Á minha amada esposa, Karina, companheira e parceira de todos os momentos que muito se doou e muito me apoiou em tudo. Á minha filha, Elisa, pelo simples fato de existir e alegrar nossas vidas. Aos meus amados pais, Cléciton e Ana, que me ensinaram os valores e princípios para a vida e sempre me amaram e apoiaram em tudo. Aos meus amados irmãos e sobrinhas. Agradecimentos A Deus, pela vida, saúde e tudo que me concedeste.

RESUMO.-A qualidade da dieta ofertada às vacas em lactação é uma preocupação dos agentes de saúde devido à possibilidade da detecção de micotoxinas prejudiciais a saúde humana e animal. Os objetivos do trabalho foram avaliar o perfil da micobiota, determinar a atividade de água (Aa) e a ocorrência natural de aflatoxina B 1 (AFB 1 ) em dietas ofertadas a vacas em lactação de fazendas leiteiras no estado de São Paulo, Brasil. As amostragens das dietas foram realizadas diretamente dos cochos de lote de 15 vacas, em dois dias consecutivos com intervalos de 24h e a cada 15 dias, perfazendo um período de 45 dias de amostragens por fazenda. A purificação e determinação de AFB 1 foram realizadas em colunas de imunoafinidade e Cromatografia Líquida de Alta Eficiência (CLAE). O estudo da micobiota presente nas amostras das dietas (288) The quality of the diet offered to lactating cows is a concern to health officials the possibility of detecting mycotoxins harmful to human and animal health. The objectives were to evaluate the profile of mycoflora, determine the water activity (Aw) and the natural occurrence of aflatoxin B 1 (AFB 1 ) in diets offered to lactating cows from dairy farms in the state of São Paulo, Brazil. Samples of the diets were taken directly from the troughs batch of 15 cows, on two consecutive days at intervals of 24 hours and every 15 days with a period of 45 sampling days per farm. Purification and determination of AFB 1 were performed on immunoaffinity columns and High Performance Liquid Chromatography (HPLC). The study of mycobiota present in samples of diets (288) . The water activity of the samples ranged from 0.91 to 0.98. We have detected the presence of AFB 1 in 31.44% of samples with levels between 1.68 a 194.51µg.kg- 1. Measures of good production, storage and use should be taken to reduce the occurrence of aflatoxin B 1 in the diet offered to lactating cow.

The objective of this study was to evaluate productive, nutritional, and economic traits in lactating cows on pasture fed diets with different cation-anion balances (DCAB). Ten lactating ¾ Holstein × ¼ Dairy Gyr cows in the middle third of lactation, at an average age of 70 ± 4.6 months and an average body weight of 400 ± 55.2 kg, were distributed into five treatments in a 5 × 5 Latin square experimental design with two simultaneous squares. Treatments consisted of diets with DCAB of +237, +258, +294, +347, or +419 mEq dry matter (DM). No effects of intake were observed. There was no significant effect of DCAB on milk yield. The milk protein content was not influenced by the DCAB. Body condition score was not significantly affected by the DCAB. The apparent digestibilities of dry matter and nutrients (crude protein, neutral detergent fiber, ether extract, non-fibrous carbohydrates, and total digestible nutrients) were not affected by the DCAB. Marginal rate of return did not show significant differences. Under good conditions of pasture, forage availability, and quality associated with the lactation phases of the cows, all diets were efficient in milk production, dry matter intake, and digestibility. However, in economic terms, the most attractive DCAB was +237 mEq kg-1 DM.

Tissue flows or morphogenesis may be defined as the dynamics of generation and expansion of the plant tissues in time and space. The leaves are the parties which have a tissue flows more intense. The dynamics of tissue flows in forage grasses is influenced by genotype forage, climatic and environmental factors and soil fertility. Mineral nutrition, mainly of nitrogen, phosphorus and potassium, appears as a practice sustainable and direct influence on the tissue flows on grasses. The nitrogen highlights, among all the essential minerals, as the most important agent accelerator of tissue flows of forage grasses.