Assessment of genetic parameters of degradability in maize grains due to indentation scores

Livia Maria Chamma Davide,Magno Antônio Patto Ramalho,Ulisses José De Figueiredo,João Cândido De Souza

doi:10.1590/s0103-90162011000300012

Abstract

Maize (Zea mays L.) cultivars with dent grains present higher starch and dry matter ruminal degradability than those with flint grains. This study aimed to assess genetic parameters of degradability in maize grains of different textures and to verify whether there is an association between grain indentation score and ruminal dry matter (RDM) degradability. The evaluated progenies were obtained from the cross between the varieties Cristal (flint) and Cunha (dent), previously selected for grain hardness. Progenies were evaluated for an indentation score using a visual grading scale ranging from 1 (flint) to 5 (dent). To assess the RDM degradability, 5 g were cut into halves, weighed (five grams), stored in bags made of 100% "failet" cloth and incubated for 24 h in the rumen of three ruminally cannulated cows. There was genetic variability for RDM degradability and heritability was 46%, indicating the possibility of success using a selection. There was no association between indentation score and RDM degradability percentage; thus, visual evaluation not always reflects grain hardness per se since it indicates the pericarp aspect but not the endosperm constitution.

Highlights

In the south of Minas Gerais State, Brazil, the most traditional farmers insist on using varieties despite the great availability of more productive hybrid cultivars in the market
The ruminal dry matter (RDM) degradability of ground grains was higher than that of grains cut into halves (Table 2)
The authors concluded that the RDM degradability of ground grains, as observed in this study, is higher than that of broken grains

Summary

Introduction

In the south of Minas Gerais State, Brazil, the most traditional farmers insist on using varieties despite the great availability of more productive hybrid cultivars in the market. These varieties are mostly used in animal feeding either as silage or as grains. There is a great variation among them concerning grain texture, since some varieties are excessively hard (flint) such as Cristal maize, as others are highly soft (dent) such as Cunha variety. Different progenies in grain hardness and, probably, in degradability can be obtained from the cross between Cristal and Cunha varieties, contributing to elucidate important genetic parameters for the success of maize breeding programs with grains of favorable texture for animal feeding. This study aimed to assess genetic parameters of maize grain degradability and to verify whether there is an association between the indentation score of visually evaluated grains and ruminal dry matter (DM) degradability

Objectives

Methods

Results