Aimed to evaluate thekinetics of ruminal fermentation of hays of different fractions of the aerial parts of cassava varieties by technical semiautomatic gas production. The experiment was conducted in a randomized block design, arranged in a 4x3 factorial design, four varieties of cassava (Amarelinha, Sabará, OlhoRoxo e Periquita) and three fraction of shoots (upper, left over planting and whole plant) Pressure readings were made of gases through pressure transducer and subsequently adjusted to the volume of gases.Were evaluated the cumulative gas production, potentially degradable insoluble fraction and soluble fraction of MS, the degradation rate of DM, the potential and effective degradability of DM, the undegradable fraction of DM, the maximum potential gas production, the rate gas production and colonization time.There was an increase in gas production with a tendency of stabilization around a 48 hours period and a greater decrease in dry matter between zero and 24 hours fermentation period. The values of cumulative gas production (PCG) hay analyzed had a maximum output of 50 mL at the end of 96 hours of fermentation.The hay of Amarelinha's superior third was considered the most nutritional kind due to its betters degradability potential (64.17%), effective dry matter (55.65%), and greater maximal potential of gas production(35.69 mL / g DM) when compared to the other varieties studied.
degradability; digestibility; roughage; ruminant