Composition and digestibility of whole plant triticale as affected by maturity stage and genotype

Maize is grown in monoculture on many dairy farms in NW Europe. Triticale for use as whole plant (WPT) may contribute to the diversification of crop rotation, resulting in a lower disease and weed pressure and higher yields. Moreover with climate changing to warmer and dryer summers, WPT offers an advantage compared with maize as it can be harvested before the summer heat. A six-year study was started to investigate the potential of WPT as alternative roughage crop for maize silage. An important objective is to study the factors affecting the digestibility of organic matter (OMd) and cell wall digestibility (NDFd). In a first field trial, 36 genotypes were harvested at 5 maturity stages and samples from these 180 WPT objects were scanned by NIRS. Based on spectral variation, 80 samples were selected to determine dry matter (DM), crude protein (CP), crude fat, crude ash, sugars, starch, NDF, ADF and ADL as well as cellulase OMd and rumen fluid NDFd. The DM content of the WPT for the 5 stages averaged 268, 285, 467, 508 and 574 g/kg, respectively. During maturing, sugar content decreased, whereas starch content increased with a clear shift from the second to the third stage. With advancing maturity there was a relative small decrease in NDF, CP and ash content. The NDFd seemed hardly affected by maturity stage with on average 53.9 and 55.4% for the first and fifth stage. On the other hand, mean OMd increased linearly with later harvesting and amounted to 63.8, 65.0, 67.9, 68.1 and 69.1%, respectively. In addition to the effect of maturity stage, there appeared a large variation among genotypes. For the last stage, OMd ranged between 67.3 and 73.2%. This variation opens perspectives to select for WPT with high nutritive value. The reference data from this first trial were used to develop NIRS calibrations in order to allow rapid feed evaluation throughout the study.