Variação estacional da composição química-bromatológica, do teor de macronutrientes minerais e da digestibilidade "in vitro" do capim elefante (Pennisetum purpureum, Schum.) variedade napier

Seasonal variation in the chemical composition, major mineral nutrients and "in vitro" digestibility of napier grass (Pennisetum purpureum, Schum)

Resumos

This paper deals with an experimental work carried out in order to estimate the chemical composition, the major minerals content and the "in vitro" dry matter and cellulose digestibility coefficients of napier grass (Pennisetum purpureum, Schum), during the year. Random blocks, including 15 m² plots with 10 treatments (cuttings) and 3 replications, was the experimental design used. The forage was harvested at 45, 75, 105, 135, 165, 195, 225, 255, 285 and 315 days of vegetative growth, and the samples collected in previously established dates, at the same day hour. It was observed a maturity effect on the chemical composition of napier grass. Higher dry matter contents were observed after the second cutting, which is considered the best stage of vegetative growth in relation to heigth of forage, for harvesting. However, after 75 days the crude protein contents were not enough to meet the minimum nutrient requirements of cattle under grazing management. The highest crude fiber contents were observed in the flowering stage. It was noted that nitrogen, phosphorus, sulfur and potassium concentrations became lower as maturity was reached. In the other hand, magnesium content showed a consistent tendency to increase in the latter cuttings. The highest calcium concentration was observed during the dry season of the year, when the forage was in the advanced stage of maturity. In relation to phosphorus, the lowest concentrations were also found during the dry season, and this fact confirms several previous observations on the seasonal defficiency of phosphorus in forage. Calcium, sulfur, potassium and magnesium contents could be considered enough to cover the nutrients requirements of cattle. However, as far as phosphorus is concerned, only during the first phase of vegetative growth (third cutting) the grass would have enough phosphorus to meet the minimum requirements of cattle. Dry matter, crude fiber and cellulose contents showed significative and negative correlations to nitrogen, phosphorus, sulfur and potassium concentrations, but to the magnesium content, the correlation was positive. On the other hand, crude protein and ash contents presented significative and positive correlations to nitrogen, phosphorus, sulfur and potassium contents, exception to magnesium content showed significative and negative correlation to ash. It was observed a negative effect of maturity on the digestibility of napier grass. "In vitro" dry matter digestibility coefficients declined from 71,64% in the first cutting at 45 days to 43,69% in the tenth cutting at 315 days, and in relation to cellulose the reduction was 78,10% to 35,47%, respectively. "In vitro" dry matter digestibility coefficients were negative and highly correlated to dry matter (r=-0,91), cellulose (r=-0,88) and crude fiber (r=-0,93) contents, and positively correlated to crude protein (r=0,88) and ash (r=0,89) contents. In the same way, it was noted a negative and high correlation between "in vitro" cellulose digestibility and dry matter (r =-0,93), cellulose (r = -0,85), and crude fiber (r=-0,91), and significative correlation to crude protein (r= 0,88) and ash (r= 0,88) contents. A positive and high correlation was observed between "in vitro" digestibility coefficients of cellulose and dry matter (r= 0,99). Significative correlation coefficients were found between "in vitro" dry matter digestibility and nitrogen (r = 0,88), phosphorus (r=0,66), sulfur (r=0,66) and potassium (r=0,90) contents, but in relation to magnesium it was observed a negative correlation (r=-0,43). The same situation was observed as "in vitro" cellulose digestibility is concerned, that is: nitrogen (r= 0,88), phosphorus (r=0,68), sulfur (r=0,68), potassium (r= 0,89) and magnesium (r=-0,41).

Variação estacional da composição química-bromatológica, do teor de macronutrientes minerais e da digestibilidade "in vitro" do capim elefante (Pennisetum purpureum, Schum.) variedade napier^*

Seasonal variation in the chemical composition, major mineral nutrients and "in vitro" digestibility of napier grass (Pennisetum purpureum, Schum)

Attilio O. Prospero

Departamento de Zootecnia da E.S.A. "Luiz de Queiroz", Piracicaba

RESUMO

Com a finalidade de estudar alguns aspectos do valor nutritivo do capim elefante (Pennisetum purpureum, Schum.) variedade Napier, procurou-se, no presente trabalho, determinar os constituintes químico-bromatológicos e 6 macronutrientes minerais (nitrogênio, fósforo, cálcio, enxofre, potássio e magnésio), assim como estimar a digestibilidade "in vitro" da matéria seca e da celulose.

A matéria seca, a proteína bruta, a fibra bruta e a cinza bruta foram determinadas pelos métodos descritos pela A.O.A.C. (1965), e a celulose pelo processo descrito por CRAMPTON e MAYNARD (1938).

Dos macronutrientes minerais estudados, o cálcio, o potássio e o magnésio foram determinados por espectrofotometria de absorção atômica, o fósforo pelo processo do vanádio-molibdato de amônio, por digestão nítrico-perclórica, e o enxofre pelo método gravimétrico do bário.

A digestibilidade "in vitro" da matéria seca e da celulose foi determinada por um período de 48 horas, utilizando-se fluido ruminal de carneiro, conforme o método descrito por CARVALHO (1967) e as modificações introduzidas por SILVEIRA (1970).

Evidenciou-se a influência da maturidade sobre os constituintes químico-bromatológicos, os macronutrientes minerais e a digestibilidade "in vitro" do capim Napier. Os teores de materia seca, de fibra bruta e de celulose se elevaram e os teores de proteína bruta e cinza bruta decresceram com a maturidade da planta. Os teores de nitrogênio, fósforo, enxofre e potássio declinaram, os teores de magnésio mostraram tendência a se elevar e os teores de cálcio apresentaram constante variação com o avançar da idade da forrageira. A digestibilidade "in vitro" da matéria seca e da celulose foi influenciada negativamente pela maturidade da planta. Foram estabelecidas correlações entre os constituintes químico-bromatológicos e a digestibilidade "in vitro" e entre esta e os macronutrientes minerais.

SUMMARY

This paper deals with an experimental work carried out in order to estimate the chemical composition, the major minerals content and the "in vitro" dry matter and cellulose digestibility coefficients of napier grass (Pennisetum purpureum, Schum), during the year. Random blocks, including 15 m² plots with 10 treatments (cuttings) and 3 replications, was the experimental design used.

The forage was harvested at 45, 75, 105, 135, 165, 195, 225, 255, 285 and 315 days of vegetative growth, and the samples collected in previously established dates, at the same day hour.

It was observed a maturity effect on the chemical composition of napier grass. Higher dry matter contents were observed after the second cutting, which is considered the best stage of vegetative growth in relation to heigth of forage, for harvesting. However, after 75 days the crude protein contents were not enough to meet the minimum nutrient requirements of cattle under grazing management. The highest crude fiber contents were observed in the flowering stage.

It was noted that nitrogen, phosphorus, sulfur and potassium concentrations became lower as maturity was reached. In the other hand, magnesium content showed a consistent tendency to increase in the latter cuttings.

The highest calcium concentration was observed during the dry season of the year, when the forage was in the advanced stage of maturity. In relation to phosphorus, the lowest concentrations were also found during the dry season, and this fact confirms several previous observations on the seasonal defficiency of phosphorus in forage. Calcium, sulfur, potassium and magnesium contents could be considered enough to cover the nutrients requirements of cattle. However, as far as phosphorus is concerned, only during the first phase of vegetative growth (third cutting) the grass would have enough phosphorus to meet the minimum requirements of cattle.

Dry matter, crude fiber and cellulose contents showed significative and negative correlations to nitrogen, phosphorus, sulfur and potassium concentrations, but to the magnesium content, the correlation was positive. On the other hand, crude protein and ash contents presented significative and positive correlations to nitrogen, phosphorus, sulfur and potassium contents, exception to magnesium content showed significative and negative correlation to ash.

It was observed a negative effect of maturity on the digestibility of napier grass. "In vitro" dry matter digestibility coefficients declined from 71,64% in the first cutting at 45 days to 43,69% in the tenth cutting at 315 days, and in relation to cellulose the reduction was 78,10% to 35,47%, respectively.

"In vitro" dry matter digestibility coefficients were negative and highly correlated to dry matter (r=-0,91), cellulose (r=-0,88) and crude fiber (r=-0,93) contents, and positively correlated to crude protein (r=0,88) and ash (r=0,89) contents. In the same way, it was noted a negative and high correlation between "in vitro" cellulose digestibility and dry matter (r =-0,93), cellulose (r = -0,85), and crude fiber (r=-0,91), and significative correlation to crude protein (r= 0,88) and ash (r= 0,88) contents. A positive and high correlation was observed between "in vitro" digestibility coefficients of cellulose and dry matter (r= 0,99).

Significative correlation coefficients were found between "in vitro" dry matter digestibility and nitrogen (r = 0,88), phosphorus (r=0,66), sulfur (r=0,66) and potassium (r=0,90) contents, but in relation to magnesium it was observed a negative correlation (r=-0,43). The same situation was observed as "in vitro" cellulose digestibility is concerned, that is: nitrogen (r= 0,88), phosphorus (r=0,68), sulfur (r=0,68), potassium (r= 0,89) and magnesium (r=-0,41).

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LITERATURA CITADA

Entregue para publicação em 21/11/72.

• ANDRADE, I. F. e J. A. GOMIDE - 1970. Curva de crescimento e valor nutritivo de capim elefante A-146 Taiwan. VII Reunião Anual da Sociedade Brasileira de Zootecnia, Piracicaba. (Mimeografado).
• ANDREASI, P., J. S. M. VEIGA, C. X. MENDONÇA JUNIOR, F. PRADA e R. C. BARNABE. - 1966-1967. Levantamento dos elementos minerais em plantas forrageiras de áreas delimitadas do estado de São Paulo. I - Cálcio, Fósforo e Magnésio. Rev. da Faculdade de Medicina Veterinária da Universidade de São Paulo 7(3):583-604.
• ANDREASI, F., C. X. MENDONÇA JUNIOR, J. S. M. VEIGA, F. PRADA e N. MASOTTI - 1966-1967. Levantamento dos elementos minerais em plantas forrageiras de áreas delimitadas do estado de São Paulo. II - Sódio e Potássio. Rev. da Faculdade de Medicina Veterinária da Universidade de São Paulo, 7(3):605-614.
• A.O.A.C. - 1965. Official Methods of Analysis. Association of Official Agricultural Chemists. Tenth edition. Washington, D. C.
• APPELMAN, H. e J. G. P. DIRVEN - 1962. The influence of the cutting interval on the chemical composition of various grasses. Surinaam. Landb, 10(3):95-102. English summary.
• ARIAS, P. J. e M. BUTTERWORTH - 1965. Crescimiento del pasto elefante. Anais do IX Congresso Internacional de Pastagens, D. P. A., São Paulo, 1:407-412.
• ARROYO-AGUILÚ, J. A. 1967. Estimation of digestibility from "in vitro" rumen fermentation data in some forages of Puerto Rico. J. Agric. Univ. Puerto Rico, 51(2):133-139.
• BURTON, G. W., J. E. JACKSON and R. H. HART - 1963. Effects of cutting frequency and nitrogen on yield, "in vitro" digestibility, and protein, fiber and carotene content of Coastal Bermudagrass. Agronomy, J., 55(5):500-502.
• CARO-COSTAS, R., J. VICENTE-CHANDLER e J. FIGARELLA - 1960. The yields and composition of five grasses growing in the humid mountains of Puerto Rico, as affected by nitrogen fertilization, season, and harvest procedures. J. Agric. Univ. Puerto Rico, 44(3):107-120.
• CARVALHO, M. M. - 1967. A técnica do rumen artificial na estimativa de digestibilidade aparente de forrageiras tropicais. Tese de M. S., Universidade Rural do Estado de Minas Gerais, Viçosa.
• CRAMPTON, E. W. and L. A. MAYNARD. - 1938. The relation of cellulose and lignin content to the nutritive value of animal feeds. J. Nutrition, 15(4):383-395.
• DEHORITY, B. A. and R. R. JOHNSON - 1961. Effect of particle size upon the "in vitro" cellulose digestibility of forages by rumen bacteria. J. Dairy Sci., 44(12):2242-2249.
• FRENCH, M. H. - 1956. The nutritive value of East African hay. Empire J. Exp. Agric., 24(93):53-60.
• FRENCH, M. H. e L. M. CHAPARRO - 1960. Contribución al estúdio de la composición química de los pastos en Venezuela durante la estación seca. Agronomia Tropical, 10(2):57-69.
• GAVILLON, O. - 1961. Levantamento da composição mineral das pastagens do Rio Grande do Sul. II. Os minerais maiores e a composição imediata. A Granja, Porto Alegre, 15(175):34-36.
• GOMIDE, J. A., C. H. NOLLER, G. O. MOTT, J. H. CONRAD e D. L. HILL, 1969. Effect of plant age and nitrogen fertilization on the chemical composition and "in vitro" cellulose digestibility of tropical grasses. Agronomy J., 61(1):116-120.
• GOMIDE, J. A., C. H. NOLLER, G. O. MOTT, J. H. CONRAD e D. L. HILL 1969a. Mineral composition of six tropical grasses as influenced by plant age and nitrogen fertilization. Agronomy J., 61(1):120-123.
• HAAG, H. P., F. A. F. MELLO, M. O. C. BRASIL SOBRINHO, A. COBRA NETTO, R. G. ANDRADE e R. G. COELHO - 1965. Estudos sobre a nutrição mineral do Pennisetum purpureum, Schum, var. Napier cultivado em solução nutritiva. Anais do IX Congresso Internacional de Pastagens, D. P. A., São Paulo, 1:691-695.
• HAAG, H. P., M. L. V. BOSE e R. G. ANDRADE - 1967. Absorção dos macronutrientes pelos capins Colonião, Gordura, Jaraguá, Napier e Pangola. Anais da E.S.A. "Luiz de Queiroz", Piracicaba, 24:177-188.
• JARDIM, W. R., A. M. PEIXOTO e C. L. MORAES - 1962. Observações sobre deficiências minerais na nutrição dos bovinos na região do Brasil Central. Boletim Técnico Científico n.ş 13. E.S.A. "Luiz de Queiroz", Piracicaba.
• LOTT, W. L., J. P. NERY, J. R. GALLO eJ. C. MEDCALF - 1956. A técnica de análise foliar aplicada ao cafeeiro. Instituto Agronômico, Campinas, Boletim n.ş 79.
• MALA VOLTA, E., H. P. HAAG, F. A. F. de MELLO e M. O. C. BRASIL SOBRINHO - 1967. Nutrição mineral de algumas culturas tropicais. Editora da Universidade de São Paulo. São Paulo.
• MORAES, C. L. de - 1970. Análise de Forragem. C.P.G. de Nutrição Animal e Pastagens, E. S. A. "Luiz de Queiroz", Piracicaba. (Mimeografado).
• MOWAT, D. N., R. S. FULKERSON, W. E. TOSSELL e J. E. WINCH. 1965. Digestibilidade "in vitro" da matéria seca de várias espécies e variedades de plantas assim como de suas partes com o aumento da maturidade. Anais do IX Congresso Internacional de Pastagens, D.P.A., São Paulo, 1:801-806.
• PERKIN-ELMER - 1966. Analytical methods for atomic absorption spectrophotometry. Connecticut, Perkin-Elmer Corp.
• SILVA, D. J. DA, J. H. CONRAD e J. CAMPOS - 1965. Da digestibilidade "in vitro" de algumas forrageiras tropicais. Anais do IX Congresso Internacional de Pastagens. D.P.A., São Paulo, 1:895-897.
• SILVEIRA, A. C. - 1970. Efeito da maturidade da planta e diferentes tratamentos sobre a digestibilidade "in vitro" de silagens de capim elefante, variedade Napier (Pennisetum purpureum, Schum.), Tese de M.S., E.S.A. "Luiz de Queiroz", Universidade de São Paulo.
• TOTH, S. J., A. L. PRINCE, A. WALLACE e D. S. MIKKELSEN - 1948. Rapid quantitative determination of eight mineral elements in plant tissues by a sistematic procedure involving use of a flame photometer. Soil Sci., 66(6):459-466.
• UNDERWOOD, E.J. - 1966. The mineral nutrition of livestock - Food and Agriculture Organization of the United Nations and Commonwealth Agricultural Bureaux. The Central Press (Aberdeen) Ltd.
• VICENTE-CHANDLER, J., S. SILVA e J. FIGARELLA - 1959. The effect of fertilization and frequency of cutting on the yield and composition of three tropical grasses. Agronomy J., 51(4):202-206.
• VIEIRA, L. M. e J. A. GOMIDE. - 1968. Composição química e produção forrageira de três variedades de capim elefante. Rev. Ceres, 15(86):245-260.
• VILLARES, J. B. e H. M. TEIXEIRA E SILVA - 1956. Contribuição para o estudo das carências minerais em bovinos no Estado de São Paulo. I - Levantamento do índice de fósforo no sangue de vacas Guzerá na Fazenda Experimental de Criação de Sertãozinho. Boletim da Indústria Animal, São Paulo, 15 (N.ş único):5-22.
• WERNER, J. C. - 1971. Estudos sobre a nutrição mineral de alguns capins tropicais. Tese de doutoramento. E.S.A. "Luiz de Queiroz", Universidade de São Paulo, Piracicaba.

*

Resumo parcial de tese de doutoramento defendida na ESALQ, em 21/3/72.

Datas de Publicação

• Publicação nesta coleção
  29 Maio 2012
• Data do Fascículo
  1972