N. Vivas - Academia.edu (original) (raw)
Papers by N. Vivas
… Congress (21; 8, …, 2008
SIDALC - Servicio de Informacion y Documentacion Agropecuaria de las Americas.
Tropical Grasslands - Forrajes Tropicales, 2015
The International Center for Tropical Agriculture (CIAT)-a member of the CGIAR Consortium-develop... more The International Center for Tropical Agriculture (CIAT)-a member of the CGIAR Consortium-develops technologies, innovative methods, and new knowledge that better enable farmers, especially smallholders, to make agriculture eco-efficient-that is, competitive and profitable as well as sustainable and resilient. Headquartered near Cali, Colombia, CIAT conducts research for development in tropical regions of Latin America, Africa, and Asia. www.ciat.cgiar.org CGIAR is a global research partnership for a food-secure future. Its science is carried out by the 15 research Centers that are members of the CGIAR Consortium in collaboration with hundreds of partner organizations. www.cgiar.org LivestockPlus The sustainable intensification of forage-based agricultural systems to improve livelihoods and ecosystem services in the tropics
British journal of pharmacology, 1996
1. The relative importance of intracellular and extracellular Ca2+ on alpha 1-adrenoceptor-mediat... more 1. The relative importance of intracellular and extracellular Ca2+ on alpha 1-adrenoceptor-mediated contraction by noradrenaline and St-587 has been studied and correlated with the binding characteristics in intact tail artery from Sprague-Dawley rats. 2. Noradrenaline and St-587 behaved as full agonists inducing a concentration-dependent vasoconstriction. 3. Nifedipine (1 microM and 10 microM) blocked by 50% (P < 0.001) and 75% (P < 0.001) respectively, the maximum contraction (Emax) induced by St-587. Nevertheless, to reach 40% inhibition of Emax on noradrenaline responses (P < 0.01), 10 microM nifedipine was necessary. 4. Both agonists induced a concentration-dependent accumulation of inositol phosphates. Noradrenaline behaved as a full agonist and St-587 as a partial agonist for this response. 5. [3H]-prazosin binding to intact tail artery rings was saturable and of high affinity (KD = 4.44 +/- 0.46 nM; Bmax = 36.35 +/- 4.22 fmol mg-1 tissue). 6. Competition curves for ...
Pharmacological Research, 1995
It has been found that vasa deferentia from age-matched spontaneously hypertensive rats (SHR) exh... more It has been found that vasa deferentia from age-matched spontaneously hypertensive rats (SHR) exhibit an altered postjunctional ~l-adrenoceptor mediated responsiveness respect to control WKY. To clarify the contradictory existing results radioligand binding and funeional studies were performed. An increased steadystate density of [3H]prazosin binding sites was observed in the vas deferens of SHR (B~,= 148 4-18 frnol.mg -1 protein) vs WKY controls (B~x=71 +9 fmol-mg 1 protein) with no changes in the dissociation constant value. Concentration-response (E/[A]) curves to noradrenaline showed a higher maximal effect in vasa deferentia from SHR compared to WKY (25.3 ___ .96 mN vs 15.64-.52 raN) but pECso were not modified. Partial alkylation with phenoxybenzamine (0.1 #M) was performed to apply the operational model of Black and Left (1983) on E/[A] curves. The affinity (KA) and efficacy (r) estimates for noradrenaline, and the parameters E m and n in each experimental group were tested for similarity by analysis of variance. The results of this analysis showed that the model could fit both sets of data by assuming the same pK A value (4.90;4.9~), different r values (logrv, xv=l.63+__0.23 and logrsnR=l.74+0.29) and a significant change in E~ (Em wrv=15.82 mN vs E~ s~=25.86 mN) for noradrenaline. The results also show that the altered responsiveness could not be only explained as an increase in cq-adrenoceptors.
PEDIATRICS, 2000
The administration of recombinant human erythropoietin (rHuEPO), started after the first 2 weeks ... more The administration of recombinant human erythropoietin (rHuEPO), started after the first 2 weeks of life, reduces the transfusion requirement in premature infants. However, its use throughout the first 2 weeks of life, when anemia results predominantly from phlebotomy losses, remains controversial. We investigated whether early use of rHuEPO would reduce the total transfusion requirement and/or the number of transfusions throughout the first 2 weeks of life. We randomized 114 infants with birth weight (BW) &amp;lt;1250 g to receive rHuEPO (1250 units/kg/week; IV; early group: n = 57) or placebo (late group: n = 57) from day 2 to day 14 of life; subsequently, all the patients received rHuEPO (750 units/kg/week, subcutaneously) for 6 additional weeks. All infants were given oral iron (6 mg/kg/day) and folic acid (2 mg/day). The early group showed higher hematocrit and reticulocyte counts than the late group in the first 3 weeks of life, but there was no difference in the total number of transfusions (early: 1.8 +/- 2.3 vs late: 1.8 +/- 2.5 transfusion/patient) or the transfusion requirement throughout the first 2 weeks of life (early:.8 +/- 1.1 vs late:.9 +/- 1.3) could be demonstrated. In infants with BW &amp;lt;800 g and total phlebotomy losses &amp;gt;30 mL/kg (n = 29), a lower number of transfusions was received by infants in the early group, compared with late group, from the second week to the end of the treatment (early: 3.4 +/- 1.1 vs late: 5.4 +/- 3.7 transfusion/patient). No clinical adverse effects were observed. Thrombocytosis was detected during the treatment with rHuEPO in 31% of the infants. In the whole population, the early administration of rHuEPO induced a rise of reticulocyte counts, but not enough to reduce the transfusion requirement. The most severely ill infants (BW &amp;lt;800 g and phlebotomy losses &amp;gt;30 mL/kg) seemed to benefit from early use of rHuEPO, and this deserves additional study.
Neuroscience Letters, 1991
The effects of acute treatment with 1,2,3,4-tetrahydro-9-aminoacridine (THA), a 4-aminopyridine d... more The effects of acute treatment with 1,2,3,4-tetrahydro-9-aminoacridine (THA), a 4-aminopyridine derivative clinically effective in Alzheimer's disease, on fl-adrenoceptor-linked cyclic AMP accumulation have been investigated in cortical and hippocampal structures of young and middle-aged rats. In a first series of experiments, pretreatment with 2.5 mg/kg THA decreased basal cyclic AMP accumulation. When a phosphodiesterase inhibitor was added to the preparation, THA again decreased cyclic AMP levels in young rats, but failed to significantly modify cyclic AMP accumulation in middle-aged animals. Finally, in isoprenaline-stimulated conditions, acute treatment with tacrine was able to diminish cyclic AMP accumulation in every group of rats. It is suggested that the neurochemical action of THA in mammalian brain is more complex than earlier has been anticipated and may involve an action on fl-adrenoceptors.
Neuropharmacology, 1995
The mechanism by which 9-amino-1,2,3,4-tetrahydroacridine (THA) inhibits beta-adrenoceptor linked... more The mechanism by which 9-amino-1,2,3,4-tetrahydroacridine (THA) inhibits beta-adrenoceptor linked cyclic AMP formation and its possible relationship with the cholinergic system were studied. In addition, the effect of THA on alpha 1-adrenoceptor coupled transduction systems was also investigated. THA was not able to influence the concentration-response curve for forskolin indicating that it is not acting on the catalytic subunit of the adenylate cyclase complex. On the other hand a cholinergic component seems to participate in the action of THA on beta-adrenoceptor stimulated adenylate cyclase activity since the blockade of muscarinic receptors with atropine (10 microM) partially prevented the reduction in cyclic AMP formation attained by THA in the hippocampus, in isoprenaline-stimulated conditions. This effect is not reproducible by another potent anticholinesterase physostigmine. Moreover, THA at concentrations up to micromolar did not affect alpha 1-adrenoceptor stimulated cyclic AMP formation or phosphoinositide hydrolysis. In conclusion, the neuropharmacological profile of THA is not to be restricted to the cholinergic system and its effectiveness in improving age-associated cognitive deterioration may involve an action on the beta-adrenoceptor coupled signal transduction system. Moreover, the action of THA on the beta-adrenergic and cholinergic systems in the brain could be relevant to the amelioration of cognitive deterioration and could lead to the development of new therapeutic strategies.
European Journal of Pharmacology: Molecular Pharmacology, 1993
The effects of 1,2,3,4-tetrahydro-9-aminoacridine (THA) and physostigmine on/3-adrenoceptor-linke... more The effects of 1,2,3,4-tetrahydro-9-aminoacridine (THA) and physostigmine on/3-adrenoceptor-linked cyclic AMP accumulation have been analyzed in vitro in rat cortex and hippocampus. A 10-min incubation with increasing concentrations of THA reduced isoprenaline (10/zM)-stimulated cyclic AMP accumulation in a concentration-dependent manner in cortical (IC50 = 1.31 + 0.13 /zM) and hippocampal (ICs0 = 0.02 + 0.003 /zM) structures. Conversely, physostigmine did not modify cyclic AMP synthesis in any experimental condition. The action of THA was non-competitive since it induced a non-parallel shift to the right of the concentration-response curve for isoprenaline. The differential effects of THA and physostigmine on the/3-adrenoceptor transduction system may account for the difference in their ability to restore cognitive function.
Clinical Neuropharmacology, 1992
British Journal of Pharmacology, 1997
1 The eect of two D 3/2 dopamine receptor agonists, LY-171555 (quinpirole) and 7-hydroxy-N,N-di-n... more 1 The eect of two D 3/2 dopamine receptor agonists, LY-171555 (quinpirole) and 7-hydroxy-N,N-di-npropyl-2-aminotetralin (7-OH-DPAT) on spontaneous [ 3 H]-acetylcholine ([ 3 H]-ACh) release were investigated in rat striatal synaptosomes. 2 Quinpirole and 7-OH-DPAT inhibited in a concentration-dependent manner the basal eux of [ 3 H]-ACh with similar E max (maximal inhibitory eect) values (29.95+2.91% and 33.19+1.21%, respectively). Signi®cant dierences were obtained between the pEC 50 (7log of molar concentration) of quinpirole (7.87+0.12) and 7-OH-DPAT (7.21+0.17; P50.01).
British Journal of Pharmacology, 1993
1 Effects of the aporphinoid alkaloid, (+)-glaucine, on rat vas deferens were investigated. 2 (+ ... more 1 Effects of the aporphinoid alkaloid, (+)-glaucine, on rat vas deferens were investigated. 2 (+ )-Glaucine (2-18 f.M) competitively inhibited contractions induced by noradrenaline and methoxamine with a pA2 value of about 6. 3 (+ )-Glaucine (2 and 18 tLM) did not change the accumulation of tritium during incubation of the vas deferens with [3H]-noradrenaline. 4 (+)-Glaucine (0.3 nM-0.1 mM) inhibited specific [3H]-prazosin binding to membranes from rat vas deferens with a pKi value of 6.63, which is close to the pA2 value obtained against noradrenaline and methoxamine in functional studies. 5 In electrically-stimulated rat vas deferens, (+)-glaucine (0.3-lO M) enhanced twitch contractions and competitively antagonized the inhibitory effect of clonidine with a pA2 value of 5.91. 6 In tissues incubated in depolarizing calcium-free high-potassium medium, (+)-glaucine (30-80 pM)
Behavioural Pharmacology, 1992
Advanced Science Letters, 2013
Drought-tolerant leguminous shrubs can enhance the sustainability of smallholder production syste... more Drought-tolerant leguminous shrubs can enhance the sustainability of smallholder production systems in the tropics through the provision, year-round, of high-quality feed and through their positive effect on soil. Desmodium velutinum is one of the few shrub species that have been identifi ed as (1) well adapted to acid tropical soils and (2) of good nutritive value (Schultze-Kraft 1996). It is a perennial, native to SE Asia and tropical Africa, growing up to 3 m high, the velutinous (velvety) surfaces of its 1-foliolate leaves being a characteristic feature. It grows well on soils ranging from pH 4.0 to alkaline, prefers high rainfall (1000 to >3000 mm/year) but tolerates up to fi ve dry months. Though previous work in west Africa (e.g. Mzamane and Agishi 1986) and South America (e.g. Thomas and Schultze-Kraft 1990) has indicated the potential of the species, there are only few studies and these are restricted to only one or a few accessions. It is important to assess the genetic diversity and agronomic variability in the germplasm collection of about 140 accessions that is now available, in order to identify a core collection and accessions with promising agronomic performance and nutritive value. Possible relationships between accession origins, morphological-agronomic characteristics, and genetic diversity need to be assessed. The fi rst-year results from a fi eld experiment on forage yield and quality are presented here. The project is fi nancially supported by the Volkswagen Stiftung, Hannover, Germany.
Tropical Grasslands - Forrajes Tropicales, 2015
As global demand for livestock products (such as meat, milk and eggs) is expected to double by 20... more As global demand for livestock products (such as meat, milk and eggs) is expected to double by 2050, necessary increases to future production must be reconciled with negative environmental impacts that livestock cause. This paper describes the LivestockPlus concept and demonstrates how the sowing of improved forages can lead to the sustainable intensification of mixed crop-forage-livestock-tree systems in the tropics by producing multiple social, economic and environmental benefits. Sustainable intensification not only improves the productivity of tropical forage-based systems but also reduces the ecological footprint of livestock production and generates a diversity of ecosystem services (ES) such as improved soil quality and reduced erosion, sedimentation and greenhouse gas (GHG) emissions. Integrating improved grass and legume forages into mixed production systems (crop-livestock, tree-livestock, crop-tree-livestock) can restore degraded lands and enhance system resilience to drought and waterlogging associated with climate change. When properly managed tropical forages accumulate large amounts of carbon in soil, fix atmospheric nitrogen (legumes), inhibit nitrification in soil and reduce nitrous oxide emissions (grasses), and reduce GHG emissions per unit livestock product.
… Congress (21; 8, …, 2008
SIDALC - Servicio de Informacion y Documentacion Agropecuaria de las Americas.
Tropical Grasslands - Forrajes Tropicales, 2015
The International Center for Tropical Agriculture (CIAT)-a member of the CGIAR Consortium-develop... more The International Center for Tropical Agriculture (CIAT)-a member of the CGIAR Consortium-develops technologies, innovative methods, and new knowledge that better enable farmers, especially smallholders, to make agriculture eco-efficient-that is, competitive and profitable as well as sustainable and resilient. Headquartered near Cali, Colombia, CIAT conducts research for development in tropical regions of Latin America, Africa, and Asia. www.ciat.cgiar.org CGIAR is a global research partnership for a food-secure future. Its science is carried out by the 15 research Centers that are members of the CGIAR Consortium in collaboration with hundreds of partner organizations. www.cgiar.org LivestockPlus The sustainable intensification of forage-based agricultural systems to improve livelihoods and ecosystem services in the tropics
British journal of pharmacology, 1996
1. The relative importance of intracellular and extracellular Ca2+ on alpha 1-adrenoceptor-mediat... more 1. The relative importance of intracellular and extracellular Ca2+ on alpha 1-adrenoceptor-mediated contraction by noradrenaline and St-587 has been studied and correlated with the binding characteristics in intact tail artery from Sprague-Dawley rats. 2. Noradrenaline and St-587 behaved as full agonists inducing a concentration-dependent vasoconstriction. 3. Nifedipine (1 microM and 10 microM) blocked by 50% (P < 0.001) and 75% (P < 0.001) respectively, the maximum contraction (Emax) induced by St-587. Nevertheless, to reach 40% inhibition of Emax on noradrenaline responses (P < 0.01), 10 microM nifedipine was necessary. 4. Both agonists induced a concentration-dependent accumulation of inositol phosphates. Noradrenaline behaved as a full agonist and St-587 as a partial agonist for this response. 5. [3H]-prazosin binding to intact tail artery rings was saturable and of high affinity (KD = 4.44 +/- 0.46 nM; Bmax = 36.35 +/- 4.22 fmol mg-1 tissue). 6. Competition curves for ...
Pharmacological Research, 1995
It has been found that vasa deferentia from age-matched spontaneously hypertensive rats (SHR) exh... more It has been found that vasa deferentia from age-matched spontaneously hypertensive rats (SHR) exhibit an altered postjunctional ~l-adrenoceptor mediated responsiveness respect to control WKY. To clarify the contradictory existing results radioligand binding and funeional studies were performed. An increased steadystate density of [3H]prazosin binding sites was observed in the vas deferens of SHR (B~,= 148 4-18 frnol.mg -1 protein) vs WKY controls (B~x=71 +9 fmol-mg 1 protein) with no changes in the dissociation constant value. Concentration-response (E/[A]) curves to noradrenaline showed a higher maximal effect in vasa deferentia from SHR compared to WKY (25.3 ___ .96 mN vs 15.64-.52 raN) but pECso were not modified. Partial alkylation with phenoxybenzamine (0.1 #M) was performed to apply the operational model of Black and Left (1983) on E/[A] curves. The affinity (KA) and efficacy (r) estimates for noradrenaline, and the parameters E m and n in each experimental group were tested for similarity by analysis of variance. The results of this analysis showed that the model could fit both sets of data by assuming the same pK A value (4.90;4.9~), different r values (logrv, xv=l.63+__0.23 and logrsnR=l.74+0.29) and a significant change in E~ (Em wrv=15.82 mN vs E~ s~=25.86 mN) for noradrenaline. The results also show that the altered responsiveness could not be only explained as an increase in cq-adrenoceptors.
PEDIATRICS, 2000
The administration of recombinant human erythropoietin (rHuEPO), started after the first 2 weeks ... more The administration of recombinant human erythropoietin (rHuEPO), started after the first 2 weeks of life, reduces the transfusion requirement in premature infants. However, its use throughout the first 2 weeks of life, when anemia results predominantly from phlebotomy losses, remains controversial. We investigated whether early use of rHuEPO would reduce the total transfusion requirement and/or the number of transfusions throughout the first 2 weeks of life. We randomized 114 infants with birth weight (BW) &amp;lt;1250 g to receive rHuEPO (1250 units/kg/week; IV; early group: n = 57) or placebo (late group: n = 57) from day 2 to day 14 of life; subsequently, all the patients received rHuEPO (750 units/kg/week, subcutaneously) for 6 additional weeks. All infants were given oral iron (6 mg/kg/day) and folic acid (2 mg/day). The early group showed higher hematocrit and reticulocyte counts than the late group in the first 3 weeks of life, but there was no difference in the total number of transfusions (early: 1.8 +/- 2.3 vs late: 1.8 +/- 2.5 transfusion/patient) or the transfusion requirement throughout the first 2 weeks of life (early:.8 +/- 1.1 vs late:.9 +/- 1.3) could be demonstrated. In infants with BW &amp;lt;800 g and total phlebotomy losses &amp;gt;30 mL/kg (n = 29), a lower number of transfusions was received by infants in the early group, compared with late group, from the second week to the end of the treatment (early: 3.4 +/- 1.1 vs late: 5.4 +/- 3.7 transfusion/patient). No clinical adverse effects were observed. Thrombocytosis was detected during the treatment with rHuEPO in 31% of the infants. In the whole population, the early administration of rHuEPO induced a rise of reticulocyte counts, but not enough to reduce the transfusion requirement. The most severely ill infants (BW &amp;lt;800 g and phlebotomy losses &amp;gt;30 mL/kg) seemed to benefit from early use of rHuEPO, and this deserves additional study.
Neuroscience Letters, 1991
The effects of acute treatment with 1,2,3,4-tetrahydro-9-aminoacridine (THA), a 4-aminopyridine d... more The effects of acute treatment with 1,2,3,4-tetrahydro-9-aminoacridine (THA), a 4-aminopyridine derivative clinically effective in Alzheimer's disease, on fl-adrenoceptor-linked cyclic AMP accumulation have been investigated in cortical and hippocampal structures of young and middle-aged rats. In a first series of experiments, pretreatment with 2.5 mg/kg THA decreased basal cyclic AMP accumulation. When a phosphodiesterase inhibitor was added to the preparation, THA again decreased cyclic AMP levels in young rats, but failed to significantly modify cyclic AMP accumulation in middle-aged animals. Finally, in isoprenaline-stimulated conditions, acute treatment with tacrine was able to diminish cyclic AMP accumulation in every group of rats. It is suggested that the neurochemical action of THA in mammalian brain is more complex than earlier has been anticipated and may involve an action on fl-adrenoceptors.
Neuropharmacology, 1995
The mechanism by which 9-amino-1,2,3,4-tetrahydroacridine (THA) inhibits beta-adrenoceptor linked... more The mechanism by which 9-amino-1,2,3,4-tetrahydroacridine (THA) inhibits beta-adrenoceptor linked cyclic AMP formation and its possible relationship with the cholinergic system were studied. In addition, the effect of THA on alpha 1-adrenoceptor coupled transduction systems was also investigated. THA was not able to influence the concentration-response curve for forskolin indicating that it is not acting on the catalytic subunit of the adenylate cyclase complex. On the other hand a cholinergic component seems to participate in the action of THA on beta-adrenoceptor stimulated adenylate cyclase activity since the blockade of muscarinic receptors with atropine (10 microM) partially prevented the reduction in cyclic AMP formation attained by THA in the hippocampus, in isoprenaline-stimulated conditions. This effect is not reproducible by another potent anticholinesterase physostigmine. Moreover, THA at concentrations up to micromolar did not affect alpha 1-adrenoceptor stimulated cyclic AMP formation or phosphoinositide hydrolysis. In conclusion, the neuropharmacological profile of THA is not to be restricted to the cholinergic system and its effectiveness in improving age-associated cognitive deterioration may involve an action on the beta-adrenoceptor coupled signal transduction system. Moreover, the action of THA on the beta-adrenergic and cholinergic systems in the brain could be relevant to the amelioration of cognitive deterioration and could lead to the development of new therapeutic strategies.
European Journal of Pharmacology: Molecular Pharmacology, 1993
The effects of 1,2,3,4-tetrahydro-9-aminoacridine (THA) and physostigmine on/3-adrenoceptor-linke... more The effects of 1,2,3,4-tetrahydro-9-aminoacridine (THA) and physostigmine on/3-adrenoceptor-linked cyclic AMP accumulation have been analyzed in vitro in rat cortex and hippocampus. A 10-min incubation with increasing concentrations of THA reduced isoprenaline (10/zM)-stimulated cyclic AMP accumulation in a concentration-dependent manner in cortical (IC50 = 1.31 + 0.13 /zM) and hippocampal (ICs0 = 0.02 + 0.003 /zM) structures. Conversely, physostigmine did not modify cyclic AMP synthesis in any experimental condition. The action of THA was non-competitive since it induced a non-parallel shift to the right of the concentration-response curve for isoprenaline. The differential effects of THA and physostigmine on the/3-adrenoceptor transduction system may account for the difference in their ability to restore cognitive function.
Clinical Neuropharmacology, 1992
British Journal of Pharmacology, 1997
1 The eect of two D 3/2 dopamine receptor agonists, LY-171555 (quinpirole) and 7-hydroxy-N,N-di-n... more 1 The eect of two D 3/2 dopamine receptor agonists, LY-171555 (quinpirole) and 7-hydroxy-N,N-di-npropyl-2-aminotetralin (7-OH-DPAT) on spontaneous [ 3 H]-acetylcholine ([ 3 H]-ACh) release were investigated in rat striatal synaptosomes. 2 Quinpirole and 7-OH-DPAT inhibited in a concentration-dependent manner the basal eux of [ 3 H]-ACh with similar E max (maximal inhibitory eect) values (29.95+2.91% and 33.19+1.21%, respectively). Signi®cant dierences were obtained between the pEC 50 (7log of molar concentration) of quinpirole (7.87+0.12) and 7-OH-DPAT (7.21+0.17; P50.01).
British Journal of Pharmacology, 1993
1 Effects of the aporphinoid alkaloid, (+)-glaucine, on rat vas deferens were investigated. 2 (+ ... more 1 Effects of the aporphinoid alkaloid, (+)-glaucine, on rat vas deferens were investigated. 2 (+ )-Glaucine (2-18 f.M) competitively inhibited contractions induced by noradrenaline and methoxamine with a pA2 value of about 6. 3 (+ )-Glaucine (2 and 18 tLM) did not change the accumulation of tritium during incubation of the vas deferens with [3H]-noradrenaline. 4 (+)-Glaucine (0.3 nM-0.1 mM) inhibited specific [3H]-prazosin binding to membranes from rat vas deferens with a pKi value of 6.63, which is close to the pA2 value obtained against noradrenaline and methoxamine in functional studies. 5 In electrically-stimulated rat vas deferens, (+)-glaucine (0.3-lO M) enhanced twitch contractions and competitively antagonized the inhibitory effect of clonidine with a pA2 value of 5.91. 6 In tissues incubated in depolarizing calcium-free high-potassium medium, (+)-glaucine (30-80 pM)
Behavioural Pharmacology, 1992
Advanced Science Letters, 2013
Drought-tolerant leguminous shrubs can enhance the sustainability of smallholder production syste... more Drought-tolerant leguminous shrubs can enhance the sustainability of smallholder production systems in the tropics through the provision, year-round, of high-quality feed and through their positive effect on soil. Desmodium velutinum is one of the few shrub species that have been identifi ed as (1) well adapted to acid tropical soils and (2) of good nutritive value (Schultze-Kraft 1996). It is a perennial, native to SE Asia and tropical Africa, growing up to 3 m high, the velutinous (velvety) surfaces of its 1-foliolate leaves being a characteristic feature. It grows well on soils ranging from pH 4.0 to alkaline, prefers high rainfall (1000 to >3000 mm/year) but tolerates up to fi ve dry months. Though previous work in west Africa (e.g. Mzamane and Agishi 1986) and South America (e.g. Thomas and Schultze-Kraft 1990) has indicated the potential of the species, there are only few studies and these are restricted to only one or a few accessions. It is important to assess the genetic diversity and agronomic variability in the germplasm collection of about 140 accessions that is now available, in order to identify a core collection and accessions with promising agronomic performance and nutritive value. Possible relationships between accession origins, morphological-agronomic characteristics, and genetic diversity need to be assessed. The fi rst-year results from a fi eld experiment on forage yield and quality are presented here. The project is fi nancially supported by the Volkswagen Stiftung, Hannover, Germany.
Tropical Grasslands - Forrajes Tropicales, 2015
As global demand for livestock products (such as meat, milk and eggs) is expected to double by 20... more As global demand for livestock products (such as meat, milk and eggs) is expected to double by 2050, necessary increases to future production must be reconciled with negative environmental impacts that livestock cause. This paper describes the LivestockPlus concept and demonstrates how the sowing of improved forages can lead to the sustainable intensification of mixed crop-forage-livestock-tree systems in the tropics by producing multiple social, economic and environmental benefits. Sustainable intensification not only improves the productivity of tropical forage-based systems but also reduces the ecological footprint of livestock production and generates a diversity of ecosystem services (ES) such as improved soil quality and reduced erosion, sedimentation and greenhouse gas (GHG) emissions. Integrating improved grass and legume forages into mixed production systems (crop-livestock, tree-livestock, crop-tree-livestock) can restore degraded lands and enhance system resilience to drought and waterlogging associated with climate change. When properly managed tropical forages accumulate large amounts of carbon in soil, fix atmospheric nitrogen (legumes), inhibit nitrification in soil and reduce nitrous oxide emissions (grasses), and reduce GHG emissions per unit livestock product.