ABSTRACT
One of the main challenges of animal rearing in Nigeria is the availability of feeds and supplements. Alternative sources of energy are being sought to reduce the pressure on the maize market. Although, Anacardium occidentale L. (Cashew) grows abundantly in the tropics, its apple is a neglected agricultural product with immense value. The aim of this research was focused on microbiological screening of livestock feed formulated from Anacardium occidentale Linn. (cashew apple residue).
The phytochemical and anti-nutrient contents of the plant were assessed using standard methods. The cashew apple residue (CAR) was subjected to soaking, boiling and fermentation treatments. The proximate composition was determined using scientific protocols. Mineral content was assessed using atomic absorbance spectrophotometer. The toxicity of the cashew apple residue was screened in albino rats at graded dosage. Broiler chicks diet was formulated from the fermented cashew apple residue by substituting it for maize at 25, 50, 75 and 100 % level. The percentage protein, fibre, lipid and metabolizable energy of the feed were determined and compared with the commercially available feed. The effect of the formulated feed on growth performance, feed conversion ratio and intestinal microflora balance of broiler chicks were evaluated. Thereafter, the shelf-life of the formulated feed was studied using standard microbiological procedures.
The results of the phytochemicals screening revealed that alkaloids, tannins, saponins, flavonoids, glycosides, phenols, anthraquinones steroids and terpenoids were present in ethanol extract of both the yellow and red varieties of the CAR. The antimicrobial activity assay of the CAR against Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Salmonella typhi, Aspergillus flavus and Candida albicans revealed a very high level of activity against the human pathogens. The minimum inhibitory concentration of the cashew apple extracts ranged from 2.5 mg/ml to 10.0 mg/ml in ethanol extracts. The bactericidal/fungicidal concentration of the extracts ranged from 5.0 mg/ml against bacteria to 12.5 mg/ml against fungi. The CAR was found to be rich in protein (15.30 %), fibre (14.09 %) and carbohydrate (54.37 %), it also contained appreciable amount of ash (6.04 %) and lipid (1.98 %). Fermentation protocols increased the protein, moisture and ash contents while the carbohydrate and fibre contents were reduced. Fermentation, soaking and boiling treatments significantly reduced all the anti-nutrients in the cashew apple. However, fermentation had the best reducing effect on the anti-nutrients. Fungi were the predominant microbial species during the first 48 hr of fermentation while lactic acid bacteria became dominant from 72 hr to 120 hr. The organisms responsible for the fermentation of the CAR were identified as Bacillus licheniformis, Bacillus subtilis, Lactobacillus plantarum, Lactobacillus acidophilus, Micrococcus luteus, Fusarium oxysporum, Geotrichum candidum, Rhizopus stolonifer and Mucor plumbeus. There were no significant difference in the level of red blood cells (RBC), platelets, packed cell volume (PCV) and haemaglobin (Hb) concentration in the blood of the tested rats, albeit, there were significant differences in the white blood cells (WBC) of the rats administered the cashew apple extract. The formulated feed had significant stabilizing effect on the gut microbiota of the broiler chicks. These results indicated that, CAR fermented spontaneously in solid state, offers an alternative to maize as a source of energy in broilers feed thereby reducing the pressure on maize in the market. It also revealed that this important agricultural waste is a great source of wealth for cashew farmers all over Nigeria.
