St Augustine grass is palatable when young but palatability and digestibility decrease with maturity (Cook et al., 2005). This decrease is not always significant and seems to be less marked than with other tropical species such as Para grass (Brachiaria mutica) (Coleman et al., 1978). St Augustine grass is a sodium accumulator (Stür et al., 1990) and it is, therefore, unnecessary to provide salt to the cattle grazing it. Because St Augustine grass can grow on very different soil types and under a wide range of edaphoclimatic conditions, the results concerning nutritive value are sometimes inconsistent (Mullen et al., 1996).
St Augustine should be grazed down to 6 cm every second week in order to keep palatability as high as possible (FAO, 2010).
Dry matter intake varies from to 45.0 g/kg LW0.75 in sheep to 85.8 g/kg LW0.75 in steers. Dry matter digestibility varies from 50% in sheep to 61% in steers (Samarakoon et al., 1990; Coleman et al., 1978).
Due to its low nitrogen content, animal production from pure St Augustine grass pastures is low but can be expected to improve when combined with herbaceous or tree legumes such as Desmodium incanum, Mimosa pudica, Vigna hosei, Leucaena leucocephala, Aeschynome americanum, Arachis pintoi, Calliandra calothyrsus or Stylosanthes scabra (Mullen et al., 1996; Stür et al., 1990). In Vanuatu, cattle grazing St Augustine grass/legume pastures reached a weight gain of 0.52 kg/head/day (Mullen, 2009).
In shaded conditions, St Augustine grass hay (dry chaff) has a higher feeding value than forages such as kikuyu grass (Pennisetum clandestinum) and should, therefore, be valuable in plantation agriculture. Shade increases the proportions of leaf in St Augustine grass (45% to 57%) and stem (4% to 11%) and decreases that of dead material. Voluntary intake is also increased in sheep from 45 to 54 g/kg LW0.75. Dry matter digestibility is not statistically increased (50% vs. 53 %), but shade increases the intake of digestible dry matter (19 to 22 g/kg LW0.75) in sheep (Samarakoon et al., 1990).
In tropical and subtropical areas where air humidity and rainfall during the primary growing season are too high, forages cannot be dried and conserved as hay. Dehydration at 148°C followed by pelleting has been proposed for St Augustine grass. Steers ingested more dehydrated forage than fresh (88 vs. 78 g OM/kg W0.75), but organic matter digestibility was lower (57% vs. 60%), resulting in similar digestible organic matter intakes. Mean retention time in the digestive tract did not differ between the two forms of forage (Coleman et al., 1978).