ABSTRAT
Gas production, carbohydrates and proteins fractions of tropical grasses and by-products
Were studied different ages of cut of tropical grasses in the carbohydrates and proteins
fractions, as well as the gas production of Bachiaria brizanta cv Marandu and the carbohydrates and
proteins fractions of the for different by-products. Three experiments were conducted, in the Campus
Juvino Oliveira, of the Universidade Estadual do Sudoeste da Bahia (UESB), district of Itapetinga-BA.
In the first experiment the grasses evaluated were Tanzania (Panicum maximum cv. Tanzania),
Braquiarão (Brachiaria brizantha cv. Marandu) and Tifton 85 (Cynodon dactylon cv. Tifton 85),
cultivated separately in stonemasons with dimensions of 9x3m cut in different ages (28, 35 and 54
days) between of December of 2005 to January of 2006. The design was used completely randomized
with portions subdivided, being the located grasses in the portions and the cut ages in the subdivided.
It was used 4 repetitions totaling 12 stonemasons. There was significant effect (P <0,05), with growing
lineal increase with the progress of the age for the percentage of dry matter (DM), neutral detergent
fiber correct to protein and ash (NDFPA), nitrogen insoluble in neutral detergent (NIDIN), total
carbohydrate (TC). The crude protein (CP) contents decline with the progress of the age for the three
grasses. For the carbohydrates fractions there was difference between the grasses and grass-marandu
presented high contents for the fraction A+B1, and B2 with averages of 25,5 and 34,8% of the CP at
28 days of age. For protein fractions the grass-marandu it was also who presented the largest
percentages of the fraction A, 28,1% of the CP to the 35 days, B1+B2, 53,8% of the CP to the 28 days,
and the smallest medium values for the fraction B3 and C (16% and 12,9% of the CP, respectively).
Grass-Tifton 85 was who presented the largest percentages for the fraction B3, 32,7% of the CP. In the
second experiment the in vitro digestibility of Brachiaria brizantha cv. Marandu, was evaluated cut to
the 28, 35 and 54 days of age, with height of 20 cm of the soil in the period of December of 2005 to
January of 2006 through the technique of gas production. The data of the gas production were adjusted
to the model logistic bicompartimental, for the obtaining of the parameters of the kinetics of gases
production and subsequent comparisons among the parameters in the different ages. The pressure
readings and volume were accomplished in the times of 2, 4, 6, 8, 10, 12, 14, 17, 20, 24, 28, 32, 48, 72
and 96 hours. The design was used completely randomized. The data were submitted to the variance
analysis and of regression, at the level of 5% of probability. There was significant effect (P <0,05), for
the variables CP, NDFPA, acid detergent fiber, NIDIN, nitrogen insoluble in acid detergent, TC, B2,
with lineal increase as it advanced the cut age. Partition factor was superior to the 35 days when
obtained larger gas production and smaller DM digestibility. For the kinetic parameters the gas
production of the A fraction was similar between the ages of 28 and 35 days, with 95,75mL and
116,8mL/1g of DM, respectively. The age recommended for obtaining of the best nutritional value of
the grass-marandu it went to the 28 days. In the third experiment samples of five by-products were
collected, cocoa meal (Theobroma cocoa), coffee hulls (Coffea rábica, L.), palm cake (Elaeis
guineensis), cassava pulp (Manihot esculenta) and the mesquite pods meal algaroba green bean
(Prosopis juliflora), to evaluate yours chemical composition. The by-products evaluated presented
chemical composition similar to the alternative feeds used in the animal feeding. The bran of the green
bean of the algaroba and the pulp of the cassava demonstrated to be excellent sources of energy for the
growth of the ruminal microorganisms. The coffee hulls presented elevated contents of the fraction C
needing larger studies in yours use in the animal feeding.
Words Key: Fractions, degradabilidade, braquiária, by-products
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*Adviser: Márcio dos Santos Pedreira, D.Sc., UESB e Co-advises: Fabiano Ferreira da Silva, D,Sc.,
UESB e Paulo Bonomo, D.Sc., UESB.