Max Lázaro Vieira Bose

Degradabilidade do capim-elefante em diferentes estágios de maturidade avaliada pelo método in vitro/gás

Elephantgrass (Pennisetum purpureum Schum.) is a tropical grass of high dry matter accumulation capacity, but its nutritive value is strongly influenced by its maturity. Considering the cellular wall intrinsic nature of different parts of the plant, the knowledge of its rates and degradation extent allow the determination of which component and which maturity stage affects its digestion. Therefore, the objective of this trial was to evaluate the elephantgrass CV Napier dry matter (DM) degradability by the in vitro/gas technique, with cuts from 45 to 105 days, with intervals of 10 days between cuts. A decrease was noticed in the elephantgrass fraction degradability with the stage maturity progress. The DM degradability regression coefficients estimated of the digestion remaining residue for leaves and stems were 0.51 and 0.89, respectively. For leaves and stems fiber degradability in neutral detergent (NDF) the regression coefficients were 0.82 and 0.92, respectively. For the total gas production the regression coefficient for leaves was 0.56 and for stems 0.90. In general, the elephantgrass stems, in relation to the progress of vegetative maturity, presented larger influence on the decrease of the DM and NDF degradability than the leaves. The progress in the elephantgrass maturity stage affects directly the stem and leave degradabilities. This is more accentuated for stems due to the more intense cellular wall lignification.

Digestibilidade in vitro/gás de volumosos exclusivos ou combinados avaliados pelo resíduo remanescente da digestão da matéria seca e produção de gás

The in vitro/gas dry matter (DM) digestibility of four roughages, mixed or not, in proportion of 50% in the DM were evaluated. Samples of 100 mg by treatment, in triplicate, in 48 h of digestion were incubated. The DM digestibilities and gas production were: sugar cane = 60.6%, 17.3 mL; sugar cane + corn silage = 63.9%, 19.6 mL; sugar cane + elephantgrass of 60 days = 60.5%, 16.9 mL; sugar cane + elephantgrass of 180 days = 48.6%, 14.1 mL; corn silage = 66.3%, 19.4 mL; corn silage + elephantgrass of 60 days = 62.1%, 16.7 mL; corn silage + elephantgrass of 180 days = 52.7%, 15.8 mL; elephantgrass of 60 days = 61.5%, 16.9 mL; elephantgrass of 180 days = 34.6%, 11.7 mL. It was verified that the association of these roughages can, in some cases, reduce the DM digestibility of those roughages of better quality.

Avaliação do sistema de monitoramento computadorizado de digestão in vitro: 3. Desaparecimento da matéria seca e/ou FDN pela produção de gás

ABSTRACT - The objective of this work was to evaluate the computerised monitoring of the in vitro gas production system andto compare with in vivo and in situ methods. In the degradation methods, corn silage samples with high/low dry matter (DM) contents,with/without inoculate, were used. Evaluating the silage degradation, by the gas production on the fermentation, the results of theextension of degradation (A+D) were 21.5; 22.6; 22.1 and 20.9 mL of gas/100 mg DM, without significant difference. The coeffici entsfor determination obtained on the total gas production in relation to the potential degradation obtained in situ showed to be high forinoculated corn silage with high DM (R 2 = 0.99), non-inoculated corn silage high DM (R 2 = 0.98), inoculated corn silage with low DM(R 2 = 0.94) and non-inoculated corn silage with low DM (R 2 = 0.93). The DM and/or neutral detergent fiber (NDF) disappearance,determined by gas production in the in vitro/gas system, presented similar results when comparing the others evaluated methods.Key Words: corn silage, gas production, in vitro digestion

Avaliação do sistema de monitoramento computadorizado de digestão in vitro: 1. Testes preliminares

The objective of this work was to test the computerized monitoring of the in vitro gas production system. This technique made easy the degradation studies of soluble and insoluble fractions of forages, determined by the gas production (CO2 e CH4) from microbial metabolism and measured by a pressure sensor. Several amounts of samples (50 to 110 mg of alfalfa hay) and other feedstuffs were tested. Also, the influence of the amount of ruminal liquid (2.0 or 3.0 mL), with or without stirs in incubator flasks, on the digestibility of 100 mg of alfalfa hay, was studied. The amount of 100 mg of sample, 2.0 mL of ruminal liquid and without agitating magnetic bar, provided lower coefficients of variance on the gas production. In conclusion, 2.0 mL of ruminal liquid, without stirrer with 100 mg of sample, presented a greater precision of the digestion curve.

Comparação do sistema de monitoramento computadorizado de digestão in vitro com os métodos in vivo e in situ: 2. Uso do resíduo da matéria seca de forragens

ABSTRACT - The objective of this work was to compare the computerized monitoring of the in vitro gas production system with thein vivo and in situ methods. On the comparisons, corn silage with high/low dry matter contents, with/without inoculation, were used. Thedigestibility of silage with high dry matter (DM) content, with/without inoculation, did not present differences among the anal yzed methods.When evaluated apart from the inoculation effect, that silage differed in vitro /gas and in situ methods; however in vivo did not differ. Nevertheless,when analyzed under the inoculation effect, only in i n situ method there was no difference. No differences were found on the silage neutral detergentfiber (NDF) digestibility with high or low DM, inoculated or not, as well as in relation to pH at the end of digestion. In con clusion, the disappearingof DM and NDF determined by the residue of the in vitro/gas system was similar to the others evaluated methods.Key Words: corn silage, gas production, in situ digestion, in vitro digestion, in vivo digestion

Ruminal parameters analyzed in remaining digestion residue of roughages in the in vitro/gas system

Animal performance is the most direct measure in the evaluation of feed quality. However, performance data are often insufficient to determine possible interactions that may take place in the ruminal environment. The purpose of the present trial was to evaluate the possible associative effects on the concentrations of volatile fatty acids (VFAs), ammoniacal nitrogen (N-NH3) and pH in the remaining liquid fraction from the dry matter (DM) digestion for exclusive roughages: sugarcane (SC), 60- (EG60) and 180-day elephantgrass (EG180), and corn silage (SIL), as well as for combined roughages: sugarcane+corn silage (SCSIL), sugarcane+60-day elephantgrass (SCEG60), sugarcane+180-day elephantgrass (SCEG180), corn silage+60-day elephantgrass (SILEG60), corn silage+180-day elephantgrass (SILEG180) associated at equal DM proportions (50%). These associative effects present positive or negative effects on bovine performance. Concentrations of VFAs and N-NH3, as well as pH for the treatments were, respectively: SC= 56.9 mmol L-1, 50.1 mg dL-1, 5.7; SCSIL= 61.4 mmol L-1, 50.7 mg dL-1, 5.8; SCEG60= 54.7 mmol L-1, 47.6 mg dL-1, 5.8; SCEG180= 45.4 mmol L-1, 49.4 mg dL-1, 6.0; SIL= 57.2 mmol L-1, 54.0 mg dL-1, 5.8; SILEG60= 57.1 mmol L-1, 53.1 mg dL-1, 5.9; SILEG180= 55.9 mmol L-1, 52.3 mg dL-1, 6.0; EG60= 58.1 mmol L-1, 49.4 mg dL-1, 5.9; and EG180= 44.0 mmol L-1, 46.4 mg dL-1, 6.1. Nonstructural carbohydrates and starch, associated with fiber and protein, contributed to positive associative effect on the 50:50 sugarcane/corn silage mixtures. The high fermentative aspect of such mixture may have promoted the best results in bovine performance.