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SUMMARY This study aimed to verify the influence of months on chemical composition and in vitro digestibility of pasture and forage selected by goats in the semiarid region of Brazil’s Pernambuco state. Six male goats fistulated in the rumen were used in a completely randomized design. Forage collection was conducted in herbaceous and shrub/tree layers, in order to simulate goat grazing, and materials were separated into leaves and branches. Extrusa and pasture collections were held in November, January and February/March. There was collection month (P <0.05) effect for pasture on dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), with average values of 458.27g/kg NM and 155.46, 521.30 and 390.13g/kg DM, respectively. For the stem (P <0.05) for DM, Organic matter (OM), mineral matter (MM), ethereal stratum (EE), ADF, acid detergent unavailable protein (AIP), total carbohydrates (TCHO) and dry matter in vitro digestibility (DMIVD), with average values of 487.47g/kg NM and 930.80, 69.07, 20.67, 440.30 and 63.78g/kg DM, respectively. About the extrusa, there was collection time effect (P <0.05) on the DM, OM, MM, CP, EE, AIP, TCHO, Non-fibrous carbohydrates (NFC) and DMIVD, with average values of 84.53g/kg DM, 863.03, 136.97, 152.90, 33.60, 14.07, 676.37 and 55.35g/kg DM, respectively. Rainfall changes in the rainy season in the caatinga altered pasture quality, causing changes in the diet selected by goats, mainly in DM, CP, CNF and DMIVD.

Condensed tannins (CTs) are plant anti-herbivore compounds with antimicrobial activity that can be used in ruminant diets as ruminal microbiome manipulators. However, not all CTs from fodder legumes are bioactive due to their wide structural diversity. The aim of our study was to investigate the effect of 10 CT-containing plants (Flemingia macrophylla, Leucaena leucocephala, Stylosanthes guianensis, Gliricidia sepium, Cratylia argentea, Cajanus cajan, Desmodium ovalifolium, Macrotiloma axilare, D. paniculatum, and Lespedeza procumbens) on in vitro fermentation kinetics of Nelore beef cattle. Polyethylene glycol (PEG), a specific CT-binding agent, was added to neutralize condensed tannin. Tifton and alfalfa hay were used as controls lacking CT. The experimental layout included a randomized complete block with factorial design and four blocks. The data were subjected to analysis of variance followed by Duncan’s test to determine differences (p < 0.05) among treatment means. The addition of PEG in browse incubations resulted in increased gas production, fermentation rate, short-chain fatty acid (SCFA) and N-NH3 release. Within our study, Lespedeza procumbens, Desmodium paniculatum, Leucaena leucocephala, Desmodium ovalifolium, and Flemingia macrophylla showed superior bioactivity compared to other species evaluated, suggesting a natural alternative for replacing ionophores to modify ruminal fermentation. Condensed tannins from L. pocumbens, D. paniculatum, L. leucocephala, D. ovalifolium, and F. macrophylla have the potential to modify rumen fermentation in beef cattle.

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