RESUMO

Avaliaram-se a acurácia, a precisão e a robustez dos indicadores cutina, lignina em detergente ácido, óxido crômico e coleta total de fezes na estimativa da digestibilidade aparente da matéria orgânica de dietas para equinos. Para tal, foram utilizados quatro equinos machos, com idade aproximada de 10 meses e média de peso de 197kg (170 a 216kg). O experimento foi realizado em quatro períodos, com duração de 11 dias cada, sendo os oito primeiros usados para adaptação às dietas e os três subsequentes, para colheita de material. O delineamento experimental foi em quadrado latino 4X4. A ponderação dos coeficientes de digestibilidade da matéria orgânica pelos indicadores foi efetuada por meio do viés. A acurácia e a precisão foram determinadas pela comparação entre os dados preditos e observados, e a robustez pela comparação dos vieses com outros fatores estudados. A cutina não se mostrou eficiente como indicador interno, pois superestimou a digestibilidade aparente da matéria orgânica e resultou em menor acurácia e precisão. O oxido crômico apresentou baixa recuperação fecal e subestimou a digestibilidade aparente da matéria orgânica, embora tenha sido o mais preciso. A lignina em detergente ácido foi o indicador que obteve a melhor recuperação fecal e foi o mais acurado, portanto, o indicador mais eficiente.

The accuracy, precision, and robustness of the cutin, acid detergent lignin (ADL), chromic oxide, and total feces collection to estimate the apparent digestibility of the organic matter of diets for equines were evaluated. For such, four male horses were used. They averaged 10 month-old and 197kg (170 to 216kg). The experiment was carried out in four periods with duration of eleven days each, being the first eight for adaptation to the diets and the three subsequent to obtain the results. The experimental design was a 4x4 latin square. The balance of the coefficients of digestibility of the organic matter for the markers was made by means of the bias. The accuracy and the precision were determined by the comparison of the predicted data with the observed ones, and the robustness by the comparison of the bias with other studied factors. The cutin did not show efficient as an internal marker, therefore it overestimated the apparent digestibility of the organic matter and showed to be less accurate and precise. The chromic oxide presented low fecal recovery and underestimated the apparent digestibility of the organic matter, even though it was more precise. The acid detergent lignin was the marker that got the best fecal recovery and was the most accurate, therefore, the most efficient marker.

Assuntos

RESUMO

Avaliaram-se a acurácia, a precisão e a robustez dos indicadores cutina, lignina em detergente ácido, óxido crômico e coleta total de fezes na estimativa da digestibilidade aparente da matéria orgânica de dietas para equinos. Para tal, foram utilizados quatro equinos machos, com idade aproximada de 10 meses e média de peso de 197kg (170 a 216kg). O experimento foi realizado em quatro períodos, com duração de 11 dias cada, sendo os oito primeiros usados para adaptação às dietas e os três subsequentes, para colheita de material. O delineamento experimental foi em quadrado latino 4X4. A ponderação dos coeficientes de digestibilidade da matéria orgânica pelos indicadores foi efetuada por meio do viés. A acurácia e a precisão foram determinadas pela comparação entre os dados preditos e observados, e a robustez pela comparação dos vieses com outros fatores estudados. A cutina não se mostrou eficiente como indicador interno, pois superestimou a digestibilidade aparente da matéria orgânica e resultou em menor acurácia e precisão. O oxido crômico apresentou baixa recuperação fecal e subestimou a digestibilidade aparente da matéria orgânica, embora tenha sido o mais preciso. A lignina em detergente ácido foi o indicador que obteve a melhor recuperação fecal e foi o mais acurado, portanto, o indicador mais eficiente.(AU)

The accuracy, precision, and robustness of the cutin, acid detergent lignin (ADL), chromic oxide, and total feces collection to estimate the apparent digestibility of the organic matter of diets for equines were evaluated. For such, four male horses were used. They averaged 10 month-old and 197kg (170 to 216kg). The experiment was carried out in four periods with duration of eleven days each, being the first eight for adaptation to the diets and the three subsequent to obtain the results. The experimental design was a 4x4 latin square. The balance of the coefficients of digestibility of the organic matter for the markers was made by means of the bias. The accuracy and the precision were determined by the comparison of the predicted data with the observed ones, and the robustness by the comparison of the bias with other studied factors. The cutin did not show efficient as an internal marker, therefore it overestimated the apparent digestibility of the organic matter and showed to be less accurate and precise. The chromic oxide presented low fecal recovery and underestimated the apparent digestibility of the organic matter, even though it was more precise. The acid detergent lignin was the marker that got the best fecal recovery and was the most accurate, therefore, the most efficient marker.(AU)

Assuntos

RESUMO

Prediction of carbohydrate fractions using equations from the Cornell Net Carbohydrate and Protein System (CNCPS) is a valuable tool to assess the nutritional value of forages. In this paper, these carbohydrate fractions were predicted using data from three sunflower (Helianthus annuus L.) cultivars, fresh or as silage. The CNCPS equations for fractions B2 and C include measurement of ash and protein-free neutral detergent fibre (NDF) as one of their components. However, NDF lacks pectin and other non-starch polysaccharides that are found in the cell wall (CW) matrix, so this work compared the use of a crude CW preparation instead of NDF in the CNCPS equations. There were no differences in the estimates of fractions B1 and C when CW replaced NDF; however, there were differences in fractions A and B2. Some of the CNCPS equations could be simplified when using CW instead of NDF. Notably, lignin could be expressed as a proportion of DM, rather than on the basis of ash and protein-free NDF, when predicting CNCPS fraction C. The CNCPS fraction B1 (starch + pectin) values were lower than pectin determined through wet chemistry. This finding, along with the results obtained by the substitution of CW for NDF in the CNCPS equations, suggests that pectin was not part of fraction B1 but present in fraction A. We suggest that pectin and other non-starch polysaccharides that are dissolved by the neutral detergent solution be allocated to a specific fraction (B2) and that another fraction (B3) be adopted for the digestible cell wall carbohydrates.

RESUMO

Lignin extracted with acidic dioxane was investigated as a possible standard for quantitatively determining lignin content in plant samples using the spectrophotometric method employing acetyl bromide. Acidic dioxane lignins were analyzed for carbohydrate, total protein, nitrobenzene oxidation products, and UV spectral characteristics. Total carbohydrate content of isolated lignins ranged from 2.21 to 5.70%, while protein ranged from 0.95 to 6.06% depending upon the plant source of the original cell wall sample. Nitrobenzene analysis indicated differences in the amount of guaiacyl and syringyl units making up the lignins, but this did not alter the UV spectrum of lignin solubilized in acetyl bromide. Regression equations developed for the acetyl bromide method using the isolated lignins for all the plant samples were similar to each other. Lignin values obtained by the acetyl bromide method were similar to the lignin values obtained as acid insoluble residues following a Klason lignin procedure.

Assuntos

RESUMO

Lignin concentration can be measured in plants by the acetyl bromide-soluble lignin spectrophotometric method; however, as with any spectrophotometric method, a reliable standard is needed. In the present experiments, lignin was extracted from each of the forages under study with the acetyl bromide reagent. The lignin isolated with acetyl bromide (LIAB) was then used as the reference standard in the acetyl bromide-soluble lignin (ABSL) analysis, which was compared with the acid detergent lignin (ADL) and potassium permanganate lignin (PerL) lignin analyses. Two maturity stages of each of the following forages were analyzed: Medicago sativa, Cynodon dactylon var. Coastal, Panicum maximum var. Centenário and var. Colonião, Cynodon plectostachyus, Pennisetum purpureum, Setaria nandi, and Avena sativa. In addition, one wood sample, Eucalyptus sp., was analyzed. In general, ABSL values were highest (P < 0.001), followed by PerL and ADL, which also differed from each other (P < 0.001). Correlations with in vitro dry matter digestibility of samples were highest with the ABSL method. Absorption spectra of LIAB, either from plants of different maturity stages or from different vegetable species, suggested the presence of differences among some of the lignins.

Assuntos