Protein-enriched animal feeds from sweet potato waste

by Mary Charlotte O. Fresco


animal feedsPoultry feeds are considered as "complete" feeds because they are formulated to contain all the protein, energy, vitamins, and minerals necessary for proper growth, egg production, and health of the birds. However, due to the continued increase in price of commercial feeds (as 60% is imported from other corn producing countries), large and small-scale raisers fail to maintain a balance diet ration for their flock. Farmers, in efforts to meet the recommended diet requirement, resort to mixing other feed ingredients, which in turn impair the balance of nutrients in the "complete" feed.

As this problem continues to pose threat to our livestock production efficiency, experts from the Tarlac College of Agriculture (TCA) in Camiling, Tarlac, developed a practical alternative to help our farmers reduce feed costs. Researchers were able to come up with a protein-enriched feed product from sweet potato pulp, a solid waste derived from making starch.

How did they do it?
The researchers of this study employed the protein enrichment technology. The technology sounds so simple yet the procedure is complex. Some of the critical processes involved are: use of non-protein nitrogen sources (urea, ammonium phosphate, ammonium sulphate) in preparing the substrate and application of fungus (Trichoderma harzianum, Aspergillus niger, Rhizopus oligosporus) to ferment the pulp. Also, they determined the degree of pulp wetness (low-moisture and high moisture) to find out which substrate can generate high percentage of crude protein. Crude protein is the amount of nitrogen present in the feeds that can be converted into protein. Results of the study showed that sweet potato pulp that underwent protein-enrichment increased its protein content to 17-20%. Sweet potato pulp with high moisture content was found to be a good fermenting material, and thus, could manufacture large amount of crude protein.

When it comes to the application of non-protein nitrogen source, sweet potato pulp (with high moisture content) applied with urea had an increase of 29.37 % in crude protein content. Meanwhile, the fungus Trichoderma harzianum worked well in fermenting the wet pulp and was found efficient in enhancing the crude protein value of the pulp.

According to the researchers of the study, the marked increase in the crude protein content of treated sweet potato pulp was brought about by the bio-conversion of carbohydrate materials present in the pulp into amino acids by microbial activity. The microbial activities are enhanced when there are sufficient amounts of nitrogen and other minerals in the pulp.

Results of on-farm feeding trial
The researchers conducted on-farm feeding trials among commercial poultry growers. They found that broilers fed with finishing mash incorporated with protein-enriched sweet potato pulp increased their body weight by 0.7 to 3.8%. Likewise, the birds' feed conversion efficiency was increased by 6.4-15.8%. Based on the cost efficiency analysis made, a farmer can save from P2.54 to P3.81 per bird at finishing stage and P0.49 to P3.06 per bird during the growing-finishing stage. Moreover, the protein-enriched sweet potato feeds are guaranteed safe since the broilers fed with this new feed product showed no mortality or allergic reactions.

The researchers added that the technology is also applicable to other agricultural and industrial by-products and wastes such as pineapple pulp, sugarcane bagasse, rice bran, corncobs, banana peeling, as well as weevil infested and non-marketable root crops.
To date, the on-farm feeding trials are now at the village level and soon will be ready for national application.

The DA-Bureau of Agricultural Research funded the this study.

For more information, please contact Ma. Teresa SJ. Vldez, Rodolfo A. Demo-os, and Mariano c. Macapili, Jr., at Tel. No. (045) 934-0752, Tarlac College of Agriculture, Camiling, Tarlac.