Use of probiotics in animal nutrition: A natural way to consume foods from healthy animals

By Guillermo Jiménez, Technical Manager

Probiotics are preparations based on live microorganisms that are consumed as food additives by humans or animals having beneficial effects on their health status.

“The probiotics help prevent unbalances and enhance the growth of the healthy dominant microflora”

The intake of food with microbiological activity is as early as the start of human civilization, fermented milks likely being the first foods containing active microorganisms. However, the scientific base of the beneficial effects derived by the consumption of fermented lactic products was not raised until the beginning of the 20th Century, when the Nobel awarded E. Metchnikoff (1907) stated that the good health and longevity of certain ethnical groups (for example Bulgarians) was due in part to the composition of their intestinal flora. E. Metchnikoff suggested that the continuous intake of yoghourt – rich in fermenter bacilli – by such populations decreased the number of bacteria with toxic activity in the colon. Later on, different studies (Bonhoff et al., 1954; Freter, 1955, 1956; Collins and Carter, 1978) demonstrated the relevant role of the intestinal microflora in the mechanisms of local and systemic defence in front of certain pathogens.

The marketing of probiotics as additives in animal nutrition started in the 1970s. The value of these new products consisting of live microorganisms was based on the hypothesis that the intake of high levels of certain specific bacteria, with no negative effects on host, could somehow reduce the capacity for the pathogenic bacteria to colonize up to undesirable levels in the digestive tract of the host (Ziggers, 2002).

As from the end of the 1970s and in the 1980s, there was a remarkable advance in the scientific and technical knowledge regarding the use of probiotics in animal nutrition, and production started at industrial scale. The studies with probiotics were designed to evaluate their effects on the digestive process, intestinal microflora, and on the growth of the food producing animals (Tournut et al., 1976; Pollman et al., 1980; Massot et al. 1982; Wolter and Henry, 1987; Ducluzeau and Raibaud, 1989; Gedek, 1989; Holister et al.; 1989). Fuller (1989) defined probiotics as “a live microbial feed supplement which beneficially affects the host animal by improving its intestinal microbial balance”. The interest of these products shown by the livestock producers and the professionals in animal health was extended to the foodstuffs producers and suppliers of feed ingredients and feed additives. The efficacy of probiotics in the animal nutrition started to be recognised by the experts, although still with a many reservations.

In the 90s, knowledge of probiotics was increased with a number of scientific, technical and economic data supporting the efficacy of probiotics in the animal nutrition (Blomberg et al., 1993; Kovacs-Zomborsky et al., 1994; Majamaa et al., 1995; Kamra et al., 1996; Mulder et al., 1997; Salmien et al., 1998; Kyriakis et al., 1999; Cebra, 1999; Ferdoka-Cray et al., 1999). For first time probiotics were considered as the alternative to the antibiotics used for many years as growth promoters in the animal nutrition.

Nowadays, the prohibition in the European Union to use antibiotics as growth promoters in the animal nutrition – as from the 1st of January, 2006 – and the strong demand by the consumers concerning the quality and safety of the foods of animal origin, have consolidated the use of probiotics in the animal nutrition as a natural way to raise healthy animals and thus to produce foods of reliable quality and safety.

Regulation (EC) No 1831/2003 of the European Parliament and Council of 22 September 2003 on additives for use in animal nutrition provides for the authorisation of probiotics, and for the grounds and procedures for granting such authorisation and placing onto the market. In order to obtain the corresponding authorisation to be used as additives in the animal nutrition, the probiotics must show evidence of not having any adverse effects on animal health, human health or the environment. Furthermore, parameters such as quality of the animal produces, natural origin, traceability, animal welfare and/or respect towards the environment are highly considered in any additive by the operators involved in the animal nutrition as the first link in the food chain.

At present in the European Union there are different types of probiotics authorised to be used in the animal nutrition based on microorganisms of the species Bacillus, Lactobacillus, Enterococcus, Kluyveromyces, Pediococcus and Saccharomyces. According to Regulation (EC) No 1831/2003, the probiotics are classified within the category “zootechnical additives” and within the functional group “gut flora stabilisers”, which when fed to animals has a positive effect on the gut flora. However, the mode of action of each probiotic is different.

Under normal conditions and good health, the intestinal tract of the monogastric animals contains between 10⁹ and 10¹¹ bacteria per gram of intestinal contents. The intestinal microflora consists of a dominant population (>90%) of bifidobacteria and lactobacilli, a subdominant population (approx. 1%) of coliforms and enterococcus and a residual flora (<0.01%) of clostridia, staphylococci, pseudomonas, yeasts and fungi (Tournut, 1997). In the case of ruminants, the reticulum is the most important part of the digestive tract where 80% of digestion and absorption of nutrients takes place. Under normal conditions there are over 10¹⁰ bacteria per gram of ruminal contents, which plays an important role in each ruminal fermentation (Russell and Rychlik, 2001).

However, in order to evaluate the effect of probiotics to maintain a good balance of the intestinal microflora, it has to be considered as one of the components of the “digestive ecosystem”; microflora, epithelium of the gastrointestinal tract, immune-lymphoid tissue associated to the epithelium and the neuron-endocrine system. The correct functioning of the digestive tract depends mainly on the numerous interactions between these four components. The role of each component is different along the digestive tract, but in all the segments these components will be responsible for keeping the balance in the absorption of nutrients and act as a barrier to possible intruders (Goddeeris et al., 2002). In this sense, the role of microflora is essential to keep the integrity of this barrier to pathogen agents or toxic substances. However, the “digestive ecosystem” is an open system and therefore it is exposed to invasion from new microorganisms that may disturb the balance of the resident microflora (dysbiosis). As a consequence this can create disruption to the digestive function and can even seriously compromise the health of the host. The probiotics help prevent unbalances and enhance the growth of the healthy dominant microflora.

The first probiotic to receive authorisation in the E.U. to be used as an additive in the animal nutrition and one of the most studied at scientific level is the microorganism Bacillus cereus var. toyoi (Bacillus toyoi, Toyocerin®). Bacillus toyoi is a strain originally isolated from soil in Japan and it is not genetically modified. It is a microorganism naturally ubiquitous in the soil, likely to be ingested by the wild animals that root in the soil, such as the wild pigs or poultry. Appart of its very long market history - not only in Europe but worldwide (for example Japan, South East countries, South America) - Bacillus toyoi has demonstrated in vitro and in vivo its capacity to inhibit the growth of pathogenic bacteria of human concern such as Salmonella and E. coli. Vila et al. (2009) observed a reduction in the prevalence of Salmonella in poultry that were fed with diets containing Bacillus toyoi.

Some E.U. countries have already developed and implemented Salmonella control programs in order to reduce at a minimum level the spread of Salmonella in food animals, food, and humans. In this sense, Bacillus toyoi has been incorporated into the diets of swine and has proven to reduce significantly the presence of Salmonella in pig carcasses at the slaughterhouse.

Therefore, Bacillus toyoi is an example that the use of probiotics in animal nutrition contribute to rearing healthy animals and to produce foods of quality, free from contaminant and undesirable bacteria.