Koronivia grass (Brachiaria humidicola)

Brachiaria humidicola can be given as green forage, hay or silage (Cook et al., 2005). Like other Brachiaria, its relatively low protein content, usually lower than 10% DM, limits microbial digestion in the rumen and an association with legumes and other protein sources is therefore recommended (see Forage management above). Urea supplementation of 3 and 6% (Rodriguez-Romero et al., 2004) or ammoniation also improved the nutritive value of koronivia grass-based diets (Barrios-Urdaneta et al., 2002; Rodriguez-Prado et al., 2009).

In spite of this limitation, Brachiaria humidicola is a good forage that compares favourably with other tropical grasses (Aregheore et al., 2006 ; Aumont et al., 1995). Brachiaria humidicola is generally considered as of lower quality than other Brachiaria species such as Brachiaria decumbens, Brachiaria brizantha and Brachiaria ruziziensis (Cook et al., 2005). Studies agree that its fibre content is slightly higher but are less conclusive for in vitro and in situ digestibility, which while usually lower, are in some cases higher than that of other Brachiaria (Aumont et al., 1995; Brito et al., 2003; Herrero et al., 2001; Lopes et al., 2010).

Ingestibility, palatability and grazing behaviour

Brachiaria humidicola is less palatable than other grasses due to the relative toughness of its leaves, but cattle readily eat it when it is kept short and leafy by frequent cutting (Béreau, 1990; Cook et al., 2005). Koronivia grass is appreciated by sheep (Artus-Poliakoff et al., 1991). Cattle tend to ingest parts of Brachiaria humidicola that are richer in leaf and poorer in stem and dead materials, and therefore of higher nutritive value (Camarao et al., 1994; Pereira et al., 1992). One particularity of koronivia grass is that plants growing on acid-infertile soils develop hard, sharp and fibrous leaf blades that are strongly pigmented with anthocyanin. Those fibrous leaves decrease palatability and may also hurt the animals (see Potential constraints above) (Cook et al., 2005).

Digestibility and energy values

There are no direct in vivo digestibility values reported for Brachiaria humidicola. Using the quadratic equation:

obtained on all Brachiaria species for in vivo and in vitro digestibility, the OM digestibilities for the 3 stages of growth described in table 1 (vegetative, bloom and mature) can be calculated as 56, 47 and 42% respectively. This corresponds to ME values of 8.0, 6.5 and 5.7 MJ/kg DM (Sauvant, 2011, unpublished). Another estimate obtained by the gas production method gave an OM digestibility of 40% and an ME of 5.9 MJ/kg (Nogueira Filho et al., 2000). These values are rather low, but actual energy values may be higher since cattle seem to choose the leafiest and most digestible parts of the plant (Moura et al., 2002; Camarao et al., 1994). Reported in situ 48 h DM digestibility values were highly variable and comprised between 49 and 71%. They were affected positively by applications of fertilizer (Jimenez et al., 2010). Effective degradability values for DM and crude protein were 38 and 46% respectively (Lopes et al., 2010). Effective DM and crude protein degradability depended on the season but not on the age at cutting (Vergara-Lopez et al., 2006).

Dairy cattle

There is scant literature on the use of Brachiaria humidicola for dairy cattle. One paper noted that native koronivia grass pastures were less efficient than Guinea grass (Megathyrsus maximus) for sustaining milk production in an intensive rotational grazing system (Goncalves et al., 2003).

Beef cattle

Most of the literature on Brachiaria humidicola refers to its use in beef cattle production. Many studies concern the effects of stocking rates while other concern legume associations.

Effect of stocking rates

The influence of stocking rate depends on the season. Common stocking rates are 3-3.5 head/ha during the rainy season and 1-1.5 head/ha during the dry season (Munoz, 1985; Béreau, 1990).

Table 2. Effect of stocking rates on growth performances:

In several trials, increasing the stocking rates led to lower daily gains but to a higher productivity per hectare (Boddey et al., 2004; Pereira et al., 2009). A statistical treatment of the published data on koronivia grass pasture (19 experiments and 20 treatments) has shown that a mean increase of 1 animal/ha induces a mean decrease in live-weight gain of 0.070 ± 0.014 kg/d and a mean increase of 58.5 ± 23.1 kg/ha/yr (Sauvant, 2011, unpublished). However, higher stocking rates can lead to higher N losses as urine and feces which may concentrate in rest and drinking areas, and contribute to the degradation of the pastures (Boddey et al., 2004).

Effect of legume association

The association of legumes with koronivia grass is generally beneficial to animal performances, but this is not always the case as shown in the following table.

Table 3. Effect of legumes grown with koronivia grass on growth performances (adapted from Cook et al., 2005):

In an eight-year trial in Brazil, the association of Brachiaria humidicola and Desmodium ovalifolium at three stocking rates showed that live weight gain was not greater for the mixed pastures. There was a slightly lower forage intake in the mixed grass/legume pastures that increased the protein content of the diet due to the presence of the legume, but further investigation showed that the animals benefited only marginally. This may be due to the high polyphenol and tannin content of the legume which renders much of the N unavailable for microbial degradation (Pereira et al., 2009).

Sheep

Stocking rates of 13-14 head/ha were found to be optimal for the productive performance of tropical 5-7 months old Morada Nova lambs continuously grazing Brachiaria humidicola (Costa et al., 2006).