Medicinal plants – prophylactic and therapeutic options for gastrointestinal and respiratory diseases in calves and piglets? A systematic review

Ayrle, Hannah; Mevissen, Meike; Kaske, Martin; Nathues, Heiko; Gruetzner, Niels; Melzig, Matthias; Walkenhorst, Michael

Traditionally, plant species with a high content of tanning agents are administered in diarrhea. Allium sativum L. does not contain tanning agents, but due to its antibacterial, antidiarrheal, anti-inflammatory and immunomodulatory effects, it may be used for prophylactic and acute treatment in diarrhea of calves and piglets. Eight in vivo and clinical studies were identified for Allium sativum L. proving these effects, and no studies disproving them. A trial conducted with neonatal calves showed that allicin, a main active compound of Allium sativum L., delayed the onset of diarrhea due to Cryptosporidium parvum [61] . Two clinical studies demonstrated antidiarrheal effects and a reduction of the fecal coliform count by Allium sativum L.. There is also evidence for an improvement of performance in pre-ruminant calves [62, 63] . The immunomodulatory activity of Allium sativum L. in pigs [64, 65] and poultry [66, 67] may hold true in immunocompromised calves to support their immune defense. Its antibacterial effects on Escherichia coli and Salmonella ssp. in vitro suggest a high probability of antibacterial activity in vivo [68-75]. Nevertheless, more clinical studies are necessary to investigate antiinfective effects of Allium sativum L. in young farm animals. Allium sativum L. has been reported to exhibit antiinflammatory activity in rats [76] . There is also mechanistic evidence for anti-inflammatory properties as well as immunostimulation showed in three in vitro studies, namely an inhibition of leucocyte migration [77] , modulation of interleukin and interferon-gamma expression [78] and a suppression of nitrogen oxide production in macrophages [79] . An anti-inflammatory effect may be useful for the treatment of systemic inflammation processes often accompanied with diarrhea. Facing animal welfare and regarding efficient synthetic non-steroidal and steroidal anti-inflammatory agents, it is debatable whether there is a need for plant-derived alternatives. While synthetic non-steroidal and steroidal anti-inflammatory agents often produce considerable adverse effects including an inhibition of mucus production [80, 81] , medicinal plants compass considerable adverse-effects because they contain several different active compounds which might reduce the potential of unwanted effects [82] . In in vivo tests for acute and chronic toxicity, the maximum tolerance dose and genotoxicity Allium sativum L. was demonstrated to be relatively safe if administered in therapeutic dosages [83] and if estimated for the animals metabolic body weight [84] . With respect to food quality, it must be assured that residues of Allium sativum L., responsible for the typical taste of this plant do not result in an altered taste of meat.