Production in Thailand increased from 3.4 million tonnes of roots in 1970 to 24.3 million tonnes in 1989 and 19.1 million tonnes in 1995 ( Garcia and Dale, 1999). High export prices from the European Economic Community in the 1970s and 1980s caused a boost in cassava production in Thailand, resulting in it becoming the largest cassava exporter. This would equate to more than 500 million tonnes a year on the current harvested area, and yield could reach 80 tonnes per hectare under optimal conditions ( FAO, 2014). The current world average yield of cassava is 12.8 tonnes per hectare (world output of approximately 290 million tonnes), but there is potential to produce an average of 23.2 tonnes of cassava roots per hectare. Approximately 70% of the estimated total 13 million hectares of cultivated area in Africa and Asia has cassava growing on it ( El-Sharkawy, 2003). The majority (70%) of the world's cassava is produced in Nigeria, Brazil, Indonesia, Democratic Republic of Congo and Thailand ( FAO, 2014). World cassava output increased by 4.6% between 20 ( FAO, 2014). Under tropical conditions it is the most productive crop in terms of energy yield per unit land area, with a yield of between 25 and 60 tonnes/ha (1 ha = 10,000 m 2) ( Garcia and Dale, 1999). The reason is that it is tolerant to poor soils, diseases and drought ( Chauynarong et al., 2009). Approximately 500 million people currently depend on it as a major carbohydrate source ( Montagnac et al., 2009), making it the third largest source of carbohydrate for human food in the world ( Fauquet and Fargette, 1990). Cassava is believed to represent the future of food security in some developing countries. This is driven by demand for cassava food products in Africa and for dried cassava and starch for use in livestock feed in Asia. World annual cassava production has increased by approximately 100 million tonnes (1 tonne = 1,000 kg) since 2000. Cassava is the highest supplier of carbohydrates among staple crops and can potentially completely replace maize as an energy source in poultry diets. Such increases in the cost of conventional raw materials have accelerated the demand to find alternative feed resources that can replace a proportion of these products in poultry diets at a lower cost of production. There have been large increases in the prices of some vegetable protein sources as well. In recent years, the cost of maize has increased considerably due to competition with the human food industry, increased production of biofuel and droughts in some parts of Africa from September 2005 to September 2015 maize price increased by 71.16% ( USDA, 2015). This paper reviews the nutrient composition of cassava products and its value as an alternative energy source in poultry diets. Extensive research has been conducted on cassava products for poultry, but there is still a lack of consistency amongst the measured nutritive values for cassava and its products, hence variation exists in results from poultry studies. With correct processing the inclusion level of cassava in poultry diets could be increased. The utilisation of cassava is, however, limited by a number of factors, including its high fibre and low energy content and the presence of anti-nutritional factors, primarily hydrocyanic acid (HCN). Efficient use of cassava products has been shown to reduce feed costs of poultry production.
As a result, cassava is becoming an increasingly important ingredient in poultry diets, largely due to its high availability. Insufficient supply, high prices and competition with the human food and biofuel industries means there is a continuous demand for alternative energy sources for poultry.
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