Dairy calves are unable to mount an effective immune response during their first weeks of life, which contributes to increased disease susceptibility during this period. Oxidative stress (OS) diminishes the immune cell capabilities of humans and adult cows, and dairy calves also experience OS during their first month of life. However, the impact that OS may have on neonatal calf immunity remains unexplored. Thus, we aimed to evaluate the impact of OS on newborn calf lymphocyte functions. For this, we conducted two experiments. First, we assessed the association of OS status throughout the first month of age and the circulating concentrations of the cytokines interferon-gamma (IFN-γ) and interleukin (IL) 4, as well as the expression of cytokine-encoding genes IFNG, IL2, IL4, and IL10 in peripheral mononuclear blood cells (PBMCs) of 12 calves. Subsequently, we isolated PBMCs from another 6 neonatal calves to investigate in vitro the effect of OS on immune responses in terms of activation of lymphocytes, cytokine expression, and antibody production following stimulation with phorbol 12-myristate 13-acetate or bovine herpesvirus-1. The results were compared statistically through mixed models. Calves exposed to high OS status in their first month of age showed higher concentrations of IL-4 and expression of IL4 and IL10 and lower concentrations of IFN-γ and expression of IFNG and IL2 than calves exposed to lower OS. In vitro, OS reduced lymphocyte activation, production of antibodies, and protein and gene expression of key cytokines. Collectively, our results demonstrate that OS can compromise some immune responses of newborn calves. Hence, further studies are needed to explore the mechanisms of how OS affects the different lymphocyte subsets and the potential of ameliorating OS in newborn calves as a strategy to augment the functional capacity of calf immune cells, as well as enhance calves’ resistance to infections.

Ruminal methanogenesis represents considerable energy loss within the fermentative processes mediated by microbial populations, by means of which up to 12% of gross energy intake is driven away from microbial protein synthesis (MPS). This review explores the relationship between methane (CH₄) synthesis and emission with MPS in beef cattle, focusing on the nutritional, biochemical, and microbial factors modulating these processes. The synthesis of CH₄ by ruminal archaea is essential for maintaining redox balance during the fermentation of carbohydrates. This process diverts metabolic H₂ from energy-efficient pathways like propionate synthesis, which could otherwise enhance microbial growth. Dietary factors, including carbohydrate fermentability, N synchronization, and passage rate, modulate MPS. Diets based on roughage might enhance CH₄ synthesis while impairing MPS efficiency by reducing diet digestibility and promoting microbial shifts towards methanogenic populations. Potential mitigation strategies, including plant secondary metabolites, CH₄ inhibitors, and controlled forage-to-concentrate ratios, demonstrate the potential to reduce CH₄ emissions while enhancing nutrient utilization. This review underscores the need for integrated approaches combining dietary strategies, advanced feed additives, and improved prediction models to optimize ruminal fermentation, enhance MPS, and reduce the environmental footprint of beef cattle systems.

By 2050, the U.S. beef industry must produce an extra 40 million tons of beef to satisfy the global demand. Such an increase in inventory will undoubtedly enhance methane (CH₄) production from livestock, which should be reduced by over 20%. The addition of plant secondary metabolites, such as anacardic acid present in cashew nutshell extract (CNSE), has shown promising results in reducing CH₄ yield, although its effects seemed to be diet dependent. This study evaluated the addition of CNSE to a high-grain diet (85:15 Grain: forage) on in vivo CH₄ emissions, nutrients digestibility, performance, feeding behavior, and ruminal fermentation parameters of beef steers. Sixteen Angus crossbred steers [599 ± 40 kg of bodyweight (BW)] and six ruminally cannulated crossbred steers (490 ± 51 kg of BW) were utilized in a crossover design with 2 experimental periods of 56 d each, composed by 14 d of adaptation, 35 d of measurement, and 7 d of washout. Following adaptation, steers were sorted by BW, and assigned to receive no additive (CON) or CNSE at 5 g/steer/d. Data were analyzed using the MIXED procedure of SAS. Inclusion of CNSE increased (P < 0.05) propionate concentration and molar proportion (MP; mol/100 mol), tended to decrease acetate MP (P = 0.10), reduced the acetate: propionate (A:P) ratio (P = 0.05), and MP of branched chain volatile fatty acids (P < 0.01). Neither in vitro organic matter digestibility nor in vitro CH₄ yield were affected by CNSE inclusion (P > 0.05). Steers receiving CNSE exhibited greater (P < 0.05) final BW, dry matter intake (DMI), and average daily gain (ADG) but lesser (P < 0.05) in vivo CH₄ emission rate (g/d), yield (g/kg of DMI), and intensity (g/kg of ADG). Meal length, bunk visit duration, and apparent total tract digestibility of DM increased (P < 0.05) after CNSE addition. Considering CNSE-supplemented steers spent more time in the feedbunk and exhibited higher DMI, CH₄ mitigation was unlikely associated with intake reduction. The addition of CNSE to a high-grain diet in beef steers demonstrated significant improvements in animal performance and reduced CH₄ emissions, as the result of shifts in ruminal fermentation patterns, favoring propionate instead acetate concentration, leading to a reduction in the A:P ratio. CNSE shows promise as a strategy to enhance beef industry sustainability.

Para evaluar dinámicas en composición nutricional de forrajes tropicales utilizados para la producción bovina en Colombia, se adelantó una revisión sistemática en un motor de búsqueda inespecífico, de investigaciones publicadas en Colombia entre 1985 y 2015 que incluyeran reportes de fracciones químicas asociadas a calidad forrajera y parámetros productivos animales. Se seleccionaron como componentes: Proteína Cruda, Fibra Detergente Neutro, Fibra Detergente Acida y Digestibilidad In Vitro de la Materia Seca. También se tuvo presente reportes de ganancia diaria de peso, producción de leche y capacidad de carga. Se realizaron regresiones lineales para cada fracción química y para cada parámetro productivo en el periodo estudiado. De la búsqueda se obtuvieron 105 estudios en 17 bases de datos, de los cuales se seleccionaron especies con más de 5 estudios publicados. No se observaron tendencias lineales significativas en el tiempo para las fracciones químicas analizadas, ni para las variables productivas asociadas a la calidad del forraje. Sin embargo, para Brachiaria sp y Paspalum s.p se advierte una tendencia significativa al aumento en UGG/Ha (r2=0,54 y 0,53 respectivamente). A pesar de la baja significancia de la regresión se observó en las 9 especies, aumento sostenido en PC y DIVMS y reducción en FDA (salvo en Lolium sp y Dichantium sp). Se identifica una ligera tendencia positiva para la capacidad de carga en la mayoría de las especies. Se concluye, que los estudios históricos constituyen una valiosa herramienta para explicar y predecir el comportamiento nutricional de especies forrajeras y su efecto en variables de interés zootécnico.

Non-protein nitrogen (NPN) supplements improve animal performance in backgrounding diets. However, there is scarce information regarding the effect of different NPN sources and combinations on ruminal fermentation profile. The current study aimed to evaluate the effect of different NPN sources and their combinations on in vitro fermentation, microbial N synthesis, and methane (CH₄) production in a backgrounding diet. Incubations were conducted on three separate days for 24 h using corn silage and cotton gin byproduct (70% and 30% of DM, respectively) as substrate. Treatments were control (without NPN), urea, and five different proportions of urea–biuret and nitrate (100:0, 75:25, 50:50, 25:75, and 0:100). Each treatment, except control, was formulated to be isonitrogenous and equivalent to 1% urea inclusion. Ruminal fluid was collected from two ruminally cannulated Angus crossbred steers fed ad libitum corn silage and cotton gin byproduct plus 100 g of a urea–biuret–nitrate mixture. The concentration of volatile fatty acids (VFAs) and ammonia nitrogen (NH₃-N) were determined at 12 and 24 h of incubation. Final pH, in vitro dry and organic matter digestibility, total gas production, and concentration of CH₄ were determined at 24 h. The supplementation of NPN increased (P < 0.05) the concentration of NH₃-N at 12 and 24 h. Although NPN supplementation increased (P < 0.05) the concentration of total VFA and acetate at 12 h, treatments did not differ (P > 0.05) at 24 h. Supplementation of NPN increased (P < 0.05) the proportion of acetate at 12 and 24 h but tended to reduce (P = 0.054) the proportion of propionate only at 12 h. Digestibility and pH were not different (P > 0.05) among treatments. Increasing nitrates in the NPN supplement increased (P < 0.05) the proportion of acetate and reduced (P < 0.05) the proportion of butyrate at 12 and 24 h. The supplementation of NPN increased (P < 0.05) microbial N synthesis. Furthermore, increasing nitrate proportion in the NPN supplement increased (P < 0.05) the microbial N synthesis and efficiency of N use. Supplementation of NPN did not modify (P > 0.05) total gas or CH₄ production. However, increasing nitrate proportion in the NPN supplement linearly reduced (P < 0.05) CH₄ production. Supplementation of NPN increased NH₃-N concentration and microbial N while increasing the inclusion of nitrate decreased the production of CH₄ and increased the microbial N synthesis in a corn silage-based substrate under in vitro conditions. The use of non-protein nitrogen (NPN) to the protein requirements of ruminants is a strategy that may lead to improved ruminal fermentation and enhanced animal production when ruminants are fed protein-deficient diets. Sources of NPN such as urea, biuret, and nitrates have been evaluated under in vitro and in vivo conditions. However, limited information is available regarding the use of NPN mixtures on fermentation and methane emissions. Different mixtures of NPN were supplemented using a backgrounding substrate in an in vitro system. Urea was used as a reference NPN source. The inclusion of NPN sources increased the ammonia nitrogen concentration and microbial N synthesis. Additionally, increasing nitrate in the NPN mixture reduced the proportion of acetate and butyrate and the production of methane. In conclusion, NPN mixtures changed the fermentation patterns relative to urea and reduced methane in vitro.

Garlic (Allium sativum) contains secondary compounds that are known to modify rumen fermentation parameters and decrease methane (CH₄) emissions. The objective was to evaluate the effects of increasing the inclusion levels and processing methods of garlic on in vitro fermentation and CH₄ production. Treatments were arranged in a randomized complete block design with a 2 × 3 × 2 + 1 factorial arrangement, where the main factors were the initial condition of garlic (intact or smashed), drying process (freeze-dried, oven-dried, or autoclaved), and garlic proportion in the diet (2.5 and 5%) and one control (without garlic supplementation). Incubations were conducted using corn silage and cotton-gin trash (80:20, respectively) as basal substrates on three different days. Final pH, the concentration of volatile fatty acids (VFA) and ammonia nitrogen (NH₃-N), in vitro organic matter digestibility (IVOMD), total gas production, and CH₄ concentration were determined after 24 h. Initial garlic condition or drying processing neither modify (p > 0.05) the in vitro fermentation nor the CH₄ production. However, increasing garlic inclusion linearly increased (p < 0.05) IVOMD, the concentration of the total VFA, and the proportion of propionate. Also, the concentration of NH₃-N and the proportion of acetate increased quadratically (p < 0.05) with greater garlic inclusions. Finally, garlic inclusion did not affect (p > 0.05) gas and CH₄ production. In conclusion, increasing garlic levels, but not the processing methods, improved in vitro fermentation but did not modify CH₄ emissions under in vitro conditions.