The Impact of Mineral and Energy Supplementation and Phytogenic Compounds on Rumen Microbial Diversity and Nitrogen Utilization in Grazing Beef Cattle.

The objective of this study was to evaluate the effect of the addition of a phytogenic compound blend (PHA) containing hydrolyzable tannins, carvacrol, and cinnamaldehyde oil to mineral salt or energy supplementation on the rumen microbiota and nitrogen metabolism of grazing Nellore cattle. Eight castrated Nellore steers were distributed in a double-Latin-square 4 × 4 design, with a 2 × 2 factorial arrangement (two types of supplements with or without the addition of the PHA), as follows: energy supplement without the PHA addition (EW); energy supplement with the PHA addition (EPHA); mineral supplement without the addition of the PHA (MW); mineral supplement with the PHA addition (MPHA). Steers that received supplements with the PHA have a lower ruminal proportion of valerate (with the PHA, 1.06%; without the PHA, 1.15%), a lower ruminal abundance of Verrucomicrobia, and a tendency for lower DM digestibility (with the PHA, 62.8%; without the PHA, 64.8%). Energy supplements allowed for higher ammonia concentrations (+2.28 mg of NH3-N/dL), increased the propionate proportion (+0.29% of total VFA), and had a higher ruminal abundance of Proteobacteria and Spirochaetae phyla in the rumen. The PHA addition in the supplement did not improve nitrogen retention, reduced the ruminal proportion of valerate, and had a negative impact on both the total dry-matter digestibility and the abundance of several ruminal bacterial groups belonging to the Firmicutes and Verrucomicrobia phyla.

Effects of condensed tannins on greenhouse gas emissions and nitrogen dynamics from urine-treated grassland soil.

Condensed tannins are a potentially important treatment option to mitigate N2O (nitrous oxide) and affect carbon dioxide (CO2) and methane (CH4) emissions; however, their effect has been poorly assessed. Here, we quantified the emissions of N2O, CH4, and CO2, soil N mineralization, and nitrification with increasing doses of condensed tannins added to the urine of cattle raised on pasture. The experiment consisted of incubation with doses of 0%, 0.5%, and 1.0% of condensed tannins added directly to the collected urine. The experimental design was completely randomized. Greenhouse gas fluxes were quantified for four weeks using static chambers and gas chromatography. The addition of condensed tannins increased N2O emissions (P < 0.05), with total emissions averaging 95.84 mg N-N2O kg-1, 265.30 mg N-N2O kg-1, and 199.32 mg N-N2O kg-1 dry soil in the treatments with 0%, 0.5%, and 1% tannins, respectively. Methane emissions were reduced with the addition of tannins (P < 0.05), with total emissions of 8.84 g CH4 kg-1, 1.87 g CH4 kg-1, and 3.34 g CH4 kg-1 dry soil in the treatments with 0%, 0.5%, and 1% tannins, respectively. Soil respiration increased with the addition of condensed tannins (P < 0.05), with total emissions of 3.80 g CO2 kg-1, 6.93 g CO2 kg-1, and 5.87 g CO2 kg-1 in dry soil, in the treatments with 0%, 0.5%, and 1% tannins, respectively. The addition of condensed tannins reduced N mineralization and nitrification. We found evidence that the use of condensed tannins might not be a suitable option to mitigate N2O emissions. However, soil CH4 emissions can be abated. The increases in soil respiration suggest that tannins affect soil microorganisms, and the effects on CH4 and N2O could be related to the variation in the soil microbiome, which requires further clarification.

Pasture management and greenhouse gases emissions

Pastures are important environments worldwide because they offer many ecosystem services and sustain meat and milk production. However, pastures ecosystems are responsible for greenhouse gas (GHG) emission. The major GHGs include CO2, CH4, and N2O. The present review summarizes GHG emission from pasture ecosystems and discusses strategies to mitigate this problem. In pastures, emissions originate from animal excretion, fertilization, and organic matter decomposition. Emissions of specific gases can be measured based on certain factors that were recently updated by the United Nation's Intergovernmental Panel on Climate Change in 2019. Urine is the main source of N2O emission. Forage structure is an important factor driving GHG transport. Forage fiber content and animal intake are the key drivers of enteric CH4 emission, and the introduction of forage legumes in pasture systems is one of the most promising strategy to mitigate GHG emission.

Effects of Replacing Cottonseed Meal with Corn Dried Distillers' Grain on Ruminal Parameters, Performance, and Enteric Methane Emissions in Young Nellore Bulls Reared in Tropical Pastures.

Two experiments were conducted to evaluate the effect of replacing cottonseed meal with DDG on ruminal parameters, methane (CH4) emissions (Experiment 1), and animal performance (Experiment 2) of young Nellore bulls grazing Marandu grass during the rainy season. Four supplementation strategies were used in both experiments: (1) Mineral supplementation (MS); (2) conventional multiple supplement (energy/protein) with cottonseed meal and citrus pulp (CMS); (3) CMS with 50% cottonseed meal replaced by DDG (50DDG); and (4) CMS with 100% cottonseed meal replaced by DDG (100DDG). The 50DDG condition resulted in greater intake of dry matter (p = 0.033), organic matter (OM) (p = 0.050), forage (p = 0.035), and digestible OM (p = 0.031) than 100DDG. The supplemented animals presented greater final body weight (BW) and average daily gain than the animals consuming MS (p = 0.011), and lower pH, acetate, and acetate:propionate (p < 0.05). However, the treatments had no influence on stocking rate, gain per area, and enteric CH4 emissions (p > 0.05). Replacing cottonseed meal with DDG does not result in great variations in ruminal parameters, animal performance, and enteric CH4 emissions of grazing Nellore cattle during the rearing phase in the wet season. Both protein sources in 0.3% BW supplementation can be used to intensify beef cattle production in pastures.

Effects of nitrogen fertilization on protein and carbohydrate fractions of Marandu palisadegrass.

The effects of nitrogen (N) fertilization levels on protein and carbohydrate fractions in Marandu palisadegrass pasture [Urochloa brizantha (Hochst. ex A. Rich.) R.D. Webster] were investigated in a pasture over five years. The experimental design was completely randomized with four levels of N (0, 90, 180, and 270 kg N ha-1, as urea) for five years, and with three replicates. The study was conducted in a continuously stocked pasture during the forage growing season (December to April) in a tropical region. The effects of N fertilization were similar across the five years. With increasing N fertilization, the concentrations of crude protein (CP) increased from 103 to 173 g kg-1 (P < 0.001), soluble fractions (Fraction A + B1) increased from 363 to 434 g kg-1 of total CP (P = 0.006); neutral detergent fiber (NDF) decreased from 609 to 556 g kg-1 (P = 0.037); indigestible NDF (P = 0.046), potentially degradable neutral detergent fiber (P = 0.037), and acid detergent fiber decreased (P = 0.05), and total digestible nutrient (TDN) increased (P < 0.001). Increasing N fertilization decreased the concentrations of Fraction C (P = 0.014) and total carbohydrates (P < 0.0001), and increased CP:organic matter digestibility (P < 0.01). Concentrations of neutral detergent fiber free of ash and protein (P = 0.003), indigestible neutral detergent fiber (P < 0.001), neutral detergent fiber potentially degradable (P = 0.11), CP (P < 0.001), Fraction A + B1 (P < 0.001), Fraction B2 (P < 0.001), Fraction B3 (P < 0.01), and non-structural carbohydrates differed (P < 0.001) across years. Therefore, N fertilization can be used to increase CP, soluble protein, and TDN.

Does the Effect of Replacing Cottonseed Meal with Dried Distiller's Grains on Nellore Bulls Finishing Phase Vary between Pasture and Feedlot?

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.

Effect of pasture management on enteric methane emissions from goats.

The effect of pasture management on CH4 emissions was investigated from goats in a tropical climate. Two experiments were conducted in a "Tanzania Guinea grass" (Panicum maximum Jacq.) pasture to assess enteric CH4 production in a completely randomized design. Emissions from light, moderate, and heavy grazing intensities were analyzed in the first experiment, and variations between grazing days were explored in the second experiment. Grazing intensity was defined as 2.4, 1.6, and 0.8 post-grazing leaf area index. Pasture management employed intermittent grazing with variable stocking rate using Anglo Nubian female adult goats. SF6 tracer gas technique was used to measure CH4 production. Grazing intensity was not found to affect CH4 emissions per animal, dry matter forage intake (DMI), and gross energy (GE) intake. However, the second experiment showed that CH4 production was influenced by the grazing day. CH4 emissions were 18.1 g day-1, and the variables were 0.88 g kg-1 of metabolic weight, 17.45 g kg-1 of DMI, and 5.5% of GE. CH4 production increased linearly with the grazing day, possibly reflecting a reduction in forage quality. These findings suggest that the day of occupation in intermittent grazing has a greater effect on CH4 emissions than that by grazing intensity and that a single day grazing of Tanzania Guinea grass could mitigate CH4 emissions.

Nitrogen supply and rainfall affect ammonia emissions from dairy cattle excreta and urea applied on warm-climate pastures.

Cattle excreta and nitrogen (N) fertilizer deposited on tropical grasslands are important sources of ammonia (NH3 ) emission. We conducted three field trials (wet, intermediate, and dry conditions) to quantify NH3 emissions from urea fertilizer and simulated excretions of heifer urine and dung on warm-climate grasslands in Brazil. Heifer excreta were derived from pastures of palisadegrass [Urochloa brizantha (Hochst. ex A. Rich.) R. D. Webster 'Marandu'] under three forms of N supply (without or with N fertilization [0 or 150 kg N ha-1  yr-1 ] or mixed with forage peanut [Arachis pintoi 'Amarillo']). Cumulative NH3 -N emissions across rainfall conditions were 7.6-16.6% (mean, 11.7%) for urine, 1.4-2.9% (mean, 2.0%) for dung, and 11.2-20.5% (mean, 14.8%) for urea. Ammonia loss from urine was significantly greater than from dung under all rainfall conditions. Emission from urine and dung differed from those when urea was applied on palisadegrass. There were greater NH3 emissions from urine in the wetter times of the year. Heifer excreta from N-fertilized pasture had greater NH3 emission than excreta from the grass-legume mixture and unfertilized palisadegrass. Urea applied on palisadegrass presented greater NH3 emissions in wet rainfall conditions compared with dry conditions but did not differ from intermediate conditions. Our study showed that N-fertilized systems increase N losses as NH3 emission from excreta, and emissions from urea fertilizer must be included in this system. Heifer excreta and urea fertilizer deposited on warm-climate grasslands increased the NH3 emissions mainly under wet conditions.

How do methane rates vary with soil moisture and compaction, N compound and rate, and dung addition in a tropical soil?

Soil moisture and compaction, and source of N and bovine urine can reduce methane (CH4) rates from agricultural soils. However, the magnitude of the effect is unknown in tropical soil under different conditions, as well as the potential of different urine-N concentration, volume, and sources of N in such an effect. This study aimed to investigate the effects of different soil conditions (moist, dry, compacted, moist-dung, moist-dung-compacted), N concentration in urine (2.5, 5.0, 10.0, and 15.0 g N L-1), volume of urine (25, 50, 100, and 200 ml kg-1 dry soil), and source of N (ammonium, nitrate, and urea) on CH4 emissions. A tropical Ferralsol soil from marandu-grass pasture was incubated during 106 days and the CH4 concentration determined by gas chromatography. The CH4 rates varied significantly according to the soil conditions when manipulated the urine-N (p < 0.01) and averaged 0.75, - 0.50, 1.14, 6.23, and 8.17 µg C-CH4 m-2 h-1for the moist, dry, compacted, moist-dung, and moist-dung-compacted soil, respectively, and, not responded to the level of N (p = 0.73) averaging 2.57 µg C-CH4 m-2 h-1. When evaluated, the volumes of urine cumulative CH4 averages were - 0.52, - 1.24, - 0.88, 14.48, and 18.56 µg C-CH4 m-2 h-1 for the moist, dry, compacted, moist-dung, and moist-dung-compacted, respectively. Soils were affected by soil treatments (p < 0.001) but not by urine volumes (p = 0.30). The source of N did not influence the CH4 rates (p = 0.1) averaging 0.88, - 1.26, and - 1.19 µg C-CH4 m-2 h-1 respectively, for urea, nitrate, and ammonium. The CH4 fluxes in tropical Ferralsols are controlled by the soil characteristics and dung addition.