The recent crisis of feedstuff prices has brought a lot of attention to otherwise obscure and neglected ingredients. I was recently contacted to offer advice concerning the use of fababeans in diets for pigs. Apparently, a low-quality lot had been offered at a very competitive price to a small pig producer and he wanted to maximize their use to reduce feed cost as much as possible.
We ended up running some analyses to determine actual levels of anti-nutritional factors, based on which we maximized the use of fababeans. From this experience, I would like to share below some general points on this minor yet very interesting legume.
Fababeans (Vicia faba) is a legume related to the garden beans (those beans consumed by humans). They contain about 26% crude protein and they are rich in lysine, but rather poor in methionine. Fababeans contain about 9 MJ NE/kg, which is rather low because their oil content is very low always below 1.5%), and the crude fiber concentration is rather elevated (above 7%).
There are two major types of fababeans: those from white-flower varieties and those from coloured flower varieties. Their chemical composition and nutritive value is about the same, but the coloured flower varieties contain more tannins.
Tannins (usally about 0.3 to 0.5%) reduce feed intake, and depress digestibility of protein and energy. Other major anti-nutritional factors in fababeans include trypsin inhibitors (at levels below those found in raw soybeans) and hemagglutinins (at levels many times those found in raw soybeans).
The presence of these anti-nutritional factors make it necessary to limit the use of raw fababeans in pigs’ diets. The maximum level above which problems start to appear is around 15%.
In diets for young pigs, a conservative approach calls for levels not exceeding 5-10%. Of course, it is possible to feed even more than 20% fababeans in diets for finishing pigs, but if the fababeans are from coloured-flower varieties, feed intake will be reduced. Feeding high levels of fababeans creates a large volume of gastrointestinal gases and this should be taken into account when they are fed to gestating and lactating sows.
I would be interested to read about your field experiences in using fababeans in pig diets!