BAR TODAY || Official Quarterly Publication of the Bureau of Agricultural Research

Cassava foliage: cheap alternative to carabao feeds
by Rita T. dela Cruz

April-June 2002
Volume 4 No. 2

Cassava (Manihot esculenta Crantz) has been an important food source in many developing countries. It's an ideal food-security crop because of its capacity to adapt to unfavorable conditions. It grows even in poor soil and in areas where other crops fail to be productive, and is resistant to drought and pest infestation.

In the Philippines, cassava tubers are dietary staple and important source of carbohydrate for both man and livestock, and are important cash crop. The cassava tubers also have industrial purposes, particularly as cassava flour, which is now being used as substitute for commercially manufactured flour.

Unknown to many, one of the potentials of cassava farming that hasn't been fully utilized is the use of cassava foliage as animal feeds.

In a recent study conducted by the Philippine Carabao Center (PCC) and the University of the Philippines Los Baños (UPLB), scientists found that cassava foliage could be used as a potential feed for ruminants. The scientists tried to evaluate the biological and economic potentials of processed cassava leaves as feed for carabaos. Headed by Dr. Caro Salces of PCC, the study was conducted at the Center in Ubay, Bohol.

The study aims to determine effective means to detoxify the cassava foliage for animal feeding purposes, to know the effect of processed cassava foliage on the growth of the carabaos, to identify the effect of sulfur feed supplement on the growth rate of carabaos that were fed with cassava foliage, and to determine the profitability of integrating livestock in a cassava-based farming.

Detoxifying the poison in cassava
One limiting factor in using cassava as animal feed is the presence of potential toxic concentrations of cyanide or hydrocyanic acid (HCN). For human consumption, the toxicity of cassava is resolved by cooking. This is the reason why it is not recommended to eat cassava uncooked.

Cassava leaves are important source of micronutrients, protein fiber and ash, which are essential in animal feeds but along with these essential elements is a high cyanide concentration which ranges from 189 parts per million (ppm) to about 2466 ppm depending on the variety.

Using 10 plant samples for this study, the researchers found that cassava foliage has relatively high crude protein, which indicates its potential as mainly roughage or as supplement in the animal diet. In terms of toxicity, fresh leaves have generally higher cyanide content compared to other cassava parts such as stem and petioles. The cyanide content found in the leaves ranged from 86 ppm to 186 ppm. This means that the leaves in its fresh form could cause health problems to animals.

To reduce the toxicity in cassava leaves, the scientists used three processes: wilting, drying, and ensiling. Based on the results, ensiling was the most effective method of detoxification, reducing the cyanide concentration to 80 ppm. The pH content of the ensilaged cassava ranged from 3.5-4.5, making it a good silage material. Ensiling of cassava leaves is usually done a month before the harvesting of tubers.

Effect of processed cassava leaves
A total of 24 carabaos, with age ranging from 2 to 3 years old, were used for the experiment. Included in the feeds were roughage and concentrate, which were given at 75:25 ratio. The feeds were fed dry. The roughage is composed of the ensilage cassava leaves and napier grass. To determine the feed efficiency, the inclusion of the cassava leaves to the roughage were approximated at different levels.

Results indicated that as the content level of the processed cassava leaves were increased, the average daily gain of the carabaos also increased. The increase ranged from 0.74 kilos to about 0.87 kilos. However, scientists also found some limiting factors in increasing the amount of ensilage cassava leaves to the feeds, one of which is the imbalance intake of essential nutrients. For instance, while the daily crude protein and calcium intake were sufficient, the digestible nutrients and the phosphorus intake were inadequate.

Sulfur as feed supplement
The scientists resolved the problem of imbalance intake of essential nutrients such as the digestible nutrients and phosphorus using sulfur as feed supplement. Sulfur amounting to two grams was added to a kilo of ensilaged cassava leaves. The feeding trial was done on 16 carabaos. Results did not indicate any relevant increase in the live weight and feed efficiency of the carabaos. The average daily gain ranged from 0.90 kilos to 1.02 kilos, which is relatively insignificant. However, the inclusion of sulfur as supplement in the cassava feeding helped decrease the toxin level of the processed cassava leaves.

Source: "Processing of Cassava (Manihot esculenta) Foliage as Feed for Water Buffalo" by Caro B. Salces, Bonifacio A. Hingpit, Domingo B. Roxas, Ulysses M. Lustria, Severino S. Capitan, Isabelita M. Pabuayon, and Florina E. Merca, published at the Philippine Journal of Veterinary Animal Science, 2000.