Importance of Fibres in Managing Rabbits’ Digestive Issues
More than half of the sanitary issues encountered on rabbit farms are related to digestion. With this in mind, farmers should be able to access and use all the existing technical tools and data available to improve the overall sanitary condition of their rabbit farm. The feed strategy is of the utmost importance in this regard, especially the fibre constituents of rabbit feeds. How can a better understanding of the role of fibres allow one to deal with rabbits’ digestive issues?
In average, fibres account for over 35% of a rabbit’s diet. They include lignin, crude fiber, hemicellulose and pectin. Their presence in plant cell walls varies depending on the raw materials used. Fibres do not all have the same nutritional characteristics when applied to rabbits, especially with regards to their digestible properties.
There are two main types of fibres, as follows:
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indigestible fibres (which include crude fiber and lignin);
digestible fibres (which include hemicellulose and pectin).
Benefits of fibres on the young rabbit
For young rabbits, fibres have a strong impact on the intestinal transit. In the digestive tract, bacteria use fibres as a substrate, especially at the cecum level (the cecum is the largest reservoir of the digestive tract; it is situated at the junction of the small intestine and colon). Fibres are the key to successful weaning. At weaning, the young rabbit has its diet switched from a single meal consisting of milk, to several solid meals a day. At this point it needs a sufficient amount of fibres for the development of fibrolytic bacteria, i.e bacteria that degrade fibres. By doing so, fibrolytic bacteria end up forming a balanced bacterial population.
Striking a balance between digestible fibres and indigestible fibres
Vegetable fibres play a crucial role for preventing digestive disorders in rabbits. Not only do they affect the way the feed transits through the digestive systems but, through their nature and amount, they also have a major impact on the animal’s health condition.
Indigestible fibres (crude fiber and lignin) are almost not digested by rabbits. By reducing the retention time of feed in the gastrointestinal tract, indigestible fibres impact their transit time, especially at the cecum level. From a sanitary point of view, indigestible fibres have a positive effect on mortality and morbidity, especially when these are associated to diarrheal symptoms.
As stated by their name, digestible fibres (hemicellulose and pectin) are well digested by rabbits. Thanks to fibrolytic bacteria (which can degrade fibres) they are beneficial to the cecum’s microbial activity. Through the process of fibre degradation, these bacteria end up releasing volatile fatty acids (VFA). VFA make up a substantial source of energy for rabbits. The higher the amount of digestible fibres ingested, the more VFA concentration increases in the cecum thereby causing a drop in pH. VFA thus create an unfavorable environment for the development of pathogenic bacteria.
Digestible fibers therefore act as a secure source of energy for rabbits. An experiment has demonstrated their benefits on death rates due to paresis (drop or arrest of the intestinal tract).
How can we obtain a diversified and balanced mix of fibres?
Fibres are a way to secure rabbits’ digestive health. Yet it is not easy to satisfy all the requirements rabbits have for fibres. By comparing two feeds containing an equal amount of fibres, studies have shown that the inclusion of various sources of fibres has more benefits than using a single fibrous source of raw material for reducing mortality.
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Rabbits’ requirements do not always match the infrastructures of feed mills
Rabbits’ high requirements for fibres, especially indigestible ones, require using specific raw materials: grape pulp, grape seed meal, beet pulp, alfalfa, etc. This means that feed mills must have entire storage silos dedicated to raw materials that may not be useful to other species. The resulting feeds may end up containing an inadequate level of fibres or fibres that are not sufficiently diversified. Such limits can hinder the efficiency of these feeds. However some specific solutions, such as mixes of fibres, are designed to conciliate rabbits’ specific needs and feed millers’ constraints.