Several studies have shown that the use of raw cassava products in cassava-producing sub-Saharan Africa would not only relieve the pressure on the demand for cereal grains but also guarantee abundant and year-round supply of energy for livestock feeding. This will ultimately reduce the high cost of feed in pig production.
Around 100g of cassava root provides 160 calories: nearly twice the calorific value of potato and perhaps one of the most highly calorific of any tropical starch-rich tubers and roots.
This said, the use of cassava in livestock feed has been limited so far due to the fear of the presence of toxic cyanogenic glucosides in its raw form; its deficiency in other important nutrients; and the high fibre content of its peel.
To remove any toxic properties of cassava, it is subjected to processing where the cellular structure is disrupted, the intracellular glucoside becomes exposed and is degraded to sugar which later dissociates to ketones.
For thousands of years, cassava tubers have been traditionally processed in Africa using a wide range of methods to reduce toxicity, improve palatability and convert the perishable fresh root into stable products for human consumption. These methods consist of different combinations of peeling, chopping, grating, soaking, drying, boiling and fermenting.
Along with reducing the toxic components in the cassava, the challenge for pig farmers today is to find the simplest, most scalable, sustainable and cost-effective way to process the crop efficiently and safely so that it can be fed to pigs without significant additional labour.
Understanding the biochemistry of the crop is important in finding processing solutions. New research has shown that the cassava peel contains the highest concentration of toxins compared to the pulp, meaning that removal of the cassava peels can reduce the cyanogenic glucoside by at least 50 percent in one simple step. This said, this process is time consuming and significant additional labour is required to undertake the peeling. Additionally, employing extra hands to peel will reduce the cost advantage of using cassava as an alternative source of carbohydrate.
The same drawbacks apply to other methods of processing: grating the whole cassava tuber exposes and destroys the cyanide; and around 90 percent of free cyanide in the raw product is removed within 15 minutes of boiling. These processes are equally time consuming and require extra labour and/ or machinery, which a typical small pig farmer may not be in a position to afford.
One processing method that is potentially more affordable and efficient, is soaking and fermenting. I believe the result is great, especially for pigs.
Soaking of cassava provides a suitably larger medium for fermentation and allows for greater extraction of the soluble cyanide. Soaking removes about 20 percent of the free cyanide in fresh root chips within the first four hours. The cyanide in raw cassava tuber reaches a consumable level after soaking in water for three days.
Fermentation, which follows soaking, is the result of the action of living microorganisms. The microorganisms produce enzymes which convert carbohydrates to organic acids to create the fermented cassava product.
During fermentation, the raw cassava is pre-digested for the pigs thus increasing the bioavailability of nutrients and phytonutrients for the pig to absorb via second digestion.
In addition, fermentation increases the protein supplied by feeding cassava root; it improves the balance of essential amino acids; and makes available the valuable B-complex group of vitamins such as folates, thiamin, pyridoxine (vitamin B-6), riboflavin, and pantothenic acid vitamins.
Furthermore, fermentation modifies the unfermented food in diverse ways, resulting in new sensory properties with enhanced aroma and flavour which appeals to the pig and, subsequently, increases feed consumption and reduces anti-nutrient content. The soaking process also changes the texture of the roots, rendering the product softer and easier for smaller pigs to consume.
The pig digestive system is well suited to managing soaked and fermented raw cassava due to the caecum, an organ that houses bacteria which aid with the digestion of plant materials, such as cellulose. The extended breakdown of plant materials by the bacteria allows the nutrients within the cassava to be assimilated. The consumption of soaked and fermented cassava can also improve microbiome diversity by directly supplying the pig digestive tract with living cultures essential for this breakdown of nutrients.
In practice, cassava can be loaded into containers and filled with water and left for three days before being fed to pigs. However, when using soaked and fermented raw cassava to feed pigs, farmers should understand that the quantity and quality of protein supplementation is critical. Adding lysine and methionine will also significantly improve protein utilisation in pigs.