Chemical composition and net energy content of alpine pasture species during the grazing season

The aim of this study was to investigate changes over time in chemical composition, digestibility and net energy for lactation (NEl) contents of 12 species of alpine pastures during the vegetative season (i.e., Agrostis tenuis, Anthoxanthum alpinum, Carex sempervirens, Festuca rubra, Nardus stricta, Phleum alpinum, Poa alpina, Poa violacea, Alchemilla vulgaris, Leontodon hispidus, Poten- tilla aurea, Trifolium repens). Wild seeds were collected from plants spontaneously occurring in mountain pastures in North-East Italy and sown in a greenhouse. Plants were transplanted in open main field plots. Each main plot was divided into sub-plots, which were cut (first cut) in succession every 10 days in two consecutive years. Herbage regrowth (second cut) was evaluated at 45, 60 and 75 days after first cut. Herbage samples were analysed for chemical composition, for in vitro organic matter digestibility (OMD), and the NEl content was estimated. During the pasture utilisation period (i.e., thermic sum between 500 and 1200 ◦ C) the species had limited variation in their average CP con- tents (81–109 g/kg DM) excluding the lowest values of F. rubra and P. violacea (74 and 71 g/kg DM, respectively; P<0.05) and the highest value of T. repens (202 g/kg DM; P<0.05). Within grasses, there were very fibrous species (>700 g NDF/kg DM, such as F. rubra, N. stricta and P. violacea) and species with medium contents (573–664 g NDF/kg DM), while forbs and the legume specie had a low content ( ≤ 403 g NDF/kg DM). The OMD ranged from P. violacea (256 g/kg DM; P<0.05) to T. repens (730 g/kg DM; P<0.05). The highest NEl content was for T. repens (6.3 MJ/kg DM; P<0.05.