Application of the new German protein evaluation system for horses in forage from species-rich meadows

The German protein evaluation system for horses is based on the pre-caecal digestible crude protein (pcdCP). Forage contents of pcdCP are available for grass-based swards, while those from species-rich swards are scarce. Grass species are low in tannin contents and interactions during protein digestion are unlikely. However, this may be relevant in forage from species-rich grasslands containing tanniferous forage species. Therefore, contents of pcdCP were quantified in fresh, wilted or ensiled forages from species-rich mountain swards and correlations with the content of condensed tannins (CT) were determined. The forages were obtained from three long-term fertiliser experiments (unfertilised or fertilised with PK or NPK) located at different mountainous sites. Forages were characterized for crude nutrient contents and CT. Ammonia content was additionally analysed in ensiled forages. Average contents of pcdCP (per kg dry matter, DM) accounted for 51.3 g, 80.5 and 52.9 g for fresh, wilted and ensiled forage, respectively. Contents of pcdCP were positively correlated with CT contents; however, this correlation was moderate for forages of the first harvest (R2=0.344) and weak (R2=0.085) for forages of the subsequent harvests. The new German protein evaluation system for horses is promising for the prediction of contents of pcdCP adequately in forage from species-rich swards.