Juan Carlos Ku-Vera

Greenhouse gas (GHG) emissions from ruminant grazing systems originates mostly from rumen fermentation processes particularly as methane. Measuring methane emissions from ruminants is essential for achieving accurate GHG inventories and developing effective strategies to mitigate GHG emissions in the context of climate change mitigation and sustainable livestock development. This Letter to the Editor aims to provide and discuss specific details about the SF6 (sulfur hexafluoride) technique which is a methodology used for assessing methane emissions from ruminants, as well as an alternative technology, namely, the Greenfeed or respiration chambers. The SF6 technique is widely used in research settings to quantify methane emissions from ruminant livestock, including cattle, sheep, and goats. Whereas the Greenfeed consists of a feeding station equipped with sensors that continuously monitor gases emitted by ruminants during feeding. Regarding respiration chambers, they function by enclosing the animals in a controlled environment where the air inflow and outflow are measured. Overall, under the Mexican grazing systems in the tropics, SF6, Greenfeed, and respiration chambers provide highly accurate data and are approaches that are required in the context of precision livestock farming.

Several authors have developed equations to estimate methane (CH4) emissions by cattle according to variables such as dry matter and nutrient intake, live weight, or weight gain. Mathematical models using these variables show a large variability of results, being necessary to identify those which provide more precise and accurate predictions. For this reason, the objective of this study was to validate enteric CH4 emissions estimated from mathematical models through a comparison with a database of CH4 emissions obtained from cattle experiments carried out in tropical regions. A database of 495 individual cattle CH4 emissions data (g day-1) obtained from 19 studies in three tropical Latin American countries was built for this study. Results showed that mathematical models developed for cattle in tropical production systems overestimated CH4 emissions when they were compared with our database. The mathematical model with higher precision and accuracy was the one that included dry matter intake and organic matter digestibility in the equation (Equation 7. R2=0.34, Cb=0.94, CCC=0.55, RMSE=60.8%, r=0.58), followed by models that included neutral detergent fiber intake data (Equation 5). Our data did not show a relationship between CH4 emissions and gross energy intake or live weight.

The aim of the experiment was to assess the effect of increasing amounts of Leucaena leucocephala forage on dry matter intake (DMI), organic matter intake (OMI), enteric methane production, rumen fermentation pattern and protozoa population in cattle fed Pennisetum purpureum and housed in respiration chambers. Five crossbred heifers (Bos taurus×Bos indicus) (BW: 295±6 kg) were fed chopped P. purpureum grass and increasing levels of L. leucocephala (0%, 20%, 40%, 60%, and 80% of dry matter [DM]) in a 5×5 Latin square design. The voluntary intake and methane production were measured for 23 h per day in respiration chambers; molar proportions of volatile fatty acids (VFAs) were determined at 6 h postprandial period. Molar concentration of VFAs in rumen liquor were similar (p>0.05) between treatments. However, methane production decreased linearly (p0.05) in rumen protozoa population were found. Inclusion of 80% of L. leucocephala in the diet of heifers fed low-quality tropical forages has the capacity to reduce up to 61.3% enteric methane emission without affecting DMI, OMI, and protozoa population in rumen liquor.

The aim of this work was to evaluate the effect of quebracho tannins extract (QTE) on feed intake, dry matter (DM) digestibility, and methane (CH₄) emissions in cattle fed low-quality Pennisetum purpureum grass. Five heifers (Bos taurus × Bos indicus) with an average live weight (LW) of 295 ± 19 kg were allotted to five treatments (0, 1, 2, 3, and 4% QTE/kg DM) in a 5 × 5 Latin square design. Intake, digestibility, and total methane emissions (L/day) were recorded for periods of 23 h when cattle were housed in open-circuit respiration chambers. Dry matter intake (DMI), organic matter intake (OMI), dry matter digestibility (DMD), and organic matter digestibility (OMD) were different between treatments with 0 and 4% of QTE/kg DM (P < 0.05). Total volatile fatty acid and the molar proportion of acetate in the rumen was not affected (P < 0.05); however, the molar proportion of propionate increased linearly (P < 0.01) for treatments with 3 and 4% QTE. Total CH₄ production decreased linearly (P < 0.01) as QTE increased in the diet, particularly with 3 and 4% concentration. When expressed as DMI and OMI by CH₄, production (L/kg) was different between treatments with 0 vs 3 and 4% QTE (P < 0.05). It is concluded that the addition of QTE at 2 or 3% of dry matter ration can decrease methane production up to 29 and 41%, respectively, without significantly compromising feed intake and nutrients digestibility.

El objetivo del presente estudio fue evaluar el efecto del consumo de energía metabolizable (CEM) sobre el contenido energético de la canal de ovejas Pelibuey. Veinticuatro (24) ovejas con un peso vivo de 37.2±4.0 kg y condición corporal de 2.5± 0.12 se asignaron al azar a cuatro grupos de seis animales. Un grupo se sacrificó al inicio del experimento para las mediciones de referencia, y las ovejas de los grupos restantes se asignaron a uno de tres niveles de CEM: bajo (B), medio (M) y alto (A) durante 65 días. El CEM fue: 0.247, 0.472 y 0.532 MJ/kgPV0.75/día para B, M y A, respectivamente. Las ovejas se sacrificaron y la canal se dividió en dos mitades; la mitad izquierda se disecó en grasa, músculo y hueso. Las ovejas en el nivel B y M removieron 55 y el 26 % de su contenido de energía inicial de la canal respectivamente, mientras que el nivel A aumentó su contenido de energía en un 14 %. Los cambios diarios en la energía en la canal fueron -1.099, -0.515 y 0.285 MJ/día para B, M y A, respectivamente. Las proporciones de la energía en canal como músculo y grasa fueron 76 y 24 %, 68 y 32 %, y 65 y 35 % para los niveles de B, M y A, respectivamente. Las ovejas Pelibuey remueven aproximadamente el 55 % del contenido de energía de la canal cuando se someten a condiciones de subalimentación severa.