Variability of the Rumen Escape Protein and Fatty Acid Composition of Grass and Clover Species and Cultivars

Increase of rumen escape protein (REP) and higher content of polyunsaturated fatty acids (PUFA) in forage are getting risen interest. In this work, fast, reliable and cheap methods were developed to predict REP and C18:3 content using dried, ground and stored samples of grasses and clovers. Prediction of REP was possible using a regression curve and robust NIRS calibrations for in vitro digestibility and ADF, as well as the determination of moisture. Evaluation of C18:3 content was also possible by NIRS. Samples from plots (3 replicates, 5 cuts, 2 N fertilizer levels) of perennial and Italian ryegrass, timothy, orchard grass, meadow fescue, tall fescue, red clover and white clover were analysed using these methods. Variation for REP and C18:3 content was present between and within most species. Orchard grass presented the highest average REP while perennial ryegrass had the lowest one. For C18:3, timothy showed on average the highest content while Italian ryegrass had the lowest one. There were no significant differences in C18:3 content and REP within the fescue species. The white clover presented significantly lower REP and higher C18:3 content than the red clover. The red clover presented no significant differences within species for REP. In general, more variation for REP was present in the grasses while the clovers presented more variation for C18:3 content.