Fresh and ensiled forage plants—total composition, silage losses and the prediction of silage composition from the crop

Abstract

Twenty ley and whole‐crop samples were analysed before and after ensiling to determine the proportion of dry matter (DM) that could be accounted for by the sum of 12 chemical assays for ash, ash‐excluded‐amylase‐treated neutral detergent fibre (aNDFom), starch, water‐soluble carbohydrates (WSC), pectin, crude protein (CP), CP in aNDFom (CPndf), ammonia, crude fat, phenolics, plant organic acids and liquid fermentation products (acids and alcohols). Crop components, utilized during silage fermentation and the possibility of predicting silage composition from that of the crop, were also investigated. Samples consisted of timothy and red and white clover, harvested at early and late maturities in two cuts per maturity and of whole‐crop barley, wheat and maize, harvested at early, intermediate and late stages of maturity. Ley crops were wilted to reach a DM content of approximately 400 g/kg, whereas whole crops (WC) were not wilted (151–757 g DM/kg) before ensiling. The average sum of analytes was 1022 and 981 g/kg DM for crops and silages respectively. An overall closeness to complete recovery indicates that no major plant components were missing from the analyses. Relative proportions of pectin, plant organic acids and phenolics, which are rarely analysed, were approximately 60:40:2 (w/w). Ash, aNDFom, crude fat and CP were almost completely recovered after ensiling, whereas partial metabolism reduced recoveries of starch (81%), CPndf (62%), plant organic acids (65%), pectin (64%) and WSC (29%). Only the four analytes with high silage recoveries could be reasonably well predicted from parent crop levels with mean prediction error from 0.065 for aNDFom to 0.167 for crude fat.

Field‐related quality management system for grass silage production

“…The average in vivo organic matter digestibility of the grass silages was slightly lower than of the fresh grass. Udén () stated that factors affecting the prediction from fresh crop are effluent losses, aerobic deterioration, fermentation loss of sugars and true protein, and products formed such as acids and alcohols. He found that if effluent losses and oxygen ingress were prevented, values for most of the components can be almost completely transferred from fresh grass to the silage.…”

“…Also, this allows for early feed planning and it is easier to sample the grass at ensiling (Pickert et al, ). Moreover, fewer samples may be needed than with conventional silo sampling (Udén, ).…”

Plant organic acids in fresh and ensiled forage plants

“…There are very few data published on the composition of the non‐WSC proportion of the “rest fraction” in forages or on what the consequences that this fraction may have on diet formulations and ensiling properties. In a previous paper, Udén () found a mean plant OA level in eleven leys and nine whole crops (see Table S1) of 65 (51–98) and 44 (14–70) g/kg DM respectively. Pectin levels ranged from 39 to 175 (mean = 86), whereas levels of soluble phenolics were below 3 g/kg DM.…”

“…Plant material, sample preparation and analytical methods were described earlier (Udén, ) and are only presented here in brief. A total of eleven ley crops of timothy, red clover and white clover from two cuts and two maturities (late 1st‐cut red clover sample missing) and nine whole crops (WC) of barley, wheat and maize from three stages of maturity were used in this study.…”

“…Plant material, sample preparation and analytical methods were described earlier (Ud en, 2017) and are only presented here in brief.…”