The effect of increased temperature and CO₂ air enrichment on the nutritive value of orchard grass (Dactylis glomerata) in permanent grassland

Abstract

High yielding ruminant livestock require high nutritive value in forage for maintenance, growth and production. Climate change has been documented as impacting on the nutritive value of forage plants. Therefore, the aim of this study was to investigate the impact of increased temperature in combination with CO2-enhancement on the nutritive value of orchard grass (cocksfoot; Dactylis glomerata L.), as a C3 model plant, widespread in mountainous permanent grassland plant communities. Functional traits and forage quality of orchard grass were investigated both under ambient (C0T0) and under simulated, future climate conditions (C2T2) with increased temperature (+3°C) and enhanced CO2 concentration (+300 ppm) under field conditions. Plant samples were taken from each of the three growths over a period of three consecutive years and numerous functional properties and forage quality parameters were determined. Special attention was paid to the determination of water-soluble carbohydrates (WSC), crude protein (CP), non-protein N (NPN) and metabolizable energy (ME) as possible indicators for different climatic conditions. It is hypothesized that (i) functional traits and (ii) forage quality of orchard grass are altered by increased temperature and higher CO2 concentration. The results showed a negative impact of C2T2 compared to C0T0 on tiller height (54.4 v. 70.6 cm) and weight (2.42 v. 3.22 g) as average over cuts and years. The NPN content was lower in C2T2 (312 g/kg CP) compared to C0T0 (339 g/kg CP). In contrast, the WSC content was higher in C2T2 (90.3 g/kg DM) compared to C0T0 (82.5 g/kg DM). Both ME content and digestibility were increased in C2T2 (9.18 ME/kg DM and 68.2%) compared to C0T0 (8.86 ME/kg DM and 65.4%). Concluding, under increased temperature and enhanced CO2, both functional traits and certain nutrients and their fractions appear to change in orchard grass.

Protein and Carbohydrate Fractionation to Evaluate Perennial Ryegrass (Lolium perenne L.) Accessions

“…In addition to the limited variability of the protein fractions, the amounts determined were generally small compared to similar studies [45]. Almost a quarter of the total protein was in the form of non-protein nitrogen (fraction A), the true protein is mainly composed of fractions B1 and B2, with a small proportion of fraction B3, and the protein fraction C represents the smallest part of the first cut total N. Such observations are consistent with others [24,42,43,45,47,48].…”

“…The use of CNCPS to evaluate forages for breeding purposes is of interest to animal nutritionists and plant breeders [42,43]. Total nonstructural carbohydrates in forages provide a source of rapidly available energy in the rumen, and increased concentrations improve the N use efficiency of dairy cows [8,44].…”