The SF ₆ gas tracer technique is extensively used to measure enteric CH ₄ emissions for scientific research in Latin‐American countries. Although guidelines on how to properly implement this technique have been published, its use has been the subject of considerable uncertainty due to a high variation within measurements when compared to results obtained with other techniques. Therefore, a detailed evaluation of this technique is important to identify the main sources of variability. The aim of this study is to summarise the key factors contributing to this variation, as reported in studies conducted in Latin America (LA). The final dataset comprised 63 studies and the variables considered within our analysis were split into two main categories: (1) Production systems and animal‐related factors driving enteric CH ₄ emissions and (2) Aspects related to the implementation of the SF ₆ gas tracer technique in research laboratories, such as: duration of the collection period, and mean permeation rate of the SF ₆ collection canisters, among others. The lack of specific details regarding the SF ₆ gas tracer technique in the compiled dataset from LA studies is notable. Despite this, the main sources of variation identified were related to both the duration of the sampling period and the SF ₆ permeation rate.

Accurate determination of dry matter digestibility (DMD) and total faecal output (FO) is necessary for estimating ruminant dry matter intake (DMI) under grazing conditions. This study evaluated the efficacy of inductively coupled plasma optical emission spectrometry (ICP-OES) for quantifying external markers [chromium oxide (Cr₂O₃) and titanium dioxide (TiO₂)] and near-infrared reflectance spectroscopy (NIRS) for quantifying external markers and indigestible NDF (iNDF) in samples from grazing ruminant systems under diverse grazing conditions in Colombia. Cr₂O₃ and TiO₂ were processed via wet acid digestion and analysed using ICP-OES, while iNDF was determined through in vitro fermentation (288 h). NIRS equations were developed using modified partial least squares method with cross-validation to prevent model overfitting. ICP-OES methodology yielded detection limits for Ti (2.97–5.95 µg·g⁻¹) and Cr (23.08–46.16 µg·g⁻¹). Ti concentration was analysed in 285 forages samples and Cr concentration in 213 samples, with mean values of 34.52 and 7.06 µg·g⁻¹, respectively. For iNDF, 1285 total samples were processed, including 421 forages, 3 commercial feed supplements, 4 partial mixed rations and 855 faecal samples, with mean values of 18.2%, 4.37%, 2.07% and 23.66% iNDF, respectively. NIRS validation for forages showed satisfactory predictive capacity for iNDF and Ti (r² = 0.88 and 0.89, respectively) and RPD (2.85 and 2.89, respectively) compared to Cr (r² = 0.42 and RPD = 1.23). In faecal samples without marker added, Ti showed a satisfactory fit (r² = 0.86 and RPD = 2.65), while for iNDF demonstrated lower accuracy (r² = 0.64 and RPD = 1.67). The ICP-OES and NIRS techniques proved efficient methods for Ti, Cr and iNDF marker determination, offering potential for accurate estimation of ruminant DMI under grazing conditions.

Including soybean hulls (SH) in ruminant diets increase the carbon circularity of livestock systems. We evaluated whether SH could partially replace corn grain (CG) in the diet of lactating cows (≈7.5% of the total diet). Six Holstein multiparous cows were fed a 50:50 (dry matter basis) corn-silage to concentrate diet for two 25-day periods in three replicated 2 × 2 Latin Squares using linear mixed models. Feed intake, milk yield and composition, N excretion, CH₄ production, and ruminal microbial profiles were measured. Enteric CH₄ was measured in respiration chambers. The DMI of cows fed SH (28 kg DM/d) was greater (p = 0.034) than those fed CG (26 kg DM/d), but no differences were observed in milk production (p = 0.557) or enteric CH₄ emission intensity (g/kg milk, p = 0.387). Enteric CH₄ emissions tended to be greater in SH-fed cows (484 g/d) than CG-fed cows (456 g/d; p = 0.075), and N excretion was significantly greater in SH than CG cows (p < 0.001). No mayor shifts in ruminal microbiota or overall ruminal environment were observed. In conclusion, SH can partially replace CG in diets of lactating dairy cows without affecting production, but potential negative environmental impacts should be considered.