Why is Browse and Fresh Forage Important?
Author : Louise Jakobsen
Historically, browse has been considered a source of enrichment. Fortunately, this has slowly turned around in recent years and browse (and fresh forage in general) is now increasingly being recognised as an essential part of the daily husbandry management of many animal species and not just an occasional treat.
One study by Mûller et al from 2011, compared the relative life expectancies of a vast amount of captive animals as a proportion of their maximum lifespan, analysing the effect of features of the animals’ biology or husbandry. The study found that browsers had a lower relative life expectancy in captivity than grazers! This is thought to indicate challenges with the complexity of providing a sufficient diet leading to alternative diets being provided and contributing to chronic health problems.
Other than this very obvious reason, there are also a number of other reasons to why we must make sure we provide our herbivores with adequate amount of suitable plant material:
- Abnormalities to the gut lining have been recorded in browsing animals with inadequate diets – this is particularly the case with ruminant browsers and one very classic example is the giraffe. There are most likely more examples out there among less studied species. The difference of the physiology in grazing and browsing ruminants is remarkable and there is still a lack of understanding of various feed types’ fibre constructions and how they break down with the correlated impact to GI tracts in the respective animals. Although there is little information readily available for hindgut fermenters, it is believed that the comparison of digestive physiologies in these animals follow similar principles.
Schematic correlation between the physical structure of forages and the anatomic adaptations of ruminant feeding types to the consequences of these physical properties. Source: EAZWV 2002, Digestive Tract Pathology of Captive Giraffe (Giraffa camelopardalis) – an unifying hypothesis.
- Provision of browse helps control the important pH levels in the GI tract – chewing is an essential part of the digestive process in herbivores; among other functions, the chewing increases the production of saliva which has several digestive related functions depending on the species. One important function is the buffering of the pH levels in the forestomach that saliva provides. It is relevant because a lot of our commercial feeds are still high in sugars and starches and many collections still feed produce to their browsing animal species. These all add to the lowering of the pH levels in the foregut, and the bacteria and protozoa etc. which helps break down the food in the gut, are highly dependent on the pH value.
- Excessive tooth wear is common in browsers fed inadequate diets – most captive diets for browsers include hay or haylage to substitute for browse and to ensure ad lib access to food. It is normally recommended to provide lucerne (alfalfa) hay or haylage but there are still collections that feed grass hay to browsing animals. Other than the obvious concerns related to grass fibres as illustrated above, grass is also high in silica which is very abrasive and wears down teeth prematurely. Even lucerne/alfalfa hay should only be seen as a better alternative to grass hay rather than an actual substitute for browse as the stems are still abrasive and somewhat indigestible (also breaks down into long fibres) although not to the same degree as grass.
- Provision of browse helps obtain normal faecal consistencies – adequate provision of the correct type of fibres for any species of animal, reflects in the faeces. For too many years, captive animals of many taxonomic groups, and especially the browsers, have been offered too high proportions of produce and feed types with inadequate fibre content. The challenge is that because it is still so commonly found, the faecal consistency of different animal species are perceived as ‘normal’ because that is all we know (the author is generalising here). Understanding how the faecal consistency of an animal would look like in the wild, is important to reflect on the diet we provide our animals.
- Provision of browse or branches helps control excessive tooth growth - even in animal species or taxonomic groups where browse isn’t an essential part to the diet, branches can still provide an important way to control tooth growth. This is, in particular (but not limited to), the case for camelids and rodents & lagomorphs, but also avian species like parrots and macaws. These animal groups have evolved to forage on foods that are tough and/or abrasive and hence, have forever growing teeth/beaks. In captivity, the diets are often much softer compared to those items in the wild and we often see issues with excessive tooth/beak growth and veterinary intervention is regularly needed. Providing these animals with branches to gnaw on can help reduce the excessive growth and reduce the frequency of having to intervene.
Benefits of forage provision from behavioural and anatomical aspects
Other than meeting nutritional and digestive requirements, forage provision in general also has a massive impact on natural behaviours such as foraging behaviours, group dynamics, stimulation and strengthening of muscles and joints and even nest building in some animal species.
Numerous observational studies have proven that the provision of browse has reduced stereotypic behaviours particularly in elephants, giraffes and great apes as well as increasing foraging behaviours and time budgets for many species across taxonomic groups.