Silage maize represents a significant energy source of nutrients for high-producing dairy cows. Intensive breeding under conditions of pronounced climate change has created a very broad and dynamic base of silage hybrids entering the market.
Growers need to understand as thoroughly as possible not only the characteristics of the hybrids they cultivate, but also the manifestation of their genetic potential under specific growing conditions. Systems for the characterization and evaluation of hybrids have a long history; however, they are often derived from the characterization of earliness in grain maize hybrids.
The basis of this publication is an analysis of the nutrient composition of 140 different hybrids classified into FAO groups from 120 to 400 in northeastern Slovakia, and 73 different hybrids classified into FAO groups from 240 to 600 in southwestern Slovakia.
Measurements of nutrient composition (dry matter content, water-soluble carbohydrates, starch, and NDF) were carried out from 2016 to 2021, and each monitored hybrid was sampled and measured in every season at least four times during its vegetative development. 
Differences in the extent and dynamics of changes in the nutrient composition of the hybrids are evaluated in relation to soil and climatic conditions, growing locations, individual experiments, as well as the classification of hybrids into FAO maturity groups.
The publication provides an extensive analysis of these relationships, which, in addition to the text, are documented in the form of more than 80 graphs, tables, and diagrams. The outcome of these processes is the definition of the concept of “silage maturity of maize,” and based on these results, a new system for evaluating the earliness of silage maize hybrids is proposed.
For practical use, a Silage Maturity Certificate for hybrids is proposed: a model of a „birth certificate” for hybrids that enables easy comparison of hybrids in the context of one’s own production conditions and the development of successful silage strategies.