Harvest management and cultivar effect on alfalfa (Medicago sativa L.) forage quality

Understanding the connection between alfalfa (Medicago sativa L.) harvesting stage and forage quality will allow optimum timing of harvest. A field experiment was established to study the variation of forage quality of six cultivars of alfalfa harvested at three flowering stage (10, 50 and 100% flowering stage at the research farm of Islamic Azad University, Varamin, Iran. The forage quality of alfalfa cultivars was significantly different at different stages of plant development. Crude fiber, NDF and ADF increased with increasing plant age ranging from 16.9%, 40.27 g 100 g− 1 DM and 23.3 g 100 g− 1 DM to 26.4%, 49.38 g 100 g− 1 DM and 41.33 g 100 g− 1 DM, respectively; while leaf to stem ratio, DMD, TDN, DMI, RFV and ME decreased from 1.54, 72.33 g 100 g− 1 DM, 71.25 g 100 g− 1 DM, 3.01 g Kg− 1 body weight, 175.33 and 10.29 MJ Kg− 1 DM to 1.12, 50.66 g 100 g− 1 DM, 48.03 g 100 g− 1 DM, 2.45 g Kg− 1 body weight, 85.25 and 6.61 MJ Kg− 1 DM. Among the six cultivars, Fasta and Meldor exhibited lower fiber fractions (NDF and ADF) and higher DMD, TDN, and RFV values. These Difference can be mainly caused by genetic diversity of plants and variation in the partitioning of assimilates to reproductive parts. The recognized superior cultivar will be used to improve the nutritional value of forage crops in the breeding programs. Our data suggests that the relationship between forage quality and harvest time had significant effect on forage quality than cultivar differences or genetic selection. In arid and semi-arid regions, the cultivars Fasta and Meldor meet all forage quality standards. Early harvesting may be an effective strategy to enhance forage quality. Lower level of protein might be the reason of loss of leaves and higher rate of stem in total canopy.