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

Abstract

<jats:p>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.</jats:p>

A meta-analysis of nutrient intake, feed efficiency and performance in cattle grazing on tropical grasslands

“…Thus, in addition to the SR impact, we only recorded a tendency to increase ADG by using a mixture of grass and legumes rather than grass alone. Although this trend was not significant, it was consistent with the results of published studies that specifically addressed these strategies (Dixon and Coates, 2008;Boval and Dixon, 2012).…”

“…The inverse of this expression of SR represents, in fact, the herbage allowance per unit of animal (kg forage per kg BW). In addition, the evolution of ADG with the herbage allowance highlighted here provides a good explanation of the variations in forage intake by grazing ruminants, as calculated previously (Sollenberger and Vanzant, 2011;Boval and Dixon, 2012).…”

“…Current farming systems must balance agro-ecological services and enhancement of biodiversity while reducing inputs and controlling output of greenhouse gases to be truly multifunctional. Thus, grassland-based systems provide many benefits that must be considered in the balance of the cost equation for production efficiency (Boval and Dixon, 2012;O'Mara, 2012).…”

A glimpse of the future in animal nutrition science. 1. Past and future challenges

“…As a result, grazing ruminants provide the most viable food production source in that region (Steiner et al, 2014). There are similarly marginal lands, encompassing nearly 26% of the world's surface, whether in arid and semi-arid climates, that have challenging topography, short growing seasons, or unstable soils where only ruminants can convert sparse, sporadic vegetation into food that humans can consume (Boval and Dixon, 2012). These lands (rangelands and grasslands) also provide an array of ecosystem services such as food, fiber, water, recreation, minerals, and medicinal plants for both rural and urban populations (Havstad et al, 2007) and are a major store of soil organic C (10 to 30% of global stock) (Scurlock and Hall, 1998).…”

“…Although small ruminants (e.g., sheep and goats) have lower conversion efficiency (feed to meat and milk) than dairy and beef cattle, raising them in non-arable, arid and semi-arid, and mountainous regions is important to provide animal products to the population of many developing countries. Without the unique ruminant digestive system to convert fibrous grasses and forbs into energy and protein, nearly a billion humans who inhabit these regions would face even greater food challenges (Boval and Dixon, 2012).…”