The Role of Feed Additives in Reducing Carbon Emissions

12 April 202214 min reading

Generalizing conscious breeding for sustainable and ecological livestock, preferring the accurate amount and quality of feed and feed additives will be highly effective in preventing the possible effects of climate change in the future.

The rapid increase in the world population changes the consumption amount and habits. The increase in consumption accelerates agriculture and livestock practices and increases industry and energy requirements. This situation causes the negative effects of greenhouse gases to intensify as the amount of animal waste increases and the amount of methane released into the atmosphere is affected (Kılıç and Boğa, 2021). Greenhouse gases, which have an important place in climatic changes, cause warming of the atmosphere by holding on to the long-wave infrared rays reflected back to the atmosphere (Koyuncu and Akgün, 2018). While 40% of global methane emissions are of natural origin, 60% are anthropogenic, that is, enteric fermentation waste from agriculture and livestock (cattle breeding), human-made waste yards, sewage plants, rice fields and biomass incineration (Nosalewicz et al., 2011). It has been reported that the share of the livestock sector in global anthropogenic greenhouse gas emissions is 18%, while its share in methane emissions is 30-50%, and the effect of ruminant breeding reaches 80% within this share, while chicken and pig farming is 8-9% effective (Bayat and Shingfield, 2012; Gerber et al, 2013; Opio et al, 2013). In summary, improper and incorrect agricultural and livestock practices increase greenhouse gas emissions such as CO2 (carbon dioxide), CH4 (methane) and N2O (nitrogen oxide). In addition, they stated that methane, which is excreted from the body with feces, urine and burping, represents 5.5-6.5% of the gross energy intake for cattle, sheep and goats (Johnson and Ward, 1996). Therefore, besides its negative impact on the environment and climate, it also causes economic losses. For this reason, strategies to reduce greenhouse gas emissions are developed, especially in ruminant feeding, and it is recommended to use appropriate feed additives in rations on top of recommendations for the use of quality raw materials and the preparation of correct ration formulations. In order to estimate the methane release to the nature correctly, besides the feeding methods, animal species and number, live weight and yield information of animals are taken into consideration.

The main factors affecting methane emission in terms of animal feeding can be listed as feed quality and conversion rate of feeds, processing of feed, adding oil to the ration, using feed additives in ration such as probiotics, organic acids, herbal extracts, enzymes, clay minerals and algae, and using substances such as tannin and saponin.

When crude cellulose is broken down by bacteria in ruminants; pyruvic, succinic and lactic acids are formed as intermediate products, and volatile fatty acids (VFA), CO2 and methane are formed as last products. For this reason, choosing quality roughage and determining the roughage/concentrated feed ratios are effective in increasing the digestibility of feeds and preventing yield losses, while also reducing methane emissions. It is estimated that the production of CH4 and N₂O produced by high-yielding animals is lower than that of low-yielding animals because they consume less roughage. Interventions such as increasing the grain ratio in the ration, choosing corn silage, and increasing the oil level are effective in reducing methane emissions. The roughage/concentrated feed ratio is also effective in regulating CH4 production, as it is effective in changing acetate : propionate levels in the rumen. Because propionic acid reduces the rumen pH, preventing the reproduction of protozoa and thus preventing the protozoa from producing more H2 for methanogens (Kılıç and Taurus, 2021). It has been reported that legume forage crops with low fiber content and high dry matter content have less methane emissions because of their rapid digestion (Beauchemin et al, 2008). Moreover, it has been determined that methane production can be reduced significantly by grinding or pelleting the feeds (Moss et al, 2000). Apart from these, it is known that the addition of fat to the rations, especially in terms of meeting the energy needs of high-yielding dairy cows, is effective in reducing methane emissions (Kılıç and Boğa, 2021). Adding fat to the ration suppresses methanogens and cellulolytic bacteria and slows down the digestion of fibrous foods, using the H2 present in the rumen through hydrogenation of fatty acids. Thanks to this effect, it has been reported that adding oil to the ration can reduce methane production by 21%. Although fats contribute to the reduction of methanogens by affecting cellulose digestibility, it should be noted that when the fat ratio in the diet is above 5-6%, it may have negative effects on cellulolytic bacteria and protozoa.

Another measure that can be taken in the field of animal nutrition in terms of reducing methane emission is the use of feed additives in rations. In this context, it is often recommended to use probiotics in rations, especially in order to maintain the balance of the rumen microbiome. Among the lactic acid bacteria, Lactococcus plantarum, L. casei, L. acidophilus and probiotics such as Enterococcus faecium, Megasphaera elsdenii, Aspergillus oryzae fermentation extract and Saccharomyces cerevisiae yeast culture that are effective in acetate and propionate production are being widely used (McAllister et al, 2011). Probiotics are effective in reducing H₂ production and CH₄ emission due to the increased number of bacteria due to the breakdown of degraded carbohydrates between microbial cells and fermented products (Newbold and Rode, 2006). In an in vitro study, it has been determined that the total volatile fatty acid production did not change with the addition of Saccharomyces cerevisiae to the ration and there was a significant decrease in the acetic acid: propionic acid ratio (Öztürk et al., 2015). The increase in propionic acid synthesis and the acceleration of fermentation in the rumen are the reasons that reduce methane production. It has been demonstrated in different studies that adding yeast to the ration increases the synthesis of propionic acid, reduces the number of protozoa, or decreases methane production by increasing animal productivity (Chaucheyras et al, 1995; Newbold et al, 1998; Öztürk et al, 2015; Gür and Öztürk, 2021). It has been reported that adding yeast to the ration accelerates the synthesis of acetic acid by acetogenic bacteria and suppresses methane synthesis through the depletion of metabolic H2 in the medium. Adding yeast to the ration also contributes to the stability of the rumen pH. Thus, it increases the resistance against subacute ruminal acidosis (SARA) in feeding with a ration containing high concentrate feed (Lila et al, 2004; Gür and Öztürk, 2021). Probiotics also prevent nitrite toxication by taking a role in the detoxification of toxic nitrite that occurs through the addition of nitrate to the ration, which is a very effective method in reducing methane production (Latham et al., 2018).

There is a consensus that methane production decreases when propionic acid production is increased in the rumen. Starting from this point of view, it has been noted that some organic acids (malic acid, fumaric acid and pyruvic acid) or sodium salts of organic acids, which are propionic acid primers, can reduce methane production by shifting the rumen fermentation towards propionic acid (Newbold and Rode, 2006; Sahoo and Jena, 2014; Carro and Underfeld, 2015). It is also known that organic acids such as malic and fumaric acid reduce enteric methane production.

The fact that antibiotics cause resistance development and residue formation in animal tissues increases the interest in natural additives in the feed additive production industry. These natural plants, which contain substances such as essential oil, saponin, and tannin, have come to the fore in regulating the rumen microbial population and nitrogen metabolism, reducing methane production, reducing the incidence of feeding-related problems such as acidosis, and improving the health and productivity of animals. Essential oils of fennel, clove, garlic, onion and ginger are known to inhibit in vitro and in vivo methane production (Kaya et al, 2012). It has been stated that there is a significant decrease in the production of CH4 and CO2 gases with the use of thyme, mint and orange oils in the rations, the number of methanogen bacteria is damaged due to the antimicrobial features of essential oils, and in this way, the production of CH4 and CO2 gas decreases with the formation of volatile fatty acids (VFA) in the rumen fluid (Canbolat et al. , 2011). It has also been determined that the addition of 400μg/ml of thymol to the rumen fluid reduces the production of CH4 gas (Evans and Martin, 2000). Tannins rich in phenolic substances have important properties that reduce nitrogen excretion in the urine, intestinal parasites and CH4 formation in the rumen. However, it should not be forgotten that the digestibility of feeds containing high tannins may decrease, cause constipation and adversely affect the performance (Beauchemin et al, 2008). Saponins, which are bioactive phytochemicals with strong antimicrobial effects that protect plants from insects and microorganisms, can also be used for similar purposes (Gür and Öztürk, 2021). It has been stated that saponins limit the presence of H₂ by reducing the number of rumen protozoa or methanogenic archaea, thus reducing the production of CH₄ (Bodas et al, 2012).

Enzymes such as cellulase and hemicellulase added to the ration are concentrated fermentation products and accelerate fiber digestion. Low fiber ratio in the ration and ration's consisting of easily digestible fibers reduce methane production. Since the acceleration of fiber digestion shortens the residence time of the content in the rumen, it has a reducing effect on methane production (Beauchemin et al, 2008). Accelerating fiber digestion also reduces the acetate: propionate ratio (Eun and Beauchemin, 2007). However, it should be noted that the effect of enzyme supplementation on fiber digestibility depends on the composition of the diet. Therefore, recommending a single enzyme formula does not seem possible (Beauchemin, 2008).

It is known that clay minerals (aluminum silicate, montmorillonite, bentonite, zeolite), which are frequently used in diets with their mycotoxin or pellet binding properties, can adsorb ammonia formed in the rumen. It has been stated that addition of zeolite (clinoptilolite) (30 g/kg) to urea-containing (20 g/kg) beef cattle rations decreased the ammonia nitrogen level, plasma urea and nitrogen levels in the rumen, increase the digestibility of the fibrous components (ADF and NDF) in the feed, but doesn't have any effect on fattening performance. (Sadeghi and Shawrang, 2006; Kaya et al, 2012).

Studies have shown that algae are also effective in reducing methane emissions. It has been determined that the use of red macroalgae, Asparagopsis taxiformis, in rations is effective in reducing CH4 released during enteric fermentation, and that microalgae may act in a similar way and cause significant improvements in the milk fatty acid profile (Janice et al, 2020).

As a result, in order to alleviate the climate crisis and global warming we are facing, feeding-based solutions have been developed especially in cattle breeding and it has been observed that different feed additives are effective in reducing methane emissions. Generalizing conscious breeding for sustainable and ecological livestock, preferring the accurate amount and quality of feed and feed additives will be highly effective in preventing the possible effects of climate change in the future.

1.Kılıç HN ve Boğa M. 2021. Hayvan Besleme Stratejileri ile Metan Emisyonunun Azaltılması. Turkish Journal of Agriculture Food Science and Technology, 9(9): 1700-1713. DOI:
2.Koyuncu M ve Akgün H. 2018. Çiftlik hayvanları ve küresel iklim değişikliği arasındaki etkileşim.U. Ü. Ziraat Fakültesi Dergisi, 32 (1): 151-164.
3.Nosalewicz M, Brzezinska M, Pasztelan M, Supryn G. 2011. Methane In the environment (a review). Acta Agrophysica, 18(2): 193.
4.Bayat A ve Shingfield KJ. 2012. Overview of nutritional strategies to lower enteric methane emissions in ruminants. Suomen Maataloustieteellisen Seuran Tiedote, (28): 1-7. DOI:
5.Gerber PJ, Steinfeld H, Henderson B, Mottet A, Opio C, Dijkman J, Falcucci A, Tempio G. 2013. Tackling climate change through livestock: a global assessment of emissions and mitigation opportunities. Food and Agriculture Organization of The United Nations (FAO), ISBN: 9789251079201.
6.Opio C, Gerber P, Mottet A, Falcucci A, Tempio G, MacLeod M, Vellinga T, Henderson B, Steinfeld H. 2013. Greenhouse gas emissions from ruminant supply chains a global life cycle assessment. Food and Agriculture Organization of The United Nations, FAO 2013.
7.Johnson DE ve Ward GM. 1996. Estimates of animal methane emissions. Environmental Monitoring and Assessment, 42(1): 133-141. DOI:
8.Beauchemin K, Kreuzer M, O’Mara F, McAllister TA. 2008. Nutritional management for enteric methane abatement: a review. Australian Journal of Experimental Agriculture, 48(2): 21-27. DOI:
9.Moss AR, Jouany JP, Newbold J. 2000. Methane production by ruminants: ıts contribution to global warming. Annales de zootechnie EDP Sciences, 49(3): 231-253. DOI:
10.McAllister TA, Beauchemin KA, Alazzeh AY, Baah J, Teather RM, Stanford K. 2011. Review: the use of direct fed microbials to mitigate pathogens and enhance production ın cattle. Canadian Journal of Animal Science, 91(2): 193-211. DOI:
11.Newbold CJ ve Rode L. 2006. Dietary additives to control methanogenesis ın the rumen. ınternational congress series. Elsevier, 1293: 138-147. DOI: j.ics.2006.03.047
12.Öztürk H, Demirbaş YS, Aydin FG, Pişkin İ, Ünler FM, Emre MB. 2015. Effects of hydrolyzed and live yeasts on rumen microbial fermentation in a semicontinuous culture system (Rusitec). Turkish Journal of Veterinary and Animal Sciences, 39(5): 556-559.
13.Chaucheyras, F, Fonty G, Bertin G, Gouet P. 1995. Effects of live Saccharomyces cerevisiae cells on zoospore germination, growth, and cellulolytic activity of the rumen anaerobic fungus, Neocallimastix frontalis MCH3. Current Microbiology, 31(4): 201-205.
14.Newbold CJ, De La Fuente G, Belanche A, Ramos-Morales E, Mcewan NR. 2015. The role of ciliate protozoa in the rumen. Frontiers in Microbiology, 6, 1313.
15.Gür G ve Öztürk H. 2021. Ruminantlarda metan salınımını azaltma stratejileri. Veteriner Farmakoloji ve Toksikoloji Derneği Bülteni, 12 (1): 43-54. 
16.Lila ZA, Mohammed N, Yasui T, Kurokawa Y, Kanda S, Itabashi H. 2004. Effects of a twin strain of Saccharomyces cerevisiae live cells on mixed ruminal microorganism fermentation in vitro. Journal of Animal Science, 82(6), 1847-1854.
17.Latham EA, Pinchak WE, Trachsel J, Allen HK, Callaway TR, Nisbet DJ, Anderson RC. 2018. Isolation, characterization and strain selection of a Paenibacillus species for use as a probiotic to aid in ruminal methane mitigation, nitrate/nitrite detoxification and food safety. Bioresource Technology, 263, 358-364.
18. Newbold CJ ve Rode L. 2006. Dietary additives to control methanogenesis ın the rumen. ınternational congress series. Elsevier, 1293: 138-147. DOI: j.ics.2006.03.047
19.Sahoo A ve Jena B. 2014. Organic acids as rumen modifiers. International Journal of Science and Research, 3, 2262-2266.
20.Carro MD ve Ungerfeld EM. 2015. Utilization of organic acids to manipulate ruminal fermentation and improve ruminant productivity. In: Puniya KA. Singh R. Kamra ND. Editors; Rumen microbiology: From evolution to revolution. New Delhi: Springer India, p. 177–197.
21.Canbolat Ö, Kalkan H, Karaman Ş, Filya İ. 2011. Esansiyel yağların sindirim, rumen fermantasyonu ve mikrobiyal protein üretimi üzerine etkileri. Kafkas Üniv. Vet. Fak. Derg., 17 (1): 557-565.
22.Evans JD, Martin SA. 2000. Effects of thymol on ruminal microorganisms. Curr Microbiol., 41: 336-340.
23.Bodas R, Prieto N, García-González R, Andrés S, Giráldez FJ, López S. 2012. Manipulation of rumen fermentation and methane production with plant secondary metabolites. Animal Feed Science and Technology, 176(1-4): 78-93. DOI:
24.Eun JS ve Beauchemin K. 2007. Assessment of the efficacy of varying experimental exogenous fibrolytic enzymes using ın vitro fermentation characteristics. Animal Feed Science and Technology, 132(3-4): 298-315. DOI: 10.1016/j.anifeedsci.2006.02.014
25.Sadeghi, A.A., Shawrang, P., 2006. The effect of natural zeolite on nutrient digestibility, carcass traits and performance of Holstein steers given a diet containing urea. Anim Sci., Cambridge Univ Press, 82: 163-167.
26.Janice MC, Labeeuw L, Jaramillo-Madrid AC, Nguyen LN, Nghiem LD, Chaves AV, Ralph PJ. 2020. Management of Enteric Methanogenesis in Ruminants by Algal-Derived Feed Additives Current Pollution Reports, 6:188–205. DOI: 10.1007/s40726-020-00151-7

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