Genetic variation of in vivo digestibility and energetic feed value of maize silage

Abstract

Variability for in vivo digestibility of organic matter (DOM) and energetic feed values UFL and UFV of maize silage , and their relationships with agronomic and others digestibility traits were reported from a compilation of 918 experiments with standard sheep. Genotype effects of DOM and UFL values were highly significant, even if the earliness of the hybrids was taken into account and brown-midrib hybrids were excluded from the study. Observed means for DOM (70.8 %), UFL and UFV values (0.90 UFL and 0.84 UFV) were similar to usual table values. The DOM of late genotypes were 2.5 points lower than that of earlier hybrids, corresponding to 0.05 UFL for energetic values. Differences between early hybrids were often about 4 points for DOM and could reach 8 points, corresponding respectively to 0.07 and 0.15 UFL. Phenotypic correlation between UFL values and grain contents was very low, but higher and negative with cellulose content. Yield was not clearly related to DOM or UFL values within each group of earliness, allowing quality improvement without agronomic drift. There was no obvious correlation between year of registration of hybrids and DOM or UFL values, but the worst values were often observed for newer hybrids. IVDOM, according to the APC process, was not a very good predictor of UFL values. But such enzymatic process could probably be used to avoid drift towards poor UFL values with hybrids bred for higher stalk strength. For a stock-breeder, a pertinent choice of a maize hybrid might allow significant increase in concentrates and money saving.