Cocoyam as Animal Feed 4: Feeding value of cocoyam leaves in animal nutrition

Published Date: 3rd August 2020

Introduction

Leaves and legume forages are usually fed to poultry and pigs under smallholder farming systems, and could be major protein feed sources for pigs at locations where affordable energy feedstuffs are low in protein. These plant materials are either fed fresh or are processed before feeding. Cocoyam produces large quantities of protein and mineral-rich leaves during its vegetation period, which could be harvested and processed into high protein feedstuff for use in livestock feeds production. Although cocoyam leaf meal has been shown to be much cheaper than conventional protein feedstuffs like soybean meal, and groundnut cake, its major limitation as a protein source for livestock is the presence of anti-nutritional factors and the imbalance of certain amino acids. The simple and effective methods of processing cocoyam leave into nutritious leaf meals were discussed in the previous article. Of these, boiling, soaking, and fermentation have been shown to be the best methods of reducing the effects of the anti-nutrients and improving the nutritional value of cocoyam leaf meals.

Ensilage has however received a lot of research attention in the pig producing areas of Asia and South America. Ensilage is a cheap and simple controlled fermentation technique carried out in a sealed anaerobic environment and used to conserve high moisture forage in many regions of the world. High moisture materials like cocoyam leaves and petioles may need to be pre-wilted prior to ensiling to improve the dry matter content, and may also need to be augmented with water-soluble carbohydrate sources like starchy tubers and molasses as an additive to enhance the ensiling process. Although smallholder farmers use cocoyam roots and leaves in feeding their animals, very limited information is available on its actual nutritional value for poultry and ruminant nutrition. Most of the available information deals with the nutritional value of cocoyam leaf meal in pig nutrition.

The nutritive value of cocoyam leaf meal for pigs

Wilted cocoyam leaves have been shown to be palatable to pigs under smallholder production systems. Researchers at UTA-TOSOLY, Socorro, Santander-Sur, Colombia, demonstrated that both fresh petioles and leaves of the tannia cocoyam, Xanthosoma sagittifolium could be fed to pigs, with the leaves being fed mostly to growing pigs, and the petioles to pregnant sows, that require lower levels of protein in the diet and can handle bulky feeds better than the growing ones. They reported that in an experiment in which 50 percent of the soybean meal (500 g/pig/day) in a sugar cane juice-based diet for growing pigs was substituted with fresh leaves of cocoyam, the dry matter intake, weight gain and feed efficiency values remained within the normal ranged obtained with such diets. Higher substitution levels were however reported to elicit a lineal decline in protein digestibility.

The need to reduce the effects of an anti-nutritional factor on animal development, conserve the extra leaves produced during periods of abundance, and also to standardize the supply of cocoyam leaves to in commercial farms has, however, led to the development of ensilage techniques for processing cocoyam leaves used in feeding pigs. Thus, ensilage has been the chief method of processing cocoyam leaves fed to pigs. Researchers at the Center for Livestock and Agriculture Development, Cambodia, however, reported that on a basal diet of rice bran + broken rice or rice bran + cassava root meal (1:1 ratio), offered at 2 percent of live weight, and sun-dried or ensiled taro leaves ad-libitum, pigs consumed almost twice more dried leaves than the ensiled form. The ensiled taro and sun-dried leaves provided 38 and 43 percent of the dietary dry matter and 75 and 82 percent of the dietary protein respectively. They attributed the apparently higher nutritive value of the sun-dried compared with the ensiled taro leaves to inadequacies in the ensiling process, resulting in a disproportionate breakdown of the protein, and poor palatability. However, properly ensiled cocoyam leaves have been successfully fed to pigs at the growing and fattening stages, as well as to gilts during gestation and lactation periods at varying inclusion levels.

In a Laotian study in which the effects of replacing soybean meal with ensiled taro leaf meal were evaluated in growing pigs, dry matter, and crude protein intakes were unaffected by increasing replacement (25 and 50 percent) of soybean crude protein with taro leaf silage crude protein in the diet. Similarly, average daily weight gain, feed conversion ratio, carcass weight, backfat thickness, and dressing percentage of the pigs fed ensiled taro leaf meal were unaffected, indicating that taro silage can be used as protein sources for growing pigs without negative effects on their performance. The effect of biochar on the growth rates of pigs fed a basal diet of ensiled banana (Musa spp) pseudostem and ensiled taro (C. esculenta) foliage was also evaluated by researchers at the National University of Laos. Growth performance was significantly improved by the addition of biochar to the basal diet, with a 20.1 percent increase in weight gain. Biochar is a co-product of pyrolysis or carbonization process during which biomass is heated in a low to the zero-oxygen state resulting in carbon-rich ingredients. Biochar is usually not pure carbon but a mixture of carbon, hydrogen, oxygen, nitrogen sulfur, and ash in various proportions. It has in recent times been used to improve gut health, nutrient uptake, and therefore growth performance in poultry, pigs, and cattle.

The nutritive value of cocoyam leaf meal for poultry

There are very few studies describing the nutritive value of cocoyam leaf meal for poultry. However, like any other protein-rich leaf, it can serve as supplementary protein, carotene, and trace mineral source in poultry diets when properly processed. It has been reported that inclusion of as low as 5 percent raw sundried C. esculenta leaf meal in broiler diets results in depressed performance. Again, feed selection and growth performance of local chickens offered taro cocoyam foliage as a protein-rich supplement were found to be low. However, in Vietnam, ensiled C. esculenta leaf meal has been used to replace up to 60 percent of rice bran in the diets of growing ducks, with positive effects on performance and carcass quality. Cambodian researchers, however, reported lower feed intake and growth rate in Muscovy ducks fed ensiled C. esculenta leaf meal.

The effect of taro leaves and silage (made from leaves and stem of Colocasia esculenta) in a rice bran-based diet on the growth performance of common ducks was also evaluated in two studies carried out at Angiang University, Vietnam. In the first study, it was found that there was no effect on average daily gain, and feed conversion ratio when a mineral-vitamin premix was added to chopped taro leaves and included up to 7 percent in the diets of common ducks.  In the second study, it was also found that ducks gained better when rice bran and taro silage were blended in their diets. The average daily gain was specifically similar over a range of ratios of rice bran and taro silage, from 80:20 to 40:60, and was 8 percent higher when the feeds were given as a mixture rather than separately.

Researchers at Haramaya University, Ethiopia, evaluated the feeding value of shed-dried C. esculenta leaves in broilers using four experimental diets containing the cocoyam leaf meal at 3, 5, and 7 percent. The diets were formulated to uniformly contain 3000 kcal/kg metabolizable energy and 22 percent crude protein during the starter phase and 3200 kcal/kg ME and 20 percent CP during the finisher phase up to 56 days of age. Highest dry matter intake, final body weight, and body weight gain were recorded in birds consuming the 5 and 7 percent cocoyam leaf meal supplemented diets, indicating that up to 7 percent of the leaf meal could be included in broiler diets. In another study at Nnamdi Azikiwe University, Awka, Nigeria, the effect of aqueous extracts from cocoyam (X. sagittifolium) leaf on the growth performance of broiler chickens fed full-fat soy meal was evaluated. The dried cocoyam leaf powder was mixed with water at the rate 100, 150, and 200 g per 6 liters of drinking water. The aqueous mixtures were then sieved to obtained cocoyam leaf extracts. The extracts served as drinking water for broiler chickens fed maize-full fat soya-based diets in a 56-day feeding trial. There was no growth performance effect as a result of the treatments, however, water consumption decreased with increasing concentration of the cocoyam leaf extract, probably because of the presence of anti-nutrients in the leaves.

The nutritive value of cocoyam leaf meal for ruminants

Again, very limited research has been carried out to determine the nutritional value of cocoyam leaf meals for ruminants. However, fresh cocoyam foliage collected for feeding ruminants are usually ensiled in order to reduce the problems associated with its high oxalate content. Some Hawaiian studies have shown that ensiled taro leaves were readily accepted by sheep, goats, water buffalos, and other animals, with dry matter intake in sheep being about 326 g per day. Voluntary intake was however too low for the upkeep of the animals, with evidence of ruminal dysfunctions and weight loss, especially when 100 percent taro silage was offered. Carpenter and coworkers have also fed lambs soybean meal mixed with either alfalfa or ensiled taro foliage and reported much lower feed intake and daily weight gain in the lambs fed the taro silage/soybean meal diet and attributed these to the high moisture content and anti-nutrients in the taro silage. Based on these facts Hassoun in his review of the subject suggested that since cocoyam leaves contain highly degradable leaf proteins they should be used as protein supplements for low digestibility forage and fibrous by-products. This could find particular application in West Africa, where the crude protein content of forage in the traditional pastoral zones could be as low as 2 to 4 percent during the dry season.  

At the traditional pastoral livestock production zone of West Africa, the productivity, chemical composition, and nutritive value of grasses are greatly affected by the cyclic drought in the zone (7 to 8 months of the dry season). During the mid-wet season, forage biomass is adequate in quality and quantity, with crude protein content reaching as high as 9 percent in most native grasses. However, in the drier Sahel zone and most of the northern pastoral zone of Nigeria, where most of the ruminant livestock are concentrated, the prolonged dry season and high temperatures accompanied by a rapid deterioration in the quality of available pasture affect the productivity of animals in a cyclic manner. As the dry season sets in the protein level in the forage biomass begin to drops, while the roughage component, including the lignin content increases, thereby depreciating voluntary feed intake. Indeed, most available forage at this time of the year are nutritionally poor, and their intake results in weight loss decreased fertility and milk yield for up to 4 – 5 months of the year.

Research evidence shows that with appropriate plant spacing of 70 cm between rows and between plants in the row, Xanthosoma cocoyam leaves, and petioles could be harvested at approximately 30-day intervals for about 20 months in the tropical rainforest zones such as southern Nigeria. The yearly fresh biomass (leaves and petioles) yield from this planting specification has been estimated at 128 ton/ha/year, made up of 14.5-ton dry matter and 1.9-ton crude protein/ha/yr. Similarly, the Colocasia cocoyam species has been reported to yield between 200 and 370 ton/ha/year of foliage, made up of leaves and petioles, with the leaves representing 50 percent of the foliage dry matter. Again, the single fresh leaf weighs between 450 and 650 g, with leaf component accounting for 40 percent and the petiole 60 percent. The average dry matter value of the fresh leaf is however about 11 percent, indicating its high moisture content. The crude fiber, protein, and energy values have been reported to be 12.4 percent, 16.0 – 26.0 percent, and 20.3-kilo calories per 100 g year-round. It is, therefore, practicable to produce and process cocoyam foliage in the southern rainforest zone of West Africa as a protein supplement for the low digestibility forage and fibrous by-products common to the pastoral zones during the extended dry season period.

Conclusion

Both the fresh, sun-dried and ensiled cocoyam foliage can serve as a protein source in pig and duck diets. Very limited information is available on its actual nutritional value for chicken and ruminants. However, considering the high biomass yield of most cocoyam species, it may be profitable to produce ensiled cocoyam foliage in the southern rainforest zone of West Africa for dry season livestock feeding in the arid pastoral zone of the sub-region.

Bibliography of References

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