As the world population continues to increase, food security on a global scale must become an even greater priority. Along with population growth, economic growth and the rise of the middle class in developing countries are expected to further increase demand for meat, milk, and eggs (FAO, 2009).The consumption of conventional feedstuffs like soybean, maize and sorghum by human being is undermining their availability to animals.The price of the conventional source of protein in livestock ration has risen due to competition between man and livestock thus, there is a big challenge of matching available feedstuff supplies with animal needs.Hence, the world is becoming increasingly aware of the looming food insecurity, the possibility of raising animal on unconventional but easily sourced and available feedstuffs in the tropics and subtropics deserves more attention (Belewu et al., 2009).
The primary constraint to livestock production in developing countries is the scarcity and fluctuating quantity and quality of the feed supply.The seed of Indigofera arrecta is an underutilized resource that has received little attention. The plant is readily and abundantly found in farms and wasteland among grasses and is destroyed alongside with grasses during the clearing of the farm. Its usage has been limited probably due to the hardness of the seed and antinutritional content. Hence the need for suitable pretreatment and treatment conditions to enhance its nutritive value. The growth of fungi in natural substrates is usually slow and this limitation must be overcome by suitable mechanical and chemical pretreatment of the raw substrate (Cen and Xia, 1999). The solid state fermentation of Indigofera arrecta with Trichoderma harzianum and Aspergillus niger may be a promising method of enhancing the usage of Indigofera arrecta thereby making available renewable feedstuff.
In Nigeria, the unbearable scarcity of animal feed motivated nutritionists to look for alternative sources of protein for livestock animals from lesser known seeds like Indigofera arrecta.
The calcium concentration of Indigofera species is relatively high ranging from 0.5 to 2.0%, where normal ranges of 0.20 to over 0.30% would satisfy animal requirement. Crude protein content of Indigofera spp is sufficiently high for consideration of these species as potential protein supplements in low protein quality diets. The amount of the nutritionally essential amino acids present in defatted seed meals of Indigofera species is comparable to that present in legumes (Van Etten et al., 1967). The quantity of non-essential amino acids, glycine, aspartic acid, and serine in these Indigofera species is more compared to the amount found in legumes (Roger et al., 1973). However, they contain several anti-nutritional factors which limit their consumption and affect the digestibility and bioavailability of its nutrients (Bressani, 1993). Antinutritional and toxic factors are considered to defend seeds against environmental vagaries and thus help to protect them. These factors though good for the plant, cause deleterious effect or are even toxic to animals and man. Therefore, fermentation being one of the oldest and most economical method of food production and preservation can be used in an attempt to reduce or eliminate those anti-nutritional factors and hence render the wild Indigofera arrecta seed useful.
The main aim of pretreatment is to increase surface area, to decrystallize cellulose, and to remove hemicellulose and lignin. Pretreatment has to overcome the resistance of the plant cell walls to deconstruction in order to separate the cellulose from lignin and hemicelluloses to make it more accessible to microbes or enzyme hydrolysis (Brodeur et al., 2011). Therefore, choosing the appropriate pretreatment for Indigofera arrecta seeds is a compromise between minimizing the degradation of the hemicellulose and cellulose components while maximizing the ease of fermentation of the substrate using mono and co-culture of Trichoderma harzianum and Aspergillus niger.