Degradabilidade in situ dos fenos e das silagens de diferentes frações da parte aérea de quatro variedades de mandioca

Abstract

This work aimed to determine the rumen degradability of dry matter, crude protein and neutral detergent fiber of silages and hays of the different fractions of shoot of four cassava varieties. The degradability assays were carried through in a design in randomized blocks in factorial scheme 4 x 3 (4 varieties and 3 shoot fractions), with 2 blocks, two crossbred steers, cannulated in rumen and with average weight of 400 kg. The experiment lasted 15 days, being 10 days of adaptation to diet and 5 days of incubation. The data were submitted to analysis of variance and for effect of comparison of averages, the Scott & Knott test was used to 5% of significance. In the DM of the hay, the soluble and potentially degradable fractions presented high values of degradation. In the potential and effective degradabilities, the „Sabará‟ and „Periquita‟ varieties showed higher degradation in the superior third fraction, with lower non-degradable fraction. In the CP of the hay, the „Olho Roxo‟ presented lower soluble fraction and higher potentially degradable fraction. Hay from „Sabará‟ and „Periquita‟ varieties showed greater effective degradability. In the NDF of the hay, the potentially degradable fraction was higher in the superior third and planting surpluses, presenting high degradation rate, being the lowest non-degradable fraction obtained from „Sabará‟ variety in the superior third. The potential degradability was greater in the hays from „Sabará‟ and „Periquita, varieties, in the superior third fraction. The effective degradability of the hays was higher in the Sabará and Periquita varieties, in the planting surpluses and whole plant fractions. In the silages of cassava shoot, the potentially degradable fraction of the DM, the degradation rate, potential degradability and effective degradability did not present greater values due to high proportion of non-degradable fraction. The silages from Sabará and Periquita varieties, in the superior third and planting surpluses, showed greater soluble fractions of CP. The „Sabará‟ and „Olho Roxo presented, respectively, in the planting surpluses, and whole plant fractions, lower potentially degradable fraction of the silages. In the degradation rate, in the superior third, the „Olho Roxo‟ variety was outstood as well as the „Sabara‟ in the planting surpluses. The silage from „Olho Roxo‟ variety had the greatest non-degradable fraction, consequently it presented the lowest potential and effective degradabilities. In the NDF, the potentially degradable fraction of silages that had higher degradation was the superior third and planting surpluses, in the degradation rate, „Periquita‟ variety was the lowest one, showing also the smallest non-degradable fraction and the highest potential degradability. The greatest effective degradability was of the „Sabará‟ variety in the superior third and planting surpluses. For hay production, „Sabará‟ and „Periquita‟ were more adequate due to better rumen degradability. The superior third and planting surpluses presented better rumen degradability. The silage from shoot of „Sabará‟ shows better effective degradability of DM, CP and NDF, mainly in the superior third fraction.