Nutritional Quality, Voluntary Intake and Enteric Methane Emissions of Diets Based on Novel Cayman Grass and Its Associations With Two Leucaena Shrub Legumes

Abstract

Methane (CH 4 ) emissions from enteric fermentation in cattle are an important source of greenhouse gases, accounting for about 40% of all agricultural emissions. Diet quality plays a fundamental role in determining the magnitude of CH 4 emissions. Specifically, the inclusion of feeds with high digestibility and nutritional value have been reported to be a viable option for reducing CH 4 emissions and, simultaneously, increase animal productivity. The present study aimed to evaluate the effect of the nutritional composition and voluntary intake of diets based on tropical forages upon CH 4 emissions from zebu steers. Five treatments (diets) were evaluated: Cay1: Urochloa hybrid cv. Cayman (harvested after 65 days of regrowth: low quality); Cay2: cv. Cayman harvested after 45 days of regrowth; CayLl: cv. Cayman + Leucaena leucocephala; CayLd: cv. Cayman + Leucaena diversifolia; Hay: Dichantium aristatum hay as a comparator of common naturalized pasture. For each diet representing different levels of intensification (naturalized pasture, improved pasture, and silvopastoral systems), CH 4 emissions were measured using the polytunnel technique with four zebu steers housed in individual chambers. The CH 4 accumulated was monitored using an infrared multigas analyzer, and the voluntary forage intake of each animal was calculated. Dry matter intake (DMI, % of body weight) ranged between 0.77 and 2.94 among diets offered. Emissions of CH 4 per kg of DMI were significantly higher (P < 0.0001) in Cay1 (60.4 g), compared to other treatments. Diets that included Leucaena forage legumes had generally higher crude protein contents and higher DMI. Cay1 and Hay which had low protein content and digestibility had a higher CH 4 emission intensity (per unit live weight gain) compared to Cay2, CayLl and CayLd. Our results suggest that grass consumed after a regrowth period of 45 days results in lower CH 4 emissions intensities compared to those observed following a regrowth period of 65 days. Diets with Leucaena inclusion showed Gaviria-Uribe et al.Methane From Cattle Tropical-Forages advantages in nutrient intake that are reflected in greater live weight gains of cattle. Consequently, the intensity of the emissions generated in the legume-based systems were lower suggesting that they are a good option for achieving the emission reduction goals of sustainable tropical cattle production.

Nutritional Evaluation of Tropical Forage Grass Alone and Grass-Legume Diets to Reduce in vitro Methane Production

“…Similarly, concentrations of phenolic compounds were lower in the grasses than the legumes. These findings concur with data reported in the literature for these tropical species (Lee, 2018;Cook et al, 2020;Gaviria-Uribe et al, 2020), where CP values for grasses can range between 40 and 140 g kg −1 DM, and for both legumes studied here, shrub and herbaceous, ranged between 190 and 250 g CP kg −1 DM. However, the CP content obtained in the present study was slightly lower than that reported by Peters et al (2002) for U. brizantha cv.…”

“…Likewise, the NDF content was within the range of 600 and 800 g kg −1 DM reported for U. brizantha sp. (Cook et al, 2020;Gaviria-Uribe et al, 2020). However, forage quality has been shown to be closely related to pasture age (Vendramini et al, 2014;Gaviria-Uribe et al, 2020) and the time of the year (Demarchi et al, 2016;Abdalla et al, 2019 Geleti et al (2013), while the ME for grasses are above those obtained by Nguku (2015) for 9 grasses of the genus Urochloa, whose values ranged between 6.6 and 5.9 MJ ME kg −1 DM.…”

“…(Cook et al, 2020;Gaviria-Uribe et al, 2020). However, forage quality has been shown to be closely related to pasture age (Vendramini et al, 2014;Gaviria-Uribe et al, 2020) and the time of the year (Demarchi et al, 2016;Abdalla et al, 2019 Geleti et al (2013), while the ME for grasses are above those obtained by Nguku (2015) for 9 grasses of the genus Urochloa, whose values ranged between 6.6 and 5.9 MJ ME kg −1 DM. However, this variable, as well as the rest of the nutritional components of the diet, can vary according to the UHC, Cayman grass; CB, Canavalia brasiliensis; LD, Leucaena diversifolia; AGP, accumulated gas production; OM, organic matter; DMD, dry matter degradability; a, maximum gas production (mL); b, difference between initial gas and final gas at an × time; c, specific gas accumulation rate; TIP, time to the inflection point, h; GIP, gas at the inflection point, mL; MRGP, maximum rate of gas production, mL/h; LP, lag phase, h; EMS, error mean square.…”

“…Likewise, cattle systems where the diet is composed of 100% low quality grasses, have low productive indexes due to the low CP concentration, required by ruminal microorganisms for the breakdown of carbohydrates, in addition to a reduction in DM intake due to the high content of structural carbohydrates (Krizsan et al, 2010). Enteric CH 4 emission rates are associated with the physicochemical characteristics of the diet (e.g., CP and NDF contents), which have a direct impact on diet intake (Gaviria-Uribe et al, 2020) and eating frequency (Grant et al, 2015). Several studies have evaluated the effect of adding a legume to a grass on CH 4 production both in vitro (Tope et al, 2013;Molina-Botero et al, 2020) and in vivo (Molina-Botero et al, 2019a,b;Gaviria-Uribe et al, 2020;Montoya-Flores et al, 2020).…”

“…Enteric CH 4 emission rates are associated with the physicochemical characteristics of the diet (e.g., CP and NDF contents), which have a direct impact on diet intake (Gaviria-Uribe et al, 2020) and eating frequency (Grant et al, 2015). Several studies have evaluated the effect of adding a legume to a grass on CH 4 production both in vitro (Tope et al, 2013;Molina-Botero et al, 2020) and in vivo (Molina-Botero et al, 2019a,b;Gaviria-Uribe et al, 2020;Montoya-Flores et al, 2020). Nevertheless, the conclusions drawn from these studies are unclear, as in some cases the addition of a legume increased in vitro CH 4 production (Carulla et al, 2005;Molina-Botero et al, 2020), but in others, it had the opposite effect (Lee et al, 2004).…”