Plant maturity and genetic influences on in vitro NDF digestibility of alfalfa.

Aging and excess of environmental stress conditions negatively affectalfalfa NDF digestibility (NDFd). This study evaluated the influenceof plant maturity on in vitro NDFd (IVNDFd) of different varietes ofalfalfa. Two cuttings from different four alfalfa varieties (A experimental,B, C and D commercial) were analyzed, each in five replicates, forchemical composition (CP, ADF, ADL, NDF) and 24h IVNDFd withTilley & Terry technique. All varieties were grown in the same locationunder the same climatic and agronomic conditions. Each varietywas cut at two stages of maturity: 20 days (II) and 30 days (III) afterprevious harvest. During the trial, temperature and amount of rainfallwere: (II) 33.1°C max, 17.3°C min and 15.7 mm ; (III) 34.01°C max,18.2°C min and 34.9 mm. Samples were harvested by hands at a 5.0 cmheight and immediately dried at 65°C in a forced air oven. No statisticaldifferences were found among varieties for CP, ADF, ADL and NDF incollection II and III, but differences (P< 0.01, Table 1) were observedfor IVNDFd. These results demonstrate that variety A maintains betterIVNDFd as maturity advances.[...]