Siriwan D. Martens

Farm-Scale Tradeoffs Between Legume Use as Forage versus Green Manure: The Case of Canavalia brasiliensis

To support a sustainable increase in agricultural productivity, the multipurpose legume Canavalia brasiliensis was integrated as forage and green manure into the smallholder crop-livestock system of the Nicaraguan hillsides. Through on-farm trials, surveys, and on-station experiments, we investigated the biophysical and socioeconomic tradeoffs in balancing livestock feeding with soil fertility management at the farm level, including farmers’ perception. Use as forage increased milk yields while use as green manure increased nutrient cycling efficiency. Short-term net annual income decreased when used as green manure and increased when used as forage. Management options to handle tradeoffs and maximize legume benefits are discussed.

Effect of ensiling treatment on secondary compounds and amino acid profile of tropical forage legumes, and implications for their pig feeding potential

BACKGROUND Smallholders in the tropics depend on local protein supplements to balance pig diets. Thus, various tropical forage legumes are a potential feeding option. Ensiling allows converting forages into a ready-to-feed-out choice, but the lactic acid fermentation may influence various (anti)nutritional components. The purpose of this study was to evaluate the effects of sucrose (SU) and a tropical Lactobacillus plantarum strain (LAB) as ensiling treatments (control, SU, LAB, LAB + SU) on the potential nutrient availability of 10 forage legume species. RESULTS Ensiling commonly reduced antinutritional compounds such as tannins (by 49-84%) and trypsin inhibitory activity (by 74-78%), as well as oxalic acid (by 51-100%). An improved potential absorbability of protein and minerals for pigs is thus inferred. There was no major loss in total amino acids. In general, the species effect was stronger than the treatment effect. A clear effect of the treatments SU, LAB and LAB + SU over all 10 forage species was only observed for oxalic acid, single amino acids and trypsin inhibitory activity. CONCLUSION Ensiling is a viable option to enhance nutrient utilization of tropical forages for pigs. Species-specific treatment of forage legumes is recommended.

Ecuaciones de calibración en espectroscopía de reflectancia en el infrarrojo cercano (NIRS) para predicción de parámetros nutritivos en forrajes tropicales

The objective of this study was to develop NIRS calibration curves to predict nutritional quality parameters of tropical forage species. For this a total of 1,991 samples of tropical forages (grasses and legumes) were employed. These samples showed a high heterogeneity in regrowth age, vegetative state and parts of the plants collected, sampling period and sample origin. Chemical analysis was performed to determine crude protein, neutral detergent fiber, acid detergent fiber (ADF), in vitro digestibility of dry matter and digestibility of neutral detergent fiber. A group of samples was used for each chemical parameter to develop the calibration curves. The curves were chosen taking into account the standard errors of: calibration; cross validation (SECV); and prediction. To evaluate the accuracy of each equation the coefficient of determination (R 2 ) and the RPD (ratio performance deviation) index (relation between standard deviation and SECV), which assesses the predictive power of the equations, were calculated. Validation was performed with external samples and results showed correlation coefficients (r) of >0.90 for all parameters except for ADF (r=0.72), demonstrating the precision of the predictive equations. However, the determination of ADF by this analytical method requires further work to increase its reliability. Keywords: Analytical methods, animal nutrition, forage quality, grasses, legumes. DOI: 10.17138/TGFT(4)139-145