Agriculture Business Week

During the seminar on Utilization of Soybean Meal, Full fat Soybean Meal and Cassava in Animal Nutrition sponsored by the American Soybean Association-International Marketing (Southeast Asia) at The Imperial Queen’s Park in Bangkok, Thailand on February 29, 2008, many important and relevant questions were asked by the Study Tour Team from the Philippines regarding the processing, quality control and utilization of cassava products in animal feeding.

Below were the questions that were satisfactorily answered during the day long seminar by Dr. Uthai Kanto, director of Suwanvajokksikit Animal R&D Institute (SARDI) and Department of Animal Science, Kasetsart University and Dr. Basilisa Pascual-Reas, technical manager, ASA-IM (SEA) and Study Tour coordinator.

How are dried cassava chips and pellets produced?
Dried cassava chips and pellets are common cassava products used in animal feeds. Freshly harvested roots are cleaned by washing or sifting, then chipped into small pieces and sundried on concrete floors for 3-6 days, depending on weather conditions and sunlight. The chips are regularly turned over by mechanical raking throughout the drying period. Dried chips normally contain 13%-14% moisture and are kept in the warehouse for a few days before shipment to the users.

Cassava chips maybe ground, steamed, and pelletized into cassava pellets which are more compact, less dusty, and very convenient for transportation and bulk shipment. However, some additives such as palm kernel cake or palm oil (copra meal and coconut oil in the Philippines) should be added in order to facilitate the pelletizing process.

What are the advantages of pelleting cassava meal?
Pelleting the cassava meal can enhance the digestibility of some micronutrients, destroy hydrocyanic acid, destroy the growth inhibition that may be present, reduce dust and dust hazards, prolong shelflife, and economize handling.

What is the ideal pelleting temperature to avoid dough formation in the pelleting chamber?
Pelleting temperature should be around 65°-70°C in order to avoid dough formation in the pelleting chamber. To improve pellet durability, one must use a higher compression ratio or use a two-step die.

What are the toxic substances in cassava?
Fresh cassava roots contain the cyanogenic-glycoside, linamarin, which is hydrolyzed into glucose and hydrocyanic acid (HCN) by the activity of linamarase enzyme when the root is damaged or cut into small pieces. The released HCN slowly evaporates into the atmosphere, so the level of HCN in the cassava products is reduced.

How do we detoxify cassava chips?
Dried cassava chips are produced by chopping the fresh roots into small pieces and then sundrying for 3-4 days; this greatly reduces the HCN content of the chips to levels that are non-toxic to animals. Research workers in Thailand have demonstrated that sundrying of cassava chips for 6 days reduced the HCN content of the chips from 111.83 to 22.97 parts per million (ppm).

Storing of dried cassava chips for five days reduced the HCN content of the product from 87.14 to 36.25 ppm. Steam-assisted pelleting of cassava further reduced the HCN content to 11.83 ppm.

It can be concluded that production of dried cassava chips involving 3-6 days of sun-drying and a few days of storage before shipment to the feed manufacturer or users lowers the HCN content in the product to non-toxic levels. Additional storage of the cassava product at the feedmill will further reduce the HCN content and provide an additional safety margin for the users. The cassava pellets eliminate any risk of HCN toxicity to the animals.

How do you characterize a good quality cassava for animal diets?
Only good quality cassava, which has the following specifications, is recommended for inclusion in animal diets:

Moisture           max. 14.0%
Crude protein   min. 1.5-2.0%
Crude fiber       max. 3.5-4.0%
Ash                   max.2.0%

The above cassava product contains 75%-80% nitrogen-free extract (NFE) and will give very good results for animal feeding. Cassava chips, with minimal or no stem or woody parts, will have crude fiber levels below this limit. High levels of sand or soil contamination will increase the ash content in the cassava products.

How do you maintain the quality of cassava chips?
Cassava chips, as previously stated, should be dried for at least 3-6 days and stored for 5-6 days before being included in animal rations. They should be clean and have no visible mold growth. With enough experience, one can estimate the starch content by breaking a piece of dry cassava chip.

How do we reduce dustiness caused by cassava grinding and mixing?

Cassava chips are very bulky and contain soft starch. Grinding of cassava chips is always very dusty and causes severe air pollution in the feedmill. To reduce dustiness, the following tips must be observed:
• Dust collection units of either the cyclone dust collector with filter bags or the automatic filter bag collector are required to prevent spreading of dust into the atmosphere.
• Addition of 4%-5% molasses in the diet eliminates the dustiness of the feed.
• Fat addition decreases the levels of molasses required for dust control in mashed cassava diets.
• Pelleted or wet feed gives no problems on dust and it does not require addition of molasses or fat in the formula.

How do we prevent hard fat accumulation in the animal body due to cassava feeding?
Cassava diets contain very low fat and may cause hard fat accumulation in the animal body. In countries where hard carcass fat is avoided, it is advisable that cassava diets contain at least 3% of soft fat in order to correct the fat condition in the animal fat. High-fat feed ingredients such as rice bran, extruded full-fat soybean or rice bran oil are recommended to be included in the cassava diets.

How do you enhance egg yolk color and skin pigmentation of poultry when using cassava-based rations?
Cassava contains no pigment and the diet may cause pale egg yolk of the poultry. Cassava diets must be supplemented with sources of pigment such as ipil-ipil leaf meal, marigold meal or synthetic pigments in order to color the yolk and skin according to the requirements of the consumers. The required supplementation is approximately 30 mg of xanthophyll/kg of diet.

What are the nutritional characteristics of cassava? Does this make cassava comparable with the energy content of grains?
Dr. Reas reveals that cassava root is an excellent source of energy due to its high carbohydrate content, with an average digestible energy (DE) of 1415 MJ/kg (3,300-3,400 kcal/kg). This makes cassava meal comparable with the energy content of grains.

Are cassava meals similar also to cereals in terms of dry matter digestibility?
Recent experiments cited by Dr. Reas show that cassava meals have an average dry matter digestibility of 75% and therefore, these are similar to cereals.

What are the advantages of using cassava in animal diets?
The results of past studies and practical field trials, according to Dr. Uthai, have indicated that good quality cassava has the following advantages in animal nutrition:
• Comparable performance but higher quality of animal products than corn diet
Good quality cassava with proper nutritional balance obtained by good diet processing has produced very comparable production performances of the animals as compared to those on cereal diets. But farmers always reported that cassava diets produced better quality animal products, including meat, milk, and eggs. Although no scientific explanation can be made, the favorable results may be due to less stress situation on cassava diets.

• Higher starch digestibility
According to Dr. Reas, cassava starch is highly digestible due. to the soft starch as it consists more than 80% amylopectin. Cassava has the highest digestibility in dry matter, organic matter and energy in the different parts of the digestive tract of growing pigs when compared to corn, sorghum, and barley.

Highly digestible starch creates less stress to the animals and stimulates more growth of non-pathogenic micro-organisms which will produce more acidic conditions and suppress the growth of the disease producing micro-organisms (E. coli, Salmonella) in the gut.

• Minimum or no mycotoxin contamination
It has been shown that cassava products contain minimal or no mycotoxins when compared to cereals, especially corn. Cassava has been successfully fed to breeder animals and ducks which are highly sensitive and vulnerable to mycotoxins, particularly zearelenone and aflatoxin. Apparently, farmers who have employed cassava in animal diets for many years have reported no aflatoxicosis or toxicity of other mycotoxins.

Aflatoxin is a powerful stressor in animal diets, which not only reduces the performance of animals, especially their feed conversion rate (FCR), but also impairs the immune system, thus causing more illnesses in the animals. Modern high-performance animals are always more sensitive to stress, including aflatoxin in the diets. The animals therefore require feeds which are not only nutritionally balanced and highly digestible but also contain no or minute levels of toxic substances which cause stress to the animals. Cassava is an ideal feed ingredient meeting this requirement.

• Animal health improvement and “green” meat production
Animals on cassava diets always have better health and require less or no antibiotics during production, compared to animals on grain cereals, especially on corn diets. The highly digestible starch and minimal aflatoxin contamination could be responsible for the advantage. Cassava diets can therefore provide “green” meat or “green” food production which is an important consideration in this new millennium.

• Minimum animal waste odor
Practical field trials have shown that manure or feces of cassava-fed animals produce less fetid smell or have less odor than those on cereal diets. Although the exact reasons are not known, the advantage helps to lessen the pollution problems of animal production units.

• Non-GMO feed ingredient
Cassava varieties grown in Thailand (even in the Philippines) have been produced through traditional breeding methodologies and are certified to be non-GMO (genetically modified organism). Cassava products can therefore be used for export, especially to European Union (EU) countries.

• Reduced animal production costs
Cassava diets lower the cost of animal production, not only by the reduction of feed cost but also by the reduction or elimination of the use of antibiotics and medication in animal production. This advantage is an important factor which farmers should consider.

How do you improve the low protein quality of cassava meal?
Cassava diets should be balanced for protein and essential amino acids according to the requirement of each type of animals. Weight by weight substitution of cassava for corn in animal diets will lead to lower protein and amino acid contents of the diet and cause poor growth, poor feed conversion, poor carcass quality, and poor productivity of the animals.

More soybean meal or extruded full-fat soybean meal need to be added when employing cassava diets. Cassava soybean diets with a proper balance of amino acids have been used successfully by the pig farmers in Thailand and the Philippines.

How about a cost comparison between corn and a combination of cassava-USDHSBM and FFSBM?
Dr. Reas made a cost comparison between corn and a combination of cassava-USDHSBM and FFSBM in terms of the energy, crude protein, and lysine and methionine content of the ingredients. Considering the latest prices, the cost of cassava-USDHSBM-FFSBM is lower by P0.15/kg. It also contains 2% higher protein and about 50 kcal/ kg more energy than corn. The extra crude protein (CP) and metabolizable energy (ME) in the combination would result in more savings, considering the current prices of oil and SBM. Moreover, the low or no mycotoxin risk of cassava can be added to the advantage of eliminating the cost of toxin binder and the better immunity level of the pigs.

It is important to note, adds Dr. Reas, that when cassava is used as the main energy-sourced ingredient in the diet, enough levels of good quality digestible protein and amino acids such as US DHSBM should be used. The addition of FFSBM will further improve the protein and amino acid content of the diet. FFSBM also improves the palatability of the feeds and reduces the natural dustiness of cassava meal.

Lastly, Dr. Reas cautioned that the levels of vitamins and minerals should also be checked and provided correctly for maximum efficiency.