Percorrer por autor "Ítavo, Luís Carlos Vinhas"
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- Effects of nitrogen fertilization on forage production, animal performance, and greenhouse gas emissions in tropical pastures: A systematic reviewPublication . Silva, Hitalo Rodrigues da; Difante, Gelson dos Santos; Roberto, Francisca Fernanda da Silva; Ferreira Júnior, Marcos Antônio; Araújo, Carolina Marques Costa; Longhini, Vanessa Zirondi; Rodrigues, Jéssica Gomes; Pereira, Marislayne de Gusmão; Montagner, Denise Baptaglin; Ítavo, Luís Carlos Vinhas; Gurgel, Antônio Leandro Chaves; Castro, MarinaThis systematic review aimed to synthesize evidence on the effects of nitrogen (N) fertilization on forage production, animal performance, and greenhouse gas emissions in tropical pastures. The research question was developed based on the PICOS strategy. A total of 84,629 documents were retrieved from six databases, of which 34 studies met the inclusion criteria due to their methodological robustness. Most studies were conducted under grazing conditions (69.7%), using Brachiaria brizantha (52.9%) and Panicum maximum (26.5%). Urea (53.2%) and ammonium nitrate (25.5%) were the most evaluated N sources, with application rates ranging from 0 to 1000 kg ha⁻¹ , often split into three applications. Nitrogen use increased stocking rate (157.7%), gain per area (189.4%), and average daily gain (31.0%) when application rates rose from 0 to 300 kg ha⁻¹ . Overall, N fertilization has potential to improve forage productivity and animal performance in tropical pastures; however, responses vary depending on rates, sources, and experimental conditions. Splitting N rates (20–60 kg ha⁻¹) and synchronizing applications with plant demand are effective strategies to reduce NH₃ and N₂O losses, enhance fertilizer use efficiency, and mitigate environmental impacts. Future research should focus on evaluating the effects of different N sources and doses on soil CO₂ and CH₄ emissions, enteric CH₄, and C/N dynamics within the soil–plant–animal system, as well as expanding studies to other forage and animal species representative of tropical grazing systems.
- Interpreting Machine Learning Models with SHAP Values: Application to Crude Protein Prediction in Tamani Grass PasturesPublication . Monteiro, Gabriela Oliveira de Aquino; Difante, Gelson dos Santos; Montagner, Denise Baptaglin; Euclides, Valéria Pacheco Batista; Castro, Marina; Rodrigues, Jéssica Gomes; Pereira, Marislayne de Gusmão; Ítavo, Luís Carlos Vinhas; Campos, Jecelen Adriane; Costa, Anderson Bessa da; Matsubara, Edson TakashiMachine learning models such as XGBoost show strong potential for predicting pasture quality metrics like crude protein (CP) content in tamani grass (Panicum maximum). However, their 'black box' nature hinders practical adoption. To address this limitation, this study applied SHapley Additive exPlanations (SHAP) to interpret an XGBoost model and uncover how management practices (grazing interval, nitrogen fertilization, and pre- and post-grazing heights) and environmental factors (precipitation, temperature, and solar radiation) jointly influence CP predictions. Data were divided into 80% for training/validation and 20% for testing. Model performance was assessed with stratified 5-fold cross-validation, and hyperparameters were tuned via grid search. The XGBoost model yielded a Pearson correlation coefficient (r) of 0.78, a mean absolute error (MAE) of 1.45, and a coefficient of determination (R2) of 0.57. The results showed that precipitation in the range of 100-180 mm increased the predicted CP content. Application of 240 kg N ha-1 year-1 positively affected predicted CP, whereas a lower dose of 80 kg N ha-1 year-1 had a negative impact, reducing predicted levels of CP. These findings highlight the importance of integrated management strategies that combine grazing height, nitrogen fertilization, and grazing intervals to optimize crude protein levels in tamani grass pastures.