Bulletin #9644, Nutritive Value of Ensilated Leaves From Selected Maine Tree And Shrub Species For Forage Production
By Jaime Garzon, Assistant Extension Professor and Forage Educator, University of Maine Cooperative Extension
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Note: The results in this bulletin are exclusively descriptive, as there was no experimental design to validate the responses statistically. Therefore, conclusions, predictions, or deductions based on the results shown should be avoided.
Introduction
Climate variability refers to the natural changes the weather experiences on different time and space scales. They are the fluctuations in average climatic conditions, such as temperature, precipitation, winds, etc., that occur regularly and cyclically. On the other hand, climate change has intensified the fluctuations observed decades ago. In Maine, this is observed with an increase in air temperature and a greater incidence of extreme events, such as very hot or very cold days in the year.
These effects directly impact the performance of Maine’s pastures. Warmer days reduce the productivity of pastures, commonly established with cool-season forages, increasing the summer slump effect. A more significant number of droughts or floods also negatively impact pasture yield, jeopardizing the primary food source for Maine livestock.
Maine also has a large acreage established with woods. Many of the state’s agricultural operations have forested areas, and their operators have observed that cattle, sheep, and goats sometimes consume tree leaves without any sign of intoxication. Therefore, the objective of this project is to evaluate the nutritive value of fresh and silage leaves from 28 tree species, all established in Maine, to bridge an informational gap that is slowing livestock farmers from productively using on-site woody perennial forages when weather challenges interfere with their grass-forage harvests.
Methodology and variables evaluated
Twenty-eight tree/shrub species were initially selected based on empirical observation of animal intake and availability at Maine operations. Foliage samples were taken between June and October 2022-2024, considering the species that were available at the time. Samples were taken primarily at four locations:
- Maine Organic Farmers and Gardeners Association. Unity (ME).
44° 35’ 23.3” N; 69° 17.25’ 25.7” W. - Y Knot Farm. Belmont (ME).
44° 24’ 24.25” N; 69° 06’ 7.3” W. - Faithful Venture Farm. Searsmont (ME).
44° 24’ 53.5” N; 69° 13’ 1.7” W. - Laufer’s Homestead. Montville (ME).
44° 27.09’ N; 69° 18’ 56.3” W.
Harvest was performed using a chain-flail leaf-separator prototype. Cutting with hand-held power-tools, and stripping leaves with this machine prototype (created by current technical advisor Karl Hallen) was 90% quicker than traditional hand-stripping, producing 2,500+ gallons of tree/shrub leaf silage in 1,000 linear feet of field edges (Figure 1).
Photo: Courtesy of Shana Hanson
After each harvest, a proportion of the fresh material was sent to the Dairy One® forage lab, while the remainder was stored in plastic barrels with enough compaction to ensure anaerobic fermentation (Figure 2). Fermentation time varied from one to four months. After that, a subsample was taken for further analysis.
Photo: Courtesy of Shana Hanson
Crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), water-soluble carbohydrates (WSC), total digestible nutrients (TDN), and relative feed value (RFV) were determined by NIR analyses in the DairyOne® lab.
Results
The project started with the evaluation of 28 tree species. However, nine species showed incomplete and/or very variable results, and box elder caused animal death, so this bulletin focused on the results of the remaining 18 species (Table 1 and Table 2).
The ensiling process showed a reduction in the mean values of CP, WSC, and TDN with an increase in ADF and NDF (Table 2). These changes are explained by the fermentation process itself, where microorganisms take soluble carbohydrates as an energy source and transform protein sources with it. It is important to note that a good quality forage is expected to have 15-25% crude protein, 15-30% ADF, 40-60% NDF, 7-10% WSC, and 60-70% TDN. Thus, the mean nutritive value of all materials after the ensiling process fits within these ranges. Moreover, fresh leaves showed greater CP, WSC, and TDN values.
Moreover, fresh leaves showed greater CP, WSC, and TDN values (Table 1). Nonetheless, tree leaves may contain antinutritional components such as alkaloids, tannins, or cyanogenic acids. These compounds are usually degraded by anaerobic silage fermentation, so it is more advisable to supply ensiled foliage instead of fresh for animals to consume. In turn, this would increase palatability and animal preference, decreasing the risk of poisoning.
An exception must also be made for monogastric animals such as poultry or pigs, or young calves, as these animals are more sensitive to poisoning due to their lack of a functional rumen. Feeding ensiled foliage to these animals is not recommended until further studies have been conducted.
Finally, basswood and black locust were the species that maintained a higher concentration of CP after the fermentation process, with 3.6 – 5.3% WSC and 61% TDN. (Table 2).
This is an ongoing research project, so new results are expected to be included in this bulletin in the near future.
Acknowledgements
The University of Maine Cooperative Extension thanks Ms. Shana Hanson for providing the data and photos that comprise this bulletin’s results.
Funding
This project was funded by Northeast Sustainable Agriculture Research and Education (NE-SARE) through FNE22-013 and FNE24-083 Farmer Grant awards.NE-SARE is funded by the National Institute of Food and Agriculture (NIFA).
Other sources
- Hanson S. (2025) A closer look to guide farm use of tree/shrub silages: Per-species & ensilement analyses for safe, nutritious rationing, plus replicable trial results. Project FNE24-083. Northeast Sustainable Agriculture Research and Education. projects.sare.org/project-reports/fne24-083/.
- Hanson S. Hallen K. (2024). Efficient leaf-dense tree/shrub silage production from field edges: Climate-resilient winter forage supplement for cattle, sheep, and goats. Project FNE22-13. Northeast Sustainable Agriculture Research and Education. https://projects.sare.org/project-reports/fne22-013/.
- Chin J. (2022). The potential use of tree leaf silage for livestock nutrition, including willow, drumstick, mulberry, and acacia species. Thesis. University of Maine. digitalcommons.library.umaine.edu/honors/719/.
- Gabriel S. (2021). Quantifying nutritional value and best practices for woody fodder management in ruminant grazing systems. Project FNE19-30. Northeast Sustainable Agriculture Research and Education. projects.sare.org/project-reports/fne19-930/.
Table 1. Nutritive value of fresh leaves from 19 tree and shrub species in Maine.
| TREE AND SHRUB SPECIES | Crude protein (%) | Acid detergent fiber (%) | Neutral detergent fiber (%) | Water soluble carbohydrates (%) | Total digestible nutrients (%) | Relative feed value |
|---|---|---|---|---|---|---|
| American beech | 12.3 | 31.0 | 52.6 | 7.7 | 64.0 | 115 |
| American elm | 11.1 | 23.1 | 53.4 | 8.3 | 58.0 | 124 |
| Arrowwood | 12.0 | 31.4 | 43.0 | 9.4 | 68.0 | 139 |
| Basswood | 19.4 | 24.0 | 42.6 | 9.5 | 65.0 | 163 |
| Big toothed aspen | 9.8 | 27.1 | 38.8 | 14.0 | 72.0 | 176 |
| Black cherry | 17.0 | 25.6 | 34.9 | 9.1 | 67.5 | 174 |
| Black locust | 17.1 | 25.5 | 36.9 | 10.0 | 67.0 | 203 |
| Gray birch | 14.1 | 30.7 | 43.0 | 6.8 | 72.0 | 146 |
| Green ash | 15.4 | 26.9 | 43.3 | 8.3 | 66.0 | 134 |
| Honeysuckle | 11.1 | 29.9 | 45.0 | 13.6 | 65.0 | 173 |
| Leatherwood | 9.5 | 27.0 | 36.5 | 16.5 | 72.0 | 205 |
| Norway maple | 12.0 | 23.6 | 41.0 | 9.3 | 68.0 | 281 |
| Red maple | 10.9 | 16.8 | 25.1 | 18.0 | 79.0 | 97 |
| Red oak | 15.6 | 27.3 | 40.4 | 6.6 | 61.0 | 126 |
| Rock maple | 11.0 | 18.7 | 32.5 | 20.1 | 69.0 | 209 |
| Smooth buckthorn | 14.3 | 20.3 | 32.5 | 15.3 | 70.0 | 308 |
| White ash | 9.9 | 25.1 | 37.1 | 7.6 | 66.0 | 145 |
| Winterberry | 11.7 | 27.6 | 43.4 | 9.6 | 69.0 | – |
| AVERAGE | 13.1 | 25.5 | 39.7 | 10.9 | 67.8 | 170 |
| Standard deviation | 2.7 | 3.9 | 6.7 | 4.0 | 4.4 | 54 |
Table 2. Nutritive value of ensiled leaves from 19 tree and shrub species in Maine.
| TREE AND SHRUB SPECIES | Crude protein (%) | Acid detergent fiber (%) | Neutral detergent fiber (%) | Water soluble carbohydrates (%) | Total digestible nutrients (%) | Relative feed value |
|---|---|---|---|---|---|---|
| American beech | 12.7 | 35.8 | 55.6 | 2.9 | 59.0 | 102 |
| American elm | 12.1 | 23.7 | 54.0 | 4.3 | 54.0 | 121 |
| Arrowwood | 12.8 | 36.2 | 49.7 | 5.1 | 60.0 | 114 |
| Basswood | 19.8 | 24.8 | 45.3 | 3.6 | 61.0 | 143 |
| Big toothed aspen | 10.8 | 28/3 | 39.6 | 8.7 | 61.0 | 157 |
| Black cherry | 13.5 | 22.2 | 30.0 | 8.8 | 64.2 | 232 |
| Black locust | 17.3 | 26.6 | 37.3 | 5.3 | 61.0 | 170 |
| Gray birch | 11.6 | 31.9 | 44.4 | 8.2 | 63.0 | 133 |
| Green ash | 12.8 | 28.4 | 40.9 | 8.3 | 59.8 | 165 |
| Honeysuckle | 11.2 | 25.8 | 36.6 | 12.0 | 64.6 | 156 |
| Leatherwood | 8.7 | 32.4 | 43.2 | 13.9 | 66.0 | 137 |
| Norway maple | 12.8 | 24.0 | 42.8 | 4.8 | 65.0 | 153 |
| Red maple | 10.0 | 23.5 | 33.3 | 14.5 | 68.8 | 220 |
| Red oak | 14.3 | 29.0 | 46.3 | 4.1 | 60.3 | 134 |
| Rock maple | 9.5 | 22.9 | 34.1 | 14.3 | 66.0 | 194 |
| Smooth buckthorn | 15.4 | 25.9 | 38.9 | 6.5 | 67.0 | 164 |
| White ash | 11.1 | 26.8 | 39.2 | 8.4 | 59.3 | 161 |
| Winterberry | 12.6 | 31.4 | 49.2 | 4.0 | 62.0 | 122 |
| AVERAGE | 12.9 | 27.5 | 41.7 | 7.5 | 62.7 | 157 |
| Standard deviation | 2.7 | 4.2 | 7.0 | 3.7 | 3.8 | 35 |
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