Sustainable intensification involves maintaining ecosystem balance and increasing productivity per animal per unit area. Phytogenic additives can be used as an alternative to achieve sustainable intensification. Tannins are phenolic compounds present in plants that are classified according to their chemical structure into hydrolyzable and condensed compounds. When added to ruminant diets, condensed tannins exert effects on rumen fermentation, such as a reduction in rumen protein degradation and enteric methane production per unit of dry matter ingested, and may also improve weight gain. The advantage of this mechanism is that it increases dietary protein utilization, reduces nitrogen excretion in urine, and reduces nitrous oxide emissions. However, the positive effects of these compounds as nutritional additives require further investigation. Therefore, the objective of this review is to demonstrate the results hitherto known of the use of condensed tannins in ruminant nutrition. The use of tannins can result in both positive and negative effects, depending on the sources and doses administered.

The inclusion of corn-dried distillers' grains (DDG) could be an alternative supplement to increase animal performance, nitrogen efficiency usage (NEU), and decrease enteric methane (CH₄) emissions. Our goal was to determine whether DDG could replace a traditional supplement (cottonseed meal) without affecting animal performance, N balance, and CH₄ emissions. The experiment was conducted during the forage growing season (December to April), with 15 d adaptation, and a 112 d experimental period. The experimental design was completely randomized with four treatments: a mineral supplement (MS), cottonseed meal supplement (CS), 50% replacement of CS by DDG (50DDG), and 100% replacement of CS by DDG (100DDG). Cottonseed meal and DDG were used as protein supplement. A total of 12 paddocks, 3 per treatment, were used to measure forage mass: morphological and chemical composition of forage, forage allowance, and animal performance. Six animals per treatment were used to evaluate DM intake, digestibility, CH₄ emissions, microbial protein production (MCP), and NEU of each treatment. Eighty-one Young Nellore bulls (48 testers, 12 per treatments and 33 adjusters) with initial BW of 255 ± 5 kg (10-12 months old) were supplemented with each supplement type at a level of 0.3% of BW. Pasture management was continuous stocking with a variable stocking rate (put-and-take). Enteric CH₄ was measured using the gas tracer technique. The MCP was quantified using purine derivatives and the NEU mass balance. No differences were found in nutrient intake (P > 0.228). Individual animal performance and gain per area were higher in the treatments with concentrates compared with that of MS; however, there was no difference among treatments CS, 50DDG, and 100DDG. The ADG was 0.83 for MS and 1.08 kg/animal/d when supplemented (P < 0.05). Gain per hectare was 709 kg/ha for MS and 915 kg/ha when supplemented with concentrates (P < 0.05). There was no difference in CH₄ production among treatments that average 180 g/animal/d; however, CH₄ per kg of gain was reduced with CS. The CH₄ conversion factor averaged 5.91%. There was no difference in the synthesis of MCP and NEU. Corn DDG can replace 100% of cottonseed meal as a protein source for supplementation of young Nellore bulls grazing in tropical pastures without affecting animal performance, NEU, MCP, and CH₄ emissions.

The study aimed to evaluate the effect of replacing cottonseed meal by dried distiller’s grains (DDG) in terms of efficiency in the productive aspects of beef cattle finishing in pasture versus feedlot. The experiment was conducted in a completely randomized design in a 2 × 3 factorial arrangement, with two production systems (pasture versus feedlot) and three supplements: CM, conventional supplement with cottonseed meal (CM) as a protein source; 50DDG: supplement with 50% replacement of CM by DDG; and 100DDG: 100% replacement. The effect of replacing CM by DDG on dry matter and nutrients intake and nutrients digestibility depends on the finishing system (p < 0.05). While in the pasture system animal consumed more nutrients in the CM, a greater intake was observed in the 100DDG in feedlot. The nutrients digestibility was lower in the pasture (p < 0.05). Animal performance and final body weight were higher in the feedlot (p < 0.0001), with averages of 1.57 kg/d and 566 kg of final body weight (FBW) for feedlot, and 0.99 kg/d and 504 kg FBW for pasture. The use of DDG does not change the animal performance finished in pasture or feedlot, and it is a viable alternative to replace conventional supplements in finishing phase in both systems in tropical environment.

Animal supplementation during the background phase may increase greenhouse gas emissions (GHG). The inclusion of tannins in the diet of Nellore bulls can mitigate nitrous oxide (N₂O), methane (CH₄), and ammonia (NH₃) production. The objective of this study was to quantify the effect of energy supplementation associated with sources of tannins in the diet of young Nellore bulls backgrounded in pastures with N₂O, CH₄, and NH₃ emissions. Two experiments were conducted in a completely randomized design. The treatments were three supplementation strategies: (1) soybean hulls 0.3% of body weight (BW), (2) sorghum grain 0.3% of the BW, and (3) peanut peel 0.3% of BW, the last two being sources of tannin. The static closed chambers method was used to quantify N₂O and CH₄ emissions and the semi-open chamber technique to estimate NH₃ volatilization. Supplementation strategies did not affect the N₂O emissions (p = 0.9116). The soil water-filled pore space explained the variation in the N₂O fluxes (p = 0.0071). The treatments did not change the total CH₄ emissions (p = 0.3599), and no explanatory variable was correlated with the CH₄ fluxes. The NH₃ volatilization did not vary according to the supplements or tannin inclusion (p = 0.5170). However, the type of excreta affected the NH₃ volatilization (p < 0.0001). Ammonia volatilization averaged 14.05, 4.16, and 2.25% of the applied N for urine, urine + dung, and dung, respectively. The energetic supplementation of Nellore bulls containing sources of tannins in the evaluated dosages was not a mitigation strategy for the emissions of N₂O, CH₄, and NH₃.