A meta-analysis was conducted to compare effects of C4 and C3 grasses as well as warm and cold climate legumes on CH 4 production of ruminants. For this purpose, a database was built using 22 in vivo studies containing 112 observations with 58 C3 grasses, 28 C4 grasses, 26 cold legumes and 12 warm legumes. Neutral detergent fibre (NDF), crude protein (CP) and total tract organic matter (OM) digestibility ranged from 415 to 753 g/kg DM versus 361 to 754 g/kg DM, from 24 to 254 g/kg DM versus 44 to 314 g/kg DM and from 0.51 to 0.71 versus 0.56 to 0.83 for C4 and C3 grasses, respectively. The NDF, CP and total tract OM digestibility ranged from 441 to 690 g/kg DM versus 252 to 684 g/kg DM, from 93 to 236 g/kg DM versus 141 to 269 g/kg DM and from 0.42 to 0.57 versus 0.38 to 0.79 for warm and cold legumes, respectively. Relationships between CH 4 production and forage characteristics were analysed by analysis of covariance. For grasses, the main factors tested as fixed effects were NDF and CP content of the diet, total tract OM digestibility, intake, animal species, forage family and random trial effect. For legumes, tannin level was included in the model. Results indicate that ruminants fed C4 grass produced 17% more CH 4 as L/kg OM intake (P<0.05) compared to those fed C3 grass. Animals fed warm legumes produced 20% less CH 4 (P<0.05) than those fed C4 grasses. In contrast, no difference in CH 4 production between C3 grasses and cold legumes. Use of some legumes in warm climates could be a strategy to reduce CH 4 emissions by ruminants.
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.
Topics discussed in this chapter include N and morphogenesis of tufted and of stoloniferous grasses, the effects on the development of leaf area index in both types of grasses, and the consequences for forage quality and grassland management. It is considered that the benefits of applying N to grasses, such as improvements in digestibility or nitrogen content may be cancelled out in stoloniferous grasses by the excessively high proportion of stems in the sward. Improving the nutritive value of stoloniferous species by selection for morphogenetic criteria is discussed. It is suggested that more rapid progress may be made by adapting N fertilizer practices, adjustment of stocking rates to herbage growth, and choosing the most appropriate date to cut or graze during the regrowth cycle.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.