All traits were influenced by location, cycle, cultivar and sampling date effects (Julier & Huyghe, 1997). Digestibility and leaf/stem ratio decreased with forage yield, as plants grew. The slope of regression between plant digestibility and yield was the same for all the cultivars but varied with the location. Digestibility decreased quicker in some locations than in others but location effects were not related to average temperatures. At harvest (beginning of flowering), no correlation between yield and digestibility was observed, showing that it is possible to identify high yielding and digestible varieties.

The seven cultivars showed differences in digestibility (Table 1), as a result of various combinations of leaf/stem ratio and stem digestibility. Both high leaf/stem ratio and high stem digestibility are required to achieve a high whole plant digestibility.

Table 1. Adjusted means of plant digestibility, stem digestibility, leaf/stem ratio, and forage yield per cut (g/m_) in analysis of variance, for seven cultivars grown in five locations, and harvested at beginning of flowering in two growing cycles.

Julier B., Huyghe C. (1997) Effect of growth and cultivar on alfalfa digestibility in a multi-site trial. agronomie 17, 481-489.