Bioconversion of Sweet Potato Leaves to Animal Feed

Abstract

Background: The high cost of conventional animal feed ingredients in Nigeria has made it necessary to search for alternative local sources of feed. Crop residues including sweet potato leaves abound in Nigeria. These have been explored as feed sources. The ability of microorganisms to convert agricultural wastes to more useful products could be harnessed to produce feed from sweet potato leaves which can be obtained in high abundance at low cost. Aim: To examine the possibility of converting sweet potato leaves to animal feed through fermentation with a co-culture of Chaetomium globosum and Saccharomyces cerevisiae. Materials and Methods: Triplicate samples of sweet potato leaves were fermented with a co-culture of C. globosum and S. cerevisiae for 21 days at 25±2°C and the effects of fermentation on nutrient composition were determined. Fermentation and control samples were analysed for proximate, amino acids, and elemental contents.  Results: Crude protein, crude fat and ash contents increased by 97.5%, 265.3% and 12.3%, respectively, while crude fibre and nitrogen free extract values decreased by 22.7% and 61.4% respectively. Energy content increased by 14.5%. The observed changes in the values of these nutritional components were significant (P = 0.05). The percentage  dry matter values of all the amino acids analyzed (lysine, histidine, arginine, aspartic acid, threonine, glutamic acid, proline, glycine, alanine, cystine, valine, methionine, isoleucine, leucine tyrosine and phenylalanine) were found to increase, with the contents of seven of the amino acids increasing significantly. Calcium, phosphorus, potassium and magnesium contents increased significantly while those of copper and iron decreased. Conclusion: Fermentation of sweet potato leaves with a co-culture of C. globosum and S. cerevisiae enhanced the feed potential of the leaves. With mineral supplementation, energy enhancement, and further crude fibre reduction, fermented sweet potato leaves could serve as feed for some animals.