Studying maize varieties according to their in vitro digestibility: comparison of maize types throughout maturation

Digestibility, as an important quality factor is included in the official variety testing system in Belgium since 1992. Although several distinct forage maize types are cultivated - such as stay-green or dry down types, early or late maturing types, pure forage or dual purpose types (silage + grain), each type is harvested approx. on the same date. However, the physiological development at harvest date influences the composition and the digestibility of the silage. For example, early varieties usually have a high ear content, while late maturing types have the highest biomass. Furthermore, the actual method to determine in vitro digestibility is questioned. The determination is based on an incubation of the material during 48 hours. This incubation time is thought to overestimate the potential digestion in lactating dairy cows, which retain feed in the rumen and the digestive track for less than 48 h.

This research aims at clarifying the effect of plant type, maturity type, harvest date and incubation time on total digestibility. To answer these questions, a number of varieties, diverging in genetic background, plant and maturity type and physiological development, will be harvested in a harvest track characterized by a dry matter content ranging from 28% to 38%. Field trials will be installed and followed during three consecutive years. A special attention will go to the effect of abiotic stress (as drought and heath) on digestibility. Total digestibility and cell wall digestibility will be determined via NIRS and chemical analyses.

The ultimate goal is to improve the quality assessment in official variety trials with forage maize and to optimize harvesting windows for different plant types.