Wednesday, 4 July 2012

Grass for cows

Cows eat grass. So all you need to do is stick a cow in a field and let her get on with it, right? Well, more or less. It you are doing this commercially, you cannot just use any grass, you plant it like a crop, and the choice of grass is very important. It´s nutritional value, how well it grows in this soil, in this climate etc etc. The most important grass for cattle production in Brazil, and in the tropics generally, is Brachiaria, or rather various strains of the Brachiaria genus.

Brachiaria evolved on the savannas of Africa. Some probably came over with the Portuguese, but it was first introduced on a commercial scale in the 1950s. First B. decumbens  in 1952 and later  B. ruziziensis in the 1960’s. It´s hard to be sure, but there might now be up to 80 milion hectares of Brachiaria grassland in Brazil. Brazil is the largest producer of Brachiaraia seeds in the Americas, although production and sales in Mexico and other countries are increasing rapidly.

Brachiaria grows incredibly quickly, up to a metre high. It can also tolerate drier conditions, more acidity and more light than most plants, giving nutritious grass on soils normally described as infertile. Most Brazilian pastures aren't fetilised so this can be important.

The problem with a crop that grows everywhere is that it DOES grow everywhere, from flooded Amazon pastures to savanna to the cerrado, and given half a chance will swamp native species. It can also swamp legumes in the pasture that might fertilise the soil. Conversely, it is very good for the local froghopper insects, who can eat so much it doesn't leave enough for the cows.

Also, rather unfortunately for a forage crop, it can poisonous. For some reason, certain individual animals can get sick and even die if they eat too much. Some individuals are more susceptible than others, and sheep are more susceptible than cows, but it is rare. The varieties that cause problems also tend to be the ones that survive best on poor soil. On the other hand, these varieties function well for the other use of Brachiaria, for erosion control by roads, railways and electricity lines.

1 comment:

Anonymous said...

Sounds complicate something apparently simple!