Rumen dynamics of neutral detergent fiber in cattle fed low-quality tropical forage and supplemented with nitrogenous compounds

Cláudia Batista Sampaio,Marjorrie Augusto De Souza,Sebastião De Campos Valadares Filho,Edenio Detmann,Isis Lazzarini,Mário Fonseca Paulino

doi:10.1590/s1516-35982009000300023

Cláudia Batista Sampaio, Marjorrie Augusto De Souza + Show 4 more

Open Access

https://doi.org/10.1590/s1516-35982009000300023

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Abstract

The aim of this work was to evaluate the effects of supplementation with nitrogenous compounds on rumen dynamics of neutral detergent fiber (NDF) in cattle fed low-quality tropical forage. Five crossbred heifers with average live weight of 180 kg and fitted with rumen cannulae were used. The animals were fed ad libitum with signal grass (Brachiaria decumbens Stapf.) hay, which had crude protein (CP) content of 4.86% of dry matter (DM). The five treatments were proposed in order to raise the CP level of diets to 0, 2, 4, 6, and 8 percentile points above the CP level of the forage. The supplement was a mixture of urea, ammonium sulfate, and albumin (4.5:0.5:1.0, respectively). The experiment was carried out according to a 5 × 5 Latin square design, with five experimental periods. The average CP levels in the diets were: 5.19, 7.11, 8.60, 11.67, and 13.02% on DM basis. The potentially degradable NDF was linearly increased according to the CP levels in diet up to 6.97% of CP. From this point, there was stabilization of estimates (47.87% of NDF). The degradation rate of potentially degradable NDF was linearly increased with the CP levels in diets. The rumen flow of fibrous particles (L) showed a linear-response-plateau pattern according to the CP levels in diets. The plateau (maximum estimate) began on 7.24% of CP. The mean retention time in the rumen and the rumen fill effect of undegradable NDF were affect by the CP levels similarly to L, with plateau (minimum) beginning on 6.90 and 6.97% of CP, respectively.

Highlights

Tropical grasses present a high forage mass production along the year
The potentially degradable neutral detergent fiber (NDF) was linearly increased according to the crude protein (CP) levels in diet up to 6.97% of CP
The optimal utilization of energy from forage fiber only will be reached by increasing the microbial utilization of potentially degradable fraction of neutral detergent fiber (NDF), which represents about 60% of tropical forages dry matter (DM) (Paulino et al, 2006)

Summary

Introduction

As the maturation occurs, the forage mass accumulation is associated with thickening and high lignin accumulation in the cell wall These alterations are constraints for microbial digestion and fermentation and decrease the forage quality (Paulino et al, 2002). Tropical forages normally present crude protein (CP) content lower than 7%, which is considered to be limiting to the microbial activity in the rumen (Minson, 1990). Under these circumstances, optimal rumen conditions (Ørskov, 2000), continuous microbial growth and adequate utilization of fibrous compounds will not be observed. The optimal utilization of energy from forage fiber only will be reached by increasing the microbial utilization of potentially degradable fraction of neutral detergent fiber (NDF), which represents about 60% of tropical forages dry matter (DM) (Paulino et al, 2006)

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