Abstract: Elephant grass (EG) (Pennisetum purpureum Schum.) have great importance in tropical and subtropical climates, especially on dairy farms. Normally, EG is established alone under high fertilization levels. EG in organic production system can improve low production costs and environmental issues, are still little known. The aim of this research was to evaluate the performance of herbage yield, nutritive value, extraction/ export nutrient and forage yield and animal responses. Three production systems of EG were analyzed: (i) EG mixed spontaneous-growing species (SGE) in warm-season and ryegrass (R) in cool-season under organic production; (ii) EG mixed SGE + R under conventional system (positive control); and (iii) EG based under conventional production (control). Holstein cows were used in a rotational stocking. Forage samples were collected to evaluate the pasture and animal responses. Seven grazing cycles were performed during the experimental period (312 days). Herbage yield, forage intake, and stocking rate were 12548; 10270; 19168 kg ha-1 and 2.5; 2.6; 2.7% and 3.3; 2.1; 4.5 AU ha-1 day-1, respectively. Crude protein of EG was 17.9; 15.4; 16.4%, respectively. Mixed pastures, in conventional and organic production, had a better forage distribution throughout the seasons. Highest forage yield and extraction/ export nutrient was reported in pure EG within the conventional system.

Nitratos e nitritos podem estar presentes naturalmente em diversos alimentos, entre eles o leite. Devido a sua toxicidade, são estabelecidos limites para a presença destes compostos nos alimentos. Assim, investigou-se os níveis de nitratos e nitritos em amostras de leite in natura, produzido por vacas submetidas aos sistemas de manejo convencional e orgânico. As amostras foram coletadas em propriedades da Região da Depressão Central do Rio Grande do Sul, Brasil. Os teores médios de nitrato e nitrito encontrados nas amostras (n=45) foram de 6,65±0,84mg/L e 1,76±0,17mg/L, respectivamente. O leite produzido no sistema orgânico apresentou 7,08mg/L de nitrato e 1,61mg/L de nitrito, enquanto o produzido no sistema convencional apresentou 6,36 e 1,87mg/L, respectivamente. Não foi observada diferença significativa entre os teores de nitrato e nitrito encontrados nas amostras de leite em função do sistema de produção avaliado, época de coleta, turno de ordenha ou local de origem, isto é, propriedade produtora.

Nitrates and nitrites can be naturally found in many foods, including milk. Due to their toxicity there is a maximum level allowed for these compounds in foods. In the present study, nitrate and nitrite levels were evaluated in raw milk samples produced in conventional and organic systems. Samples were collected from farms of the Depressão Central of Rio Grande do Sul, Brazil. The average levels of nitrate and nitrite in samples (n=45) were 6.65±0.84mg/L and 1.76±0.17mg/L, respectively. Milk produced in the organic system exhibited 7.08mg/L nitrate and 1.61mg/L nitrite, while milk produced in the conventional system exhibited 6.36 and 1.87mg/L, respectively. Nitrate and nitrite levels in raw milk were not affected by the production system, the period of collection, milking shift or the site of production (farm).