Methane is a potent greenhouse gas (GHG) emitted from several anthropogenic sources, most notably enteric fermentation in domestic ruminants, primarily during exhalation. To date, however, it is unclear whether the excretion route of methane exhaled by ruminants occurs through the mouth or nostrils and what the pattern of excretion is; this is important in designing equipment and methods to measure the methane emitted by ruminants. Thus, the objective of this experiment was to quantify the exhaled methane excreted by dairy cows via the nostrils and mouth while resting, grazing, and ruminating, as well as the pattern of concentration during and between belching. Four tests were conducted in this study with four dairy cows each. In the first test, resting cows, carrying an electronic spirometry mask (ESM) assembled with a methane sensor in its outlet, were used to measure the concentration of methane in the air expelled through the nostrils and to model the methane concentration between belches; in the second test, a mouth mask was used to measure methane excreted through the mouth; in the third test, an ESM with a methane sensor assembled over the mouth was used to measure methane excreted through the mouth; finally, in the fourth test, a methane sensor was manually placed at 2.0–3.0 cm in front of the mouth of ruminating cows to measure the methane concentration. In the first test, a pattern of methane concentration between belches was identified, as well as a pattern of the methane concentration and volume of air exhaled during belching. Methane excretion through the mouth was not detected in any of the tests; hence, it is concluded that dairy cows, while resting, ruminating, and grazing, emit enteric methane only through the nostrils under normal respiration conditions. This is important in the respiratory physiology of ruminants and in designing equipment and methodology to measure cranial methane excretion.

Objetivos. Evaluar el efecto de la extrusión húmeda sobre la digestibilidad in vitro (pepsina-celulasa) de la materia seca (DIVMS) y la fibra en detergente neutro (DIVFDN) del pasto kikuyo (Cenchrus clandestinus (Hochst ex Chiov)). Materiales y métodos. Se recolectaron seis muestras de esta gramínea cosechadas a los 35 días de rebrote (5.0 kg/muestra), que fueron picadas a 2.0 cm; de cada muestra se tomó una submuestra con la formación de una mezcla compuesta del pasto crudo en la que se determinó el contenido de proteína cruda (PC), fibra en detergente neutro (FDN), fibra en detergente ácido (FDA), lignina en detergente ácido (LDA), cenizas (Cen), calcio (Ca), fósforo (P), potasio (K), la DIVMS y la DIVFDN; la cantidad restante de cada una de las seis muestra fue sometida la a extrusión húmeda en un extrusor de un solo tornillo cónico con salida de 2.0 mm que giraba a 1300 rpm. En los bagazos obtenidos de cada muestra se efectuaron los mismos análisis que en la muestra cruda. Los datos fueron analizados mediante una prueba de T de Student de dos colas. Resultados. Los bagazos obtenidos por extrusión húmeda del pasto kikuyo presentaron mayor contenido de FDN y FDA y menor de PC y C en en que el pasto crudo, al tiempo que se incrementó en más del 8% la DIVMS y en más del 36% de la DIVFDN. Conclusiones. La extrusión húmeda mejora significativamente la DIVMS y la DIVFDN del pasto kikuyo.

Objectives. Test the effect of wet extrusion and the application of two alkaline compounds on the in vitro digestibility of dry matter (IVDDM) and neutral detergent fiber (IVDNDF) of maralfalfa grass. Methods. 48 samples of 51 days of regrowth were chopped and assigned to eight treatments: raw, chopped, and dehydrated grass (CTRL); raw, chopped, and extruded grass (EXTR); EXTR treated with 0.45, 0.90, and 1.35% of lime (Ca(OH)2) or urea for 21 days in micro-silos under aerobic conditions (EXTR0.45Ca, EXTR0.90Ca, EXTR1.35Ca, EXTR0.45U, EXTR0.90U, and EXTR1.35U, respectively). The content of dry matter (DM), nitrogen (N), calcium (Ca), neutral detergent fiber (NDF), acid detergent lignin (ADL) and the in vitro digestibility of dry matter (IVDDM) and NDF (IVDNDF) were determined for each sample. Results. The EXTR presented lower N content, higher NDF content, and higher IVDNDF than the CTRL. On the other hand, the EXTR1.35Ca treatment showed the highest Ca concentration and the highest IVDDM and IVDNDF, while the EXTR0.90U treatment presented the highest N concentration and an IVDNDF statistically similar to that of the EXTR1.35Ca. Conclusions. The wet extrusion of maralfalfa grass alone increases IVDNDF; however, IVDDM and IVDNDF are maximized when treated with 1.35% of Ca(OH)2.

Se evaluó el efecto de la extrusión del pasto maralfalfa (Pennisetum sp) sobre la composición química de la pared celular y la digestibilidad in vitro de la materia seca y de la fibra en detergente neutro. Para ello se recolectaron siete muestras (10,0 kg/muestra) del mismo lote, con 51 días de rebrote y se picaron a 2 cm. Tres de estas muestras, tomadas al azar, se procesaron frescas en un extrusor de tornillo cónico girando a 1050 rpm y con salida de 3 mm, mientras que las otras cuatro fueron extruidas en el mismo equipo con salida de 1 mm. En las muestras de pasto crudo y en las de los bagazos procedentes de la extrusión se determinó el contenido de fibra en detergente neutro, fibra en detergente ácido, lignina en detergente ácido, digestibilidad in vitro de la materia seca y digestibilidad in vitro de la fibra en detergente neutro. Se aplicó la prueba de T de Student para analizar el efecto del tipo de tratamiento, tanto entre ellos como respecto al pasto fresco. Los resultados indican que, con relación al pasto fresco, la extrusión generó un bagazo con alto contenido de fibra en detergente neutro, incrementó la digestibilidad in vitro de la materia seca en 8,81% y la de la digestibilidad in vitro de la fibra en detergente neutro en 20,6%, pero no diferencia con el tamaño de la salida del extrusor (p<0,1). Se concluye que el proceso de extrusión como fue aplicado al pasto maralfalfa en este experimento mejora la digestibilidad de la materia seca y de la fibra en detergente neutro.

Enteric methane emissions (EMEs) from grazing dairy systems in tropical regions remain poorly quantified, increasing uncertainty in national greenhouse gas inventories. This study aimed to quantify EMEs using electronic spirometry masks (ESMs) in dairy cows in the Colombian high tropics during two precipitation seasons in two adjacent milk production management systems. Six cows of a high-milk-yield management system (HMYMS; >30 L/d) and six cows of a low-milk-yield management system (LMYMS; <15 L/d) grazing kikuyu grass (Cenchrus clandestinus) and supplemented with concentrate feed were monitored by EMEs, exhaled air volume, feed intake, milk yield and composition. Data were analyzed in a 2 × 2 factorial arrangement (season × production system). Season affected kikuyu chemical composition (p < 0.05) but not dry matter intake (DMI), milk production, quality, nor EMEs (p > 0.05). However, the absence of seasonal effects on these variables may be due to the sample size. Although HMY cows had a higher DMI (kg DM/d; p < 0.01) and EME (g/d, L/d; p < 0.05), they exhibited a lower methane intensity (both, L/L milk yield and L/kg fat-corrected milk) and gross energy intake lost as methane (p < 0.05). Positive correlations were found between EMEs and total dry matter intake (r = 0.638) and milk production (r = 0.726). The observed methane yield was comparable to previous studies for tropical kikuyu-based systems but lower than reports from temperate regions, suggesting seasonal-driven kikuyu quality does not translate into EME changes in high tropic regions. Animal productivity level was a key driver of EME magnitude and efficiency.

Dual-purpose livestock farming in the Colombian low tropics faces nutritional limitations that affect productivity and increase enteric methane (CH₄) emissions. Therefore, it is necessary to evaluate supplementation strategies that optimize the use of nutrients and reduce environmental impacts. The objective of this study was to evaluate the effects of three types of dietary supplementation—mineralized salt (MS), proteinized salt (PS), and concentrated feed (CO)—on milk production, efficiency in the deposition of dairy nutrients, and enteric CH₄ emissions in dual-purpose grazing cows in the Colombian Amazon. Twenty-four F1 Holstein × Gyr cows were used in a completely randomized block design. Nutrient intake, digestibility, composition, and efficiency in the milk deposition of Ca, P, K, and N were measured; additionally, CH₄ emissions were assessed using a portable electronic spirometry mask. The results indicated that the treatments did not modify the total intake of dry matter or the production and composition of milk. CO and MS supplementation improved the efficiency of Ca and P (p < 0.03) deposition in milk, while no differences were observed for N and K. CH₄ emissions (196 ± 17.9 g/cow/day) were not affected by the supplements and were within the ranges reported for dual-purpose tropical systems. However, with the supplementation with CO was a lower losses of gross energy intake as CH₄ (Y_m) (p < 0.05). In conclusion, supplementation with the evaluated products did not impact milk production or CH₄ emissions, although with CO was lower energy losses as CH₄ and, CO and MS improved the use of Ca and P, which highlights the importance of adjusting supplementation to optimize nutritional efficiency without increasing greenhouse gas emissions.