Monitoring forage quality is one of the most important factors of essential and good management of a farm. The most important factor about plants and forage quality is growing stage which can help to identify the optimum time of harvest. As different varieties of plants have different harvest times and quality, in order to search the variety effect on forage yield and quality traits, three varieties of common millet (Panicum miliaceum), namely, KCM2, KCM7, and KCM9 in three phenological growth stages, including booting, milky, and seed maturity stages were studied. Experiments in factorial form were surveyed in Karaj district, Iran with three replications in the form of randomize complete blocks design in 2009. Except ash percentage, there were significant differences among three growth stages in other quality traits and forage yield (P < 0.01). Significant differences among varieties for dry and wet forage yield, dry matter digestibility (DMD), water soluble carbohydrates, and acid detergent fiber percentage were also observed. However, interaction effect of variety and phenological growth stage were not significantly different on acid detergent fiber, crude fiber (CF), and ash percentages. Almost in all varieties, the amount of crude protein (CP) and DMD decreased during developing growth stages, while the amount of CP increased. KCM2 variety had the highest forage quality based on measurement indices and it was chosen as the best variety with regard to the most desirable forage yield. Booting stage (first phenological stage) was the most desirable in quality traits among the three growth stages. However, considering the little difference between the first and second stages in dietary energy, the second stage (milky stage) was recommended as the most suitable time for harvesting, because of high yield and compatibility of farm to plant.

Key words: Quality traits, forage yield, dry matter digestibility, crude protein, growth stage, crude fiber.