Methane Mitigation Potential of Foliage of Fodder Trees Mixed at Two Levels with a Tropical Grass

Abstract

Enteric methane (CH4) emitted by ruminant species is known as one of the main greenhouse gases produced by the agricultural sector. The objective of this study was to assess the potential the potential for CH4 mitigation and additionally the chemical composition, in vitro gas production, dry matter degradation (DMD), digestibility and CO2 production of five tropical tree species with novel forage potential including: Spondias mombin, Acacia pennatula, Parmentiera aculeata, Brosimum alicastrum and Bursera simaruba mixed at two levels of inclusion (15 and 30%) with a tropical grass (Pennisetum purpureum). The forage samples were incubated for 48 h, and a randomized complete block design was used. Crude protein content was similar across treatments (135 ± 42 g kg−1 DM), while P. purpureum was characterized by a high content of acid detergent fiber (335.9 g kg−1 DM) and B. simaruba by a high concentration of condensed tannins (20 g kg−1 DM). Likewise, A. pennatula and P. aculeata were characterized by a high content of cyanogenic glycosides and alkaloids respectively. Treatments SM30-PP70 (30% S. mombin + 70% P. purpureum) and BA30-PP70 (30% B. alicastrum + 70% P. purpureum) resulted in superior degradability at 48h than P. purpureum, while in the AP30-PP70 (30% A. pennatula + 70% P. purpureum) was lower than the control treatment (p ≤ 0.05). At 24 and 48 h, treatments that contained P. aculeata and B. alicastrum yield higher CH4 mL g−1 DOM than P. purpureum (p ≤ 0.05). The inclusion of these forage species had no statistical effect on the reduction of CH4 emissions per unit of DM incubated or degraded at 24 and 48 h with respect to P. purpureum although reductions were observed. The use of fodders locally available is an economic and viable strategy for the mitigation of the environmental impact generated from tropical livestock systems.

Relationship between Chemical Composition and In Vitro Methane Production of High Andean Grasses

“…As previously indicated, degradability is inversely related to the amount of NDF present in the feed, as corroborated by several in vitro studies in which different types of grasses, legumes or tropical fruits have been incubated [ 5 , 8 , 29 , 30 ]. It is also indirectly correlated with the time of year, this is demonstrated by Salazar [ 31 ], in a study carried out in both seasons of the year with the species Alchemilla pinnata and Hipochaeris taraxacoides , where DOM in the dry season was 66 and 59%, while in the rainy season this value increased by between 2 and 14%.…”

“…In the rumen of cattle, microorganisms such as bacteria, protozoa and fungi hydrolyze plant nutritional compounds to produce products such as acetate, propionate, butyrate, CO 2 and hydrogen, among others. These last two compounds are utilized by archaea to produce CH 4 [ 8 ]. Changes in the chemical composition of the forage can affect the amount of CH 4 produced in the rumen [ 9 , 10 ].…”

Ruminant grazing feeding and methane production

“…These grasses are fermented by rumen microorganisms producing volatile fatty acids (VFA) that feed the energy metabolism of these animals, taking advantage of their capacity to degrade cellulose (Church, 1988;Reyes Gutiérrez, 2012). Grazing of tropical grasses, incorporating structural carbohydrates in different proportions, produces more methane and promotes a higher acetic acid:propionic acid ratio than fermentation of non-structural carbohydrates (Hyland et al, 2016;Valencia-Salazar et al, 2022). In these diets, energy losses to form methane are 8 to 12 % of the gross energy (GE) consumed by the animal, but in the case of diets where commercial concentrates (more than 90 % grain and high energy) are incorporated, methane losses can be as low as 2 to 3 % of GE intake (Johnson and Johnson, 1995;Methol, 2005;Hyland et al, 2016).…”