Fairly or not, the fact is that the concern of European authorities for the risk that, in their view, certain antibiotics used in animal husbandry and human medicine pose to human health is increasing unstoppably. Thus, in recent weeks, the European Food Safety Agency and the European Centre for Disease Prevention and Disease Control have released their latest report on antimicrobial resistance in Europe, warning of increased resistance to widely used antibiotics. Of special interest to the pig sector is the allusion, in that report, to an increase in the resistance of very important zoonotic bacteria, such as Salmonella spp. or Escherichia coli, to treatment with colistin, a last resort antibiotic used in human medicine against multidrug-resistant bacteria. In this regard, it is worth noting that cases of resistance to colistin have recently been detected in China, Denmark and Germany. The European Medicines Agency, in response to a request from the European Commission, is undertaking a review of its recommendation on the use of colistin in veterinary medicine, expected to be completed during the first half of the year.
It is in this context that the use of phytogenetic products —based on parts or active ingredients of medicinal plants or certain fruits— in feeds for pigs is being promoted as a possible prophylactic and metaphylactic alternative against intestinal and diarrhoeal diseases. These botanicals are also being positioned as growth promoters in animal nutrition. However, it is important to note that knowledge of such products, as regards their mode of action and their application in intensive animal husbandry systems, it is still being built. In addition, animal husbandry and therapeutic effectiveness of phytogenetic products may vary widely depending on the botanical origin and chemical composition of the plants included, as well as the various production processes they've been subjected to.
Currently, the use of phytogenetic products in animal husbandry is contemplated within the European legislative framework for animal feed. Thus, some compounds are recognized as sensory additives (Reg. 1831/2003) whilst others can be used as raw materials in feeds (Reg. 68/2013 and Reg. 767/2009).
According to Hasehemi and Davoodi (2011), phytogenic products exert their positive effects on animal productive performance and health mainly due to the following actions: antimicrobial and stabilizing of the intestinal microbiota, antioxidant, anti-stress, nutrigenomic and immunomodulatory; their antimicrobial and immunomodulatory properties being particularly relevant when these products are added to post-weaning piglet diets. Table 1 shows the number of biologically active compounds identified in various medicinal plants.
Table 1. Number of biologically active compounds identified in various plants and spices (Hasehemi and Davoodi, 2011)
|Name of plant or spice||Number of biologically active compounds identified|
Regarding antimicrobial activity in vivo, it is worth mentioning the work of Xia et al. (2014), who studied the therapeutic efficacy of an oral administration of three doses (7, 10 and 15ml / animal / day) of a liquid phytogenic product containing berberine, magnolol and honokiol (970μg / ml, 130μg / ml and 300μg / ml, respectively) to piglets with colibacilosis diarrhea. They also compared these doses of phytogenic product with the following treatments: 4% ofloxacin (intramuscular, 0.1ml / kg / day), 10% norfloxacin (oral, 1ml / day) 4% ofloxacin + 10% norfloxacin. As shown in Table 2, the three groups of pigs treated with various doses of the phytogenic agent had a higher percentage of animals cured after treatment than the groups that received one of the two antibiotics alone for the same duration of treatment. However, as indicated by Windisch and col. (2008), from the University of Vienna, further research is needed on effective antimicrobial doses of numerous phytogenic compounds available for swine nutrition and health. According to these authors, the minimum inhibitory concentrations (MIC) of plants, fruits, spices, and pure active substances extracts, often far exceed the doses usually added to the feed.
Table 2. Effect of different oral doses of a phytogenic product on piglets affected by colibacillosis (Xia et al., 2014)
|Phytogenic product 7 ml / day||75%|
|Phytogenic product 10 ml / day||88,9%|
|Phytogenic product 15 ml / day||83,3%|
|Ofloxacin (4%) + Norfloxacin (10%)||81%|
By contrast, the immunomodulatory effect —particularly anti-inflammatory— of phytogenic products added to the diet does seem to play a crucial role in addressing intestinal clinical pictures in pigs. Liu et al (2014), in their research on the addition of phytogenic products in diets for weaned piglets, concluded that such addition regulated the expression of up to 490 genes associated with the immune response at the level of the ileal mucosa. The anti-inflammatory effect of phytogenic compounds has also been studied by Gräber et al. (2014) in Halle (Germany), who proved that piglets with Escherichia coli (LPS) antigen-induced inflammation, fed diets supplemented with the plant Agrimonia procera (0.87 g / kg) showed a lower expression of certain proinflammatory cytokines, such as tumor necrosis factor alpha (TNFα) and IL-1β. This anti-inflammatory effect of phytogenic products on gene expression in the gut of piglets was recently corroborated by Grilli et al. (2015), by feeding weaned piglets diets with a mixture of thyme, vanilla and organic acids (5 g / kg) (Figure 1).
Figure 1. Effect of the addition of a mixture of thyme, vanilla and organic acids on gene expression
in various pro-inflammatory cytokines in the gut of piglets (Grilli et al., 2015)
Although this paper presents only a few examples of the positive effects supplementation with phytogenic products has on piglets, many studies are being carried out in pigs with this type of product. Given the growing need for alternatives to certain antibiotics routinely added to the feed, it is imperative that researchers, suppliers, pork producers, nutritionists and veterinarians combine efforts to advance clinical knowledge of the use of such botanical origin products in swine nutrition and health.