Forage is any plant including browse, herbage and mast that are mass harvested for feeding livestock and for better management of the environment (Stür and Horne 2001, Barnes et al. 2007). It also includes live grasses and legumes grazed directly by grazing animals (Grimaud et al. 2006), as well as cut-and-carry biomass and other forage such as hay, leaves, shredded sugarcane, chopped maize cobs, and dried cassava chips. Perennial grasses and some of the annual grasses are preferred by cattle (Kassahum et al. 2008).
Currently there is severe loss of plant communities, including forage for livestock, which has led to poor sustainable development of livestock (ILRI 2008d). Considering the growth of high demand of animal products especially meat, milk, and milk-derived
products in the next decades, there is a need of forage options capable of meeting high quality and biomass to increase livestock production (CIAT 2001). The latter propose a replacement of indigenous with exotic forage species, which are adapted to the local environment and give high nutritional value. According to Cain et al. (2007), in Pakistan dairy cows need a high quality and quantity of fodder in order to meet the requirement of milk production. Studies on animal feeding indicate that forage of 70% digestibility leads to feed intake of 3.3% of body weight of a ruminant and is able to increase milk production in kilograms up to ten times of its feeds intake (Waldo and Jorgensen 1981).
This shows that forages are important feed resources in the world and grasses are the main feed for livestock ruminants (Holmes 1989). In the tropics, a good pasture species should have high yields of good quality, good persistence, should be easy to propagate and should have the ability to grow with a companion crop, especially a crop legume (McDowell 1972). Even if natural pasture species exist, they can be replaced by selected sown pasture species or might have other improved pastures grown with the natural pasture species (Humphreys 1987). Cultivated pasture should meet the following criteria:
increase quality forage; produce high quality green forage; increase the level of animal production per unit area of land; provide hay for drought periods and provide forage throughout the year (Aucamp 2000). These characteristics of fodder crops can reduce the need for feed supplements, and raise the potential for lager herds (Rivingston et al. 2007).
In many tropical regions, pastures are grown on infertile soils that are not suited to food crops and this leads to low forage yield for livestock (Humphreys 1987). In southern and eastern Australia where dry-land salinity is becoming a threat to the agriculture, O‟Connell et al. (2006), indicated that pastures tolerant of salinity could help farmers to increase agricultural productivity in these areas. Forage can be utilised as a feed resource for livestock and play an important role in maintaining the natural resource base. For example, in western Australia, Medicago sativa (Lucerne) has been used in crop rotation to reduce the invasion of weeds in cropping land (Doole and Pannell 2008). In southern Australia, a range of forage grown for non-irrigated farms helped farmers to feed dairy cows year-round and could be a reserve during the period of feed shortage (Chapman et al. 2008). It is important for farmers to exploit the synergy between crop and livestock production in order to minimise the dependence on external inputs and to enhance the
overall productivity of the system (Peters et al. 2003). Research on animal nutrition found that the better the supply of energy in animals‟ diet the more they increased production (Roothaert et al. 2003). The latter authors confirmed that in the Philippines only a few farmers could succeed in satisfying the needs of their animals because they planted enough legumes for optimal production. In developing countries, most animal feeds are collected from different indigenous or introduced tropical pasture species. These indigenous pastures may have low nutritive value and lead to low livestock productivity and then hamper the sustainability of livestock production (CIAT 2007b). To overcome this problem in Mexico, farmers developed a forage seed company, for multiplying and commercialising the first hybrid Brachiaria cultivar Mulato. Its prime attributes were high yield and feed quality. However, its commercial success was limited by its low seed yield potential (Miles et al. 2004). A second hybrid Brachiaria cultivar Mulato II was released to the commercial market in 2005. Cultivar Mulato II has better spittlebug resistance than Mulato and is more drought tolerant but also had low seed yield. The limited seed availability of Mulato II in 2005 has been overcome and seed is commercially available in most countries of Latin America (Miles et al. 2007). Many other Brachiaria hybrids kept at CIAT‟s forage programme (e.g. Hybrid Bro2/0465, Hybrid Bro2/1485, hybrid Bro2/1452) are still under testing and their literature is limited.
Their agronomic aspects are evaluated in different places in southern America, south Asia and Africa on small plots and on large-scale trial for animal production (Hayward 1999).
The interest and success of the adoption of the Brachiaria hybrids were due to their resistance to abiotic and biotic stress conditions (e.g. drought and diseases respectively).
These new grasses were spread in Latin America and far away in the world like New Caledonia, Vanuatu and Thailand (CIAT 2007c). The latter author reported that farmers compared their indigenous grasses with the new grasses by feeding their animals and found that the new grasses were able to increase beef and milk production much more than the indigenous grasses. In addition to feeding animals, the forage species can generate income for farmers if sold for forage seed or forage biomass for animals (CIAT 2007c). Other benefits are the increase in agricultural productivity by maintaining
soil fertility, reducing the need for deforestation, erosion control and mitigating climate change (Peters 2008).
2.7 Availability of feed resources