Alternative Forages (part 4)

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Published in the Horses and People Magazine & Hoofbeats Magazine

Forage trees & shrubs for horses

 By Mariette van den Berg BAppSc.(Hons), MSc. (Equine Nutrition)

Introduction

Adding trees in and around pastures can be beneficial for a number of reasons: it not only plays a major role in the hydration of the land and the control of erosion, but can also provide shade, shelter, and fodder. Many of us may now be familiar with feeding tree and shrub forage to livestock, but fewer horse owners know about the use of fodder tree and shrub for horses. In this section, we describe the benefits of trees and shrubs as fodder and suggest a selection of potential forage trees and shrubs for horses.

Primarily grazer or mixed feeder?

Feeding behaviour represents a large part of the total time-budget of horses. Several studies that investigated the time-budget of free-roaming horses in the American West, the Camargue region of France, the New Forest of England^, and the steppes of Mongolia show that horses spend about 60% of their time on grazing and browsing.(^1–7) This also appears to be true for pastured horses: like free-roaming horses, pastured horses can graze and browse for up to sixteen to eighteen hours every day, selectively foraging on a wide variety of plant species.^(8,9)

Free-roaming and pastured horses select a broad range of forages, include ‘browse’. Browsing is the feeding on vegetation other than grasses, which can comprise up to 50% of the total diet.^(10-12) In Australia, free-roaming horses have been observed to consume various parts of shrubs and trees, including bark of select eucalypt species.^(13-16) Domesticated horses in Australia will consume a wide range of browse species when they available in their paddock or pasture environment.⁽¹⁷⁾

Choosing the right trees and shrubs

To satisfy our horses’ browsing behaviour, it is important that we select the right tree and shrub species for each pasture or paddock or cut-and-carry system. There are various native and introduced species to choose from, but species differ in their site requirements and ideal soil type. Some tree and shrub species may be toxic to horses when eaten in large quantities and should therefore be avoided around and within horse pastures and paddocks.

Plants have co-evolved with — and are eaten by — bacteria, insects, fungi, and grazing animals.⁽¹⁸⁾ Because of these interactions, plants have developed a range of defence mechanisms to aid their survival. Tree legumes often have thorns, fibrous foliage, and high tree crowns. Many plants also produce chemicals that are not directly involved in the process of plant growth and are, for this reason, called secondary compounds. These chemicals can protect the tree or shrub against insect and fungal attack. However, these compounds also affect animals and modify the nutritive value of forages.⁽¹⁸⁾ Mycotoxins, which are produced by certain types of fungi, are a potential source of toxins in forages. Ryegrass and Paspalum grasses can contain mycotoxins, which can cause staggers in livestock and horses. The effects of both secondary compounds and mycotoxins differ across animal species. Non-ruminants (e.g. pigs, poultry, and horses) are usually more susceptible to these toxins than ruminants, which have the capacity to neutralise potential toxins in the rumen.⁽¹⁸⁾

Another concern for horse owners to consider when selecting trees is the potential risk of housing populations of flying foxes, which can spread the Hendra virus, or caterpillars, which may cause Equine Amnionitis and Foetal Loss (EAFL) in broodmares. Horse owners should look closely at their property layouts or farm designs when planting forage trees.

Nutritive value of forage trees and shrubs for horses

Forage trees and shrubs must have nutritive value to be useful as forage. The nutritive value of tree and shrub forage is determined by their ability to provide the nutrient required by an animal. Tree and shrub forage have been primarily used as feed for ruminants (cattle, sheep, goats), although some reports exist about their inclusion in the diet of non-ruminants (poultry, pigs, horses).^(18-20) Even though information is available concerning the toxicity of certain plants and trees for horses, fewer reports outline the feeding value and palatability of tree and shrub forage for horses.

When selecting forage trees and shrubs, we must take into account this limited information about the use of trees and shrubs for horses; moreover, we must make note of contradictions in the literature regarding the acceptability of fodder from trees and shrubs for horses. The following points help to explain these gaps in research:

• Acceptability of a plant to a horse can change over the course of the year. Animals may select only young leaves, for example. With maturing of the leaves, the secondary compounds may increase and animals may not like the taste of the leaves anymore.
• In some cases, it may take some time for animals to accept a new feed, but, once accustomed, they may consume it readily.
• Preference for one feed over another does not mean that an animal will not accept a particular feed when the choice is limited.
• Within a single species, differences can exist between varieties, individual trees, and even between parts of the same tree. Acceptability can be influenced by climate and soil conditions

Benefits and selection of forage trees and shrubs for horses

Trees and shrubs can potentially supplement the quantity and quality of pastures for grazing horses and reduce feeding cost of roughage. They can function as a substitute when there is seasonal shortage or risk of drought. Tree fodder systems can deliver additional benefits such as shelter, soil conservation, rough timber, and habitat. However, the leaves, stems, pods, and fruits of trees and shrubs should still only be used as a supplement to primary feed. Tree and shrub fodder as a sole diet is not suitable for horses. Moreover, as with many other feed products, it is important to gradually introduce horses to the fodder to have them accept their new feed.

As we highlighted in the previous section, limited information exists about the use of tree and shrub fodder as a feed source for horses. More research is required to determine the nutritive value, palatability, and, if applicable, toxicity levels (amount that can be safely fed) of various potential fodder trees and shrubs for horses.(21) The following tree and shrub species (a selection of native and introduced species) have been reported to be acceptable as browse by horses⁽¹⁷⁾:

 Saltbush (Atriplex spp.) is a halophytic (‘salt tolerant’) shrub and has a long-term survival rate on moderately saline and waterlogged soils. It is drought-tolerant and can be used as a fodder with other feeds. A number of Atriplex species are native to Australia. Old Man saltbush (Atriplex Nummularia), River saltbush (Atriplex Amnicola), Wavy-leaf saltbush (Atriplex undulate; introduced from Argentina), and Quailbush (Atriplex lentiformis) show the best results in environmental tolerance (salinity, drought, frost, water-logging, and flooding), palatability, and recovery after grazing.⁽²²⁾ Much of the research that focuses on the nutritive values of saltbush species for animals concentrates on ruminants, especially sheep.^(22,23) Ruminants tend to prefer saltbush more than horses, but horses have been observed to browse saltbush if it is present in their pastures. In particular, the leaves of the Old Man saltbush can be used as a fodder. Several companies in Australia sell dried leaves as a fodder and herbal remedy to horse owners. Please note, however, that saltbush contains oxalates, which can cause big head (if it is offered as a sole diet) and nitrates, which can be toxic for livestock and horses when consumed in high levels.  

Bitter pea (Daviesia spp.)–  are several native shrubs that belong to the Fabaceae (pea) family. They can be found in most states in Australia. The fruits have a bitter flavour that various animals seem to enjoy. It is reported that livestock and horses prefer the leaves and young twigs of two kinds of species: Clustered bitter pea (Daviesia corymbosa) and Hop bitter pea (Daviesia latifolia).⁽²⁴⁾

 

 

 

 

Dogwood (Jacksonia scoparia) is a native pea-flowered shrub or small tree that reaches approximately 4 metres (13 feet) high. It belongs to the Fabaceae (pea) family and is found in southeast Queensland and eastern New South Wales. Dogwood can be used as a drought fodder and is reported to be relished by cattle and horses.⁽²⁴⁾

 

 

 

 

 

Tagasaste (Chamaecytisus palmensis) or Tree Lucerne is a small spreading evergreen tree that grows to a height and crown diameter of about 5 metres (16 feet). It is a member of the Fabaceae (pea) family and is indigenous to the Canary Islands (Spain). Tagasaste is grown in Australia, New Zealand, and many other countries as fodder crop.⁽²²⁾ The trees can have long drooping or upright, leafy branches. The white flowers develop into flattened pods about 5 centimetres (2 inches) long, which can contain up to ten seeds. The nutritive value of leaves is similar to that of lucerne (Medicago sativa). Analysis of the edible fraction of these trees (leaves plus stems <5 millimetres) indicates that crude fibre varies from 16–25% over a year, while crude protein levels in summer ranged from 17–21%.⁽²³⁾ Leaves are high in vitamin A and reported as highly palatable. However, animals take a little time to get used to Tagasaste as a feed. No reports exist to indicate that Tagasaste contains compounds toxic to animals.⁽²⁵⁾ Levels of tannins are also low. Moreover, the trees are extremely drought-tolerant, fast growing, and frost-tolerant. However, they will not tolerate poor drainage or water-logging. Tagasaste can become invasive and overgrow bush land if it is allowed to set seed.

Carob tree (Ceratonia siliqua) or St John’s Bread is a small- to medium-sized long-lived evergreen tree with dense foliage that grows up to 10 metres (32 feet) tall. It is also a member of the Fabaceae (pea) family and is native to the Mediterranean region.⁽²⁶⁾ The plants are cultivated for their edible seedpods. The trees develop dark brown flattened pods (fruit) about 10–30 centimetres long and 2.5 centimetres wide. The pods contain pulp that has a sweet, chocolate taste and a number of bean-like seeds. Carob has a long history as a source of food, mainly for humans, but it is well recognised in parts of the world as a source of fodder for animals (i.e. goats, cattle, donkeys, horses).⁽²⁷⁾ The pods of the carob, not the leaves, are consumed. The pods provide between 2–7% crude protein, 37–62% carbohydrates, and up to 2% crude fat.⁽²⁶⁾ Due to their chemical composition, the carob pods are used in both food and medicine.⁽²⁷⁾ Carob is economically important as a cocoa substitute and a foodstuff. Carob trees are drought- and salt-tolerant, and can tolerate any soil type except heavy clay

 

Bamboo is a group of evergreens that belongs to the true grass family Poaceae (subfamily Bambusoideae). There are various species of bamboo that are used for gardens, building materials, paper pulp, and textiles, but the shoots and leaves can also be used as a food source for humans and animals. A variety of bamboo species have been explored as a drought or winter fodder for livestock,^(19,28,29) but a number of studies also report the inclusion of bamboo in the diet of horses.^{(19,20,30,31)} Bamboo is high in fibre and contains approximately 10–20% crude protein. However, the consumption of large amounts of Bambusa vulgaris (Yellow Bamboo) has shown to be toxic for horses.⁽³²⁾

 

 

 

 

 

Acacia saligna, commonly known by various names, including coojong, golden wreath wattle, orange wattle, blue-leafed wattle, or Western Australian golden wattle. Acacia saligna is a small tree in the family Fabaceae. Native to Australia, it is widely distributed throughout the southwest corner of Western Australia. It has large leaves and is a good fodder for sheep, goats, and cattle.⁽¹²⁾ Horses have been reported to browse on a variety of acacia species.⁽¹⁷⁾ Acacia saligna could therefore be a potential fodder for horses: it is a fast-growing, fire-retardant, nitrogen-fixing shrub that grows up to 4 metres (13 feet). It is suitable for soil-stabilisation and does well in sand near coastal areas. It is also ideal for windbreak and erosion control.

The best place of trees

Planting trees just outside the fence around a pasture boundary is usually adequate. Trees grow branches, which extend over the fences and into the pasture to provide shade. For large fields, we can place a few fenced-off patches of trees within pastures or we can have separate blocks of various forage trees. For young trees, fencing is necessary to protect the trees from damage caused by the animals. Fencing prevents rubbing injuries to trees from horses that like to scratch. Even mature, full-grown trees should remain fenced off from horses to ensure survival of the trees.

How to feed fodder-trees and shrubs

Horses can either browse trees and shrubs while they are grazing in the pasture or feed from branches that we cut and carry to their pastures or stables. A cut-and-carry system is preferable, because it’s easier to control the amount of fodder fed to our horses. We can also collect pod legumes and seeds and feed these separately or mixed (for better digestibility, crush or boil seeds) into the (hard) feed for horses.

The forage trees and shrubs we list in this article represent merely a selection; there may be other trees more suitable for specific environments (declared status, climate, soil conditions, rain fall etc.) that you can use. Moreover, as we noted earlier, information remains limited concerning the nutritive value, palatability, and toxicity of forage trees and shrubs for horses.

For more information about the practical application of (forage) trees and shrubs for your property please contact MB Equine Services.

Further reading:

1. Salter, R.E., and Hudson, R.J.1979. Feeding Ecology of Feral Horses in Western Alberta. Journal of Range Management 32, 221-225.
2. Berger, J. 1986. Wild Horses of the Great Basin: Social Competition and Population Size. University of Chicago Press, Chicago, Illinois, USA.
3. Duncan, P. 1980. Time-Budgets of Camargue Horses: II. Time-Budgets of Adult Horses and Weaned Sub-Adults. Behaviour 72, 49.
4. Mayes, E. and Duncan, P. 1986. Temporal Patterns of Feeding in Free-Ranging Horses. Behaviour 96, 105-129.
5. Tyler, S.J.1972. The Behavior and Socialorganization of the New Forest Ponies. Animal Behavior Monographs 5, 87-194.
6. Boyd, L. 1998. The 24-h Time Budget of a Takh Harem Stallion (Equus ferus przewalskii) Pre- and Post-Reintroduction. Applied Animal Behaviour Science 60, 291-299.
7. Boyd, L. and Bandi, N. 2002. Reintroduction of Takhi, Equus ferus przewalskii, to Hustai National Park, Mongolia: Time Budget and Synchrony of Activity Pre- and Post-Release. Applied Animal Behaviour Science 78, 87-102.
8. Archer, M. 1971. Preliminary Studies on the Palatability of Grasses, Legumes and Herbs to Horses. The Veterinary Record 89, 236-240.
9. Archer, M. 1973. The Species Preferences of Grazing Horses. Journal of the British Grassland Society 28, 123-128.
10. Hansen, R.M.1976. Foods of Free-Roaming Horses in Southern New Mexico. Journal of Range Management 29, 347.
11. Hubbard, R.E. & Hansen, R.M. 1976. Diets of Wild Horses, Cattle, and Mule Deer in the Piceance Basin, Colorado. Journal of Range Management 29, 389-392.
12. Putman, R.J., Pratt, R.M., Ekins, J.R., and Edwards, P.J. 1987. Food and Feeding-Behavior of Cattle and Ponies in the New Forest, Hampshire. Journal of Applied Ecology 24, 369-380.
13. Nadolny, C. 1983. Eucalypt Dieback on the Northern Tablelands of New South Wales, Environmental Science & Natural Resources, University of New England, Armidale, NSW, Australia.
14. Berman, D.M. 1991. The Ecology of Feral Horses in Central Australia, University of New England, Armidale, NSW, Australia.
15. Ashton, A. 2005. Bark Chewing by Wild Horses of Guy Fawkes River National Park, NSW: Impacts and Causes., University of New England, Armidale, NSW, Australia.
16. Hampson, B.A. Owens, E., Watts, K.A., Mills, P.C., Pollitt, C.C., and de Laat, M.A. 2011. Nutritional Analysis of Gastric Contents and Body Condition Score at a Single Time Point in Feral Horses in Australia. American Journal of Veterinary Research 72, 1226-1233.
17. van den Berg, M. 2013. A Survey of Management Practices and Foraging Behaviour of Pastured Horses in Australia, University of New England, Armidale NSW, Australia.
18. Norton, B.W. 1998. The Nutritive Value of Tree Legumes, in: Gutteridge, R.C., Shelton, H.M. (Eds.), Forage Tree Legumes in Tropical Agriculture, CAB International, Wallingford, Oxford, UK, pp. 177-191.
19. Nelson, G., Keller M. and Cheeke, P.R. 1997. Evaluation of Temperate Bamboo Species as Forage for Livestock. Pacific Northwest Bamboo Agroforestry Workshop Port Townsend. p 7-1 to 7-8., Washington, USA.
20. Kawai, M., S. Kondo, H. Hata, and M. Okubo. 1998. Seasonal Changes of Plant Weight and Chemical Composition on Sasa Nipponica Grassland for Grazing Hokkaido Native Horses. Research Bulletin of the Hokkaido University Forests 55: 56-62.
21. Van den Berg, Lee, C and Brown W.Y. 2012. “Browsing – an Overlooked Aspect of Feeding Management in Horses?” Proceedings of the Australasian Equine Science Symposium 2012, p71
22. Lefroy, E.C., Dawn, P.R., Wildin, J.H., Wesley-Smith, R.N. and McGowan, A.A. 1992. Trees and shrubs as Sources of Fodder in Australia. Agroferestry Systems 20:117-139.
23. Lefroy, E.C. 2002. Forage Trees and Shrubs in Australia: Their Current Use and Future Potential. Rural Industries Research and Development Corporation (RIRDC) No. 02/039.
24. Maiden, J.H. 1913. Some Native Australian Fodder Plants (Other Than Grasses and Salt-Bushes) – Australian Bureau of Statistics (ABS) Year Book Australia 1913, Canberra, Australia.
25. Dann, P. & George, B. 2003. Tagasaste (tree lucerne) – Agfact sheet. NSW Agriculture, Australia
26. Batlle, I. and J. Tous. 1997. Carob tree. Ceratonia siliqua L. Promoting the Conservation and Use of Underutilized and Neglected Crops. 17. Institute of Plant Genetics and Crop Plant Research, Gatersleben/International Plant Genetic Resources Institute, Rome, Italy.
27. Vekiari, S.A., Ouzounidou, G., Ozturk, M. and Görk, G. 2011. Variation of Quality Characteristics in Greek and Turkish Carob Pods During Fruit Development. Procedia Social and Behavioral Science 19: 750-755.
28. Farrelly, D. 1984. The Book of Bamboo. p 280. Sierra Club Books, San Francisco, USA.
29. Halvorson, J. J., K. A. Cassida, and K. E. Turner. 2004 “Nutritive Quality of Bamboo Browse for Livestock.” American Forage and Grassland Council Conference Proceedings. Vol. 13, p. 417.
30. Triebe, C, van den Berg, M. and Brown, W.Y. 2012. “Tagasaste versus Golden Bamboo: Which do Horses Prefer?” Proceedings of the Australasian Equine Science Symposium Vol 4, p41
31. Greenway, S.L. 1999. Evaluation of Bamboo as Livestock Forage and Applications of Yucca schidigera and Quillaja saponaria Products in Agriculture. Master’s Thesis. Oregon State University, USA.
32. Barbosa, J.D., de Oliveira, C.M.C., Duarte, M.D., Riet-Correa, G. Peixoto, P.V. and Tokarnia, C.H. 2006. Poisoning of Horses by Bamboo Bambusa vulgaris. Journal of Equine Veterinary Science 26 (9): 393-398.

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