Cell wall digestibility outperforms ear in maintaining digestibility even under severe combined water and heat stress

Abstract

Forage maize is a central pillar of dairy cow feeding in France, directly influencing milk production. Drought significantly affects both its yield and digestibility, which are essential for registration purposes. Research on inbred lines revealed droughts notable effect on dry matter and cell wall digestibilities, directly impacting forage quality. Nevertheless, further investigation is warranted due to increasing frequency of drought. To delve deeper, we grew a range of modern forage maize hybrids for two years under four different field water-monitored modalities, representing a total of eight environmental conditions. The resulting dataset allowed us to perform a multiscale analysis, integrating agroclimatic, agronomic, biochemical and histological traits. By establishing a comprehensive heat and water stress index, we classified the environmental conditions. We demonstrated that under severe stress, ear production decreases significantly, but dry matter digestibility can be maintained through increased cell wall digestibility. This boost in cell wall digestibility was due to a reduction in p-hydroxycinnamic acid content, while lignin content remained relatively stable between environments. The significance of lignin distribution increased with the severity of the stress, reaching an extreme threshold where biochemical parameters solely account for digestibility variations.