Background and Aim: Mexico is the fifth largest producer of mangoes in the world. For the conservation of agro-industrial waste and crop residues, the ensiling technique has shown good results. This study aimed to evaluate the effect of increasing the level of mango silage (86% waste mango and 14% pangola grass hay) in calf diets on in vitro gas production, in situ digestibility, intake, apparent digestibility, and ruminal characteristics. Materials and Methods: The diets contained 0 (T0), 30 (T1), 45 (T2), and 60% (T3) mango silage. The partial (24, 48, and 72 h) and cumulative (72 h) biogas, CH4 production, and degradation were determined in the in vitro evaluation. In situ digestibility and estimators of fermentation kinetics of dry matter (DM) and organic matter (OM) were determined. Intake, apparent nutrient digestibility, and rumen parameters of calves (200 kg) were evaluated in a 4 × 4 Latin square design. Response to increased mango silage was calculated by linear and quadratic orthogonal contrasts. Results: In vitro partial and cumulative biogas production decreased linearly (p < 0.05), and the partial and cumulative CH4 production did not show linear or quadratic contrast (p > 0.05); in vitro DM degradation, in vitro neutral detergent fiber degradation, and in vitro acid detergent fiber degradation showed a linear increase (p < 0.05). In situ dry matter digestibility (DMDis), in situ organic matter digestibility (OMDis), b, a + b, c, and effective digestibility (ED) of DMDis, a, a + b, c, and ED of OMDis increased linearly (p < 0.05). Dry matter intake, OM intake, and crude protein intake showed a linear increase (p < 0.05); NDF intake and ADF intake presented a quadratic behavior (p < 0.05). Apparent digestibility of DM, OM, CP, and hemicellulose, pH, N-NH3, total bacterial count, acetate, propionate, butyrate, volatile fatty acids, acetate: propionate ratio, cellulolytic bacteria, and protozoa did not present a linear or quadratic orthogonal effect (p > 0.05). Conclusion: The in vitro, in situ, and in vivo variables demonstrated that up to 60% mango silage can be used for the intensive fattening of calves in confinement. Keywords: alternative feed, alternative feeding, cattle, silage, tropics.

Rumen methane emissions contribute to global warming and energy loss in cattle. The use of plants rich in secondary metabolites to mitigate methane emissions has been extensively studied, with varying outcomes. The primary aim of this meta-analysis was to assess the impact of secondary metabolites on methane production, productive performance, and ruminal fermentation in beef cattle supplemented with plant-based additives. In accordance with the PRISMA guidelines, 43 of the 578 studies were selected for analysis, employing random-effects models to estimate the raw and standardized mean differences (RStudio: metafor and ggplot, with significance thresholds of p ≤ 0.05 and p ≤ 0.1). Heterogeneity was evaluated using the I² statistic, alongside a subgroup meta-regression examining variables such as dose, additive type, additive form, and forage-to-concentrate ratio. After performing Egger’s test and trim and fill analysis, it was determined that tannins reduced methane yield (g/kg DM, adjusted SDM = −0.463), increased propionate production (%, RMD = 0.066, p = 0.001), rumen pH (adjusted SMD = 0.307), and organic matter intake (RMD = 0.066, p = 0.01). Despite phenolic compounds, flavonoids, terpenes, and terpenoids successfully modulating methane production, fermentative parameters, and nutrient intake, the limited number of comparisons and publication bias suggest caution in generalizing these results. In conclusion, supplementation with plant-based additives containing tannins offers a promising nutritional strategy for reducing enteric methane emissions while maintaining beef cattle performance.

The effect of increasing levels of coconut oil (CO: 0, 100, 200, and 300 g/kg of supplement DM) on productive performance, feed intake, rumen fermentation, microbiota, and gene expression was evaluated in 24 calves (Bos indicus × Bos taurus; 180 ± 10 kg BW) on rotational grazing (Cynodon dactylon) in a completely randomized design (n = 6) for 112 days. Supplement intake (offer–refusal) and forage intake (external marker: chromium) were measured. On day 112, rumen fluid (fermentation profile, protozoa, and metagenomic analysis: 16S rRNA V3-V4) and total blood (DNA microarray: M22k) were collected. Genomic analyses were performed by comparing the control vs. the group with the best productive response. For statistical analysis, SAS PROC GLM (initial weight as a covariate), orthogonal polynomials, the Tukey test, and Spearman correlation were used, considering significant effects (p ≤ 0.05) and trend (p ≤ 0.1). The inclusion of 200 g CO/kg supplement DM showed the best average daily gain (p = 0.018; +0.139 kg/d) with the highest retained energy (p = 0.02; +0.631 Mcal/d) versus the control group. In the rumen, propionate increased (p ≤ 0.05), while protozoa decreased (p < 0.0001) and the methanogenic archaea tended to decrease (Methanobacteriaceae −44%, p = 0.08; Thermoplasmatales −35%, p = 0.06). At the transcriptional level, 19 hub genes were modulated by CO, suggesting a lower intracellular signaling (cAMP-PKA-CREB) associated with a lower stress condition and better energy metabolism regulation. In conclusion, 200 g CO/kg supplement DM is a viable strategy for improving the productive performance of livestock in tropical systems.

El presente estudio comparo los valores bromatológicos, la degradación in vitro y digestibilidad in situ de la pasta de coco (Cocos nucifera L.) y cacahuananche (Gliricidia sepium L.) para caracterizar su valor biológico y la pertinencia de uso en ensayos in vivo. El estudio se realizó en el Laboratorio de Nutrición Animal de la Facultad de Medicina Veterinaria y Zootecnia de la Universidad Autónoma de Guerrero, México. Las muestras se ajustaron a un diseño completamente al azar, y se analizaron con el software InfoStat; las diferencias de medias se determinaron mediante la prueba de Tukey (P < 0.05). Los valores bromatológicos mostraron que ambas pastas presentaron contenido similar de materia seca, cenizas y materia organiza (P > 0.05). La pasta de cacahuananche destacó con un 159 % más de proteína cruda, mientras que la de coco presentó un 151 % más de fibra detergente neutro y un 136 % más de fibra detergente ácido (P < 0.05). En el ensayo in vitro, la pasta de cacahuananche mostró mayor degradabilidad de la materia seca a las 12, 24 y 48 horas, mientras que la pasta de coco presentó mayor degradación a las 72 horas (P < 0.05). Los resultados de la cinética de digestibilidad in situ indicaron que la pasta de cacahuananche presentó fracciones mayores y una correlación positiva que la pasta de coco (P < 0.05). En conclusión, la pasta de cacahuananche al compararla con la pasta de coco muestra una alternativa de proteína para rumiantes, sugiriendo estudios in vivo para confirmar su eficacia en dietas formuladas.