Alternative animal feed protein sources: faba beans, lentils
Minor legumes are an attractive proposition in times when soybean meal prices skyrocket, but these feed ingredients do not come without their own problems that restrict use in poultry and pig diets.
Faba beans (Vicia faba) is a legume related to the garden beans (those beans consumed by humans). There are two major types of faba beans: those from white-flower varieties and those from colored-flower varieties. Their chemical composition and nutritive value is about the same, but the colored-flower varieties contain more tannins.
Tannins (usually about 0.3 to 0.5 percent in faba beans) reduce animal feed intake and depress digestibility of protein and energy. Other major anti-nutritional factors in faba beans include trypsin inhibitors (but, 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 necessary the use of raw faba beans in limited levels in diets for poultry and pigs. The maximum level below which problems are few is around 10-15, depending on faba bean variety, and animal species and age.
Pig, poultry diets
In diets for young pigs, for example, this level should be no more than 5 percent. In contrast, it is possible to feed up to 20 percent faba beans in diets for finishing pigs, but if the faba beans are from colored-flower varieties, feed intake will be reduced. Feeding high levels of faba beans creates a large volume of gastrointestinal gases that cause constipation in lactating and gestating sows.
In general, faba beans should be introduced gradually in pig diets starting from 5 percent and not exceeding 20 percent. For poultry, beans are of limited value due to their extremely low concentration methionine and cystine, but otherwise, they can be used at levels not exceeding 5-10 percent.
Lentils ( Lens culinary ) become occasionally available to the animal feed industry, especially when they suffer from quality problems (such as frost damage, discoloration, or seed damage). Nevertheless, these issues do not pose any problems when such lentils are fed to pigs and poultry of all ages.
Care should be taken when using lentils: the diets should be balanced on digestible and not total amino acids because not all crude protein in lentils is true protein – lentils contain about 7 percent non-protein nitrogen!
The major anti-nutritional factor in lentils is protease inhibitors, but this is not present in sufficient quantities to depress animal performance. Thus, up to 30 percent raw lentils have been used with success in pig diets, as shown in Table 1 . In diets for very young pigs it is always prudent to use conservative levels, starting at no more than 10 percent in high-quality formulations.
For poultry, a 10 percent maximum inclusion rate is suggested, unless lentils are decorticated. In layer diets, addition of lentils has had limited success, even in limited amounts, possibly due to the lack of taking into account the issues with protein quality and low levels of sulfur-containing amino acids.