Research proves livestock can self-medicate within diverse pasture systems

A contribution to the Frontiers in Sustainable Food Systems Journal examined the importance of a diverse range of plant and phytochemical compounds for animal nutrition, welfare and health (Distel et al. 2020). The article also explores the importance of considered pasture design so that graziers and their stock can reap the benefits of these systems.

In many traditional grazing systems, feeding is almost exclusively based on the primary metabolites (mostly carbohydrates and proteins) which are the kind of metabolites involved in normal growth and reproduction. This is likely due to the simplification of agricultural systems for inexpensive, rapid livestock production, coupled with the view that plant secondary metabolites (PSMs) are harmful to animal health in high doses. The research indicates that while some PSMs can be toxic, at the appropriate dose and under the right circumstances they can offer medicinal benefits.

Dr Fred Provenza (1995) found that when allowed to select among alternative forages of different types and concentrations of nutrients and PSMs, ruminant animals learn to select varied diets that meet their nutritional requirements while avoiding toxicity and nutritional disorder.

Ruminants have been found to even use combinations of plant species to counteract any ill effects of PSMs while gaining medicinal benefits. For example, when they eat foods high in tannins, sheep learn to ingest medicinal plants that contain polyethylene glycol (PEG), a substance that reduces the adverse effects of tannins. They also adjust their 'dose' of PEG to counteract the precise amount of tannins they consume (Villalba and Provenza 2007).

Studies have also found that PSMs such as alkaloids, terpenes, sesquiterpene lactones and phenolics can benefit livestock by controlling populations of parasites and pathogens and enhancing nutrition (Villalba and Provenza 2007).

Ruminants have been found to even use combinations of plant species to counteract any ill effects of PSMs while gaining medicinal benefits.

The paper describes natural landscapes with diverse mixes of plant species as 'nutrition centres' and 'pharmacies' with a vast array of primary and secondary compounds vital to animal nutrition. Evidence presented in this paper suggests herbivores can meet their needs for nutrients and 'write their own prescriptions'.

While these studies prove that plant diversity in pastures has the potential to enhance animal nutrition, health and welfare, they highlight the importance of considered pasture design. Simply mixing and planting as many forage species as possible will not have good outcomes for stock health or productivity (Distel et al. 2020).

Simply mixing and planting as many forage species as possible will not have good outcomes for stock health or productivity (Distel et al. 2020).

Species identity, abundance and spatial distribution are all important factors to consider. Additionally, environment, climate, soil type and landscape position mean that a one-size-fits-all approach will not be successful. There are some resources available for graziers wanting to incorporate or adjust their multi-species forage mixes, such as regional guides and local land care experts, but more are needed.

Distel et al. (2020) recommend that along with whatever resources are available in your region, this three-step approach should be used:

1. Identify plant species and numbers that satisfy the specific goals of the system. (For example, you may be trying to achieve maximum plant biomass, biodiversity or animal production.)
2. Examine whether these species and numbers will tolerate the environmental conditions in your region and consider how best to arrange the pasture, for example, in mixes or blocks.
3. Finally, develop a long-term plan for monitoring, managing and adapting the pasture.

Responsible management practices are key to the success of diverse pastures. Specifically, rotational grazing and the incorporation of 'rest' have been found to boost pasture and animal health (Distel et al. 2020).

With a considered approach to multi-species pasture planning it is possible to create multi-species mixes that enhance productivity and allow ruminants to efficiently use primary and secondary compounds for comprehensive nutrition and health.

References

Distel RA, Arroquy JI, Lagrange S and Villalba JJ (2020) 'Designing Diverse Agricultural Pastures for Improving Ruminant Production Systems', Frontiers in Sustainable Food Systems, 4, https://www.frontiersin.org/articles/10.3389/fsufs.2020.596869, accessed 15 May 2023.

Provenza FD (1995) 'Postingestive Feedback as an Elementary Determinant of Food Preference and Intake in Ruminants', Journal of Range Management, 48(1):2-17, doi:10.2307/4002498.

Villalba JJ and Provenza FD (2007) 'Self-medication and homeostatic behaviour in herbivores: learning about the benefits of nature's pharmacy', Animal, 1(9):1360-1370, doi:10.1017/S1751731107000134.