Quantifying methane emissions during dry season and estimating emission factors in alpacas grazing Andean grasslands

This study aimed to (1) measure methane emissions from alpacas grazing in Andean grasslands during the dry season and compare them with those of sheep under similar conditions, and (2) estimate the methane conversion and emission factor for alpacas grazing in Andean grasslands, considering methodology, animal class, and season. The comparison involved nine alpacas and nine sheep, with measurements taken for dry matter intake, diet composition, and enteric methane emissions measured with the sulfur hexafluoride technique. Alpacas selected a more digestible diet than sheep (0.62 vs. 0.50 g/g of dry matter), even with limited feed availability. Methane emissions were similar between the two species. For the second objective, the study used observations from the first objective and mean treatments from a literature review. The developed model predicted methane conversion factors, considering animal class and measurement methodology, with no significant influence observed for season. The predicted methane conversion factors (% gross energy in feed converted to methane) for alpacas grazing in Andean grasslands were 7.71 for juveniles (i.e., tuis) alpacas and 8.71 for adults, corresponding to emission factors of 6.49 and 9.77 g per alpaca and day, respectively. These results emphasize the importance of considering animal class, measurement methods, and regional variations when estimating methane emission factors for alpacas.