The Effects Of Anti-Nutritive Compounds In Tropical. Legumes On Ruminant Nutrient Utilization, Excretion And Decomposition Of Manure In The Soil

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Date
2003
Authors
David Mwaura Mbugua
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David Mwaura Mbugua
Abstract
Tropical legumes accumulate a variety of anti-nutritive compounds whose impact on the nutritional value of these feeds to livestock is not well understood. An in vitro investigation was conducted to study the role of condensed tannins (CT) and alkaloids on nutrient use by ruminants. Napier grass (Pennisetum purpureum: NG) and its isolated NDF (iNDF) were incubated with four levels (0, 0.14, 0.28 and 0.42 mg mL-I) of CT extracted from Calliandra calothyrsus, a tropical leguminous shrub, and four levels (0, 0.25, 0.50, 0.75 mg mL-I) of sparteine (SP), a quinolizidine alkaloid. Neutral detergent fiber digestibility of intact NG was significantly (P < 0.001) lower compared to iNDF (43.1% versus 59.8% respectively). No interaction between the metabolites was observed in NDF digestibility. However, sparteine depressed NDF digestibility by 5.4 percentage units and CT by 11.5 percentage units. Neutral detergent fiber digestibility was linearly related to CT in iNDF (y = -4.24x + 70.5; R2 = 0.9992), and intact NG (y = -3.26x + 51.3; R2 = 0.9764). Sparteine did not significantly (P > 0.05) affect final gas volume or its rate of production. Condensed tannins at 0.42 mg mL-I CT decreased final gas volume from 13.4 mL (control) to 11.4 mL and the rates of gas production from 0.053 h-I to 0.037 h-I, respectively. However, a significant (P < 0.01) interaction between the metabolites affected rates of gas production
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