In vitro assessment of ruminal fermentation, digestibility and methane production of three species of Desmanthus for application in northern Australian grazing systems

Abstract

Three species of Desmanthus adapted to the heavy clay soils of northern Australia were studied to determine their nutritive value and effects on in vitro fermentation with rumen fluid, compared with Rhodes grass (Chloris gayana) hay. Leaves and stems of D. leptophyllus cv. JCU 1, D. virgatus cv. JCU 2 and D. bicornutus cv. JCU 4 were collected in summer, winter and spring of 2014 and analysed for chemical composition. Apparent digestibility as in vitro organic matter digestibility (IVD-OM) and fermentation parameters including methane (CH4) production were measured during 72-h fermentations using rumen fluid from steer donors grazing tropical grasses and legumes. Desmanthus bicornutus was on average more digestible than both D. leptophyllus and D. virgatus at 24, 48 and 72 h of incubation. This species also demonstrated an anti-methanogenic potential, in particular when harvested in summer with a reduction in CH4 production of 26% compared with Rhodes grass hay after 72 h of incubation. At this time point, D. leptophyllus produced higher volatile fatty acids (VFA per g of organic matter fermented) compared with the other forages. This legume also reduced the CH4 production up to 36% compared with the Rhodes grass hay reference. However, D. leptophyllus showed lower IVD-OM. Overall, Desmanthus species produced lower in vitro CH4 and lower volatile fatty acids concentration compared with the reference grass hay. These effects may be due to presence of secondary compounds such as hydrolysable tannins, condensed tannins and/or their combination in Desmanthus species. The IVD-OM was influenced by the season after 72 h of incubation; the digestibility was higher in plants collected in spring. This study suggests that contrasting fermentative profiles in Desmanthus cultivars may offer the opportunity to reduce the greenhouse gas contribution of the beef industry. The next step in demonstration of these promising in vitro results is demonstration of Desmanthus in vivo as proof of concept confirming the productivity and CH4 reduction ability of these legumes in the pastoral systems of northern Australia.

Diet and Genetics Influence Beef Cattle Performance and Meat Quality Characteristics

“…Desmanthus has gained attention in recent years due to its palatability, high protein content, non-toxic characteristics, anti-methanogenesis demonstrated in vitro [92] and its ability to establish and persist well in clay soils [88][89][90]. Two varieties of Desmanthus, D. virgatus and D. leptophyllus, were found in old trial sites after 25 years of establishment on black cracking clay soil surviving droughts, floods, frost and commercial grazing [93].…”

“…LDM of lambs fed Sulla (Hedysarum coronarium L.) containing 1.8% condensed tannins had 24% more ALA compared to lambs fed Sulla and drenched with polyethylene glycol, a compound that binds and inactivates tannins [151]. Desmanthus contains up to 4.5% condensed tannins [92], hence grazing cattle on Desmanthus pastures may increase n-3 PUFA in beef.…”

Methane emissions of extensive grazing breeding herds in relation to the weaning and yearling stages in the Eastern Plains of Colombia

“…Those discrepancies plus significative differences between temperate and tropical diets in the metabolizable energy intake and digestible energy intake ratio throughout the year are probably indicative of more accurate CH 4 measurements in our study, while supporting evidence of the fact is also represented by the dynamic LW change in dams and calves to derive precise DMI and enteric CH 4 emissions. The main physiological driver of CH 4 production is DMI (Jonker et al 2018), but this effect appears to be masked if the digestive effects of plant secondary compounds are considered Durmic et al 2017;Vandermeulen et al 2018).…”

Methane Emissions and the Use of Desmanthus in Beef Cattle Production in Northern Australia

“…For instance, the addition of Leucaena can be toxic due to high mimosine content [67], and Calliandra can decrease feed digestibility [64]. Only Desmanthus , a tropical legume containing CT, has so far shown promising results in reducing methane emissions [68,81] and improving animal growth performance [82,83,84,85].…”

“…As depicted in Table 2, Vandermeulen et al [81] evaluated organic matter degradability (OMD) and methane production via in vitro incubation of ruminal fluid from grazing Brahman ( Bos indicus ) steers on Rhodes grass (as control), Desmanthus bicornutus , D. leptophyllus and D. virgatus harvested from Agrimix Pty. Ltd. commercial plots.…”