Eragrostis curvula is generally considered to be a poor forage for grazing livestock and its main advantages are its agronomic characteristics, such as its relatively low seeding cost, ease of establishment, high productivity and drought tolerance (Torell et al., 2000).
Digestibility and intake
DM digestibility of fresh or dry Eragrostis curvula forage is relatively low and varies between 43 and 60% (Marchi et al., 1973a; Castro et al., 1984; Snyman, 1991). In an experiment in Argentina, chopped (and dusty) hay was found to be much less digestible than whole hay (by 15 percentage points). Urea fertilizer increased forage yield; DM intake and digestibility were slightly improved (Marchi et al., 1973a). In situ DM degradabililty was lower for Eragrostis curvula than for Guinea grass (Megathyrsus maximus) and golden millet (Setaria sphacelata) (Vieyra et al., 1995). However, it has been suggested that those poor results are often obtained on mature, frosted and senesced forage, and that a more appropriate management system could result in higher nutritive values (Johnston, 1989).
Eragrostis curvula is not a very palatable species, though it may be more palatable to sheep than to cattle, according to a study in Zimbabwe (Mills, 1977). Some palatable and some unpalatable accessions have also been identified in Australia. What reduces palatability is unclear since it is not correlated with high fibre, low protein or low in vitro digestibility (Johnston, 1989). In Japan, Eragrostis curvula was among the least preferred, by cattle, of 10 winter winter pasture species (Nada, 1985), and in South Africa, of 18 subtropical grasses and legumes (Grunow et al., 1978). In the Argentine Pampas, semi-arid species such as Pennisetum orientale and Panicum virgatum were preferred to Eragrostis curvula in the spring and summer seasons (Rabotnikof et al., 2005). In South Africa, similar results have been obtained with sheep. In Natal, it was one of the least acceptable of 7 grasses, due to its structure and leaf quality, as animals preferred species that were short, not stemmy, with leaves of low DM, low tensile strength, and high protein content (O'Reagain, 1993). It was also less preferred than Digitaria eriantha, with no effect of fertilizer level and stage of maturity (Dannhauser et al., 1986). However, another trial ranked the palatability of Eragrostis curvula, Eragrostis racemosa and Eragrostis capensis as intermediate for sheep (Barnes et al., 1992).
Eragrostis curvula is used in extensive beef production, but the performance of animals grazing it has been variable. It does well when compared to low-productive native grass: in Mexico, beef cattle grazing Eragrostis curvula had better performance than those grazing native grass (0.6 vs. 0.45 kg/d; 0.3 vs. 0.1 kg/d; 0.7 vs. 0.5 kg/d for heifers, lactating cows and calves respectively), which was due to the much higher (400%) forage productivity of Eragrostis (Esqueda et al., 2001). Other trials have been disappointing. In South Africa, trials in the early 1970s did not turn well, as beef cattle grazing Eragrostis curvula did not have good performance, probably due to a lack of knowledge at that time regarding its nutrional value and the amount of supplementation required (Rethman et al., 1977b). A large scale trial in New Mexico in the 1990s concluded that grazing Eragrostis curvula pastures did not appear to be an economically viable alternative, as the average daily gain of yearlings declined rapidly as the grazing season progressed, from 1.36 kg/d in May to less than 0.45 kg/d by the end of August (Torell et al., 2000).
Supplementation has been the key to better performance. In Argentina, supplementation of Eragrostis curvula hay with a mixture of oats and sunflower meal promoted more gain in Angus calves (516 g/d) than oats alone, which resulted in weight loss. The energy brought by oats alone was not enough to overcome the low protein content of the hay (Arelovich et al., 1992). In Argentina, sowing Eragrostis curvula with a legume (Melilotus officinalis) increased the average daily gain of 200 kg steers from 346 to 585 g/d and the number of grazing days from 1469 to 1763 (Cairnie, 1988). Large round bales were a good method of preserving Eragrostis curvula hay to feed 20-month-old steers and a proposed supplement was 1 kg broken maize + 0.05 kg urea/d (Giraudo et al., 1986).
In South Africa, Eragrostis curvula hay gave better weight gains and nitrogen retention in lambs than maize stover (both forages being milled and treated with 2% urea) (Snyman, 1991). Supplementating Eragrostis curvula hay with a legume forage (tree lucerne Chamaecytisus palmensis) improved OM and cellulose digestibility, rumen ammonia levels and intake (the latter for low and medium quality hays) (Niekerk et al., 1995; Niekerk et al., 1996). Experiments with abomasal administration of casein, which increased intake, average daily gain, wool growth, non-ammonia N flow to the abomasum and N-retention, suggest that essential amino acids, rather than energy, are limiting with such a poor-quality forage (Meissner et al., 1989b).
Several trials have compared Eragrostis curvula and alfalfa for sheep farming. In Australia, both forages were able to sustain high stocking rates for lengthy periods in spring and summer (more than 12 head/ha). While sheep grazing alfalfa tended to be heavier with more wool, alfalfa was more difficult to establish and costs for weed and insect control were higher. It was concluded that Eragrostis curvula has a complimentary role to alfalfa for sowing on landscapes and in situations to which alfalfa is poorly adapted (Johnston et al., 2005b). As weeping love grass was more productive in summer and autumn than alfalfa, using it for grazing strategies such as rotational grazing would help to improve management flexibility for common perennial pastures such as alfalfa (Johnston et al., 2005a).