Nutritional performance of cattle grazing on low-quality tropical forage supplemented with nitrogenous compounds and/or starch

Ísis Lazzarini,Edenio Detmann,Rilene Ferreira Diniz Valadares,Mário Fonseca Paulino,William Lima Santiago Dos Reis,Sebastião De Campos Valadares Filho,Poliana Teixeira Da Silva,Fabrício Albani Oliveira

doi:10.1590/s1516-35982013000900009

Ísis Lazzarini, Edenio Detmann + Show 6 more

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https://doi.org/10.1590/s1516-35982013000900009

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Abstract

The objective of this work was to evaluate the effects of protein and/or starch supplementation on the nutritional performance of cattle grazing on low-quality tropical forage. Five crossbred steers (Holstein × Gyr) with an average body weight (BW) of 397 kg that were fitted with ruminal and abomasal cannulae were used. The animals were kept in individual signal-grass (Bracharia decumbens) paddocks. Five treatments were evaluated: 1 - control (without supplementation); 2 - supplementation with 1 g of crude protein (CP) per kg of BW; 3 - supplementation with 2.5 g of starch per kg of BW; 4 - supplementation with CP and starch as described for treatments 2 and 3; and 5 - supplementation as described for treatment 4 but replacing the corn starch with a mixture of corn starch and nitrogenous compounds, thereby resulting in an energy supplement of 150 g CP/kg of dry matter. The experiment was performed according to a 5 × 5 Latin square design in a 2 × 2 + 1 factorial arrangement. The forage intake was not affected by any of the factors evaluated in this study. The production of microbial nitrogen in the rumen was not affected by nitrogen or starch supplementation. The apparent nitrogen balance was only increased when both starch and nitrogen were supplied. Supplementation with both starch and nitrogenous compounds for cattle grazing on low-quality tropical forage is characterized by an interactive metabolic effect that increases nitrogen accretion by the animals.

Highlights

Most Brazilian beef cattle production systems have used tropical grasses as basal forage resources, as they provide low-cost energy from the potentially digestible fraction of neutral detergent fiber (NDF) (Detmann et al, 2008; Paulino et al, 2008).tropical grasses are rarely available as an equilibrated diet for grazing cattle because they invariably exhibit a nutritional constraint that will limit pasture intake and digestibility
Nitrogen Starch Nitrogen × Starch supplementation with nitrogenous compounds increased the intake of dry matter (DM) from forage, NDF and digested NDF (DNDF) by 19.3, 20.6 and 27.9%, respectively, compared with the control treatment, albeit without significance (P>0.10; Table 3)
Analysis of this effect revealed that nitrogen supplementation increased crude protein (CP) intake (P

Summary

Introduction

Tropical grasses are rarely available as an equilibrated diet for grazing cattle because they invariably exhibit a nutritional constraint that will limit pasture intake and digestibility. The limited CP availability provides the critical threshold for adequate microbial growth on the fibrous carbohydrates in basal forage (Henessy et al, 1983; Leng, 1990; Lazzarini et al, 2009). This CP deficiency implies poor utilization of potentially degradable cell wall by microorganisms and results in decreased intake and animal performance (Paulino et al, 2008)

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