Successes and failures of small ruminant breeding programmes in the tropics: a review

Despite the large numbers and importance of adapted indigenous sheep and goats in the tropics, information on sustainable conventional breeding programmes for them is scarce and often unavailable. This paper reviews within-breed selection strategies for indigenous small ruminants in the tropics, highlighting aspects determining their success or failure. The aim is to better understand opportunities for genetic improvement of small ruminants by the resource-poor farmers in traditional smallholder and pastoral farming systems. Dismal performance of programmes involving breed substitution of exotics for indigenous breeds and crossbreeding with temperate breeds have stimulated a recent re-orientation of breeding programmes in tropical countries to utilize indigenous breeds, and most programmes are incipient. The success rate of some breeding programmes involving native breeds is encouraging. Definition of comprehensive breeding objectives incorporating the specific, immediate, and long-term social and economic circumstances of the target group as well as ecological constraints was found lacking in some projects that failed. To achieve success, it is necessary to look at the production system holistically, and involve the producer at every stage in the planning and operation of the breeding programme, integrating traditional behaviour and values.     

Diets/Dietary habits and certain gastrointestinal disorders in the tropics: a review.

Against the background that what one eats affects the gastrointestinal tract (G.I T), the role of diet and dietary habits including fibres, food additives and preservatives on the aetiology of gastric cancers, colorectal cancers and other G.I disorders in the tropics are herein reviewed. Carcinomas of the gut believed to be on the decline in the developed countries have plateaued and increasing cases are being reported in the tropics. Africa and Nigeria in particular, with little or no cases previously are currently experiencing patterns of incidence similar to those of the Western Hemisphere. All these developments are premeditated by the nature of diets and dietary factors contained therein. Some of these factors contain chemical carcinogens, irritants as additives or preservatives, high cholesterol, highly spiced foods, alcohol, nicotine, xanthines, caffeine, most of which provoke gastric acid secretions dyspepsia and heartburn, and they lack vegetables and dietary fibres known to protect the G.I tract against various diseases. The roles of dietary hygiene implicating certain microorganisms associated with G.I diseases like Helicobacter Pylori are also discussed. It presupposes that well articulated diet and proper dietary manipulations remain the cure for all diet induced G.I disorders while avoidance of such habits that predispose to them must be encouraged to ensure proper and healthy G.I.T.     

Forage plants as an alternative feed resource for sustainable pig production in the tropics: a review

Globally, pressure on concentrate feed resources is increasing, especially in the tropics where many countries are net importers of food. Forage plants are a possible alternative, but their use as feed ingredients for pigs raises several issues related to their higher fibre and plant secondary metabolites contents as well as their lower nutritive value. In this paper, the nutritive value of several forage species and the parameters that influence this nutritive value in relationship to the plant family, the physiological stage, the plant part and the preservation method (fresh, hay and silage) are reviewed. The influence of the breed and the physiological status of the animal on animal voluntary intake of fibre-rich ingredients, digestibility as related to gastrointestinal volume and transit time and growth performances are also discussed. The final section highlights the advantages and drawbacks of forage plants in pig diets and stresses the need for proper economic evaluation to conclude on the benefits of the use of forage plants in pig feed.     

Hibernation in the tropics: lessons from a primate

The Malagasy primate Cheirogaleus medius hibernates in tree holes for 7 months, although ambient temperatures during hibernation rise above 30°C in their natural environment. In a field study we show that during hibernation the body temperature of most lemurs fluctuates between about 10°C and 30°C, closely tracking the diurnal fluctuations of ambient temperature passively. These lemurs do not interrupt hibernation by spontaneous arousals, previously thought to be obligatory for all mammalian hibernators. However, some lemurs hibernate in large trees, which provide better thermal insulation. Their body temperature fluctuates only little around 25°C, but they show regular arousals, as known from temperate and arctic hibernators. The results from this study demonstrate that maximum body temperature is a key factor necessitating the occurrence of arousals. Furthermore, we show that hibernation is not necessarily coupled to low body temperature and, therefore, low body temperature should no longer be included in the definition of hibernation.     

Dendroecology of Prosopis flexuosa woodlands in the Monte desert: Implications for their management

In the Monte desert of Argentina open woodlands of several species of Prosopis occur in areas with accessible underground water. The great latitudinal extent of the Monte (26–43°S) exhibits strong climatic gradients involving temperature, rainfall seasonality, and wind regime. Prosopis woodlands have been a source of subsistence for human communities for several centuries and continue to be exploited by the local inhabitants. The “mining” of this resource has led to severe desertification and consequent impoverishment of the local people. In order to suggest strategies for the better management and recuperation of these woodlands we studied the population structure and productivity of Prosopis flexuosa from multiple plots at Pipanaco (27°58′S), Telteca (32°20′S), and Ñacuñán (34°03′S). For each plot we measured the density of P. flexuosa trees, number of stems, basal diameter (DAB), height and canopy diameter of each tree. Tree ring data were used to determine the growth rates, annual wood production and biological rotation age for each area. The ecological structure of the woodlands differs between the three sites. Along this north–south transect, there is a decrease in adult tree density, mean basal diameter, mean tree height, canopy cover, productivity and total wood biomass. Consequently, the potential sustainable use of these woodlands varies. Only the northern, Pipanaco, woodlands have the potential for lumber production. In contrast, the short, multi-stem and low-productivity trees in the Telteca and Ñacuñán areas can only sustain a combination of local firewood production and activities such as extensive grazing by livestock. The present, uniform regulations for harvesting wood in these areas must be changed to acknowledge these differences in order to optimize wood production in, and conservation of, these woodlands.     

Ancient DNA and the tropics: a rodent's tale

Most genetic studies of Holocene fauna have been performed with ancient samples from dry and cold regions, in which preservation of fossils is facilitated and molecular damage is reduced. Ancient DNA work from tropical regions has been precluded owing to factors that limit DNA preservation (e.g. temperature, hydrolytic damage). We analysed ancient DNA from rodent jawbones identified as Ototylomys phyllotis, found in Holocene and Late Pleistocene stratigraphic layers from Loltún, a humid tropical cave located in the Yucatan peninsula. We extracted DNA and amplified six short overlapping fragments of the cytochrome b gene, totalling 666 bp, which represents an unprecedented success considering tropical ancient DNA samples. We performed genetic, phylogenetic and divergence time analyses, combining sequences from ancient and modern O. phyllotis, in order to assess the ancestry of the Loltún samples. Results show that all ancient samples fall into a unique clade that diverged prior to the divergence of the modern O. phyllotis, supporting it as a distinct Pleistocene form of the Ototylomys genus. Hence, this rodent''s tale suggests that the sister group to modern O. phyllotis arose during the Miocene–Pliocene, diversified during the Pleistocene and went extinct in the Holocene.     

Dendroecology of Prosopis flexuosa woodlands in the Monte desert: Implications for their management

In the Monte desert of Argentina open woodlands of several species of Prosopis occur in areas with accessible underground water. The great latitudinal extent of the Monte (26–43°S) exhibits strong climatic gradients involving temperature, rainfall seasonality, and wind regime. Prosopis woodlands have been a source of subsistence for human communities for several centuries and continue to be exploited by the local inhabitants. The “mining” of this resource has led to severe desertification and consequent impoverishment of the local people. In order to suggest strategies for the better management and recuperation of these woodlands we studied the population structure and productivity of Prosopis flexuosa from multiple plots at Pipanaco (27°58′S), Telteca (32°20′S), and Ñacuñán (34°03′S). For each plot we measured the density of P. flexuosa trees, number of stems, basal diameter (DAB), height and canopy diameter of each tree. Tree ring data were used to determine the growth rates, annual wood production and biological rotation age for each area. The ecological structure of the woodlands differs between the three sites. Along this north–south transect, there is a decrease in adult tree density, mean basal diameter, mean tree height, canopy cover, productivity and total wood biomass. Consequently, the potential sustainable use of these woodlands varies. Only the northern, Pipanaco, woodlands have the potential for lumber production. In contrast, the short, multi-stem and low-productivity trees in the Telteca and Ñacuñán areas can only sustain a combination of local firewood production and activities such as extensive grazing by livestock. The present, uniform regulations for harvesting wood in these areas must be changed to acknowledge these differences in order to optimize wood production in, and conservation of, these woodlands.     

The importance of grasslands for animal production and other functions: a review on management and methodological progress in the tropics

The global importance of grasslands is indicated by their extent; they comprise some 26% of total land area and 80% of agriculturally productive land. The majority of grasslands are located in tropical developing countries where they are particularly important to the livelihoods of some one billion poor peoples. Grasslands clearly provide the feed base for grazing livestock and thus numerous high-quality foods, but such livestock also provide products such as fertilizer, transport, traction, fibre and leather. In addition, grasslands provide important services and roles including as water catchments, biodiversity reserves, for cultural and recreational needs, and potentially a carbon sink to alleviate greenhouse gas emissions. Inevitably, such functions may conflict with management for production of livestock products. Much of the increasing global demand for meat and milk, particularly from developing countries, will have to be supplied from grassland ecosystems, and this will provide difficult challenges. Increased production of meat and milk generally requires increased intake of metabolizable energy, and thus increased voluntary intake and/or digestibility of diets selected by grazing animals. These will require more widespread and effective application of improved management. Strategies to improve productivity include fertilizer application, grazing management, greater use of crop by-products, legumes and supplements and manipulation of stocking rate and herbage allowance. However, it is often difficult to predict the efficiency and cost-effectiveness of such strategies, particularly in tropical developing country production systems. Evaluation and on-going adjustment of grazing systems require appropriate and reliable assessment criteria, but these are often lacking. A number of emerging technologies may contribute to timely low-cost acquisition of quantitative information to better understand the soil-pasture-animal interactions and animal management in grassland systems. Development of remote imaging of vegetation, global positioning technology, improved diet markers, near IR spectroscopy and modelling provide improved tools for knowledge-based decisions on the productivity constraints of grazing animals. Individual electronic identification of animals offers opportunities for precision management on an individual animal basis for improved productivity. Improved outcomes in the form of livestock products, services and/or other outcomes from grasslands should be possible, but clearly a diversity of solutions are needed for the vast range of environments and social circumstances of global grasslands.     

Beyond the tropics: forest structure in a temperate forest mapped plot

Question: How do the diversity, size structure, and spatial pattern of woody species in a temperate (Mediterranean climate) forest compare to temperate and tropical forests? Location: Mixed evergreen coastal forest in the Santa Cruz Mountains, California, USA. Methods: We mapped, tagged, identified, and measured all woody stems (≥1 cm diameter) in a 6‐ha forest plot, following Center for Tropical Forest Science protocols. We compared patterns to those found in 14 tropical and 12 temperate forest plots. Results: The forest is dominated by Douglas‐fir (Pseudotsuga menziesii) and three species of Fagaceae (Quercus agrifolia, Q. parvula var. shrevei, and Lithocarpus densiflorus), and includes 31 woody species and 8180 individuals. Much of the diversity was in small‐diameter shrubs, treelets, and vines that have not been included in most other temperate forest plots because stems <5‐cm diameter had been excluded from study. The density of woody stems (1363 stems ha^?1) was lower than that in all but one tropical plot. The density of large trees (diameter ≥30 cm) and basal area were higher than in any tropical plot. Stem density and basal area were similar to most other temperate plots, but were less than in low‐diversity conifer forests. Rare species were strongly aggregated, with the degree of aggregation decreasing with abundance so that the most common species were significantly more regular than random. Conclusions: The patterns raise questions about differences in structure and dynamics between tropical and temperate forests; these need to be confirmed with additional temperate zone mapped plots that include small‐diameter individuals.     

Mobile organisms in a geologically complex area: Lepidoptera in the Indo-Australian tropics

The Indo-Australian tropical archipelagos have increased in extent and proximity through the Tertiary whilst also changing their configuration. The development of new land areas between old cratonic ones involves extensive dispersals of plants and animals from the latter to the former. The vicariance approach, though suited to the study of the fragmentation of old, cratonic land areas, is of uncertain value in this situation; the representation of emergence or convergence and fusion of land areas in cladogram form presents immense problems and to attempt it may be pointless.
Distribution of Lepidoptera species largely reflects the present day geography of the area for both lowland and montane habitats. Significant discordances at a higher taxonomic level can be examined in the light of hypotheses of past geography such as those concerning the evolution of the Melanesian Arcs.
There are many advantages and some disadvantages in using Lepidoptera for such studies, involving their taxonomy, completeness of geographical coverage, range of dispersal ability and specificity to environmental conditions. Both cladistic and phenetic methods can provide basic data for biogeographic studies. The importance of an understanding of habitat preferences is stressed.
Patterns of probable recent development involving well-defined groups of very similar species are examined in the hope they will provide a yardstick whereby potentially older patterns can be assessed, and lead in time to methodology that will satisfy the stringent requirements of current thinking in the philosophy of science.     

Dendrochronology in the dry tropics: the Ethiopian case

Dendrochronology is developing outside temperate and boreal regions. Over the past decade substantial progress has been made in Mediterranean and wet tropical regions. However, research in dry tropical regions, notably those of sub-Saharan Africa, has remained fragmentary. Here, we try to identify the unique challenges and opportunities of dendrochronology in the dry tropics. First, we briefly review the status of dendrochronology outside temperate and boreal regions with an emphasis on sub-Saharan Africa. Subsequently, we focus upon one of those areas where dendrochronology in the dry tropics is at the forefront of scientific advance: Ethiopia. A detailed review of tree ring studies in the lowlands and highlands highlights the complexity of ring formation and made us identify four major types of growth ring expression: anatomically not distinct rings, multiple rings per year, annual rings and multiple missing rings. This complex tree growth behaviour is associated with large-scale variations in precipitation regime (unimodal to multimodal) and relatively small-scale variations in tree sensitivity to water availability. Literature results are used to develop a scheme that can be used to predict differences in growth ring formation along gradients in these two factors. Because of the exceptional growth sensitivity of and the importance of local site conditions (topography, biological factors, etc.) for most trees sampled, those growing at the limits of their ecological amplitude are prone to possess multiple rings per year or multiple missing rings. In such circumstances, site selection should not always take place at the limits of the ecological amplitude of a species, but may sometimes have to be diverted to more mesic environments. Successful studies are now appearing, such as those reporting correlations between tree ring chronologies and Blue Nile river flows.     

Early intensification of backyard poultry systems in the tropics: a case study

Poultry production is an important way of enhancing the livelihoods of rural populations, especially in low- and middle-income countries (LMICs). As poultry production in LMICs remains dominated by backyard systems with low inputs and low outputs, considerable yield gaps exist. Intensification can increase poultry productivity, production and income. This process is relatively recent in LMICs compared to high-income countries. The management practices and the constraints faced by smallholders trying to scale-up their production, in the early stages of intensification, are poorly understood and described. We thus investigated the features of the small-scale commercial chicken sector in a rural area distant from major production centres. We surveyed 111 commercial chicken farms in Kenya in 2016. We targeted farms that sell the majority of their production, owning at least 50 chickens, partly or wholly confined and provided with feeds. We developed a typology of semi-intensive farms. Farms were found mainly to raise dual-purpose chickens of local and improved breeds, in association with crops and were not specialized in any single product or market. We identified four types of semi-intensive farms that were characterized based on two groups of variables related to intensification and accessibility: (i) remote, small-scale old farms, with small flocks, growing a lot of their own feed; (ii) medium-scale, old farms with a larger flock and well located in relation to markets and (iii) large-scale recently established farms, with large flocks, (iii-a) well located and buying chicks from third-party providers and (iii-b) remotely located and hatching their own chicks. The semi-intensive farms we surveyed were highly heterogeneous in terms of size, age, accessibility, management, opportunities and challenges. Farm location affects market access and influences the opportunities available to farmers, resulting in further diversity in farm profiles. The future of these semi-intensive farms could be compromised by several factors, including the competition with large-scale intensive farmers and with importations. Our study suggests that intensification trajectories in rural areas of LMICs are potentially complex, diverse and non-linear. A better understanding of intensification trajectories should, however, be based on longitudinal data. This could, in turn, help designing interventions to support small-scale farmers.     

Plant reproductive intervals and pollinators in the aseasonal tropics: a new model

What factors determine reproductive intervals and modes of pollination in plants of the aseasonal tropics? To answer this general question, we present a new explanation for some community patterns of plant reproductive intervals and pollinators observed in a lowland dipterocarp forest in Sarawak, Malaysia, using a mathematical model featuring different display effects for different types of pollinators. Predictions from the model matched with the following observed patterns: (i) flowering intervals were different among forest strata (forest floor < understorey < canopy < subcanopy and emergent), and not in the exact order of stratum height; (ii) among generalist pollinators, the proportion of social foragers was maximum in intermediate forest stratum; and (iii) plants pollinated by specialist pollinators were found on the forest floor and in gaps.