As with other Brachiaria species, Brachiaria brizantha is of high nutritive value. In countries where Brachiaria spp. has been well managed as a forage crop, standard agronomic practices have resulted in very impressive animal performance (Urio et al., 1988).
Nutritive values
The mean in vivo organic matter digestibility (OMD) obtained on 25 samples of Brachiaria species was 57.8 ± 9.2% (range 40-77%). It corresponds to a ME content of 8.0 ± 1.7 MJ/kg DM (range 4.6-11.7). Addition of fertilizer may also have an effect on chemical composition and nutritive value as shown in the table below.
Effect of nitrogen application on yield, crude protein content, and in vitro degradability of Brachiaria brizantha in Tanzania (Fredericksen et al., 1980)
|
N level (kg/ha) |
Yield (t DM/ha) |
Crude protein (% DM) |
In vitro OM degradability % |
|
0 |
2.85 |
5.7 |
51.5 |
|
62.5 |
6.0 |
5.0 |
54.0 |
|
125 |
8.25 |
6.4 |
56.5 |
|
187.5 |
9.0 |
6.8 |
55.0 |
Pasture
Brachiaria brizantha is well accepted by grazing livestock. It is considered to be slightly more palatable than Brachiaria decumbens though slightly less digestible. Most of the trials have been carried out in Brazil.
Cattle
Frequent light grazing of Brachiaria brizantha results in a high proportion of nutritious leaf material in the diet of cattle (Trindade et al., 2007). Reduced grazing time may be compensated by higher bite rates to regulate total forage intake (Zanine et al., 2007). A low herbage allowance (5 kg herbage /100 kg live weight) is advisable for cattle grazing Brachiaria brizantha in a rotational grazing system, since the sward is sensitive to overgrazing (Braga et al., 2006).
An experiment with steers grazing Brachiaria brizantha showed that the intake rate (IR, g DM/min), which is a major determinant of daily DM intake, was positively influenced by the proportion of green leaves (GL, %), total forage mass (FMA, t/ha) and average sward height (SH, cm), but negatively affected by the NDF content of leaves (NDFL, % DM), as described by the following equation:
Growing and fattening cattle
Brachiaria brizantha can support variable growth rate, ranging from 290 kg/ha/year to 924 kg/ha/year, depending on the season, stocking rate or association with other crops, as shown in the table below.
Effect of season, crop association and stocking rate on production
In an agroforestry system of Costa Rica, Brachiaria brizantha sown under high (27% of the area), medium (14%) and low (7%) tree cover and grazed by Brahman heifers resulted in higher growth rate (+13-14%) under the heaviest cover. During the dry season, heifers under high tree cover lost less weight (Restrepo-Saenz et al., 2006).
Pasture supplementation
Response to concentrate supplementation during the dry season
Supplementing young grazing bulls with 0.5 kg/day of concentrate resulted in a better economic outcome but they did not achieve the appropriate slaughter weight (Brito et al., 2008). Increasing the level of concentrate in fattening crossbred Nelore steers grazing Brachiaria brizantha pasture had a positive influence on daily live weight gain. Supplementation is therefore technically and economically viable, with better results at a level of 0.76% of body weight (Baiao et al., 2005). With Santa Gertrudis and Simmental breeds the best results were obtained with a supplement of 0.125% live weight, with an efficiency rate of 1.62 (Goes et al., 2005a). Increasing the concentrate level up to 0.6% of live weight increased daily weight gains linearly, but the best economical return was obtained at 0.4% live weight (Leao et al., 2005). Maize and soybean meal supplementation (24% crude protein) provided higher values of weight gain at 0.5 and 1.0% live weight and higher efficiencies at 0.125 and 0.25% LW (Goes et al., 2005b).
Response to concentrate supplementation during the rainy season
Energy and protein supplementation during the rainy season results in a greater profit margin (Barbosa et al., 2008). In Nellore-Blonde d'Aquitaine crossbred steers, supplementation increased animal weight gain from 0.77 to 1.06 kg/day/animal (Fernandes et al., 2010).
Response to protein supplementation
Due to its low crude protein content, Brachiaria brizantha has to be supplemented with protein-rich concentrates or with urea. Supplementation with increasing urea levels showed a quadratic response to total DM intake and DM intake from pasture, with the best response at 1.6% urea (diet as fed) (Acedo et al., 2007). Weight gains of 0.5-0.6 kg/day could be obtained using only maize grain, urea and a mineral mix in multiple supplements for finishing beef cattle (Sales et al., 2008). Supplementation with protein sources provided viable economic returns, regardless of the protein source evaluated in relation to the control group (Porto et al., 2009).
Supplementation frequency
The supplementation frequency of steers on Brachiaria brizantha pasture did not affect the forage DM intake, total diet DM intake and DM degradability (Morais, 2009). Moreover, reducing supplementation frequency may decrease feeding and labour costs with no influence on steer performance during the dry season (Canesin et al., 2007; Goes et al., 2005a).
Dairy cattle
There are few published data on the use of Bracharia brizantha for milk production. Supplementation with an energy-protein concentrate in lactating cows fed with Bracharia brizantha during the beginning of the dry season was beneficial to the performance of calves and cows (Sampaio et al., 2010).
Silage
Cattle
Though Bracharia brizantha silage may result in low nutrient intake and thus lower animal performance, it may be a valuable alternative as a forage source in beef cattle diets. Its optimal use depends on the appropriate integration of pasture management and forage surplus conservation in the form of silage (Pereira et al., 2008).
A bread grass/sorghum silage ratio of 67:33 fed to Nelore steers resulted in similar intake and body weight gains compared to the diet containing only sorghum silage (Chizzotti et al., 2005).
Sheep
In 12-24 month Santa Ines sheep grazing Brachiara brizantha, average daily gain was greater with animals that also received Desmodium heterocarpon subsp. ovalifolium hay (Magalhaes et al., 2005).
Hay
Bread grass hay can be combined with tree foliage. Moringa (Moringa oleifera) foliage included as a protein supplement to bread grass hay-based diet fed to dairy cattle increased DM intake and digestibility of the diet as well as milk production without affecting milk composition (Sanchez et al., 2006).
