DSpace Coleção: Artigo em periódico indexado (CNPGC)

Alterações clínicas, patológicos e laboratoriais na intoxicação crônica por cobre em ovinos.

Wed, 01 Jan 1997 00:00:00 GMT

Título: Alterações clínicas, patológicos e laboratoriais na intoxicação crônica por cobre em ovinos. Autoria: LEMOS, R. A. A.; RANGEL, J. M. R.; OSORIO, A. L. A. R.; MORAES, S. D. S.; NAKAZATO, L.; SALVADOR, S. C.; MARTINS, S. Conteúdo: Resumo: Com o objetivo de avaliar a toxicidade do cobre em ovinos, administrou-se sulfato de cobre a quatro grupos, nas dosagens de 15, 30, 60 e 120ppm, até surgirem os sinais da intoxicação; um quinto grupo permaneceu como controle. Estes animais foram submetidos a exames clínicos diários e a determinações periódicas dos níveis séricos de trasaminase glutâmico oxalacética (AST) e gamaglutamiltransferase (gGT). Aqueles que morreram durante o experimento foram necropsiados, sendo os fragmentos dos principais órgãos analisados histologicamente; adicionalmente foram determinados os níveis de cobre hepático. Em todos os grupos houve casos de intoxicação, os quais ocorreram entre 80 e 116 dias. Os principais sinais clínicos da intoxicação foram: depressão, icterícia, hemoglobinúria e diarréia. Elevações dos níveis de gGT e AST foram observadas entre 21 e 43 dias antes do aparecimento dos sinais clínicos, atingindo valor máximo durante o quadro clínico. As principais alterações histológicas foram observadas no fígado e rins, revelando lesões degenerativas. Os valores de cobre hepático variaram entre 1097,5 e 1366,9ppm, evidenciando níveis iguais ou superiorres a duas vezes o valor considerado como limite máximo normal, confirmando-se assim que este elemento foi responsável pelo quadro clínico patológico. Todas as dosagens usadas no experimento foram consideradas como potencialmente tóxicas para esta espécie animal. Abstract: In order to evaluate the copper toxicity in sheep, 4 groups of animals have been administered Copper sulfate at the dosagens 15, 30, 60 and 120ppm, until signs of intoxication occurred. There was still a 5th group, as control. These animals have been submitted to daily physical examination and periodical determinations of AST and gGT serum levels. Those that have died during the study have been necropsied and the fragments of the main organs have been histologically examined. The liver copper levels have also been determined. In all groups there have been cases of intoxication, which occurred between the 80th and 116th day. The principal clinical signs of intoxication were: depression, jaundice, haemoglobinuria and diarrhea. It has been observed raised levels of gGT and AST between 21st and 43rd day before the clinical signs appeared, getting the maximum value during the clinical stage. The main histological changes were present in the liver and kidneys, showing degeneration lesions. Lever copper values varied from 1097.5 is 1366.9ppm, showing the same level or twice the value considered to be the maximum normal limit, assuring thus that this element has been responsible for the pathological clinical process. All the dosagens used in the study have been considered potentially toxic to this species.

Potassium fertilization reduces the severity of leaf spot complex and mosaic in Megathyrsus maximus cultivars.

Thu, 01 Jan 2026 00:00:00 GMT

Título: Potassium fertilization reduces the severity of leaf spot complex and mosaic in Megathyrsus maximus cultivars. Autoria: VÉRAS, E. L. de L.; DIFANTE, G. dos S.; MONTAGNER, D. B.; ARAUJO, A. R. de; MACEDO, M. C. M.; THEODORO, G. de F.; ARAÚJO, C. M. C.; GURGEL, A. L. C.; MONTEIRO, G. O. de A.; RODRIGUES, J. G.; PEREIRA, M. de G.; SANTANA, J. C. S. Conteúdo: ABSTRACT - The objective of this study was to evaluate the effects of potassium (K) on disease severity and the chemical composition of Megathyrsus maximus cultivars. The experiment was conducted in a randomized block design in a 6 × 4 factorial arrangement, consisting of six Megathyrsus maximus cultivars (Massai, Mombaça, Tamani, Tanzânia, Quênia, and Zuri) and four K doses (0, 205, 410, and 820 mg dm−3 ). The severity of the leaf spot complex, caused by Bipolaris maydis and B. yamadae, was assessed using a diagrammatic scale. A significant interaction between K doses and cultivars was observed for all evaluated diseases. At K doses of 0 and 205 mg dm−3 , the Tanzânia cultivar showed lower leaf spot severity compared with the other cultivars, whereas at higher doses, no disease symptoms were observed in any cultivar. The area under the disease progress curve (AUDPC) for mosaic followed a linear model only for the Tanzânia cultivar, whereas quadratic regression models best described the response for the remaining cultivars, with maximum mosaic severity values of 67.74% for Quênia, 72.34% for Mombaça, 76.99% for Zuri, 74.88% for Massai, and 68.93% for Tamani. Increasing K doses reduced the severity of both the leaf spot complex and mosaic. However, the leaf spot complex did not affect the nutritional value of the evaluated cultivars.

Effects of nitrogen fertilization on forage production, animal performance, and greenhouse gas emissions in tropical pastures: a systematic review.

Thu, 01 Jan 2026 00:00:00 GMT

Título: Effects of nitrogen fertilization on forage production, animal performance, and greenhouse gas emissions in tropical pastures: a systematic review. Autoria: SILVA, H. R. da; DIFANTE, G. dos S.; ROBERTO, F. F. da S.; FERREIRA JUNIOR, M. A.; ARAÚJO, C. M. C.; LONGHINI, V. Z.; RODRIGUES, J. G.; PEREIRA, M. de G.; MONTAGNER, D. B.; ÍTAVO, L. C. V.; GURGEL, A. L. C.; CASTRO, M. M. P. M. F. de Conteúdo: ABSTRACT - This 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.

Machine learning models for crude protein prediction in Tamani grass pastures.

Thu, 01 Jan 2026 00:00:00 GMT

Título: Machine learning models for crude protein prediction in Tamani grass pastures. Autoria: MONTEIRO, G. O. de A.; DIFANTE, G. dos S.; MONTAGNER, D. B.; EUCLIDES, V. P. B.; CASTRO, M.; RODRIGUES, J. G.; PEREIRA, M. de G.; SANTANA, J. C. S.; ITAVO, L. C. V.; NANTES, R. T.; CAMPOS, J. A.; COSTA, A. B. da; MATSUBARA, E. T. Conteúdo: Understanding forage quality is essential for meeting animal demands and optimizing production. This study aimed to: (i) test the applicability of machine learning models with tabular data such as climate variables, light interception (LI), nitrogen dose (N dose), interval between grazing (GI), and pre- (HPRE) and post-grazing height (HPOST) to predict leaf crude protein (CP) content of tamani grass pastures; (ii) identify which variables contribute most to CP prediction. A set of 90 instances was used with 80% for training and validation and 20% for testing. The hyperparameters were adjusted with grid-search on the training set. We tested Linear Regression (LR), Multilayer Perceptron (MLP), Decision Trees (DT), Random Forest (RF), and XGBoost. The MLP (r=0.75, R2 =44.18%, MAE=1.55), RF (r=0.78, R2 =49.07%, MAE=1.59) and XGBoost (r=0.78, R2 =56.65% MAE=1.45) models presented the best prediction results (p<0.001). The variables most important in predicting CP content were GI, followed by N dose, HPRE and HPOST. XGBoost outperformed other tested models (p<0.001). Tabular data, including N dose, GI, HPRE, HPOST, LI, and climatic variables, is a viable alternative for predicting CP. In conclusion, the results of this study suggest that management practices may have a greater influence on the chemical composition of Tamani grass than environmental conditions, although further research with larger and more diverse datasets is needed to confirm these findings