Cassava peels can be used as a roughage and as an energy feed in ruminant diets. However, sun drying, ensiling and fermentation should be used to prevent HCN poisoning when feeding bitter cassava varieties (Pipat Lounglawan et al., 2011; Smith, 1988). Cassava peels should not be fed alone, as their protein and mineral content cannot support optimum rumen function and productivity. Their optimal utilization requires supplementation with readily fermentable protein and by-pass protein, as well as micronutrients including sulphur, phosphorus, and vitamin B. If fed in a balanced diet, cassava peels are a valuable feed for ruminants (Smith, 1988).
Digestibility and degradability
Cassava peels are highly digestible products, with reported values of 78% and 81% for DM and OM total tract digestibility respectively (Baah et al., 1999). Dry matter degradability is also high, with reported values more than 70% (Smith, 1988).
In Ghana, weight gains of 0.29 or 0.33 kg/day (vs. 0.07 kg/day for the control diet) were recorded with crossbred grazing bullocks supplemented with dried or ensiled peels (Larsen et al., 1976). In an experiment with bulls in Vietnam, total DMI increased with the amount of cassava peels while grass DMI decreased (Pham Ho Hai et al., 2009). Because of their high degradability, cassava peels are also used as an energy supplement in cattle: cassava peels can partly replace (30% of total DMI) energy concentrates, with no influence on the intake, digestibility, microbial efficiency, and nitrogen retention (Azevêdo et al., 2011).
Many trials have been carried out with sheep in Sub-Saharan Africa. In Ghana, Djallonké lambs lost weight after consuming a total diet of cassava peels: supplementation with Ficus exasperata leaves resulted in weight gains and in a significant increase in cassava peels DMI (from 44 to 58 g W0.75/d) (Baah et al., 1999). In Cameroon, sheep fed either 0, 35 or 70% of the diet as cassava peels (and 70, 35 and 0% Pennisetum purpureum), with cottonseed cake as the protein source, gained 45, 107 and 227 g/d respectively. Dry matter intake, digestibility and growth rate increased linearly with increasing dietary levels of cassava peels (Fomunyan et al., 1987). Sheep may use ensiled cassava peels better than sun-dried peel: in Nigeria, sheep fed a diet containing 80% ensiled cassava peels had greater daily gains (81 vs. 59 g/d) than those fed sun-dried peels (Asaolu, 1988 cited by Smith, 1988).
In Nigeria, a 60:20:20 ensiled mixture of grass-legume (Guinea grass and tropical kudzu Pueraria phaseoloides), cassava peels and poultry excreta fed to West African Dwarf goats resulted in favorable consumption and digestibility, as well as normal rumen and blood metabolites. It was recommended to use cassava peels as an energy supplement in anticipation of dry-season feeding (Okeke et al., 1987). In Red Sokoto goats, ensiling cassava peels with Pennisetum purpureum had beneficial effects on silage properties, intake and digestibility, and it was proposed that cassava leaves form at least 30% of silage made from Pennisetum purpureum to improve productivity during the dry season (Olorunnisomo, 2011). Sun-dried cassava peels included at up to 74% in supplement rations where they completely replaced maize offal did not affect liveweight changes in pregnant Red Sokoto goats grazing native pasture (Lakpini et al., 1997).
Cassava pomace has a lower feeding value than cassava roots but can be included in ruminant diets.