Leaf and stem dry matter digestibility and ruminal undegradable proteins of alfalfa cultivars

Increased dry matter digestibility and ruminal undegradable protein (RUP) concentration are traits highly ranked to improve the nutritive value of forage legumes. Whole-plant, leaf, and stem samples of 27 alfalfa cultivars grown in eastern Canada were analysed for total nitrogen (TN), in vitro RUP, and in vitro dry matter digestibility (IVDMD). The objectives were to determine if significant variation exists among these cultivars, and to establish the relationship between nutritive value parameters of leaves and stems, and those of whole plants. Cultivars were seeded in triplicate on 2 consecutive years and evaluated during the 2 subsequent production years with two harvests per year. There were significant differences among cultivars in IVDMD of stems and plants in spring growth and summer regrowth. Cultivar differences in leaf IVDMD were significant only in spring growth, but this variation was negligible in practical terms. Cultivars with high forage IVDMD also had high stem IVDMD and this relationship...