Volatilização do HCN e determinação do ponto de feno em ramas de mandioca (Manihot esculenta Crantz)

Abstract

Cassava belongs to Euphorbiaceae family, being utilized for human and animal feeding as well. It is considered an excellent forage plant due to its capacity to produce feculent roots and a great deal of foliage. It is reported the results of two studies using cassava foliage. The experiments were carried out in Nossa Senhora das Candeias farm, located in Cruz das Almas, Bahia, Brazil, in the period from December 02 to 06, 2002 and the laboratorial analyses were done in the Plant Physiology and Food Technology laboratories of EMBRAPA/CNPMF. The objective of the first work was to verify the influence of two processes and five times of drying upon HCN volatilization of cassava foliage (Manihot esculenta Crantz) of Cigana black variety. It was used a completely randomized design in a factorial scheme (2x5) with two drying processes (under sun and at shade), both on black plastic sheets, and six times of drying (0, 9, 18, 27, 36 and 45 hours) with five replications. The drying treatments caused a reduction of the HCN contents of cassava foliage. However, the ones submitted to drying under the sun presented a greater HCN content as compared to the ones at shade, that showed the least HCN contents. The drying process of the cassava foliage under the sun, on black plastic sheets, caused retention of the HCN contents on levels considered toxic to animals until 45 hours of drying. In the second work, it was used a completely randomized design in a factorial scheme (2x15) with two drying (0, 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, 39 and 42 hours) processes (under sun and at shade), both on black plastic sheets, and fifteen times of drying with four replications. Foliage dehydration by process 1 (under the sun) achieved the hay point with 21 hours of exposition; and the one dried by process 2 (at shade) got the hay point with 30 hours of drying. The drying process under the sun produces hay with less time of drying reducing the labor expense and use of installation facilities. However, as it was observed in the first work, hay made from dehydration of cassava foliage under the sun for 45 hours still have HCN content in toxic level to the animals. So, taking into consideration the HCN content 1 as well as the time to achieve the hay point, it is advisable to dehydrate cassava foliage at shade.