Genetic and environmental influences on in vitro digestibility of alfalfa

To study the relationships between in vitro NDF or true dry matter digestibility (NDFD and IVTDMD) and forage fibre content, 95 alfalfa samples from 5 cultivars grown in 3 different locations and from different cuts were analysed for fibre fractions and evaluated for NDFD and IVTDMD. NDFD was mainly influenced by order of cut and age of the fields. The multifoliate cultivar controlled did not appear to differ for fibre composition and NDFD from the other ones. Fibre fractions contents explained a large part of the difference in NDFD and IVTDMD, and no significant differences in this relationships appeared for first-cut vs. aftermath forage. The best predictive equation of NDFD from fibre factions was: NDFD = 73.61 -0.62 * NDF (% DM) - 56.33 * ADL/NDF (R2=0.39). Variations in fibre content and quality do not completely explain differences in NDFD suggesting the interference of other factors that are worth to be better studied.