Associations Between Benzoxazinoids, Plant Development and Nutritional Parameters in Different Maize Maturing...

Maize (Zea mays L.) silage is a major energy source in ruminant diets and provides fermentable substrate for the rumen microbiota. In addition, forage maize contains benzoxazinoids (BXs), defence-related secondary metabolites with antimicrobial activity that remain detectable after ensiling. For ruminant nutrition, it is important to know whether variation in BX is associated with changes in forage nutritive value. This study evaluated 14 commercially relevant forage maize genotypes in dairy-producing regions, comprising seven early and seven mid-early maturing genotypes selected from the official Swiss maize trial network. At harvest, plant developmental traits were recorded, nutrient composition was analyzed by near-infrared spectroscopy, and BX concentrations were quantified by ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS). Maturity groups were compared using Wilcoxon rank-sum tests with Benjamini-Hochberg correction, while associations among variables were assessed using Spearman rank correlations, linear regression models and exploratory principal component analysis (PCA). No significant differences in BX concentrations or nutrient composition were observed between early and mid-early maturing genotypes (all FDR-adjusted p > 0.05). Consistently, PCA did not indicate a separation between maturity groups, and permutational multivariate analysis of variance showed no significant maturity-group effect on the multivariate profile (F = 1.66, R² = 0.121, p = 0.216). Neutral detergent fibre content was negatively correlated with starch concentration (ρ_S = - 0.70, P_S = 0.010, R² = 0.66, P_lm < 0.001), whereas digestible organic matter was correlated with calculated net energy values (ρ_S ≥ 0.95, P_S < 0.001, R² ≥ 0.94, P_lm < 0.001). Several BX metabolite concentrations were negatively correlated with European corn borer incidence, most notably MBOA (ρ_S = - 0.74, P_S = 0.002, R² = 0.16, P_lm = 0.153). Concentrations of DIMBOA and DIMBOA-Glc were positively associated with net energy for lactation (ρ_S = 0.64 and 0.68, P_S = 0.015 and 0.007, R² = 0.32 and 0.34, P_lm = 0.037 and 0.029, respectively). These findings indicate that plant defence capacity and high forage quality can co-occur under practical growing conditions.