by influencing the microorganisms in the gastrointestinal tract or the digestibility of feed, or have a coccidiostatic or histomonostatic effect. Generally, additive substances may be categorized as technological (e.g., preservatives, antioxidants, emulsifiers, stabilizing agents, acidity regulators, silage (grass or other green fodder compacted and stored in airtight conditions, typically in a silo) additives); sensory (e.g., flavorings, colorants); nutritional (e.g., vitamins, minerals, amino acids, trace elements); zootechnical (e.g., digestibility enhancers, gut flora stabilizers); coccidiostats; and histomonostats [127]. Based on its function, there are two types of feed additives: nutritive feed additive and non-nutritive feed additive. Nutritive feed additives are compounds added to the feed ration to improve the nutrient values (e.g., amino acid, vitamin, and mineral), while non-nutritive feed additives are compounds added to the ration to improve values other than nutrients such as palatability (by adding color and odor), preserve the feed quality (by adding antioxidant), or as a pathogen inhibitor [127].

Adding antibiotic feed additives to ruminant diets during the reproductive period can improve absorption of nutrients and reproductive performance, which also has resulted in various positive health advantages. However, their use in ruminant diets is debatable due to the possibility of their deposition into meat and milk as well as the expansion of antimicrobial resistance brought on by the misuse of antibiotics, which has drawn attention to the need for new antibiotic alternatives in the field of animal nutrition [27, 80, 119]. Even in countries such as Indonesia and EU, feed additives that contain antibiotic growth promotors (AGP) are banned. This has drawn the researcher’s attentions to find alternative feed additives from natural sources, such as herbs and spices, which are affordable, effective, and eco-friendly. Many studies of feed additives have been established and it is proven that adding feed additives to the diet can increase performances in ruminant animals. The summary of several additives piloted to ruminant animals is outlined in Table 1.

Feed additive type(s)	Experiment object	Effects	References
Green tea extract (GTE)	Buffalo bulls	Fertility rate improves by 16.56%	Ahmed et al. [2]
Yeast	Dairy cattle	Health and productivity improvement	Miller-Webster et al. [87]
Phytochemicals, nitrate (NO3^−)	Beef cattle	Reduce CH4 production	Alemu et al. [3]
Apple bagasse yeast	Non-lactating rumen fluid of dairy cattle	Increases feed consumption	Castillo-Castillo et al. [22]
Yeast	Lactating dairy cattle	Milk production, DMI, and live weight gain	Dann et al. [31]
Yeast	Lactating ruminal fluid of dairy cows (Jersey cows)	Improving DMI, NDF digestibility, and naturally modifying rumen fermentation	Lila et al. [75]
Fumaric acid	Beef cattle	Increases total VFA production	Beauchemin and McGinn [7]
Sunflower oil	Angus heifer	Increases digestibility energy intake and the rate of gain cattle, reduces CH4	Beauchemin et al. [8]
Acacia mearnsii (black wattle) tannin	Sheep	Decreases ruminal ammonia, urinal nitrogen, and methane production	Carulla et al. [21]
Lactobacillus spp.	Pre-ruminant calves	Decreases coliform count, reduces scouring, improves feed intake, liveweight gain	Beeman [11]; Gilliland et al. [40]; Lee and Botts [73]
Lactobacillus spp.	Pre-ruminant lambs	Lower mortality, improves feed intake and liveweight gain	Pond & Goode [122]; Umberger et al. [149]
Garlic and citrus extract	Sheep	Decreases methane emission, increasing ruminal activity	Ahmed et al., [1]
Hemicellulose extract	Dairy cattle	Improve fiber degradation	Herrick et al. [52]
Microalgae and rapeseed meal	Dairy cattle	Improve fiber and nitrogen digestibility, increase NH3 concentration	Lamminen et al. [71]
Tannin	Beef cattle	Reduces NH3 and CH4, improves propionate and butyrate concentration	Orzuna-Orzuna et al. [109]
Lipid	Beef cattle	Increases propionate molar proportion, lowering acetate molar proportion and VFA	Dai and Faciola [28]
Macroalgae (Sargassum fulvellum)	Beef cattle	Increase DMD, total gas emission, and VFA	Choi et al. [26]

Table 1.

Various feed additive sources and their effects on ruminants.

DMI: dry matter intake, NDF: neutral detergent fiber, VFA: volatile fatty acid, DMD: dry matter digestibility.

2.2 Tannin utilization and benefit as ruminant feed additive

Tannins, usually called tannic acid, are a group of phenolic compounds that are regularly found in woody flowering plants used to deter herbivores from consuming them. Tannins have both positive and negative impacts when applied. There are various positive impacts including enhanced protein consumption, rapid body weight gain or wool production, higher milk production, increased fertility, and improved animal well-being and comfort through the reduction of worm loads and the prevention of bloat [96]. According to Goel et al. [41], tannins may be toxic to certain rumen microbes and may have negative effects on ruminant metabolism [126]. Low palatability and impaired diet digestibility are further negative consequences that have been linked to decreased performance [79, 148]. However, the source and concentration of tannins are the main factors that determine whether they are beneficial or not [61].

Tannins are varied among plants and primarily differentiated based on their molecular structure including hydrolysable tannins (HT; polyesters of gallic acid and different individual sugars), condensed tannins (CT; polymers of flavonoids), and mixtures of these two fundamental structures [86]. Condensed tannins are oligomeric and polymeric proanthocyanidins formed by polymerization of flavan-3-ols. CT cannot easily separate because it possesses protein-binding ability, which are flavonoid units linked by carbon-to-carbon bonds and cannot be separated by hydrolysis [141]. The main components of HT are gallotannins and ellagitannins, which can be easily separated by acids, bases, and enzymes [47]. When consumed, HT do not show anti-nutritional effects and give health benefits to livestock feed because of their strong antibacterial, anti-inflammatory, antioxidant, and anti-parasitic effects in animals [164].

2.3 Saponin utilization and benefit as ruminant feed additive

Saponins are secondary compounds that have extensively abundant supply in nature and usually known as non-volatile, surface-active compounds. The word “saponin” is derived from the Latin word “sapo,” which means “soap.” This is because when saponin molecules are combined with water, foam is formed. Saponins have been found in over 100 plant families, in several marine sources, and even there are a small number of fish that produce saponins as shark repellants [139]. The primary role of saponin is providing defense against many pathogens and herbivores [110, 111, 129]. Saponins are usually located in tissues that are most susceptible to bacterial or fungal infection or insect predation. There are three main categories of saponin: triterpenoid saponin, steroid saponin, and alkaloid saponin. Triterpenoid saponin is the most distributed in the plant kingdom and it is a phrase that denotes three monoterpene molecules, each of which has three carbon atoms. This indicates that there are six molecules totaling 30 carbon atoms. [35]. Triterpene saponin consists of two types (e.g., monodesmosidic and didesmosidic), where mono- and didesmosidic have single and double sugar chain, respectively [42, 78]. Steroid saponin is a type of triterpenoid saponin that has undergone modification. Its structure is made up of 27 carbon atoms in bicyclic five-membered rings and tetracyclic six-membered rings. Alkaloid saponin have structure similar to steroid saponins, the only difference is that the alkaloid saponin has piperidine ring (a six-membered ring carrying N atom) rather than pyranose ring (a six-membered ring carrying O atom) [35]. Numerous activities of saponin (e.g., antimicrobial, antihelminthic, insecticidal, larvicidal, and molluscicidal) have already been documented [104]. In ruminant animals, dietary saponins have significant effects on all phases of metabolism, including feed ingestion and waste excretion [39]. Also, it has been reported that saponins are effective antifungal and antiviral agents [32]. Several sources of saponins have been discovered to be devastating to protozoa and have been named as potential defaunating agents in the rumen [105, 152].

2.4 Pellet processing effects on value-added product

Pelleting is the process of forcing a pulverized mixture of feed materials through a metal plate with cylindrical holes [125]. Pelleting is one of the ways to reduce particle size to accelerate nutrient fermentation in rumen. Gustafson [43] characterized the forces occurring on the pellets as impact, compression, and shear; impact forces break the pellet outer layer and any existing cleavage planes in the pellet; compression forces crush the pellet and create failure along cleavage planes; shear pressures abrade the pellet’s corners and exterior. Reducing feed particle size in daily livestock feed has different impacts on digestion that affect each other: (1) increasing dry matter intake (DMI), (2) increasing the surface area for bacteria to attach, resulting in improvement of ruminal degradation, (3) affecting chewing time and saliva production, which have further effects on ruminal pH because saliva acts as a buffer, and (4) affecting rumen retention, which possibly supports the improvement of subacute ruminal acidosis (SARA) [16, 65, 89]. Furthermore, blended feed substances processed into pellets can balance amino acid delivery, enhance and optimize nutritional supply, and alter rumen fermentation behavior [147]. Pelleting has various technical advantages, including enhanced stability (because of very low moisture content) and simpler handling, storage, and transportation [16]. Additionally, Johnson and Johnson [62] reported that grinding or pelleting forage diets have been shown to lower enteric CH4 emissions by 20–40% at high intakes. This might be explained by the faster rate of feed transit, which reduces the amount of time the feed is exposed to ruminal digestion [84].

3. Ruminant methane emission

3.1 Methane emission mechanism

Methane also known as marsh gas or methyl hydrate was discovered and isolated by Alessandro Volta in November 1776 in Lake Maggiore, Italy. Methane is a colorless and fragrantless gas widely found in nature as a result from the decay/decomposition of organic matter by certain bacteria and usually used by humans as fuel to make heat and light. Methane is the most basic of the paraffin series of hydrocarbons and the simplest member of the alkane family, which is a group of organic compounds consisting only of carbon and hydrogen atoms and one of the most potent greenhouse gases (GHG), and it has the molecular formula CH₄. According to Britannica [17], the characteristic of methane has a specific gravity of 0.554, making it lighter than air, hardly dissolves in water but dispersible in organic solvent, and quickly burns in the presence of air; releasing carbon dioxide and water vapor, the flame is fierce, pale, and barely bright, has a melting point of 182.5°C (296.5°F) and a boiling temperature of 162°C (259.6°F). The general methane formation equation is:

$$C{O}_2+{\text{8H}}^{+}+\text{8e}-\to C{H}_4+{\text{2H}}_2\text{O}$$E1

Methane can also be produced by polygastric animal such as cows and lambs as a natural by-product of the digestion and fermentation that occurs in the ruminal guts (rumen) through a process called methanogenesis. Methanogenesis is an anaerobic reprocess where C atom contained in CO or CO₂ reduced to CH_4, with the intention to avoid hydrogen accretion, which subsequently inhibits dehydrogenase enzyme activity and disturbs the fermentation mechanism [81]. According to Janssen and Kirs [57], there are 113 species and up to 28 genera of methanogens that have been discovered in nature, while Methanobrevibacter (61,6%) is regarded as the most dominant methanogen in the rumen. Methanogens are the primary component of the Euryarchaeota and are separated into five orders including Methanococcales, Methanobacteriales, and Methanomicrobiales [38]. These methanogenic bacteria already exist in cows, even in the stage of pre-ruminant [44, 136]. Methane is mostly produced in rumen (80–95%), while other small quantity is produced in large intestine (5–20%). Methanogenesis can occur via CO₂ reduction utilizing H₂ as an electron source, methyl-group reduction, or acetate reduction [76].

Ruminant animals consume plant materials as their primary source of nutrition that contains structural carbohydrates, proteins, and other feed components (Figure 1). These complex structures are hydrolyzed to simpler monomers, and then are subsequently fermented by rumen microorganisms to produce VFA (acetate, propionate, butyrate, and small amount of valerate), CO₂, CH₄, and H₂ [91]. Under anaerobic conditions in the rumen, oxidation reactions require ATP to release hydrogen. The amount of hydrogen produced is highly dependent on the type of feed and the type of microbes that work to ferment the feed in the rumen [81]. The methanogenic archaea bacteria and other microorganisms that reside in the rumen utilize hydrogen (H₂) that has been mainly produced during hydrogenase microbial fermentation, carbon dioxide (CO₂), and a certain amount of intermediate fermentation products that have been produced by other microbes as substrates to generate methane (CH₄), which is their only method for energy acquisition.

Figure 1.

Methane production in rumen (adapted from [10]).

There are three major pathways for rumen fermentation: the hydrogenotrophic pathway converts H₂ and CO₂ produced by bacteria, fungi, and protozoa into CH₄ [82, 83]. The most prevalent hydrogenotrophic bacteria are from the genus Methanobrevibacter, which is classified into two groupings, the SGMT clade (Mbb. gottschalkii, Mbb. smithii, Mbb. Thaueri, and Mbb. millerae) and the RO clade (Mbb. ruminantium and Mbb olleyae) [57, 67]; and methyl groups, which are found in methylamines and methanol [103, 124]. Methylamines are formed from glycine betaine (derived from beetroot) and choline (which is found in plant membranes), whereas methanol is generated from the hydrolysis of methanolic side groups in plant polysaccharides; the aceticlastic pathway is reviewed by Morgavi et al. [92]. As for methane excretion, ruminants have unique digestive system that allows them to regurgitate and re-chew their partially fermented feed as cud. During this process, the accumulated gases including methane are released in the form of exhaust gas (farts and burps) as well as in feces [81, 107].

3.2 Factors affecting ruminant methane emission

3.2.1 Type and quality of feed

Type and quality of feed can influence the synthesis of methane in the rumen. Broucek [18] reported that forage species, forage processing, forage fraction in the diet, and grain supply affect the CH₄ generation in ruminants. These are mostly linked with carbon supply that will affect the whole activities of ruminant microorganisms. Improved feed quality is also intended to improve animal performance. Thus, improved diet quality can be an efficient way of lowering emissions per unit of animal product [84]. Certain feed components, such as high-fiber forages, promote more extensive fermentation and higher methane emissions compared to low-fiber or grain-based diets because fiber-rich feeds require extensive microbial activity to digest, leading to increased methane production. Methane production tends to decrease as feed protein concentration increases, but it also increases when feed fiber content increases [62, 135]. When compared to a lower concentrate diet (around 30 or 40%), a higher concentrate diet (around 80 to 90%) can minimize gross energy loss caused by methane by 2 to 3% [131]. Recent research conducted by Olijhoek et al. [108] on Holstein and Jersey cows fed with high concentrate diet (up to 91%) showed that there was a noticeable connection between breed and diet between Holstein cows and Jersey cows (48 and 22%, respectively). Although dietary adjustments to consume less forage may lower methane generation, they may cause other physiological problems that could possibly devaluate pH and lead to severe ruminal acidosis [121].

3.2.2 Level and feed intake

Enteric methane emissions are clearly linked to dry matter intake (DMI) either in dairy or in beef cattle [24]. According to Shibata and Terada [135], CH₄ generation normally increases as the daily feed intake increases. Generally, when ruminants consume more feed, and their rumen becomes more active, leading to increased fermentation and higher methane production. In the rumen, which is the first chamber of a ruminant’s multi-compartment stomach, microbes break down the carbohydrates present in the feed into monomer or oligomer compounds, producing volatile fatty acids (VFAs), which then also produce metabolic by-products. Energy is produced by the ruminants’ digestion of carbohydrates, which also produces enteric methane (CH₄) emissions [142]. Methane emissions were lower on a high concentration diet (920 g/kg DM) than on a mixed (forage/concentrate) diet (500 g/kg DM) [33]. When it comes to neutral detergent fiber (NDF) intake, the CH₄ production is higher when cattle consume high-fiber digestibility diets, which can boost the acetic acid (CH₃COOH) production that exceeds the propionic acid (CH₃CH₂COOH). The acetic acid subsequently results in the release of H, which is utilized by methanogens to form CH₄ [84].

3.2.3 Rumen microbial content

The rumen is the primary generator of methane and specific microbiome characteristics are linked to low/high methane levels. In the rumen, ciliate protozoa synthesize H₂, which is the principal substrate for methanogenesis in the rumen, and removing them (defaunation) resulted in 11% less methane emissions [145]. Intuitively, the methanogenic bacteria population should be linked to methane emission. However, some researches in dairy cattle, sheep, and beef cattle showed that there is a weak, or even no correlation between methanogens’ overall abundance with methane emission [29, 30, 66, 93, 134, 153, 165].

Rumen microbial contents are more likely affected and closely related to the type and composition of feed given to the ruminants. Thus, the feed-contained-nutrient decides the amount of H₂ produced in the process of forming acetate and butyrate and the use of H₂ which can be oxidized to H₂O, accompanied by the reduction of CO₂ to CH₄. Research conducted using steers showed that rumen fluid from concentrate-fed steers had more propionic acid and less acetic acid, as well as less archaea and protozoa than mixed-fed steers; these rumen contents, particularly protozoa and archaea, show a strong association with CH₄ emissions (g/kg DMI) [33, 153].

3.2.4 Environment temperature

In tropical climate regions, which typically have higher temperatures, it affects the quality of forages. The forage’s cell wall, acid detergent fiber, and lignin tend to rise, resulting in declined digestibility of feed and increased energy loss, which continuously leads to decreased feed intake and an increase in CH₄ generation due to a drop in animal production efficiency [70, 72, 135]. It is also attributed to extended preservation time in the rumen and a reduced rate of methanogen outflow from the rumen to the abomasum [70]. Furthermore, Lee et al. [72] found that elevated temperatures may result in an increase in methane generation of 0.9% every 1°C of temperature rise and 4.5% every 5°C of temperature rise. Methane generation per DMI rose and was nearly 10% greater at temperatures over 26°C than at 18°C temperatures in cows at the preservation level of feeding [70].

Overheat temperature can cause severe heat stress and also inflict on cattle itself. Cattle usually will drink more and eat less when the temperature rises. Heat stress can increase rectal temperature, respiratory rate, pulse rate, and water intake, while subsequently reduce body weight gain, dry matter intake, and CH₄ emission. A heat stress experiment on ruminants conducted by Yadav et al. [162] using non-lactating crossbreed dairy cows showed that CH₄ emissions fell significantly with increasing temperature up to >35°C. Furthermore, as animals begin to suffer from heat exhaustion, their food intake decreases, and their metabolism slows [85].

4. Ruminant methane mitigation

4.1 Effect of methane production for ruminants

Ruminant livestock production plays a significant role in global agricultural systems, providing a valuable source of meat, milk, and fabrics for humans. However, ruminants, such as cattle, sheep, and goats, are known to produce and release substantial amounts of anthropogenic methane (CH₄) during their digestive process (around 250 to 500 L per day) to the open world and can cause greenhouse effect to the environment that may occur in the next 50–100 years, resulting on climate change and risen the average temperature of the earth [62, 90]. Methane is one of the potent greenhouse gases produced during the anaerobic fermentation of feed in ruminants, contributing to global warming and climate change of approximately 15% of the world’s total methane emission [95]. Methane only lasts for a relatively brief time in the atmosphere (around 8, 4 to 12 years) compared to other greenhouse gases which lasted for a longer period [CO₂ (300–100 years), CFC (40–150 years), N₂O (114 years), SF₆ (3200 years), NF₃ (740 years), HFC (270 years), PFC (2600–5000 years)]. It is reported that methane is 21 times as potent as carbon dioxide (CO₂) at trapping heat in the atmosphere [23, 34, 37]. Additionally, methane formed by the ruminants can also inflict around 2 to 12% of energy loss [163], causing feed inefficiency and financial waste. Animal species, DMI, type of forage fed, overall ratio of concentrate to forage, feed conversion efficiency, addition of lipids or ionophores to the diet, plant secondary metabolites, alteration in the ruminal microflora, and rumen fermentation features, such as VFA and hydrogen (H₂), all affect the CH₄ synthesis [62, 143, 150, 160]. Furthermore, according to Broucek [18], not only diet but also different types of ruminants can produce different amount of methane emission (Table 2).

Ruminant types	CH4 production
Dairy cows (avg.)	151–497 g/day
Holstein	299 g/day
Crossbread	264 g/day
Lactating cows	354 g/day
Non-lactating cows	269 g/day
Heifers (avg.)	223 g/day
Heifers grazing on fertilized pasture	223 g/day
Heifers grazing on unfertilized pasture	179 g/day
Dairy ewes	23 g/day
Beef cattle (avg.)	161–323 g/day
Mature beef	240–396 g/day
Cattle feed with pasture	230 g/day
Cattle feed with high grain	70 g/day
Suffolk sheep	22–25 g/day
Bison	200 g/year

Table 2.

Ruminant CH₄ production.

Source: ([18]; [112]).

4.2 Diet manipulation to mitigate ruminant methane

Methane is produced as part of an inevitable and natural rumen fermentation outcome. Over the decades, scientists and researchers have tried numerous methods to suppress the ruminant methane emission, such as production intensification, altering diet management, diet manipulation, rumen manipulation, and selection of low-CH₄-producing animals [9]. Adding feed additives to dietary feed is one of the most common methods conducted by many researchers. Dietary manipulation method can decrease CH₄ emission by 40% [12]. Even in another study, it was found that improved nutrition may allow for a reduction in CH₄ emissions of up to 75% [94]. There are two broad groups of dietary tactics: (1) enhancing the forage quality and adjusting the diet’s percentages and (2) feeding chemicals to animals that either directly prevent methanogens or modify metabolic pathways to reduce the substrate for methanogenesis as a feed additive [46]. Notably, there are at least eight dietary intervention types that have been conducted from 2000 to 2020 (i.e., oils, macroalgae, nitrate, ionophores, protozoa controls, phytochemicals, essential oils, and 3-nitrooxypropanols). The development of feed additive made from oregano and green tea extract can reduce CH₄ gas emission in dairy cows [69], feed additive made from the mixture of xylanase and Saccharomyces cerevisiae has been proven to lower the CH₄ of agricultural calf farms [51], and feed additive developed from algae; Ulva sp. decreased CH₄, NH₃, and VFA production, while Sargassum horneri decreased rumen CH₄ and NH₃ [113]. Wang et al. [156] reported that the methane reduction strategy through diet manipulation has its own benefit and drawbacks; therefore, further research is required (Table 3).

Strategy	Mechanism	Effects on CH4	Problem
Ionophores	Inhibiting H2 producer activity	Medium	Bacterial resistance Residue
Halogenated compounds	Inhibiting methanogens activity	High	Toxic Residues Bacterial resistance
Phytochemicals	A broad antimicrobial activity	Medium	Expensive Bacterial resistance Performance decline
Lipids	Inhibiting methanogens activity	High	Expensive Negative effects on performance
Nitrooxy compounds	Inhibiting methanogens activity	High	Expensive Potential bacterial resistance
Algae	Inhibiting methanogens activity	High	Affect rumen fermentation Residue
Propionate precursors	Competing with methanogenesis for hydrogen source	Low	Expensive Inefficiency
Concentrates	Competing with methanogenesis for hydrogen source	Medium	Costs Acidosis risk
Forages	Lowering CH4 emissions per unit of meat and milk	—	Increasing the absolute emission
Non-forage fiber sources	Competing with methanogenesis for hydrogen source	Low	Inefficiency

Table 3.

Methane reduction strategies through diet manipulation.

Source: [4, 156].

5. Tannin and saponin utilization to reduce methane emission

With the benefits of efficiency, plant extracts and their secondary metabolites have a high potential for ruminant methane mitigation. Incorporating saponin as ruminant feed can potentially suppress the production of methane, one of the biggest contributors to global warming [130]. Adding plant tannins to ruminant dietary can help mitigating methane emissions by reducing methanogenesis in rumen. This may be related to the antibacterial qualities of the tannins by decreasing fiber digestion and causing the ruminal microbial bacteria to not fully digest the feed [88]. Plant tannins, as feed supplements or as tanniferous forage diets, have shown a potential for reducing enteric CH₄ emissions by up to 20% [151, 159]. Many studies have assessed, both in vitro and in vivo, the connection between tannin-rich diets and ruminal CH₄ formation. The CH₄ reaction to tannin administration varies greatly based on the origin, variety, and molecular weight of the tannins, as well as the methanogenic ecosystem prevalent in the animal [10]. Tannins have anti-methanogenic ability, which has been demonstrated through in vitro evaluation. They can do this directly by suppressing methanogens or indirectly by affecting protozoa inside the rumen [15, 59]. Adding tannin to ruminant feed, either a tannin-containing diet or tannin extracts, can reduce enteric methane production [61]. A recent report using in vivo and in vitro methods assessed by Zhang et al. [163] showed that the addition of 30 and 60 g/kg of hydrolysable tannins (HT) to ruminant dietary was able to significantly reduce rumen CH₄ production by 37.6 and 36.4%, respectively. The effects of tannin addition in ruminant feed and its effect on methane mitigation are summarized in Table 4.

Tannin origin	Diets	Methane reduction effect	References
Rain tree pod meal (6 g/kg of total DMI)	Total mixed ration (concentrate + rice straw treated with urea) at 25 g/kg BW	10%	Anantasook et al. [5]
Autocarpus integrifolia leaf (186 g/kg DM) of CT Ficus religiosa leaf (13.5 g/kg DM) of HT Jatropha curcus (5.6 g/kg DM) of HT Sesbania grandiflora (13.1 g/kg DM) of HT	Elusine coracana straw and commercial concentrate mixture in 1:1 ratio	4.73 (mL/total gas reduction) (mL/total gas reduction) (mL/total gas reduction) 2.02 (mL/total gas reduction)	Bhatta et al. [14]
Acacia (Acacia molissima) tannin extract	Forages (600–800 g/kg) and concentrates (200–400 g/kg)	Goat (13%) Sheep (23%) Buffalo (22%) Cattle (9%)	Bueno et al. [19]
Acacia mearnsil extract (82% CT) Schinopsis balansae extract (90.4% CT) Castanea sativa extract (5.7% CT and 75.5% HT) Quercus aegilops extract (8.0% CT and 71.2% HT)	Total mixed ration (forage /concentrate)	12%, 21%, 32%, and 38% NE, 23%, 34%, and 40% 13%, 23%, 31%, and 40% 11%, 19%, 26%, and 36%	Hassanat and Benchaar [48]
Sainfoin (Onobrychis viciifolia) accessions: Rees “A” CPI63763 Cotswold Common CPI63767	50 mg lucerne (tannin free) / 30 ml of inoculum	30% 45% 30% 48%	Hatew et al. [49]
Chestnut Sumac Mimosa Quebracho	380 mg (concentrate + hay) (30:70) / 30 mL of inoculum	23% 30% 23% 27%	Jayanegara et al. [59]
Trigonella foenumgraecum leaf Sesbania sesban leaf	Hay: concentrate (50:50)	2. 20%	Jayanegara et al. [60]
Purified chestnut Sumac	Hay: concentrate (70:30)	6.5% 7.2%	Jayanegara et al. [58]
Panicled-tick clover (PCT) Sericea lespedeza (SL)	Alfalfa: corn	65% 24,4%	Naumann et al. [101]
Quebracho condensed tannin extract (75–77% QCT)	Corn: alfalfa	Ns, ns, ns	Pinski et al. [120]
Acacia cyanopylla (CT 63%)	Dates by-products and the vetch-oat	56.25% and 36.50%	Rira et al. [128]
Leucaena		41.4 mL/g TDOM 47.4 (−14%) 1/kg DOM	Soltan et al. [137]
Acacia saligna leaves (6.3% CT) Leucaena leucochepala leaves (4.6% CT) prosopis julifara leaves (0.04% CT) atriplex halimus leaves (0.02% CT)	Acasia saligna Leucaena leucochepala Prosopis julifora Atriplex halimus	38% 36% NE NE	Soltan et al. [138]
Leucaena leucochepala extract (100% CT) 10,15, 20, 25, and 30 mg	Guinea grass	−33%, −47%, −57%, −59%, and − 63%, respectively	Tan et al. [144]
Mangosteen peel powder		7%	Wanapat et al. [154]
Chestnut (castaena sativa) Valonea (quercus valonea)	Grass silage (100%)	63% 34%	Wischer et al. [158]

Table 4.

Effect of tannin addition on methane emission.

DMI: dry matter intake, DM: dry matter, NA: not applicable, NE: no effect, ns: not significant, −: decrease compared to control, BW: body weight, CT: condensed tannin, HT: hydrolysable tannin, TDOM: truly degraded organic matter, DOM: degraded organic matter.

Adding saponin extract can also reduce methane emissions produced by ruminants, such as sheep and cattle (dairy and beef). It has been demonstrated that the extract from the leaf of Sesbania sesban or lucerne roots’ saponins can significantly lower protozoa populations [68, 77, 105], which are crucial for the protein degradation of ruminal feed [63]. It is going to be difficult to determine the ideal doses of saponins to have a beneficial effect on rumen fermentation or ruminant production because saponins are typically supplied as extracts or as ground materials [64]. Very recent research conducted by Zhang et al. [163] reported that the addition of tea saponin extracts (5 g, 10 g, 20 g/kg DMI) was able to significantly reduce methane (CH₄) by 6.17 L, 7.86 L, and 10.53 L/kg DMI, respectively. Tannins and saponins extracts are recently available in the commercial market, and the newly developed hydrolysable tannins and tea saponin products are commercially available at very affordable prices (Biolink Biotechnology, Co, LTD, Beijing). The lowest market prices for these products are $11/kg (purity>81%) for hydrolysable tannins and $11/kg (purity>65%) for tea saponin products. When applying phytochemicals as feed additives, the amount and purity should be carefully monitored, as they may have anti-nutritional properties in larger quantities [4]. The effects of saponin addition in ruminant feed and its effect on methane mitigation are summarized in Table 5.

Saponin origin	Diets	Methane reduction effect	Reference
Purified saponin (1.55, 3.10, 4.65, and 6.20 mg/30 mL rumen inoculum)	Hybrid cumbu; Napier grass	14.04, 21.90, 34.30, and 37.60%	Bharathidhasan et al. [13]
Papaya leaf (7.5, 12.5, and 25% of diet)	Concentrate (50%) + alfalfa (50%)	17, 34, and 37%	Jafari et al. [54, 56]
Papaya leaf methanol extract (PLE; 5, 10, and 15 mg of PLE/0.25 g DM)	Concentrate (50%) + alfalfa (50%)	Ns, ns, and 34%	Jafari et al. [54, 56]
Papaya leaf solvent fractions (PLF; 15 mg of PLF/0.25 g DM)	Concentrate (50%) + alfalfa (50%)	25%, 29%, ns, 25% and ns	Jafari et al. [55]
Yucca saponin (8.5% saponin)	Total mixed ration (forage/concentrate)	NA	Li and Powers [74]
Yucca schidigera	Forage and concentrate (65:35)	15%	Narvaez et al. [98]
Quillaja saponin (0.6 g/L) Quillaja saponin (1.2 g/L) Quillaja saponin (1.2 g/L) + propionic acid (8 mM) + nitrate (10 mM)	Corn silage (45%) + alfalfa hay (10%) + dairy protein product (20%) + concentrate mixture (25%)	11% 24% 85%	Patra and Yu [115]
Quillaja saponin (0.6 g/L) Quillaja saponin (0.6 g/L) + nitrate (5 mM) and sulfate (5 mM)	Corn silage (45%) + alfalfa hay (10%) + dairy protein product (20%) + concentrate mixture (25%)	8% 47%	Patra and Yu [116]
Quillaja saponin Saponin + garlic Saponin + nitrate Saponin + garlic + nitrate	Concentrate and alfalfa (70:30)	36% 45% 55% 70%	Patra and Yu [117]
Yucca schidigera (4.4% saponin)	Dates by-product + the vetch + oat	60%	Rira et al. [128]
Mangosteen peel powder (10.9% saponin)	Concentrate + rice straw	7%	Wanapat et al. [154]

Table 5.

Effect of saponin addition on methane emission.

DM: dry matter, NA: not applicable, ns: not significant.

6. Summary, conclusion, and future study

Based on the scientific findings presented in this chapter, the following most important conclusions can be drawn:

1. Canadian Prairie region has an abundant amount of unused products with affordable prices that can possibly be used as a source of ruminant feed that offers high energy and starch contents, but it is not recommended to be used directly without processing.

2. It is founded that pellet processing of blended feed substances can balance amino acid delivery, enhance and optimize nutritional supply, and alter rumen fermentation behavior in ruminants and can also reinforce technical advantages including enhanced stability, simpler handling, and storage.

3. Greenhouse gas (GHG) emission has become a joint challenge in the last few decades and numerous attempts have been made to reduce CH₄ production in ruminants with different approaches. However, those approaches still have some drawbacks (e.g., costly, resistant, residue, toxic) which detain its effectivity and application.

4. Tannin and saponin are two phytochemicals derived from plant materials with approved methane reduction agents. However, there is no literature on the effects of unused prairie products combined with those newly developed hydrolysable tannins (or saponins) at different levels. Therefore, a further investigation is necessary to study the effect of pellet processing of this combination on (1) bioactive compound (CT) levels, (2) amino acid profile, (3) physiochemical and nutrient profiles, (4) nutrient fermentation on GHG emission, utilization, and availability in rumen and intestine in ruminants, (5) protein and energy metabolic characteristics and truly absorbed nutrient supply in ruminant system, (6) changes on molecular structure in relation to nutrient utilization availability, and (7) animal metabolic characteristics and production performance.

Acknowledgments

The Ministry of Agriculture Strategic Research Chair (PY) Research Programs have been financially supported by various grants from the Natural Sciences and Engineering Research Council of Canada (NSERC-Individual Discovery Grant and NSERC-CRD Grant), Saskatchewan Agriculture Strategic Feed Research Program Fund, Agricultural Development Fund (ADF), SaskMilk, SaskCanola, AlbertaMilk, Saskatchewan Forage Network (SNK), Western Grain Research Foundation (WGRF), SaskPulse Growers, Prairie Oat Growers Association (POGA), etc. The JH research programs are supported by Inner Mongolia Autonomous Region Science and Technology Plan Project, National Foreign Experts Introduction Project, Technical Innovation System of Sheep Industry in Inner Mongolia, and Ordos Major Project in Inner Mongolia. The Feed Molecular Structure Research Programs have been supported by Canadian Light Sources (CLS, University of Saskatchewan, Canada), National Synchrotron Light Sources- Brookhaven National Lab (NSLS-BNL, New York, U.S. Department of Energy, USA), Advanced Light Source-Berkeley Lawrence National Lab (ALS -BLNL, Berkeley, U.S. Department of Energy, USA).