# Prediction of water-soluble carbohydrate contents in hay from their content in fresh forage and drying time

Bertrand Deroche, Annette Morvan-Bertrand, Ueli Wyss, M. Aoun, René Baumont

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Bertrand Deroche, Annette Morvan-Bertrand, Ueli Wyss, M. Aoun, René Baumont. Prediction of water-soluble carbohydrate contents in hay from their content in fresh forage and drying time. EGF General Meeting on "Grassland at the heart of circular and sustainable food systems", Jun 2022, Caen, France. Grassland Science, 27, 2022. [hal-05249650](https://hal.science/hal-05249650v1)

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**29th GENERAL MEETING**

GRASSLAND AT THE HEART OF CIRCULAR AND SUSTAINABLE FOOD SYSTEMS

JUNE 26-30, 2022 • CAEN, FRANCE

# Grassland at the heart of circular and sustainable food systems

Edited by

L. Delaby
R. Baumont
V. Brocard
S. Lemauviel-Lavenant
S. Plantureux
F. Vertès
J.L. Peyraud

<figure><img src="image_4.png" /></figure>

Volume 27
Grassland Science in Europe
# Prediction of water-soluble carbohydrate contents in hay from their content in fresh forage and drying time

Deroche B.¹,², Morvan-Bertrand A.³, Le Morvan A.¹, Wyss U.⁴, Aoun M.² and Baumont R.¹

¹Université Clermont Auvergne, INRAE, VetAgro Sup, UMR Herbivores, 63122 Saint-Genès-Champanelle, France; ²IDENA, 44880 Sautron, France; ³Normandie Univ. UNICAEN, UMR INRAE 950 EVA, 14000 Caen, France; ⁴AGROSCOPE, 1725 Posieux, Suisse

## Abstract

Soluble carbohydrates influence the forage feed value. Total water-soluble carbohydrates (WSC) content and composition, particularly fructans, may change during grass drying after cutting. We aimed to predict WSC and fructans contents in hay from their content measured in fresh forage and the time of drying, which is known to induce a decrease in the content of soluble constituents. Twenty plots of multi-species grasslands were studied in three semi-mountain areas. Biochemical components were measured on fresh forage at cutting and the corresponding hay. The drying time (DT) was recorded from cutting to baling or entrance to the hay barn. WSC content was 187±64.9 and 167±63.7 g kg⁻¹ dry matter (DM), and fructans content was 111±47.5 and 89.6±37.9 g kg⁻¹ DM, in fresh forage and hay respectively, the decrease being non-significant. WSC and fructans content of hay can be predicted by their content in fresh forage (R²=0.76 and 0.55; RMSE=32.4 and 26.2 g kg⁻¹ DM, respectively). DT was negatively correlated with WSC and fructans content of hay and significantly improved the accuracy of the prediction equations (R²=0.89 and 0.76; RMSE=21.5 and 18.7 g kg⁻¹ DM respectively). Finally, soluble carbohydrate content of hay depends mainly on their content in the fresh forage and to a lesser extent on the DT between cutting and hay baling.

**Keywords:** hay, fresh forage, water soluble carbohydrate, fructans, drying time

## Introduction

Total water-soluble carbohydrates (WSC) influence positively grass digestibility (Humphreys, 1989), and thus forage feed value. Fructans constitute the major part of WSC in temperate grasslands (Chatterton et al., 1989). During drying, plants continue to breathe and a part of soluble carbohydrates (McGechan, 1989) are consumed modifying WSC content and their composition (Ould-Ahmed et al., 2015; Peng et al., 2018). To date, no prediction model of WSC content in hay exists. We aimed to predict WSC and fructans contents of hay from their content measured on fresh forage and considering the drying time (DT).

## Materials and methods

During 2017, twenty plots of multi-species grasslands, including four sown plots intensively and 16 permanent pasture plots extensively managed, were studied in three semi mountain areas: Friburg foothills (Switzerland; n=4), Jura (France; n=8) and Massif Central (France, n=8). The plots were studied during the 1st vegetation cycle except four of the eight plots in Massif Central that were studied during the 2nd vegetation cycle. For each plot, representative samples of fresh forage were collected at cutting and of the corresponding hay after drying and storage that lasted between 149 and 348 days (261±79.6 days on average). DT was recorded for each plot between cutting and baling for sun dried hays (n=16) or between cutting and the entrance in the barn for barn dried hays (n=4). Dry matter (DM), ash, crude protein (CP), neutral detergent fibre (NDF), acid detergent fibre (ADF), WSC and fructans contents were measured on all fresh forage and hay samples. Correlations between WSC or fructans contents of hay and chemical criteria of fresh forage or DT were calculated using Spearman's correlation. Stepwise
linear regression procedure (SAS 5.1) was used to establish prediction equations of WSC and fructans content of hay from chemical constituents of fresh forage and DT.

## Results and discussion

On average, the grasslands contained 75.9±10.9% of grass species (between 57.2 and 93.9%), 7.6±9.4% of legumes (0.2-35.8%) and 16.5±9.1% of forbs (2.5-35.0%). The average stage of maturity at cutting was heading (between stem elongation and flowering) and onset of stem elongation for 1st and 2nd vegetation cycle, respectively.

Due to good weather conditions DT between cutting and harvesting hays were short (2.24±0.497 and 1.70±0.320 days for 1st and 2nd vegetation cycle, respectively). The mean values of WSC, fructans and CP content decreased between fresh forage and hay, whereas NDF and ADF content increased (Table 1), in accordance with literature (Peng et al., 2018). The decrease was not significant for WSC and fructans. This may be due to the short DT since it has been shown that WSC and fructans content in grass forage did not decrease during a 24-hour wilting period (Ould-Ahmed et al., 2015). The range of variation of chemical constituents' contents were high, particularly for WSC and fructans contents that varied in a ratio of more than 1 to 3 (Table 1). This high variability may be linked to the different botanical composition, maturity stage and drying conditions between plots (temperature, light) which modify the kinetics of evolution of soluble carbohydrate contents during drying (Ould-Ahmed et al., 2015). Spearman's correlation analysis showed that the WSC and fructans contents of hay were highly negatively correlated with the NDF and ADF contents and positively with the WSC and fructans contents of the corresponding fresh forages (Table 1).

Stepwise linear regression showed that the WSC and fructans contents of hay were best predicted by their contents measured on the corresponding fresh forage (Table 2). Accuracy of the prediction equations was highly improved by the addition of DT (respectively +13.0% and +21.1%) having a negative coefficient, consistently with the negative correlation of DT with these criteria measured on hay (-0.640, *P*<0.01 and 0.713, *P*<0.001 for WSC and fructans respectively). Part of the variability remains unexplained and could come from the storage period or the drying conditions (temperature, light).

<table><caption>Table 1. Chemical composition (in g kg⁻<fnref n="1" /> DM, except in g kg⁻<fnref n="1" /> for dry matter) of fresh forages and the corresponding hays from multi-species grassland plots (n=20), and Spearman's correlation coefficients between WSC and fructans contents in hay and chemical constituents of fresh forages.<fnref n="1" /></caption><thead><tr><th rowspan="2">Variables</th><th colspan="4">Fresh forage (FF)</th><th colspan="4">Hay</th><th rowspan="2">WSC of hay<br>Correlation with FF</th><th rowspan="2">Fructans of hay</th></tr><tr><th>Mean</th><th>SD</th><th>Min</th><th>Max</th><th>Mean</th><th>SD</th><th>Min</th><th>Max</th></tr></thead><tbody><tr><td>DM</td><td>241</td><td>34.3</td><td>179</td><td>325</td><td>914</td><td>2.46</td><td>908</td><td>918</td><td>-0.620**</td><td>-0.63**</td></tr><tr><td>Ash</td><td>80.4</td><td>15.5</td><td>57.9</td><td>112</td><td>76.2</td><td>8.97</td><td>62.2</td><td>93.2</td><td>0.420†</td><td>0.427†</td></tr><tr><td>CP</td><td>116</td><td>19.0</td><td>93.8</td><td>152</td><td>107</td><td>17.9</td><td>81.2</td><td>138</td><td>0.469*</td><td>0.480*</td></tr><tr><td>NDF</td><td>541</td><td>67.1</td><td>411</td><td>654</td><td>565</td><td>70.1</td><td>433</td><td>678</td><td>-0.907***</td><td>-0.880***</td></tr><tr><td>ADF</td><td>282</td><td>43.9</td><td>209</td><td>365</td><td>296</td><td>43.8</td><td>228</td><td>376</td><td>-0.866***</td><td>-0.824***</td></tr><tr><td>WSC</td><td>187</td><td>64.9</td><td>100</td><td>323</td><td>167</td><td>63.7</td><td>108</td><td>308</td><td>0.735***</td><td>0.710***</td></tr><tr><td>Fructans</td><td>111</td><td>47.5</td><td>57.4</td><td>227</td><td>89.6</td><td>37.9</td><td>58.7</td><td>184</td><td>0.690**</td><td>0.671**</td></tr></tbody></table>

<footnote n="1">¹SD = standard deviation; Min = minimum; Max = maximum. Significance: *** *P*<0.001; ** *P*<0.01; * *P*<0.05; † *P*<0.10.</footnote>
<table><caption>Table 2. Prediction equations of WSC and fructans contents in hay (H) from WSC and fructans content in the corresponding fresh forage (FF) and DT (n=20).<fnref n="1" /></caption><thead><tr><th></th><th>Model components</th><th>R<sup>2</sup></th><th>RMSE</th></tr></thead><tbody><tr><td rowspan="2">WSC_H (g kg<sup>-1</sup> DM)</td><td>7.8 + 0.854 × WSCFFE (g kg<sup>-1</sup> DM)</td><td>0.756</td><td>32.35</td></tr><tr><td>165.2 + 0.701 × WSCFFE (g kg<sup>-1</sup> DM) - 59.1 × DT <sup>(3)</sup> (days)</td><td>0.886</td><td>21.52</td></tr><tr><td rowspan="2">Fructans_H (g kg<sup>-1</sup> DM)</td><td>23.9 + 0.590 × FructansFFE (g kg<sup>-1</sup> DM)</td><td>0.547</td><td>26.24</td></tr><tr><td>112.8 + 0.501 × FructansFFE (g kg<sup>-1</sup> DM) - 37.09 × DT (days)</td><td>0.758</td><td>18.66</td></tr></tbody></table>

## Conclusions

This study demonstrated that soluble carbohydrate content of hay depends mainly on their content in the corresponding fresh forage and to a lesser extent on the drying time between cutting and hay baling. Longer DT will induce higher decrease in soluble carbohydrate in the hay. The effect of storage period and drying conditions should be studied to try to improve these predictions.

## Acknowledgements

This research was supported by a grant from the 'Association Nationale de la Recherche et de la Technologie' (Grant N° 2016/0889) and by IDENA and PHILICOT companies. The authors are grateful to the staff from IDENA, PHILICOT, AGROSCOPE Posicux and INRAE Herbipôle (https://doi.org/10.1545 4/1.5572318050509348E12) for help on data collection, and from UMR EVA for their assistance on soluble carbohydrate measurement.

## References

* Chatterton N.J., Harrison P.A., Bennett J.H. and Asay K.H. (1989) Carbohydrate partitioning in 185 accessions of gramineae grown under warm and cool temperatures. *Journal of Plant Physiology* 134, 169-179.

* Humphreys M.O. (1989) Water-soluble carbohydrates in perennial ryegrass breeding. III. Relationships with herbage production, digestibility and crude protein content. *Grass and Forage Science* 44, 423-430.

* McGechan M.B. (1989) A review of losses arising during conservation of grass forage: part 1, field losses. *Journal of Agricultural Engineering Research* 44, 1-21.

* Ould-Ahmed M., Decau M.-L., Morvan-Bertrand A., Prud'homme M.-P., Lafrenière C. and Drouin P. (2015) Fructan, sucrose and related enzyme activities are preserved in timothy (*Phleum pratense* L.) during wilting. *Grass and Forage Science* 72, 64-79.

* Peng K., Huang Q., Xu Z., McAllister T., Acharya S., Mueller-Harvey I., Drake C., Cao J., Huang Y., Sun Y., Wang S. and Wang Y. (2018) Characterization of condensed tannins from purple prairie clover (*Dalea purpurea* vent.) conserved as either freeze-dried forage, sun-cured hay or silage. *Molecules* 23, 586.

<footnote n="1">¹ RMSE = root mean square error.</footnote>