Enteric methane emissions by lactating and dry cows in the high Andes of Peru.

The objective of the study was to determine enteric methane emissions using the sulfur hexafluoride (SF6) technique and comparing with The Intergovernmental Panel on Climate Change (IPCC) methodology in lactating cows (LC) and dry cows (DC) in the Peruvian highlands. Enteric methane (CH4) emissions were measured on 5 LC and 6 DC Brown Swiss in a grazing system without concentrate. Forages samples were collected and analyzed for dry matter, crude protein, and neutral detergent fiber. Milk samples were collected and analyzed for fat, crude protein, and lactose to estimate energy-corrected milk. Animal intakes were measured using the external marker titanium dioxide (production of feces) and crude protein in feces (organic digestibility of the feed) and estimated by using performance data. The enteric methane emissions of LC were higher than methane emissions of DC (325 and 266 g CH4/cow/day for LC and DC, respectively (P < 0.001)). Methane emissions were 358.5 g CH4/day by SF6 technique and 291.6 g CH4/day by IPCC methodology for LC and 337.4 g CH4/day by SF6 technique and 195.8 g CH4/day by IPCC methodology for DC. Methane yields measured by SF6 were higher than methane yields estimated by IPCC methodology (29 g CH4/kg DM and 22 g CH4/kg DM using SF6 technique and IPCC methodology, respectively (P < 0.001)). Methane yields were differently for all expressions by physiological stage and method. The methane conversion factor (Ym) was 9.7% for LC and 9.6% for DC. Methane intensities were similar by method (P > 0.05). It was concluded that IPCC's methodology underestimate the CH4 emissions of dairy systems in the Peruvian Andes; therefore, in order to obtain precise Ym, direct measurements of enteric CH4 in the different regions of Peruvian highlands are required.