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A key contribution to study the cycling of nutrients in soil/plant/animal systems is the evaluation of the consumption of forage and their nutrients by cattle. The objective of this study was to test techniques to evaluate faecal production, in vitro digestibility, forage consumption and the proportion of legume in the acquired diet. Five Zebu steer calves were confined and fed five diets of different combinations of Brachiaria dictyoneura and Desmodium ovalifolium. All quantities of faeces were collected per animal and these values were found to compare favourably with those derived from using the chromium oxide technique. In vitro digestibility ranged from 7 to 10% higher than the actual in vivo digestibility. Faecal samples from steers fed with diets with 25% or more of grass in the mixture were found to be depleted in δ 13 C between 1.7 and 2.1‰, but no depletion was observed when the diet was 100% D. ovalifolium. There was a positive linear regression (r 2 = 0.97***) of the δ 13 C of the diet with the δ 13 C of faeces, but if the acquired diet contained a very high proportion of legume, the legume content could be underestimated by as much as 10%. None of the internal indicators, such as lignin or ash content of the diets, were useful to predict feed intake, but the chromium oxide external indicator performed satisfactorily. The 13 C analysis of the faeces was an effective predictor of the proportion of the legume in the consumed diet. Key words: Brachiaria dictyoneura, Desmodium ovalifolium, 13 C abundance, digestibility, forage intake Consumo e composição da forragem ingerida por bovinos alimentados com Brachiaria e uma leguminosa RESUMO: Uma contribuição fundamental para o estudo da ciclagem de nutrientes no sistema solo/planta/ animal é a avaliação do consumo pelo gado de forragem e dos nutrientes nela contidos. Testaram-se, sob condições controladas, técnicas para avaliar a produção fecal, digestibilidade in vitro, consumo de forragem e a proporção de leguminosa ingerida na dieta. Cinco novilhos de Zebu foram confinados e alimentados com quantidades conhecidas de cinco rações com diferentes proporções de Brachiaria dictyoneura e Desmodium ovalifolium. Todas as fezes bovinas foram recolhidas e pesadas e estes valores foram comparáveis com as estimativas da produção fecal derivadas do uso da técnica de óxido de cromo. A digestibilidade in vitro variou de 7 a 10% acima da digestibilidade in vivo atual. Amostras de fezes de novilhos alimentados com dietas com 25% ou mais de capim na mistura apresentaram abundância de 13 C por entre 1,7 e 2,1‰, mas este empobrecimento isotópico não foi observado quando a dieta era com 100% D. ovalifolium. Houve correlação positiva linear (r 2 = 0,97***) entre δ 13 C da dieta com o δ 13 C das fezes, mas o conteúdo de leguminosa foi subestimado em mais de 10% quando a dieta ingerida foi de 100% de leguminosa. Nenhum dos indicadores internos, como o conteúdo de lignina ou cinzas, foram úteis para prever o consumo de forragem, mas os resultados da técnica utilizando ó...

Excessive intensification of dairy and beef cattle production systems in the industrialised countries has led to serious problems of pollution of water resources and the atmosphere. In order to develop an appropriate alternative, a few studies have been made by various research teams in Brazil, using low fertiliser inputs and modest animal stocking rates. The objective of this present study was to evaluate the effect of different stocking rates of beef cattle, and the introduction of a forage legume (Desmodium ovalifolium (Prain) Wall.), on the long-term sustainability of pastures of Brachiaria humidicola (Rendle) Schweick established in the Atlantic forest region of Brazil in the extreme south of the State of Bahia. Annual maintenance fertilisation was restricted to additions of 11 and 6 kg ha -1 of P and K, respectively (and no N). Live weight gain (LWG) of Zebu steers was evaluated for stocking rates of 2, 3 and 4 head ha -1 during six grazing periods from 1988 to 1997. Forage intake and the proportion of legume in the acquired ration was determined using steers fitted with oesophageal fistulae. The bolus samples were analysed manually in 1988-1989, and using the 13 C natural abundance technique in 1995. There was no significant response of LWG to the presence of the legume in the acquired ration. LWG in the final grazing period (1995)(1996) was similar to that recorded in 1988-1989 at all stocking rates, suggesting that this management regime resulted in long-term sustainable production even in the absence of the legume or of a N fertiliser input. This was confirmed by the soil fertility analyses for 1988 and 1997, where only levels of P showed a significant decrease. The net aerial primary productivity (NAPP) of the pasture was determined for 1995, the largest component being deposited litter (21-33 Mg DM ha -1 year -1 ), followed by forage intake (6.4-12.2 Mg DM ha -1 year -1 ).

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This study aimed to evaluate soil fertility and the horizontal structure of three demonstration units of Agroforestry Systems (ASs), Sapucaia, RJ, Brazil. Twenty-four plots (25 m 2) were delineated in each AS. Soil fertility was evaluated through pH, organic carbon, total nitrogen, phosphorus and potassium. The estimated phytosociological parameters were frequency, density, dominance, importance value and the diversity index of Shannon. Magnesium was more pronounced in ASas with more management intensity due to the incorporation of banana biomass (AS 1 and 2). The AS 1 highlights were for banana and coffee (about 45% IV), AS 2 banana and physic nuts (about 50% IV) and AS 3 cassava and 'fumo-bravo' (VI=52.2%). This study suggests that diversity contributes to the maintenance of ecosystem services on a local scale, mainly for the conservation and maintenance of soil fertility, as well as to increase food security in the property. The use of physic nuts has not shown to be a favorable option as a source of energy for the farm studied. However, it can contribute to the increase of local value added. These responses support the importance of ASs for the establishment of more sustainable production models.