Harnessing Tanzania's Rangelands to Mitigate Methane Emissions from Livestock Enteric Fermentation

: Methane emissions from livestock being a major contributor to climate change as methane possesses more global warming potential than carbon dioxide, exacerbating the issue. Therefore, reducing methane emissions is crucial in addressing climate change and promoting sustainable agriculture. Tanzania is endowed with a large livestock population and vast rangelands. The resultant enteric methane emissions share in the agriculture sector was estimated to be 39.71% in 2014. This data suggests that interventions to lower methane emissions in agriculture sectors need to focus on livestock especially ruminants to provide significant reduction. The study found that normalisation of emissions can be facilitated by a set of measures, namely: a) increasing the energy content or quality of ruminant feed to reduce the intensity of methane production in the gut; b) addressing existing problems in pasture use, including deforestation, uncontrolled burning, overgrazing, water shortages and invasive species; c) improving feeding in combination with other livestock management practices to achieve the expected productive effect while reducing methane emissions.

Livestock farming is crucial in meeting the world's growing demand for animal products (Herrero, et al., 2013;Alexandratos, & Bruinsma, 2012).However, the environmental impacts of this industry are a matter of concern with methane emissions from livestock being a major contributor to climate change as methane possesses 25 times more global warming potential than carbon dioxide, exacerbating the issue (Ribeiro, et al., 2015).Therefore, reducing methane emissions is crucial in addressing climate change and promoting sustainable agriculture.
From animals, methane is produced by the enteric fermentation process which involves the breakdown of complex organic compounds by microorganisms in their digestive systems (Broucek, 2014).The process allows animals to break down and digest their feed and thus methane is released as a byproduct and emitted into the atmosphere by exhaling it through the nostrils and mouth (Knapp, et al., 2014).Globally, ruminant livestock produces about 2.7 Gt of carbon dioxide equivalent enteric methane annually or about 5.5% of total global greenhouse gas emissions from human activities (Gerber, et al., 2013).Various factors such as feed level of intake, type, and quality of feeds, energy consumption, animal breeds, physiological status, animal health, animal size, age, level of production, and environmental temperature may influence an animal's methane production (Broucek, 2014).Scientists are investigating the potential of incorporating additives like lipids, fats, oils, and tannins into livestock diets to manipulate the microbial population in the rumen, consequently lowering methane production by adjusting the composition of livestock diets by including more easily digestible feed or enhancing the quality of forages to mitigate methane emissions is being considered (Gerber, et al., 2013).

Suggested Citation
Tanzania is endowed with a large livestock population and vast rangelands covering approximately 60 million hectares capable of supporting over 20 million Tropical Livestock Units (TLU) (United Republic of Tanzania, 2014).The resultant enteric methane emissions share in the agriculture sector was estimated to be 39.71% in 2014 (Majule, et al., 2015).This data suggests that interventions to lower methane emissions in agriculture sectors need to focus on livestock especially ruminants to provide significant reduction.
In Tanzania, over 90% of livestock are raised using a combination of traditional and extensive production methods (Wakhungu, et al., 2014).Utilization of rangelands presents a multifaceted approach to mitigate enteric methane emissions because fodders and shrubs available on rangelands can produce a considerable quantity of forage to mitigate enteric methane emissions.The diversity of these plants is not only critical in providing adequate feed and the nutritional needs of livestock but also ground pods of tropical trees and shrubs, when incorporated in cattle rations, can decrease methane yield from the animals (Andualem, Kechero, & Abraham, 2023).Foliages and seeds of tropical trees and shrubs containing either condensed tannins, saponins, or starch, as well as other compounds such as nitrates and by-products such as vegetable oils can be fed to cattle to mitigate enteric methane emissions through direct toxic effects on microbial bacteria (Ku-Vera, et al., 2020).Besides, rangelands are resilient, complex adaptive systems and are able in self-regulatory homeostasis to maintain consistent livestock production and reduce the need for supplementary feeds that can contribute to methane emissions (Sundt, 2010).
Moreover, a study carried out to identify potential of indigenous browse species observes that Browse species like Dodoniaviscosa, Acacia asak, Acacia previspica, Croton machrostachyus, Salix subserrata, Helichrysumcitrispinum, Croton dichogamus and Maesalanceolata had a crude protein content greater than 18%, suggesting the possibility of considering their use as an alternative plant protein source to improve the nutritive values of poor quality feeds (Mohammed, & Mekonnin, 2020).
Despite these rangelands having the potential to produce adequate feed for animal production and mitigate enteric methane emissions, the rangelands of Tanzania are facing several challenges such as deforestation, uncontrolled burning, overgrazing, lack of water, and invasion by alien invasive species which hinder its maximum utilization and its potential (Mbwambo, et al., 2016).

Utilization of Rangelands to Mitigate Emissions from Enteric Fermentation
Firstly, increasing the energy content or quality of ruminant feed to reduce enteric methane production intensity, particularly for grazing livestock, can be achieved by providing forage with higher digestibility (e.g., legumes or higher nutritive value grasses) from rangelands forages such as Acacia and birdsfoot trefoil, as they contain secondary compounds like saponins and tannins, which can decrease enteric methane production.
Secondly, Addressing the existing challenges in rangeland utilization, including deforestation, uncontrolled burning, overgrazing, water scarcity, and invasion by alien species, requires the implementation of effective grazing management practices.By adopting appropriate strategies, rangeland utilization can be enhanced, and pasture quality improved.These measures may include conducting reseeding on bared land, controlling invasive plant species and bushes, developing and maintaining water points such as boreholes, wells, and dams to provide reliable water sources for livestock, integrating agroforestry into rangelands by planting trees including multipurpose trees such as Leucaena leucocephala.This management may lead to vigorous plant growth, additional forage, and improved feeds and digestibility as a result methane emission from ruminant livestock will be reduced.
Lastly, improved feeding needs to go hand in hand with other animal husbandry practices to achieve the expected production response while lowering methane emissions.Combining various management approaches including improving animal breeds by introducing improved breeds to replace less productive animals, selecting animals with lower methane emissions, improving animal health in particular the treatment of intestinal parasites by regularly using anthelmintic, control of tick-borne diseases with regular spraying or dipping and reducing the age at which meat animals are slaughtered offers a holistic strategy to address enteric fermentation emissions widely.

Figure 1 .
Figure 1.Methane Production Process and Cattle Grazing in One of the Rangelands in Tanzania Source: Author