In the tropics, environmental constraints such as drought limit forage supply, and thus livestock production and competitiveness of livestock systems. Forage conservation technologies could mitigate the dry season feed problems but their adoption in smallholder systems has so far been low. The present work, carried out in Honduras, examined factors that influenced the uptake of promoted silage technologies in order to derive suggestions for further R&D interventions. A total of about 250 farmers participated in training sessions and field days. Information was gathered using interviews with 222 participants.Maize and sorghum were the most common crops (>60%) used for silage making, with grass being ensiled to a limited extent. All silo types were used (mean of approximate to 2 silos/farm) with earth and heap silos being most widely accepted. Financial and farm resources, farmers' education, extension continuity and intensity, and the presence of key innovators, motivated farmer groups and favourable milk market conditions contributed to increased adoption. The most common reasons for non-adoption were the lack of a chopper (small and medium farms), silage too expensive (medium farms) and silage not needed (large farms). Extension strategies need to be adapted to specific conditions to efficiently support a sustainable forage and livestock development process. Continuous promotion can lead to significant and sustained adoption with subsequent potential benefits for more smallholders via increased locally available know-how and easier access to machinery and markets.
Forages are most important for feeding cattle in Central America; however, the adoption of forage options is still limited. This paper develops an approach to prioritise forage options according to efficiency scales, using Olancho in Honduras as a case study. Farm management characteristics and their effects on resource use efficiency were assessed for 76 farms, classified into a sequence from very low to top performers using net income per cow from milk in the dry season as the indicator of resource use efficiency. Chances for and con straints to the adoption of forage options were derived for specific contexts. Both nutritional conditions on farm and the genetic potential of the herd were critical in determining the performance level of the farm. Purchased supplements were the most important cost driver in the dry season. Farmers rated as either very low or low performers did not benefit adequately from their herd owing to inadequate feeding, with only a small amount of high quality farm-produced feed, and low genetic potential of their herds. Medium performers placed more emphasis on feed produced on-farm. Positive examples showed that improvement of the forage component was an important step to better resource use efficiency. Possible options for improving productivity, especially in very low and low producing herds, are discussed.
A rotational grazing experiment was carried out to determine the effects of post-grazing height on morphogenic characteristics of guinea grass (Panicum maximum) cv. Mombaca between October 2004 and June 2005. The grass was subjected to 2 severities of rotational grazing, represented by post-grazing stubble heights of 30 and 50 cm, and animals were reintroduced when pastures intercepted 95% of incident light. Swards managed with 30 cm post-grazing stubble height had smaller leaf elongation rate (LER) and final leaf length (FLL) and greater tiller population density (TPD), tiller appearance rate (TAR) and tiller mortality rate (TMR) than those grazed to 50 cm. During the second grazing cycle, stem elongation rate (SER) was lower in paddocks grazed to 30 cm stubble height. Grazing cycle had significant effects on plant morphology. Leaf appearance rate (LAR), LER and TAR peaked in the second grazing cycle, while SER, TPD and TMR peaked in cycles 3 and 4. The more intense grazing management (30 cm stubble) resulted in higher levels of tiller renewal and tiller turnover and lower stem elongation. How these changes relate to pasture yields and animal performance is yet to be determined.
In plantation crops, perennial tropical legumes are grown as understory plants, where they receive limited irradiance and can be subjected to elevated levels of CO2. Independent short-term effects of photosynthetic photon flux density (PPFD), external carbon dioxide concentration [CO2] and temperature on net photosynthesis (Pn), internal CO2 (Ci), stomatal conductance (Gs) and transpiration (E) were assessed in 5 tropical perennial legume cover crops (calopo, jack bean, mucuna, white lead tree and perennial peanut). These legumes responded differently to changing PPFD, external [CO2] and temperature. In all legume species studied, reducing PPFD from 1000 to 50 mu mol/m(2)/s reduced Pn to less than 10% of that at the higher light level. Increasing the external [CO2] from 250 to 700 cm(3)/m(3) doubled Pn. Increasing temperature from 30 degrees C to 35 degrees C reduced Pn in calopo, jack bean and mucuna and increased Pn in white lead tree and perennial peanut, but magnitude of the differences was small. Gs increased with PPFD in all species except perennial peanut, but decreased substantially as external [CO2] increased only in white lead tree. Early in the establishment of plantations, soils receive nearly full sunlight. However, with increasing age, the amount of light reaching ground level is decreased drastically, to as low as 80-200 mu mol/m(2)/s. Cover crops that can grow in low light might survive longer and better protect the soil from erosion. Responses of these perennial legumes under the conditions imposed have shown that white lead tree and calopo would perform better than the other species as cover crops in tree plantations, where they would be subjected to high levels of shading. However, management of the tree canopy would be important to allow sufficient light through to achieve acceptable growth rates in the cover crops.
A pilot survey to measure organic carbon storage in soils under different land uses was carried out within a 100 km radius of Taree, New South Wales, Australia in 2007. The area has a subtropical climate with annual rainfall of 900-1600 mm. Soil organic carbon (SOC) levels under forests to 20 cm depth varied from 37 to 134 t/ha C, with a mean of 77 t/ha C. Levels under pastures varied from 44 to 96 t/ha C, with a mean of 73 t/ha C. The data suggest that soils under introduced perennial pastures (mainly tropical C-4 perennials) can potentially store similar amounts of soil carbon as those under native forests (mainly woodlands with C-3 tree species). Our results indicated improved pastures can store more carbon than native pastures. Further research is needed to fully quantify the effects of pasture type, fertiliser strategies and management practices on SOC storage potential, with extension of the sampling horizons to greater depths.
Response patterns of guinea grass to defoliation were assessed over a 4-month period at the Federal University of Vicosa using a randomised complete block design with 3 replications. The treatments were combinations of cutting height (25 and 50 cm) and cutting interval (2, 3 and 4 new leaves per tiller) and were arranged in a 2 x 3 factorial design. Morphological and structural characteristics, regrowth period and forage accumulation were assessed. The average regrowth period was similar for the cutting intensities assessed. Stem elongation, final leaf length and number of live leaves per tiller were greater with the 50 cm cutting height. Increasing the number of leaves/tiller at harvest increased period between harvests, canopy height at harvest and stem relative to leaf elongation, causing reduction of the leaf: stem ratio. It appears that cutting at the 3-leaf stage at 25 cm height would be the most appropriate for Momba a guinea grass. However, a more practical standard would be cutting at a canopy height of about 90 cm. Longer-term studies are needed to confirm these preliminary findings, along with feeding studies to determine production benefits from this regime.
Kudzu (Pueraria phaseoloides) is an ecologically and economically important forage legume and cover crop in tropical and subtropical regions. The effects of foliar application of different concentrations (30, 100 and 300 mg/L) of 5-aminolevulinic acid (ALA) on photosynthesis, growth, chemical composition and medicinal components of seedlings of kudzu were tested in a pot experiment. Seedlings were sprayed twice weekly for 3 weeks and parameters measured at 8 weeks after the initial application. Treatment with ALA at 100 mg/L significantly increased DM yield of total plants plus chlorophyll concentration, photosynthetic rate and stomatal conductivity of kudzu leaves and reduced CO2 concentration in the leaf, but had no significant effect on transpiration rate. Application of ALA (100 mg/L) significantly increased nitrogen, phosphorus, potassium and calcium concentrations in leaves as well as the soluble sugar, starch and vitamin C concentrations. Furthermore, the accumulation of medicinal components including flavonoids and puerarin was also significantly increased by ALA application. While this study suggests that ALA application could promote yield and quality of kudzu, further work is needed to determine optimal application rates and treatment regimes before recommendations could be made on the commercial application of this technology.
Field experiments were conducted between 2008 and 2009 cropping seasons to evaluate growth, nitrogen fixation and fodder quality of Arachis pintoi (CIAT 18744) at 5 sites in western Kenya. Differences in seedling emergence (33–52%), start of flowering (49–60 days after planting) and cumulative dry matter production were measured. The highest dry matter yield (3.1 t/ha) was produced on a moderately fertile alfisol and the lowest (1.7 t/ha) on a degraded ultisol, with corresponding pod yields of 1.3 t/ha and 0.8 t/ha. Estimates of nitrogen derived from the atmosphere (%Ndfa) by 15 N natural abundance were greater than 50% across the 5 sites with the highest percentage on a moderately fertile nitisol. Nitrogen fixation ranged from 23 to 46 kg/ha N and was significantly related (r 2 =0.77 *** ) to dry matter production. Crude protein and soluble tannin concentrations and dry matter digestibility of forage were 16–18%, 1.2–1.8% and 60–62%, respectively. These preliminary results are promising but longer-term studies to assess persistence and dry matter yield, especially when A. pintoi is planted with a grass and grazed, are warranted. Further studies should address the issue of how the legume might be incorporated in the production systems of farmers.
Sainfoin is a cross-pollinating plant and segregates when material is multiplied from seed during breeding programs. While the use of cuttings allows rapid and reliable multiplication of selected material for vegetative propagation, cuttings often do not root well. This study examined the root development of sainfoin cuttings after dipping in solutions containing 0, 25, 50, 100 and 200 mg/L indole-3-acetic acid (IAA), alpha-naphthalene acetic acid (NAA) and indole-3-butyric acid (IBA) for 8, 16 and 24 h. The hormones were dissolved in either liquid Murashige and Skoog (MS) medium or distilled water. While untreated cuttings produced virtually no roots, all auxin treatments stimulated rooting on some cuttings. Dipping treatments using liquid MS medium as the base for the auxin solution produced better root development than those using distilled water. IBA was less effective than IAA or NAA in stimulating root production on cuttings. Dipping cuttings in a solution of IAA at 100 mg/L for 8 h in liquid MS medium would seem to be adequate to produce satisfactory root development. Rooted plantlets were transferred to pots and grew successfully under greenhouse conditions.
The aim of this study was to determine the potential nutritive value of a wild narrow-leaved clover (Trifolium angustifolium) hay harvested at 3 maturity stages (pre-flowering, flowering and seeding) in terms of chemical composition and in vitro gas production. In vitro gas production of Trifolium angustifolium hay was determined at incubation times of 0, 3, 6, 12, 24, 48, 72 and 96 h and the gas production kinetics were described using the equation y = a + b (1-e(-ct)). Maturity had a significant effect on both chemical composition and in vitro gas production kinetics. Neutral detergent fibre (NDF), acid detergent fibre and condensed tannin (CT) concentrations increased with maturity, while crude protein (CP) concentration decreased from 16.9% pre-flowering to 13.2% at seeding. The condensed tannin concentration of Trifolium angustifolium hay ranged from 2.16 to 3.71%.Estimated gas production decreased with increasing maturity of Trifolium angustifolium hay. ME, OMD, a+b, a and CP concentration were negatively correlated with NDF, ADF and CT. It appears that wild Trifolium angustifolium, harvested even at the seeding stage, offers considerable potential as medium quality forage for ruminant animals during the winter period.
A study was conducted to examine rangeland resource utilisation practices of pastoralists and rangeland degradation in Rayitu district, south- east Ethiopia. A single-visit survey method was used to gather data through a structuredues- a structuredues- tionnaire (90 households), group discussions and direct observations. Free grazing of communal land (100%), use of enclosures (89%), division of herds based on species and class of animal (59%), migration (79%) and seasonal assessments of the condition of rangeland were the basic traditional rangeland management practices. About 91% of pastoralists indicated that the condition of their rangelands was poor. The most dominant use for woody plants was for construction (91%), fol- lowed by browse (68%) and medicinal purposes (25%). More than 86% of the respondents con- sidered that their grazing lands now carried more bushes and shrubs than they did 30 years ago. Feed and water shortages and drought were iden- tified as current challenges for pastoralists, with migration the main coping strategy, in spite of the hardships it entails. Rejuvenating the existing rangelands reuires the development of a range- land management strategy involving pastoralists and other stakeholders, with all participants fully committed to a successful outcome. A reduction in livestock numbers must be an essential compo- nent of any future strategy.
In a feeding experiment, 2 groups of 6 male lambs (13.1 +/- 0.52 kg) were offered cowpea hay ad lib and barley grain grown under inorganic and organic management and feed intake and liveweight change were measured. After 60 days, a digestion trial was conducted to assess the dietary effects on nutrient digestibility and N metabolism. After 195 days, rumen liquor and blood samples were collected for determination of rumen metabolites, microbial activity and blood parameters. Dry matter intake was similar in lambs in both groups, while nutrient digestibility was 2-2.5 units higher in lambs fed the organic diet (P>0.05). Eating pattern and rate of feed intake were comparable in both groups. Lower urinary nitrogen concentration in the organic group resulted in higher N retention in this group. At 4 h post feeding, total volatile fatty acid and total N concentrations were higher (P<0.05) in rumen liquor from the organic group than the inorganic group. Blood metabolites of lambs were comparable in lambs of both dietary groups. Total bacterial count, total protozoa and entodiniomorph counts were higher (P<0.05) in the organic group. Growth rates were comparable in both groups, while wool yield was slightly higher in the organic group (P>0.05). Results indicate that lambs fed a diet based on organically produced cowpea hay and barley grain should perform at a similar level to those fed on a conventional diet produced with inorganic fertilisers.
A historical review of pasture research and development in the Australian tropics and subtropics identifies the key role that pastoralists have played in developing the twin objectives of: observing, utilising and conserving the native pasture resources; and introducing and exploiting exotic plant species that could improve livestock production. These two objectives were established during the earliest days of settlement by Europeans, were maintained during an era of intense scientific activity from about World War II (WW II) until the 1990s and will probably continue for some time. The scientific activity led to the publication of thousands of scientific papers and to the commercial release of approximately 150 cultivars of a range of pasture species, notably in the genus Stylosanthes, which, in terms of sown area, is now the predominant legume genus in tropical pastures globally. Research on the natural resource base enhanced our understanding of the structure and function of Australia’s savanna lands and tropical grasslands and provided a scientific foundation for decisions on land use. For a period of almost 50 years, the Tropical Grassland Society of Australia provided a forum for interaction between graziers and scientists and its journal, Tropical Grasslands, recorded the rapid growth in knowledge of tropical pasture science and provided a medium for the publication of the results of research that had a practical focus.
The effectiveness of 31 strains of Bradyrhizobium in producing nodules on and fixing nitrogen with 31 accessions of Stylosanthes macrocephala was assessed in 3 experiments using nitrogen-free sand-culture conditions in a glasshouse. Most strains of Bradyrhizobium isolated from S. macrocephala formed effective nitrogenfixing associations with the range of S. macrocephala accessions. Variability of the responses was greater with strains of bradyrhizobia isolated from S. seabrana, which has a similar geographic distribution, and with strains isolated from S. capitata, which has the same geographic distribution and is botanically closely related.
Cratylia argentea is a high-quality forage legume shrub, with particular potential for the subhumid tropics owing to its adaptation to acid and infertile soils and drought tolerance. However, lack of knowledge about the ability of this species to self-pollinate makes purity maintenance of accessions difficult. Studies were conducted to investigate whether the gametes of C. argentea flowers are self-compatible, and to verify the dependence of reproduction on insects. Pod set and seed production were assessed in a pollination experiment with 4 treatments (spontaneous self-pollination, artificial self-pollination, insect pollination and artificial cross-pollination). Our results (0–1.2% pod set after selfing, 3.4% after insect pollination and 20.3% after artificial crossing) suggest that C. argentea is mostly self-incompatible. Seed:ovule ratios were 0.63 with insect pollination and 0.78 with artificial crossing. We found that pollen grains mature before the stigma becomes receptive, which suggests that the species is cross-pollinated. We also found evidence that C. argentea depends on large solitary bees for pollination, based on flower structure and the stigma becoming receptive only after tripping of the flower. Xylocopa frontalis and 2 Centris species were identified as key pollinators. In view of its simplicity, the research procedure utilised is suggested for other tropical legume species pollinated by large insects.
Experiments at 2 sites in subtropical eastern Australia investigated the variation in agronomic attributes, quality and genetic structure existing within: naturally-occurring populations of kikuyu (Pennisetum clandestinum) from within Australia; selections produced from the treatment of Whittet seed with mutagenic chemicals; and available cultivars. Runners were collected from coastal areas extending from Western Australia to the Atherton Tableland in north Queensland. One experiment evaluated 10 mutagenic selections and 4 cultivars in a lattice design and the other evaluated 12 ecotypes and 3 cultivars in a randomised block design. The experimental unit was single plants, which were sown on a 1.5 m grid into a weed-free seed-bed (Mutdapilly) or a killed kikuyu stand (Wollongbar), both of which were kept clear of weeds and other kikuyu plants for the duration of the experiments. Foliage height, forage production and runner yield were assessed. Leaf material was analysed for concentrations of crude protein (CP), acid detergent fibre (ADF) and neutral detergent fibre (NDF) and for in vitro dry matter digestibility (IVDDM) in autumn, winter and spring. DNA was extracted from each plant in the ecotype comparison and subjected to a modified DAF (DNA amplification fingerprinting) analysis to determine the level of genetic relatedness.In the first experiment, none of the mutagenic lines derived from Whittet yielded significantly more or was more digestible than commercial Whittet material, although some selections were superior to the other commercial kikuyu cultivars, Noonan and Crofts, and 'common' kikuyu. However, there were significant differences in plant height and runner expansion. In the second experiment, significant differences in plant height, foliage yield, runner development, and leaf CP, ADF, NDF and IVDDM concentrations were demonstrated between the ecotypes, mutagenic selections and cultivars. There was a 4- to 6-fold difference in plant yield and a 6- to 10-fold difference in runner production between the ecotypes at the 2 sites. Quality of the leaf ranged from 200 to 270 g/kg (CP), from 700 to 770 g/kg (IVDDM), from 170 to 250 g/kg (ADF) and from 470 to 550 g/kg (NDF). Improvements in quality and agronomic attributes were not mutually exclusive.Genetic fingerprint analysis of the kikuyu lines indicated that they formed 2 broad groupings. Most of the regional ecotypes were grouped with 'common' kikuyu as represented by the material collected from Wollongbar, and the Beechmont, Atherton Tableland and Gympie ecotypes were grouped with the registered cultivars Whittet, Noonan and Crofts. Two lines produced by mutagenesis from Whittet remained closely linked to Whittet. These results suggest that there was variation between populations of kikuyu in yield, quality and genetic diversity but that mutagenesis by treating seed with sodium azide and diethylene sulphide did not achieve a significant change in the digestibility of leaf over cv. Whittet.
The perennial grass Eriachne benthamii (Hartley swamp wanderrie) (Poaceae) is native to central Australia. The present laboratory study demonstrates that the ability of this species to survive in seasonally wet grasslands is already present at an early seedling stage. While flooding of seedlings for 1–4 weeks at ages of 4–9 weeks reduced shoot weight, height, number of leaves and leaf area, plants survived and grew well. Research is required on the morphological and/or physiological mechanisms, which lead to the observed tolerance to flooding in E. benthamii. Since it can tolerate prolonged flooding, E. benthamii may be a useful species for the rehabilitation of disturbed and degraded rangeland areas, which are prone to periodic flooding.
Two experiments were conducted in southwestern Nigeria to determine the responses of Stylosanthes scabra cvv. Seca and Fitzroy to seeding rate (1.7, 3.4, 5.1 and 6.8 kg/ha), row spacing (30, 45 and 60 cm), nitrogen (0, 5.75, 11.5 and 23 kg/ha N) and phosphorus (0, 20 and 40 kg/ha P) rates on a soil containing 2.70 ppm available P over a 2-year period. There was an interaction between sowing rate and row spacing for DM production with closer row spacing increasing yields at low sowing rates but the reverse occurring at high sowing rates. Yields of leaf ranged from 3.1 to 8.7 t/ha in Year 1 and from 3.2 to 8.4 t/ha in Year 2, while corresponding values for stem were 8.4-19.4 t/ha and 9.6-19.5 t/ha. There were very few differences between cultivars. While application of N fertiliser had minimal effect on growth overall, application of P fertiliser increased both DM yields and P concentrations in both leaf and stem. In the absence of added N, P application increased DM yield by more than 60%.Crude protein (CP) concentrations in leaf ranged from 15.5 to 21% in Year 1 and 14.6 to 19.7% in Year 2, while corresponding values for stem were 5.6 to 8.8% and 5.3 to 8.2%. Application of P fertiliser increased P concentrations in leaf from 0.13-0.17% to 0.16-0.24% and in stems from 0.06-0.08% to 0.08-0.13%. The concentrations of CP and P were higher (P<0.05) in Fitzroy than in Seca in both years. Sowing Seca or Fitzroy at 3.5-4 kg/ha in rows 45 cm apart into a prepared seedbed on these soils and applying 20 kg/ha P should give satisfactory establishment and yields of forage for feeding to stock during the dry season.
