Valor nutritivo do capim-Tanzânia (Panicum maximum Jacq. cv. Tanzânia-1) pastejado em diferentes alturas

Abstract

RESUMO -Avaliaram-se as concentrações de proteína bruta (PB), de fibra em detergente neutro (FDN), de fibra em detergente ácido (FDA), de fósforo (P), de potássio (K), de cálcio (Ca) e de magnésio (Mg) e a digestibilidade in vitro da matéria seca (DIVMS) nas frações lâminas foliares e colmos + bainhas em pastagem de capim-Tanzânia (Panicum maximum Jacq. cv. Tanzânia-1) manejada em quatro alturas de dossel forrageiro (20, 40, 60 e 80 cm). O método de pastejo foi o de lotação contínua, com taxa de lotação variável, e os animais utilizados foram novilhos da raça Nelore, com peso médio de 340 kg. Utilizou-se o delineamento experimental inteiramente casualizado com duas repetições, sendo realizadas cinco avaliações no período (112 dias). O aumento na altura do dossel promoveu redução nas concentrações de PB, Ca, P, Mg e DIVMS e elevação nas concentrações de FDN, FDA e K para as frações lâmina foliar e colmo + bainha. As lâminas foliares apresentaram melhor composição química que colmos + bainhas em todas as alturas de dossel e em todos os períodos de avaliação. A altura de dossel de 40 a 50 cm propiciou boa composição química e DIVMS.Palavras-chave: DIVMS, fibra em detergente neutro, fibra em detergente ácido, minerais, proteína bruta Nutritive Value of Tanzaniagrass (Panicum maximum Jacq. cv. Tanzânia-1) Grazed at Different Heights ABSTRACT-Crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg) and in vitro dry matter digestibility (IVDMD) contents were assessed in the leaf blade and stem + leaf sheath fractions of Tanzaniagrass (Panicum maximum Jacq. cv. Tanzania-1) managed at four sward heights (20, 40, 50 and 65 cm). The grazing method was the continuous stocking and variable stocking rate, and used Nelore steers with an average weight of 340 kg. The completely randomized experimental design was used with two replications, and five evaluations were performed during a period of 112 days. The CP, IVDMD, Ca, P and Mg contents decreased while NDF, ADF and K concentrations increased in the leaf blade and stem + leaf sheath fraction in response to grazing height as well as period of evaluation. Leaf blades exibited higher quality than stem + leaf sheath regardless of grazing height and evaluation time. Tanzaniagrass grazed to 40 and 50 cm presents good chemical composition and IVDMD.

Forage yield and nutritive value of Panicum maximum genotypes in the Brazilian savannah

“…Aruana, Tanzânia, Vencedor, PM40, PM43 and PM46 presented the highest values of OMD. In Tanzânia pastures managed with four sward heights (0.2, 0.4, 0.6 and 0.8 m) OMD of leaves decreased linearly from 740 to 670 g kg -1 as sward height increased (Cano et al, 2004). As expected, OMD showed a high negative correlation with ADF (-0.67; p < 0.001) and moderately negative with NDF (-0.37; p < 0.001) and a positive correlation with CP (0.80; p < 0.001).…”

“…For high yielding tropical grasses managed under intermittent stocking, use of targets such as sward height in the pre-and post-grazing helps to control the growth of stems that can be harmful to intake and cattle performance Benvenutti et al, 2008). For the same reason, continuous stocking management is not recommended for P. maximum because of its tendency towards heterogeneity in sward structure that results in patches with excessive stem growth, although Tanzania pastures had been assessed by continuous stocking systems too (Cano et al, 2004). So, the choice of productive species with a high proportion of leaves, a better quality plant component than stems is benefi cial.…”

Valor nutritivo de gramíneas nativas do Rio Grande do Sul/Brasil, classificadas segundo uma tipologia funcional, sob queima e pastejo

“…Entende-se como valor nutritivo a concentração e digestibilidade de nutrientes junto com a natureza da digestão dos produtos finais (MOTT & MOORE, 1970). Por isso, é importante o estudo da composição química da forragem e sua digestibilidade, a fim de conhecer a qualidade do pasto ao qual os animais terão acesso em pastejo (CANO et al, 2004). O valor nutricional de plantas forrageiras é dependente principalmente da proporção entre tecidos de alta e de baixa digestibilidade, o que pode explicar diferenças qualitativas entre espécies e/ou cultivares (WILSON, 1997).…”

Frequencies and intensities of defoliation in Aruana Guineagrass swards: accumulation and morphological composition of forage

“…In a study on Mombasa-grass subjected to intermittent stocking strategies, Da Silva et al (2009) observed that pre-and postgrazing forage masses were lower with 95% light interception treatments compared with 100% light interception; however, the proportion of leaves was higher and the proportion of stems and dead plant material was lower in the former treatment. Cano et al (2004) studied Tanzaniagrass and concluded that the nutritional value of leaf blades was higher compared with the stem + sheath fraction, regardless of forage canopy height and study duration, indicating that grass management should focus on the contribution of leaf forage mass. As a rule, prolonged regrowth periods of species exhibiting early stem elongation make it more difficult to control the forage canopy, and this might limit subsequent leaf blade accumulation and the production of high-quality forage.…”