It is known that nitrate inhibits ruminal methanogenesis, mainly through competition with hydrogenotrophic methanogens for available hydrogen (H₂) and also through toxic effects on the methanogens. However, there is limited knowledge about its effects on the others members of ruminal microbiota and their metabolites. In this study, we investigated the effects of dietary nitrate inclusion on enteric methane (CH₄) emission, temporal changes in ruminal microbiota, and fermentation in Holstein calves. Eighteen animals were maintained in individual pens for 45 d. Animals were randomly allocated to either a control (CTR) or nitrate (NIT, containing 15 g of calcium nitrate/kg dry matter) diets. Methane emissions were estimated using the sulfur hexafluoride (SF₆) tracer method. Ruminal microbiota changes and ruminal fermentation were evaluated at 0, 4, and 8 h post-feeding. In this study, feed dry matter intake (DMI) did not differ between dietary treatments (P > 0.05). Diets containing NIT reduced CH₄ emissions by 27% (g/d) and yield by 21% (g/kg DMI) compared to the CTR (P < 0.05). The pH values and total volatile fatty acids (VFA) concentration did not differ between dietary treatments (P > 0.05) but differed with time, and post-feeding (P < 0.05). Increases in the concentrations of ruminal ammonia nitrogen (NH₃–N) and acetate were observed, whereas propionate decreased at 4 h post-feeding with the NIT diet (P < 0.05). Feeding the NIT diet reduced the populations of total bacteria, total methanogens, Ruminococcus albus and Ruminococcus flavefaciens, and the abundance of Succiniclasticum, Coprococcus, Treponema, Shuttlewortia, Succinivibrio, Sharpea, Pseudobutyrivibrio, and Selenomona (P < 0.05); whereas, the population of total fungi, protozoa, Fibrobacter succinogenes, Atopobium and Erysipelotrichaceae L7A_E11 increased (P < 0.05). In conclusion, feeding nitrate reduces enteric CH₄ emissions and the methanogens population, whereas it decreases the propionate concentration and the abundance of bacteria involved in the succinate and acrylate pathways. Despite the altered fermentation profile and ruminal microbiota, DMI was not influenced by dietary nitrate. These findings suggest that nitrate has a predominantly direct effect on the reduction of methanogenesis and propionate synthesis.

In this study, we developed new sets of primers to detect Brucella spp. and M. avium subsp. paratuberculosis (MAP) through isothermal amplification. We selected a previously well-characterized target gene, bscp31, specific for Brucella spp. and IS900 for MAP. The limits of detection using the loop-mediated isothermal amplification (LAMP) protocols described herein were similar to those of conventional PCR targeting the same sequences. Hydroxynaphtol blue and SYBR Green^TM allowed direct naked-eye detection with identical sensitivity as agarose gel electrophoresis. We included the LAMP-based protocol in a rapid identification scheme of the respective pathogens, and all tested isolates were correctly identified within 2 to 3 h. In addition, both protocols were suitable for specifically identifying the respective pathogens; in the case of Brucella, it also allowed the identification of all the biovars tested. We conclude that LAMP is a suitable rapid molecular typing tool that could help to shorten the time required to identify insidious bacteria in low-complexity laboratories, mainly in developing countries.

This study evaluated enteric methane (CH₄) emissions, dry matter intake (DMI), and performance in rearing beef heifers fed either a Guinea-grass-only diet (0WCS) or Guinea grass supplemented with whole cottonseed (WCS) at 0.5% of body weight (BW). Twenty-four Braford heifers were randomly allocated into four pens (three animals per pen) per treatment over two experimental periods. Methane emissions were measured using the SF₆ tracer technique. Heifers receiving WCS supplementation produced 29% less CH₄ (120.64 vs. 169.54 g/day for 0.5WCS and 0WCS, respectively; p = 0.02) and showed a 22% reduction in CH₄ yield (7.30% vs. 9.41% of gross energy intake; p = 0.02). Methane intensity was 33% lower in supplemented heifers (0.37 vs. 0.55 g CH₄/kg BW; p = 0.01). However, WCS supplementation significantly reduced total DMI and forage DMI (p = 0.01 and p < 0.01, respectively). In terms of performance, heifers in the 0.5WCS group gained 0.28 kg/day, while those in the 0WCS group lost 0.10 kg/day. These results indicate that WCS supplementation mitigates CH₄ emissions while improving weight gain in beef heifers fed low-quality forage diets, making it a promising strategy for enhancing the sustainability of beef cattle production systems.

This study aims to quantify enteric methane (CH₄) emission and dry matter intake (DMI) in beef steers under two rotational grazing systems: (i) a mixture of cover crops (vetch + ryegrass + forage radish) (CC) and (ii) alfalfa and fescue pasture (AFP). Eighteen Hereford steers were divided into two groups (nine steers per group), assigned to either the CC or AFP. Methane emissions were measured using the SF₆ tracer technique. The results showed that steers grazing CC produced 29% less CH₄ in g/d compared to those on the AFP (119.1 vs. 167.1 g/d for CC and AFP, p < 0.05) and 36% less CH₄ yield (4.3 vs. 6.7% of gross energy intake). However, average daily gain (ADG), DMI, and CH₄ intensity (gCH₄/kg ADG) did not significantly differ between treatments. The integration of CC in a cattle grazing system has the potential to reduce CH₄ emissions by improving forage quality.

While concerns about greenhouse gas (GHG) emissions and animal welfare persist, livestock farming offers unique ecosystem services. In Argentina, where livestock significantly contributes to GHG emissions, particularly enteric methane (CH ₄ ), urgent action is required to develop effective mitigation strategies while maintaining animal performance. This study assesses the potential of the inclusion of Lotus tenuis in natural grasslands to mitigate CH ₄ emissions and improve forage quality in the Salado River basin, Argentina. Twenty‐four beef heifers (361 ±  19 kg LW) were assigned to two treatments with contrasting botanical composition (LOT: > 80% Lotus tenuis and NG: > 60% grasses). LOT showed better forage quality and reduced CH ₄ emissions (−17% gCH ₄ /day, p < 0.01; Ym : ‐ 7 to −30%, p < 0.05) compared to NG. However, the condensed tannin content in LOT was insufficient to conclusively attribute any impact on CH ₄ emissions. This study underscores the potential of promoted Lotus tenuis pastures in the Salado River basin to enhance forage quality and mitigate enteric CH ₄ emissions in free‐ranging cattle systems, albeit additional research is necessary to fully comprehend how this practice interacts within the ecosystem and optimise its benefits.