Ruminal degradability of hard or soft texture corn grain at three maturity stages

Marcos Neves Pereira,Gabriela Arruda Calestine,Ralph Guilherme Da Silva Bruno,Renzo Garcia Von Pinho

doi:10.1590/s0103-90162004000400002

Marcos Neves Pereira, Gabriela Arruda Calestine + Show 2 more

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https://doi.org/10.1590/s0103-90162004000400002

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Journal: Scientia Agricola	Publication Date: Jan 1, 2004
Citations: 48	License type: cc-by

Affiliation: Universidade Federal de Lavras

Abstract

The predominance of vitreous endosperm in hard texture flint corn (Zea mays L.) can decrease ruminal starch digestion comparatively to the farinaceous endosperm of dent corn, reducing energy content of the grain. The objective of this experiment was to evaluate the effects of texture and maturity stage on ruminal degradability of corn grain. Two dent and two flint hybrids were harvested at the early dent, half milk line, and black layer stages. The proportion of vitreous endosperm (vitreousness) in dent hybrids was 44.3%, while in flint it was 67.0%. There was a linear increase in vitreousness with advancing maturity. Flint hybrids at the early dent stage were more vitreous than dent at the black layer stage. The increase in vitreousness per maturation day was greater for flint hybrids. Grains were incubated in situ in the rumen of 6 cows. The 24-hour ruminal dry matter degradation was 63.3% for dent corn and 52.4% for flint corn. The 72-hour incubation residues of dent and flint hybrids were 7.6% and 15.6%, respectively. Ruminal degradability was similar between hybrids at the early dent and half milk line stages. There was a marked texture effect on ruminal degradability at the black layer stage (quadratic effect of maturity stage and interaction between texture and maturity stage). Use of dent hybrids, compared to flint hybrids, may result in smaller relative reduction in ruminal starch digestion in situations of late grain harvesting.

Highlights

High energetic value resulting from low fiber content, high dry matter yield per unit area, easy mechanical harvesting and good silage fermentation pattern without the need for additives or wilting are characteristics that make the corn plant one of the most utilized forages for dairy cattle in Brazil
Two dent and two flint hybrids were harvested at the early dent, half milk line, and black layer stages
The soft hybrids used in this study most likely represent the lowest end of vitreousness available in the Brazilian market of corn seeds

Summary

Introduction

High energetic value resulting from low fiber content, high dry matter yield per unit area, easy mechanical harvesting and good silage fermentation pattern without the need for additives or wilting are characteristics that make the corn plant one of the most utilized forages for dairy cattle in Brazil. Ruminal degradability of grain non-fibrous carbohydrates determines the energy value of this feed (Allen et al, 1997). The texture of the corn grain is determined by the amount of vitreous endosperm proportionally to the farinaceous endosperm (Watson, 1988). In the farinaceous endosperm, which is opaque and soft-textured, the protein matrix is discontinuous and has few protein bodies, and the starch granules are spherical, larger, less aggregated and surrounded by air spaces (Robutti et al, 1974; Pratt et al, 1995). The protein matrix seems to limit the enzymatic digestion of starch in cereals (Kotarski et al, 1992) and is responsible for differences in ruminal degradability of grains (McAllister et al, 1993; Rooney & Pflugfelder, 1986). There is evidence that hard-textured corn grain is less degraded in the rumen than soft grain (Philippeau & Michalet-Doreau, 1997)

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