Cocoyam as Animal Feed 2: Feeding value of cocoyam root meal in animal nutrition

Published Date: 20th July 2020

Considerations in formulating cocoyam root meal-based diets

The nutritional quality of cocoyam root meal compares favorable with cassava root meal, therefore making it a potential substitute for grains in animal feeds. The major factor affecting the use of cocoyam root meal in animal nutrition is the presence of the acridity factor, which on ingestion causes irritation and burning sensation in the mouth and throat. This problem has been linked to the presence of calcium oxalate crystals, phytate, tannins, saponin, hydrogen cyanide, trypsin and alpha-amylase inhibitors, which are commonly found in cocoyam corm. Techniques for reducing the acridity factor have been developed and include peeling, grating, soaking, drying, boiling, baking, frying, ethanol extraction, and fermentation processes. Attempts have also been made to breed non-or low acrid cocoyam cultivars. Cocoyam root meal is also low in protein, although there is tannia (Xanthosoma) varieties that contain as high as 8 – 9 percent crude protein, similar to the level found in some grains. Leucine, lysine, and tryptophan are the three major essential amino acids found in the cocoyam root meal.

Most importantly, many cocoyam varieties are no longer priority foods for men in many cocoyam growing countries, where they are eaten only as a last resort when cassava or yam cannot be accessed. They are therefore readily available for use as cheap unconventional animal feed raw materials. Cocoyam root meal can serve as an energy source in the diets of many monogastric and ruminant animals. There is however the need to eliminate or reduce the anti-nutrients to safe levels and also enhance the protein content of the diets through supplementation with protein-rich feedstuffs and synthetic essential amino acids. Excellent research results that could be adopted by the livestock industry have been generated from several feeding trails using poultry, pig, and ruminants.

The nutritive value of cocoyam root meal for poultry

In many tropical countries, research has recognized processed cocoyam root products as cheaper carbohydrate sources than grains and other tuber meal products like cassava. Thus, they are regarded as non-conventional feedstuff that contains easily digestible carbohydrates and therefore is used to provide cheap and readily available energy in poultry diets. Several study reports have suggested that properly processed cocoyam root meal could effectively replace up to 50 percent of the maize in broiler diets as an energy source and for profit maximization.

Researchers at the University of Calabar, Nigeria, reported the results of a study in which cocoyam root meal served as a substitute for maize in finisher broiler diets, such that raw sundried and boiled sundried tannia (Xanthosoma sagittifolium) meals replaced maize at 0, 25, 50 and 100 percent levels. Performance-wise, the birds fed the boiled cocoyam meal consumed more feed and gained higher weight than the ones fed raw sun-dried cocoyam meal, indicating that boiling was more effective than sun-drying alone in improving the nutrient value of the cocoyam meal. The study also showed that properly boiled and raw sun-dried X. sagittifolium root meals will effectively replace maize at 50 and 25 percent level of inclusion respectively in finisher broiler diets. However, 100 percent replacement of maize with the boiled cocoyam meal did not have any adverse effect on carcass characteristics. The optimal average cost per kilogram feed was achieved at 50 percent replacement, even though the 100 percent replacement gave the lowest value.
A Researcher at the University of Science and Technology of Southern Philippines, also evaluated the meat yield and quality of broiler chicken fed sun-dried X. sagittifulium root meal at 5, 10 and 15 percent inclusion levels in commercial finisher broiler ration. Results of the study showed that at a 15 percent inclusion level, the cocoyam meal did not significantly affect meat quality in terms of flavor, juiciness, texture, aroma, and tenderness. The weights of choice meat cuts such as thigh, wing, drumstick, breast, and back were also similar to those obtained from chicken fed only the commercial ration. Raw meat quality attributes like meat color, water holding capacity, and acceptability were equally not affected by the cocoyam root meal.

Researchers at the University of Calabar, Nigeria, investigated the effects of sun-dried and boiled taro (Colocasia esculenta) meals at 0, 25, 50, and 100 percent inclusion in maize-based diets on broiler performance and reported highest feed intake value at 50 percent inclusion level. However, body weight gain decreased with an increase in cocoyam inclusion level, with birds on 100 percent inclusion level passing waterier feces than other groups. The researchers concluded that raw sundried and boiled taro cocoyam meals could effectively replace maize at 25 and 50 percent respectively as an energy source in broiler diets. The reports by Olajide on the effects of feeding broilers with soaked C. esculenta as a replacement for maize also highlighted that such processed cocoyam meal can economically replace 30 percent of maize in the diets of broiler finishers, with no deleterious effects on carcass quality and health of the birds. Other reports from the Federal University of Technology Owerri and Imo State University Owerri, Nigeria, have also shown that broilers could tolerate up to 20 percent inclusion levels of the boiled wild variegated cocoyam, Caladium hortulanum, and C. bicolor in their diets as a substitute for maize. At this inclusion level, broiler production was more profitable, due to reduced cost of feed per kilogram weight gain.

Very few cocoyam studies have however been carried out with laying birds. Olajide, working in Nigeria, investigated the performance and economy of production in laying hens fed fermented taro corm-based diets at 0, 10, 20, and 30 percent as graded replacements of maize. Cost of feed per dozen egg was found to decrease up to 20 percent fermented cocoyam replacement level, while the cost was highest at 30 percent replacement level, indicating that the ingredient can be incorporated in layer diets as an alternative energy source at 20 percent level. Researchers at the University of South Pacific, Samoa, replaced maize with the giant taro (Alocasia macrorrhiza) root meal with or without adding coconut oil slurry (9:1 ratio) in layer diets at 10 and 20 percent levels. They reported no marked effect on feed intake, while percentage hen-day production and feed conversion ratio were depressed at 20 percent level of inclusion, but were overcome by coconut oil slurry addition in the diet. Egg mass also increased in birds fed the 20 percent cocoyam root meal with or without coconut oil slurry addition in the diet.  They concluded that the treatment of the giant taro root meal with coconut oil slurry at 9:1 ratio overcomes the adverse effects of the root meal in laying hens.

The nutritive value of cocoyam root meal for pigs

Surprisingly, very limited studies have been carried out on the nutrient value of cocoyam root meal for pigs, even though some literature suggests that local farmers, especially in Asia use it in pig feeding. Similar to what obtains in poultry, however, cocoyam roots intended for utilization as pig feed need to be further processed by cooking prior to drying and feeding, to ensure removal of the toxic substances present in the root meal. Nigerian scientists had earlier experimented on feeding raw cocoyam to growing pigs at 50 percent replacement of grains and reported poor growth and incidence of diarrhea. The poor growth and diarrhea were however reversed by feeding boiled cocoyam to the pigs, indicating that heat treatment such as boiling is needed for optimal utilization of cocoyam roots in pig feeding.

Since cocoyam cormels are usually in demand as human food at many tropical locations, it is the main or mother corm that is processed as pig feed. The processing method involves first washing the corms with water to remove soils attached to them, then cutting the corms into about 1 cm thick pieces. The cut pieces are packed in a basket and immersed in a drum of boiling water and allowed to boil for about one hour, after which the basket and its content is removed and washed with clean water. The boiled cocoyam corms are then dried in the sun or by means of artificial drier and milled to the desired particle size. The product can store for many months under tropical conditions and is similar to the gelatinized cassava grains produced by researchers at the Federal University of Technology Owerri, Nigeria. Studies have however shown that cocoyam meal alone being poor in protein cannot maintain optimal growth in pigs without proper protein supplementation.

Researchers at the Universidad Estatal Amazónica, Departamento de Ciencias, Ecuador, studied the digestibility of the nutrients in dried taro (C. esculenta) meal in fattening pigs and reported high utilization rates, when 20 and 40 percent of taro root meal were included in the diet, indicating that it has satisfactory nutritional features for fattening pigs. Other South American studies have reported similar results in pigs fed X. sagitifolia. The effects of replacing maize with boiled taro cocoyam (C. esculenta) root meal on the performance of grower pigs were also investigated by researchers at the University of Calabar, Nigeria. The boiled taro cocoyam was included in the diets at the rate of 50 and 100 percent without deleterious effects on their performance in terms of body weight gain, feed intake, feed efficiency, and feed cost. There is a need for more studies on the nutritive value of different cocoyam species for pigs, especially the abundant wild and freely growing cocoyam species.

The nutritive value of cocoyam root meal for ruminants

Processing of cocoyam into food and starch generates a lot of waste and residues that make up a sizable percentage of the entire cocoyam production. Several studies have reported the routine use of kitchen derived cocoyam wastes in ruminant feeding. For example, studies conducted in southeastern Nigeria have shown that many small ruminant keepers feed cocoyam wastes to their animals. These wastes include discarded cormels, and peels of raw and boiled cocoyam corms, which usually are not subjected to further processing before they are offered to the animals.

These wastes however need to be further processed to reduce the inherent anti-nutrients to safe levels recommended for ruminant feedstuffs. One of the reported methods used to enhance the nutrient value of cocoyam wastes is solid-state fermentation with fungal organisms to achieve an up to 50 percent increase in the protein content of the waste. The effects of submerged fermentation on the nutrient value of whole C. esculenta corms were studied by a researcher at the University of Ibadan, Nigeria. Specifically, soaking in boiled or cold water for 9 days after size reduction resulted in a substantial decrease in dry matter content, but a marginal increase in crude protein, although below the 7 percent recommended for ruminants, indicating the need for supplementation with extra nitrogen sources. The high energy value and enhanced organic matter digestibility recorded in the end products were indicative of their potentials as energy feeds for different classes of livestock. The fermentation treatments also reduced the inherent anti-nutrients in cocoyam roots to safe levels for livestock feeding.

Researchers at the Federal College of Animal Health and Production Technology, Ibadan, Nigeria, studied the growth performance of West African dwarf goats fed urea treated taro (C. esculenta) root meal. The cocoyam roots were processed as raw, urea treated, urea treated cooked and urea treated fermented meals. Goats fed the urea treated cooked cocoyam meal recorded the best feed conversion ratio, and daily weight gain compared to other dietary treatments, indicating that addition of urea during processing, further improves the utilization of the cocoyam root meal-based diets by goats.

Conclusion

Both cocoyam corms and their wastes can be utilized as feeds by different classes of livestock and poultry. However, appropriate processing methods such as drying, soaking, boiling, and fermentation should be applied to reduce the inherent anti-nutrients to safe levels, thereby, enhancing their nutrient value and intake by animals.  There are still very limited studies on the nutrient value of either cocoyam roots or their wastes for livestock feeding. Fungal organism aided solid-state fermentation seems to hold better promise than other methods in enhancing the nutrient value cocoyam roots and wastes for ruminant feeding.

Bibliographic references

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