Reindeer Feeding

Forest reindeer male in Helsinki Zoo

Welcome back! In the first two parts of this article series we have covered the basics of reindeer nutrition and wild diets. Let’s take a quick trip down the memory lane before diving in to practical reindeer feeding:

  • Reindeer is an intermediate ruminant with the ability to use grazing strategy during winter and browsing strategy during summer
  • Their physiology resembles more that of a browsing ruminants
  • Reindeers diet changes drastically throughout the year
  • They have physiological adaptations for surviving on very different diets
  • They grow periodically and lose and gain weight according to seasons

In case you missed the first two parts, you can check out the first article on nutrition here and the second article on diets here.

Two diets – One for summer and one for winter

Reindeer need to have different diets during summer and winter. Reindeer go through metabolic and physiological changes that are controller by a hormonal cascade. This cascade starts with melatonin, a hormone that’s production and secretion from the pineal gland is controlled by changes in light.

The countries that have suitable climate for reindeers to be kept in captivity have different lengths of day in summer and winter. Reindeer do well in extreme coldness, for example the surface temperature of their feet can drop to just a few degrees Celsius. On the other hand, they are very sensitive to heat and heat stress.

Because the changes in the metabolism and physiology are triggered by a stimulus out of our control, the day length, we need to accommodate these changes by changing the diet. Correct diet and feeding are a major welfare issue and a common reason behind inability to reproduce and premature deaths.

Forest reindeer in Ähtäri Zoo
Forest reindeer (Rangifer tranadus fennicus) feeding on fresh browse in Ähtäri Zoo

Feeding in the summer

Although the peculiarity of reindeers’ diet is undoubtedly lichen, a composite organism of cyanobacteria or algae and fungi, the summer diet determines the success of the diet. As we remember the reindeer increase in body condition during summer and autumn and then mobilize body reserves on winter. This means that the summer diet must be high in metabolizable energy and protein for the reindeer to gain enough weight and body reserves for upcoming winter. After Christmas the reindeer are unable to put on anymore weight; the hormonal changes have decreased their appetite so that the reindeer won’t eat enough, no matter how much high-quality feed is offered.

Staples in the diet

Staple of the diet should be high-quality browse from deciduous, non-toxic trees. Good options are willow, aspen, rowan and birch. Fresh cut browse is better accepted than dried browse and should be used when available. Drying browse for winter supplement and enrichment is a good idea. Another way to conserve browse for winter is ensiling. You can read more about making browse silage at the Facebook page of Browse Poster. They also have great booklets and posters on safe browse species for different animal groups. I am not affiliated to Browse Poster but I have used their booklets for a few years now.

Second most important feed item is a suitable concentrated feed. It should be high in protein and metabolizable energy and offered ad libitum, if there are no contraindications for unrestricted energy intake in the animal group. Especially gravid and lactating females have a high energy and protein need, castrated males and non-reproducing females have lower needs. Most browser pellets are suitable for reindeer summer diets. Also grains and beet pulp are used in reindeer diets. De-hulled oats are a good option with low glycemic index and good protein content. Grains and beet pulp have inadequate protein content for gravid or lactating females and breeding males, so a protein feed is also needed. With browser pellets no additional protein feed is needed.

Supplements

As a supplementary feed some fresh cut hay or dried hay can be offered. Hay from second harvest and so-called autumn hay are good options as they have less insoluble fiber. A mineral supplement maybe in order, depending on the browse quality and concentrates that are offered. Calculating the nutrient content of the diet is advisable as it prevents overdosing supplements and nutrient deficiencies. Mineral supplement should be a pelleted mineral that is offered mixed with the concentrated feeds. Mineral stones can have uneven ratio of vitamins and minerals and the dosage each animal gets may vary. Some animals like to lick the mineral stones which poses a risk of overdose. A salt lick of pure natrium chloride should always be available.

A small amount of lichen can be kept in the summer diet. Lichen protects the rumen and rest of the digestive tract and can prevent runny stools. Especially males have been observed to eat lichen in the wild during summer and can benefit from it. The amount should be kept small and is best offered first in the morning. This way it stabilizes the rumen and gut function before the concentrate feeds are offered.

Summary

By the end of autumn, the reindeer should have body reserves to make it through winter. Gaining weight during summer is important in captivity too, because the reindeer lose appetite during the winter and are unable to gain weight after Christmas. If the body condition is not sufficient by this time, the reindeer will lose too much body reserves and start breaking down muscle tissues. Gaining back the muscle and fat during next summer will demand even more energy and protein. If the summer diet is insufficient you have a vicious cycle that will slowly affect the ability to breed and longevity of animals. Body condition scoring is great way to stay on top of the body reserves building up and breaking down. Regular scoring will tell you when to make corrections to feeding before the animals reach a critical condition and start showing severe symptoms.

Fresh cut hay and the summer diet in general can make stool runnier than during winter. Regular fecal scoring is advisable to know what is normal for your animals and what should raise the alarm. Always consult a veterinarian familiar with reindeer if you have any concerns. It’s also important to rule out any medical conditions that could be the source of the problems before altering the diet.

The transitioning to winter diet usually starts in October. Males can lose some of their body reserves during rut. If this happens, make sure the male can get back to proper condition before switching to winter diet. This can be done by giving males the summer diet for longer, even up until Christmas in some cases. The transition between diets should be slow and span over two to three weeks. This gives the rumen microbiome time to adjust to the change. The rumen microbiome is controlled almost entirely by the diet fed to the ruminant. This means that this change, unlike other changes in reindeer nutritional physiology, is controlled by the feed we give them.

Two forest reindeer (Rangifer tarandus fennicus) in early autumn in the wild. © LUKE (Natural Resources Institute Finland)

Feeding in the winter

Winter diet plays a smaller role in the overall nutrition of reindeer. During winter the reindeer become excellent in conserving energy and nitrogen obtained from the diet and catabolized from body tissues.

Staples in the diet

Staple of the winter diet in the nature is lichen. In captivity this can sometimes be hard to provide in adequate levels. Reindeer readily accept many types of lichen. In Finland they have been recorded to prefer Cladonia spp. which is consequently known as reindeer moss (though it’s a lichen and not a moss). Providing lichen at least at a minimum level has benefits in that it stabilizes the rumen and gut functions. Reindeer have special microbes in their rumen that break down lichen and need it to exist.

Lichen in essence is soluble carbohydrates with minimal protein and mineral content. Beet pulp has been suggested as a replacement and it seems to work well in practice too. Beet pulp comes as molassed or un-molassed. Molassed beet pulp has some of the sugary syrup added back to the mass where it has been industrially compressed out. It increases the energy content and palatability of the beet pulp. It also increases the amount of quickly fermentable carbohydrates. These carbohydrates can cause the rumen pH to drop too fast too low, so be careful when using products high in sugar.

Another staple in the winter diet is concentrate feed. This should be different from the high energy and protein feed used in the summer diet. In the winter the need for energy and especially protein is lower. Many concentrates marketed as reindeer feeds are suitable for winter diets.

All ruminants can cycle urea in their system, and reindeer are especially efficient in this. Their ability increases during winter. Urea contains nitrogen needed in forming microbial protein in the rumen. As you remember, this microbial protein is the protein source of the ruminant. If there is too much protein in the winter diet, the nitrogen conserved in the urea cycle and provided in the diet exceeds the needs. This causes stress on the kidneys as the excess is excreted in the urine and increases the need to drink. In extreme cases the reindeer start “sweating” the nitrogen out through the skin on their abdomen which causes them to get wet bellies. Being wet in subzero temperatures predisposes the animals to other health problems.

Supplements

Reindeer, especially the gestating females are known to eat dead plant parts in the winter. These have higher protein contents than lichen. In captivity the reindeer winter diet can be supplemented with dried or ensilaged browse.

Dry hay can also be a supplemental element in the winter diet. In the winter the hay needs to meet the same standards as in summer. It needs to be fine with minimal stem and maximal leaf concentration. Second or third harvest or autumn hay are suitable options.

The winter diet can and should also be supplemented with minerals and vitamins. These can be obtained from the same supplements used in the summer. The dosage can be a bit lower to mimic the natural conditions. The natural winter diet is poor in minerals because lichen doesn’t contain much of them and can also bind minerals to insoluble forms. Therefore, it’s advisable to feed the mineral supplement separate from the lichen.  

Summary

In the wild, the late winter and spring are nutritionally most demanding. The body reserves can be used up and the winter pastures also start to reach their limit. The lichen can also be covered with a hard crust on top of the snow, making it impossible to dig them up. In captivity the amount of food is staple, but you should see a decrease in the body condition in the spring. If not, your winter diet might be too high in energy and possibly also in protein.

Keeping up with body condition scoring and fecal scoring in the winter are also important. They give you valuable information about how the diet works for your animals.

Wrap-up

To summarize everything we have learned in these three articles, here is your take home message:

  • Reindeer is an intermediate ruminant
  • Reindeer has adapted to changing environment and these physiological changes happen in captivity too
  • Reindeer needs a cyclic diet to cover the changing needs
  • High energy and high protein diet in the summer
  • Low energy and low protein diet in the winter
  • In the summer the reindeer needs to put on weight
  • This weight should be shed during the winter
  • Reindeer doesn’t usually do well on high-fiber, long fiber diets that stratificate the rumen contents
  • Better options than hay are lichen, deciduous browse (either fresh, dry or ensiled) and reindeer or browser pellets depending whether it’s summer or winter.
  • Fine autumn hay can be a part of the diet. Make sure you have high leaf to stem ratio meaning that the hay has more leaves and less stems.

Thank you so much for reading this article series on reindeer nutrition, diets and feeding! If you have any questions, ideas or insights you can contact me via email at aino [at] feralanimalnutrition.com or with my contact form.

What else? Tell me what topics you’d like to know more about in zoo animal nutrition. You can send requests on topics via contact form.

References & further reading

Barboza, P. & Parker, K. 2006, Body Protein Stores and Isotopic Indicators of N Balance in Female Reindeer (Rangifer tarandus) during Winter, Physiological and Biochemical Zoology, 79 (3), s. 628-644.

Boertje, R.D. 1990, Diet Quality and Intake Requirements of Adult Female Caribou of the Denali Herd, Alaska, Journal of Applied Ecology, 27 (2), s. 420-434.

Case, R.L. 1997, Adaptations of northern ungulates to seasonal cycles in nitrogen intake., dissertation, University of Alberta.

Clauss, M., Hofmann, R.R., Streich, W.J., Fickel, J. & Hummel, J. 2010, Convergence in the macroscopic anatomy of the reticulum in wild ruminant species of different feeding types and a new resulting hypothesis on reticular function, Journal of Zoology, 281 (1), s. 26-38.

Clauss, M., Hofmann, R.R., Fickel, J., Streich, W.J. & Hummel, J. 2009, The intraruminal papillation gradient in wild ruminants of different feeding types: Implications for rumen physiology, Journal of morphology, 270 (8), s. 929-942.

Danell, K., Utsi, P.M., Palo, R.T. & Eriksson, O. 1994, Food Plant Selection by Reindeer during Winter in Relation to Plant Quality, Ecography, 17 (2), s. 153-158.

Heggberget, T.M., Gaare, E. & Ball, J.P. 2002, Reindeer (Rangifer tarandus) and climate change: Importance of winter forage, Rangifer, 22 (1), s. 13-31.

Heiskari, U. & Nieminen, M. 1992, The effect of the diet on the digestive organ size of reindeer, Rangifer, 12 (3), s. 167-168.

Hofmann, R.R. 2011, Functional and comparative digestive system anatomy of Arctic ungulates, Rangifer, 20 (2-3), s. 71-81.

Hofmann, R.R. 1989, Evolutionary Steps of Ecophysiological Adaptation and Diversification of Ruminants: A Comparative View of Their Digestive System, Oecologia, 78 (4), s. 443-457.

Joly, K., Wasser, S.K. & Booth, R. 2015, Non-invasive assessment of the interrelationships of diet, pregnancy rate, group composition, and physiological and nutritional stress of barren-ground caribou in late winter, PLoS ONE, 10 (6).

Josefsen, T.D., Aagnes, T.H. & Mathiesen, S.D. 1996, Influence of diet on the morphology of the ruminal papillae in reindeer calves (Rangifer tarandus tarandus L.), Rangifer, 16 (3), s. 119-128.

Klein, D.R. 1990, Variation in quality of caribou and reindeer forage plants associated with season, plant part, and phenology, Rangifer, 10 (3), s. 123-130.

Maijala, V., Heiskari, U. & Nieminen, M. 2004, The adaptation of the digestive system of a reindeer to a yearly additional feeding, Finnish Game and Fisheries Research Institute, Helsinki.

Mathiesen, S.D., Vader, M.A., Raedergård, V.B., Sørmo, W., Haga, O.E., Tyler, N.J. & Hofmann, R.R. 2000a, Functional anatomy of the omasum in high Arctic Svalbard reindeer (Rangifer tarandus platyrhynchus) and Norwegian reindeer (Rangifer tarandus tarandus). Acta Vet Scand, 41 (1), s. 25-40.

Mathiesen, S.D., Haga, ØE., Kaino, T. & Tyler, N.J.C. 2000b, Diet composition, rumen papillation and maintenance of carcass mass in female Norwegian reindeer (Rangifer tarandus tarandus) in winter, Journal of Zoology, 251 (1), s. 129-138.

Nieminen, M. 1980, Nutritional and seasonal effects on the haematology and blood chemistry in reindeer (Rangifer tarandus tarandus L.), Comparative Biochemistry and Physiology — Part A: Physiology, 66 (3), s. 399-413.

Nieminen, M. & Heiskari, U. 1989, Diets of freely grazing and captive reindeer during summer and winter, Rangifer, 9 (1), s. 17-34.

Ophof, A.A., Oldeboer, K.W. & Kumpula, J. 2013, Intake and chemical composition of winter and spring forage plants consumed by semi-domesticated reindeer (Rangifer tarandus tarandus) in Northern Finland, Animal Feed Science and Technology, 185 (3-4), s. 190.

Podterob, A. 2008, Chemical composition of lichens and their medical applications, Pharmaceutical Chemistry Journal, 42 (10), s. 582-588.

Pösö, A.R., Heiskari, U., Lindström, M., Nieminen, M. & Soveri, T. 2001, Muscle fibre growth in undernourished reindeer calves (Rangifer tarandus tarandus L.) during winter, Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 129 (2), s. 495-500.

Rankama, T. & Ukkonen, P. 2001, On the early history of the wild reindeer (Rangifer tarandus L.) in Finland 30, Blackwell Publishing Ltd, s. 131-147.

Säkkinen, H., Timisjärvi, J., Eloranta, E., Heiskari, U., Nieminen, M. & Puukka, M. 1999, Nutrition-induced changes in blood chemical parameters of pregnant reindeer hinds (Rangifer tarandus tarandus), Small Ruminant Research, 32 (3), s. 211-221.

Sjaastad, ØV., Hove, K. & Sand, O. 2010, Physiology of domestic animals, 2nd ed. p., Scandinavian Veterinary Press, Oslo.

Sørmo, W. & Mathiesen, S.D. 1993, Bacteria in the small intestine of lichen-fed Norwegian reindeer (Rangifer tarandus tarandus), Letters in Applied Microbiology, 16 (3), s. 170-172.

Soveri, T. & Nieminen, M. 2007, Papillar Morphology of the Rumen of Forest Reindeer (Rangifer tarandus fennicus) and Semidomesticated Reindeer (R. t. tarandus), Anantomia Histologia Embryologia, 36 (5), Blackwell Publishing Ltd, s. 366-370.

Soveri, T., Sankari, S. & Nieminen, M. 1992, Blood chemistry of reindeer calves (Rangifer tarandus) during the winter season, Comparative Biochemistry and Physiology — Part A: Physiology, 102 (1), s. 191-196.

Staaland, H., Jacobsen, E. & White, R.G. 1979, Comparison of the Digestive Tract in Svalbard and Norwegian Reindeer, Arctic and Alpine Research, 11 (4), s. 457-466.

Thompson, D.P. & Barboza, P.S. 2017, Seasonal energy and protein requirements for Siberian reindeer (Rangifer tarandus), Journal of Mammalogy, 98 (6), s. 1558-1567.

Thompson, D.p. & Barboza, P.s. 2013, Responses of caribou and reindeer ( Rangifer tarandus) to acute food shortages in spring, Canadian Journal of Zoology, 91 (9), s. 610-618.

Tryland, M., & Kutz, S. J. (Eds.). 2018. Reindeer and Caribou: Health and Disease. CRC Press.

Valtonen, M. 1979, Renal responses of reindeer to high and low protein diet and sodium supplement, University of Helsinki.

Warenberg, K., Dannel, Ö, Gaare, E. & Nieminen, M. 1997, Porolaidunten kasvillisuus, Pohjoismainen Porontutkimuselin (NOR), Landbruksforlaget.

White, R.G. 1983, Foraging Patterns and Their Multiplier Effects on Productivity of Northern Ungulates, Oikos, 40 (3), s. 377-384.

White, R.G., Jacobsen, E. & Staaland, H. 1984, Secretion and absorption of nutrients in the alimentary tract of reindeer fed lichens or concentrates during the winter, Canadian Journal of Zoology, 62 (12), s. 2364-2376.

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