Quantification of enteric methane according to physiological state in high producing dairy cows in Costa Rica | Cuantificación de metano entérico según estado fisiológico en vacas lecheras de alta producción en Costa Rica

إنجليزي. This research quantifies the enteric methane emission in highly productive Holstein cows in a commercial dairy farm, by using the SF6 technique. The objective was to determine enteric methane emission in Holstein cows in different physiological states in an intensive grazing milk production system. Nine Holstein cows were selected which represented the typical conformation of the herd in age (5.7±0.6 years), number of lactations (3.6±0.4 births), average milk production (7924±280 kg) and live weight (672±36 kg), in different physiological states: dry (D), pre-partum (PP), early lactation (EL), and in medium/final (M/F) lactation state. Forages and supplements provided prior to milking were weighed and sampled in order to determine dry matter intake and digestibility (67.8±1.9%). In each methane measurement period, samples were collected from pastures to determine crude protein (15.9±0.3%), neutral detergent fiber This research quantifies the enteric methane emission in highly productive Holstein cows in a commercial dairy farm, by using the SF6 technique. The objective was to determine enteric methane emission in Holstein cows in different physiological states in an intensive grazing milk production system. Nine Holstein cows were selected which represented the typical conformation of the herd in age (5.7±0.6 years), number of lactations (3.6±0.4 births), average milk production (7924±280 kg) and live weight (672±36 kg), in different physiological states: dry (D), pre-partum (PP), early lactation (EL), and in medium/final (M/F) lactation state. Forages and supplements provided prior to milking were weighed and sampled in order to determine dry matter intake and digestibility (67.8±1.9%). In each methane measurement period, samples were collected from pastures to determine crude protein (15.9±0.3%), neutral detergent fiber This research quantifies the enteric methane emission in highly productive Holstein cows in a commercial dairy farm, by using the SF6 technique. The objective was to determine enteric methane emission in Holstein cows in different physiological states in an intensive grazing milk production system. Nine Holstein cows were selected which represented the typical conformation of the herd in age (5.7±0.6 years), number of lactations (3.6±0.4 births), average milk production (7924±280 kg) and live weight (672±36 kg), in different physiological states: dry (D), pre-partum (PP), early lactation (EL), and in medium/final (M/F) lactation state. Forages and supplements provided prior to milking were weighed and sampled in order to determine dry matter intake and digestibility (67.8±1.9%). In each methane measurement period, samples were collected from pastures to determine crude protein (15.9±0.3%), neutral detergent fiber (63.0±0.9%) and in vitro dry matter digestibility. Daily methane emission per cow was similar (p>0.05) in D, PP and in M/F, and higher (p<0.05) in EL, with ranges (g.c-1.d-1) between 240 and 443 in D, from 238 to 483 in PP, from 277 to 506 in EL, and from 281 to 470 in M/F. A linear relationship was determined between total dry matter intake and methane emission (r2 varied between 0.42 and 0.78 depending on physiological state), as well as between methane produced and milk production per day (r2=0.71). High producing cows emit more methane but are less methane emitters per liter of milk produced. The Ym varied depending on physiological state of the cows, and the annual value was similar to that suggested by IPCC.  Keywords: Enteric methane; dairy cows; grazing; tropics; SF6; greenhouse gases.

الأسبانية؛ قشتالية. Esta investigación cuantifica, mediante la técnica del SF6, el metano entérico en vacas altamente productoras en una finca comercial. El objetivo fue determinar la emisión de metano entérico en vacas Holstein en diferentes estados fisiológicos en un sistema de producción de leche intensivo bajo pastoreo. Para ello, se seleccionaron 9 vacas Holstein que representaron la conformación típica del hato en edad (5,7±0,6 años), número de lactancias (3,6±0,4 partos), producción promedio de leche por lactancia (7924±280 kg leche) y peso (672±36 kg) en diferentes estados fisiológicos: secas (VS), preparto (VPP), primer tercio de lactancia (VPTL) y en medio/final (VM/F) estado de lactación. Los forrajes y suplementeos proporcionados, previo al ordeño, fueron pesados y muestreados para determinar consumo y digestibilidad de la materia seca. En cada período de medición de metano, se realizaron muestreos de las pasturas y se determinó proteína cruda (15,9±0,3%), fibra neutro detergente (63,0±0,9%) y digestibilidad in vitro de la materia seca (67,8±1,9%) del forraje en oferta. La emisión diaria de metano por vaca fue similar (p>0,05) en VS, VPP y en VM/F, y mayores (p<0,05) en VPTL, con rangos (g.v-1.d-1) entre 240 y 443 en VS, de 238 a 483 en VPP, de 277 a 506 en VPTL, y de 281 a 470 en VM/F. Se determinó la relación lineal entre el consumo total de materia seca y la emisión de metano (r2 varió entre 0,42 y 0,78 según el estado fisiológico), así como también entre el metano producido y la producción de leche por día (r2=0,71). Las vacas más productoras emiten más metano, pero son menos emisoras de metano por litro de leche producida. El Pm varió conforme al estado fisiológico y el valor anual fue similar al sugerido por el IPCC.  Palabras clave: Metano entérico; ganado de leche; pastoreo; trópico; SF6; gases con efecto invernadero.