By Jolan Lemmens

While humans have the luxury of words, cows can’t really tell us when they experience pain. Consequently, they rely on subtler cues to show their distress. Responding to a cow's pain can therefore be a challenging task. In this blog, I focus on the usage of Salix Alba, also known as white willow. The wood and fiber of willow-species are used for paper production, making furniture, biomass fuel and countless other applications. In this blog we will focus on a whole different side of the plant, its powers to combat pain.

Figure 1: White willow

Well, you can’t really ask them, can you?

Pain is a complex sensation that emerges from the interaction of physical, chemical, and neurological processes in the body and the brain. Pain begins when nociceptors (specialized sensory neurons) detect painful stimuli. These stimuli can be mechanical (like a cut), thermal (heat or cold) or chemical (substances released during tissue damage, such as prostaglandins or histamine). After detecting these stimuli, the nociceptors will send signals to the spinal cord and the brain to warn about a possible threat [1]. In this way, pain keeps us safe and is crucial to our survival. It is a warning system.

But what when you can’t tell anyone that you’re in pain, like cows? A number of methods have been described to evaluate pain objectively and subjectively in cattle. Measuring plasma cortisol levels will give an indication of the physiological stress responses while vocalization is an example of changing behavior patterns. In contrast, the subjective methods rely on the judgement of a human observer like the farmer or veterinarian [2]. Alternatively, the Cow Pain Scale is an attempt to objectify this judgement by using a scale that identifies seven behaviors. The attention towards the surroundings, head position, ear position, facial expression, response to approach, back position and lameness will all be given a score of zero to five, depending on the behavior. If the score is higher than five, the cow is most likely in pain [3].

Figure 2: the Cow Pain Scale [3]

Ease the pain, naturally.

For centuries, natural products have been used as medicinal remedies to address both human and animal illnesses. In earlier blogs we already described how garlic extracts keep the udder healthy, and which essential oils influence coccidia. In this essay we focus on the effect of white willow on pain. White willow was already used 6 000 years ago in Mesopotamia and Hippocrates himself recommended chewing bark to alleviate fever, inflammation, and pain, and using willow leaves for childbirth pain [4]. Fast forward to 2024, and the pursuit of sustainable and natural alternatives has become paramount again, both for the benefit of animal and human health.

What is Salix alba?

White willow (or Salix alba) is a plant with silvery, oblong leaves mostly growing in the Northern hemisphere that belongs to the family of the Salicaceae (which includes around 1 220 species). Willows are a remarkably diverse group of plants ranging from small bushes to gigantic trees. This diversity provides a chemical plethora of 322 secondary metabolites (which are identified up until August 2024), such as flavonoids (95) and organic acids (28) [5]. It is needless to say that this chemical composition offers big pharmacological opportunities (but I said it anyway).

The active compound we are looking for in white willow is salicin (not to be confused with the allicin in garlic). Salicin is known for its anti-inflammatory and pain-relieving properties. So, where does this pain-relieving effect come from? Well, salicin is chemically similar to aspirin and serves as a precursor to the synthesis of acetylsalicylic acid, which is the active ingredient in aspirin [5]. And we all know that aspirin is a popular drug (NSAID) used to reduce pain, fever, and inflammation. Remarkable is that more than 80% of salicin in willow extract is absorbed after ingestion. Once absorbed, the intestinal flora will metabolize the salicin into salicyl alcohol, which in its turn will be absorbed and metabolized by the liver to the beloved and much needed salicylic acid [6].

Figure 3: Salicin

But salicin is only one side of the explanation of the great effects of Salix alba. In addition, flavonoids (e.g., amelopsin) play their part as antioxidants [7]. Different species contain different flavonoids such as flavones, flavanols, chalcones, and flavan-3-ols, and the number of different flavonoids also differs in leaves, bark, stem, twigs, and roots. If you are really passioned about flavonoids (and who isn’t?), feel free to dive into the 95 flavonoids described on seven pages in the review by Nora Tawfeek and her colleagues [8]. A study by Sulaiman and colleagues (2013) showed the antioxidant effect of white willow extract as their study indicated a good free radical scavenging activity of Salix alba extract. This activity is likely due to the polyphenols. They conclude that this antioxidant potential supports the antimicrobial effect of white willow [4].

Okay, but how does it work?

So, how does this salicylic acid (the metabolized form of salicin) and the flavonoids help in reducing pain and inflammation? Let us go back to how pain works. Earlier I mentioned that the activation of nociceptors starts the process by which pain is experienced. The sensitivity of these nociceptors (specialized sensory neurons) is increased by so-called prostaglandins. In this way, it are the prostaglandins that cause pain, inflammation, and swelling. These prostaglandins are produced by the enzyme called cyclooxygenase-2 (COX-2). Salicylic acid will stop this process from happening, and as such, will reduce the inflammation and will stop you (or the cow in this case) from experiencing pain [8]. You can see a depiction of this process in figure 4.

Figure 4: How COX-2 inhibitors work

Secondly, white willow demonstrates strong anti-inflammatory effects. Not only the salicin derivates, but also catechin and flavonoids reduce the production of pro-inflammatory molecules TNF-α (tumor necrosis factor). TNF-α is released once macrophages detect an infection, activating the inflammatory response [6].

Finally, as mentioned above, white willow is a good antioxidant thanks to the free radical scavenging activity [4,8]. In the body oxidative stress is induced by an excess of so-called reactive oxygen species (ROS). These ROS are unstable molecules called free radicals that contain oxygen. Free radicals can damage cells by stealing their electrons in a process called oxidation (see figure 5). Antioxidants work by eliminating free radicals, by donating hydrogen, which makes the free radicals harmless.

Figure 5: free radical scavenging

Aspitop bolus

There is an enormous potential in the market for natural alternatives to replace antibiotics and medicines and white willow highlights the ongoing tradition of using plant-based remedies for healing.

To ease the pain and inflammation in cows, Resco developed the Aspitop bolus. This bolus doesn’t only contain white willow, but also propolis and citrus extracts. Just like white willow, propolis also has distinct antimicrobial, antioxidant, and anti-inflammatory properties which you can read in our blog “Propolis, the natural 'sting' operation against microbes!.” The citrus extracts contain an abundant source of natural antioxidants, with various effects: general protection of the immune system, anti-stress, and prevention of inflammatory and allergic reactions (histamines, prostaglandins, leukotrienes).

Figure 6: Resco’s Aspitop bolus

Aspitop is a fast-acting, natural painkiller that targets pain, fever, and inflammation. It can be used at calving, hoof trimming, in case of mastitis, metritis or other injures or moments when the cow doesn’t seem fit. Aspitop will lower the farm’s, need for medicines, will improve your animal’s welfare and will in the end increase your production and revenue.

Source list

[1] K, M. (1997). [What is nociceptor]. PubMed, 11(5), 353–366.

[2] Hudson, C., Whay, H., & Huxley, J. (2008). Recognition and management of pain in cattle. In Practice, 30(3), 126–134.

[3] Gleerup, K. B. (2017). Identifying Pain Behaviors in Dairy Cattle (29).

[4] Sulaiman, N. (2013). Phenolic content, antioxidant, antimicrobial and cytotoxic activities of ethanolic extract of Salix alba American Journal of Biochemistry & Biotechnology/American Journal of Biochemistry and Biotechnology, 9(1), 41–46.

[5] Andrei, M., Tefaniu, A., Ene, N., Pintilie, L., Radu, N., Tomescu, A. J., & Raiciu, A. D. (2024). Multiple natural approaches of Salix alba. Archives of Microbiology & Immunology, 8(3).

[6] Shara, M., & J. Stohs, S. (2015). Efficacy and safety of white willow bark (Salix alba) extracts. Phytotherapy Research, 29, 1112–1116.

[7] Agnolet, S., Wiese, S., Verpoorte, R., & Staerk, D. (2012). Comprehensive analysis of commercial willow bark extracts by new technology platform: Combined use of metabolomics, high-performance liquid chromatography–solid-phase extraction–nuclear magnetic resonance spectroscopy and high-resolution radical scavenging assay. Journal Of Chromatography A, 1262, 130–137.

[8] Tawfeek, N., F. Mahmoud, M., I Hamdan, D., Sobeh, M., Farrag, N., Wink, M., & M. El-Shazly, A. (2021). Phytochemistry, pharmacology and medicinal uses of plants of the genus Salix: an updated review. Frontiers in Pharmacology, 12.