Methane emissions and dry matter intake in first-calf cows grazing on rangeland.

LOZA C.; ALVAREZ OXILEY A.; PICASSO V.; GERE J. I.; MODERNEL P.; ORCASBERRO M. S; ASTIGARRAGA L.; JULIARENA P.; SOCA P.

Colonia

Conferencia; III Conferencia de Gases de Efecto Invernadero en Sistemas Agropecuarios de Latinoamérica (GALA 2017); 2017

INIA

Introduction. In beef production systems, the cow-calf phase may account from 63% to 80% of the total carbon footprint (indicator of GHG emissions generated per unit of product) (Pelletier et al., 2010; Beachmin et al., 2010). The livestock sector, and mostly the breeding phase, accounts for more than 70% of Uruguay´s greenhouse gas (GHG) emissions (Becoña, 2012) using IPCC (2006) emission factors, but there are any research that have measured methane emission (CH4) and methane yield (Ym) of beef cows during gestation and early lactation, in natural grassland. Objective. The aim of the study was to evaluate the variation on CH4 and dry matter intake (DMI) of first-calf cows during gestation and early lactation, on continuous grazing. Materials and Methods. The experiment was conducted at the Bernardo Rosengurtt Research Station, Cerro Largo, Uruguay (32°22´S, 54°26´W) and was designed to evaluate the effect of two herbage allowance (High-8 and Low-5 kg DM/kg LW) with 40 (Hereford and Aberdeen Angus) primiparous cows (20 per treatment), in early gestation (aprox. 90 days) at the beginning of the trial and under continuous grazing, but only average results per period of measurements (may, august, november 2015) are shown. The trial design was a complete generalized block with 2 blocks that represent contrasting soils and two replicates per block. CH4 emission was determined using the technique of sulfur hexafluoride (SF6) as a tracer gas according to Johnson et al. (1994) and adapted by Gere and Gratton (2010), and the DMI was estimated using chromium oxide as an indigestible marker and estimated digestible organic matter. Results and Discussion. CH4 (165±11.4; 141±10.7; 328±11.8 g/d), DMI (8.1±0.38, 7.1±0.40, 12.0±0.35 kg DM/d), biomass (1533±173, 1485±173, 3142±173 kg DM/ha), height (6.9±0.44, 4.4±0.44, 8.5±0.44 cm) and LW (355±6.1 vs 337±6.1 vs 383±6.3 kg) were significantly affected by the period (P