Read more content on nutriNews International November 2022
Read more content on nutriNews International November 2022
Stevia presents itself as an interesting natural additive for poultry feed. For many years, research related to bird nutrition has focused on different dietary components that improve productive efficiency and are not expensive, such as antibiotic growth promoters. These are compounds used for therapeutic purposes to increase the health and welfare of animals, or for prophylactic purposes. Aiming to increase growth range and achieve more efficient conversion rates.
However, due to the emergence of microorganisms resistant to antibiotics and the presence of residues in poultry meat or eggs, their use in animals of productive interest has been restricted.
This has opened the door for additives known as natural growth promoter (NGPs) which generate better productive yields in animals through various mechanisms. Most of which are closely linked to better intestinal health.
The aim of this review is to broaden the knowledge about the use of natural growth promoters in poultry production. With a special focus on Stevia, as a possible alternative of natural origin to antibiotic growth promoters. [register]
Productive efficiency and gut health
For approximately 20 years, numerous investigations have focused on the intestinal health of production animals. Due to the fact that it has been shown to have an intimate relationships witht their poductive efficiency.
Intestinal health not only involves the digestive system but also the immune system associated with the intestine and the intestinal microbiota. All of these, interact through different mechanisms, tending to achieve intestinal homeostasis.
Different investigations agree that the interaction of these three elements (digestive system, immune system associated with the intestine and intestinal microbiota) are crucial in the first weeks of life of commercial birds. When the growth and development of the digestive system, and especially the intestine occurs.
Together with this event, in the first weeks of the bird’s life the microbiota colonizes the different portions of the intestine and establishes this interaction with the digestive system and with the immune system associated with the intestine (Bar Shira et al., 2005; Friedman et al., 2005; Peralta et al., 2016).
Immune maturation is the last event that occurs in the first weeks of life. The microbiota and the different components of the bird’s diet are amongst its most most important stimuli.
Therefore, research related to the different dietary additives of natural origin, which improve intestinal health are essential.
These include:
Probiotics
Prebiotics
Organic acids
Enzymes
Phytogenics
Phytogenics
They are natural bioactive components, derived from herbs, spices or plant extracts (essential oils) that:
Stimulate food intake.
They have antioxidant, antimicrobial, coccidiostat, anthelmintic and immunostimulant properties, which translates into an improvement in productive efficiency in birds (Grashorn, 2011; Gadde et al., 2017).
The main component of phytogenics are polyphenols; their composition and concentration vary according to the phytogenic that is used:
Among the phytogenics commonly used in avian nutrition there is a wide variety of herbs and spices, such as:
Whole seeds or extracts of black cumin(Nigella sativa)
Oregano (Origanum vulgare)
Rosemary (Rosmarinus officinalis)
Salvia (Salvia officinalis)
Thyme (Thymus vulgaris)
Research in poultry farming has also been conducted using:
All have improved the productive efficiency and health of the studied animals. (Grashorn, 2010; Huyghebaert et al., 2011; Hong et al., 2012; Allen et al., 2013; Smet, 2016).
Stevia
Stevia (Stevia rebaudiana Bertoni), is a perennial plant, native to Paraguay and Brazil, known worldwide for its sweetening properties.
Both dried Stevia leaves and their bioactive compounds mainly from the leaf, stems and flowers, have been shown to possess other very interesting positive effects, such as antioxidants, antimicrobial activity, and increased immunity.(Wood et al. , 1996; Ghosh et al. , 2008; Jayaraman et al., 2008; Christaki et al., 2013; Shivanna et al. , 2013; Shukla & Mehta, 2015).
The antibacterial effect of Stevia (either against Gram+ or Gram-) was confirmed through numerous tests using compounds obtained from Stevia leaves (Wood et al., 1996; Geuns, 2003; Ghosh et al., 2008).
These results are very important for poultry production, especially for the colonization of the microbiota in the first weeks of life, avoiding the colonization of pathogenic enterobacteria such as E. coli, S. typhimurium and others. These pathogens produce diseases with high mortality and morbidity rates in adult birds. Resulting in great economic losses. Some of these bacteria are zoonotic agents(Peralta et al., 2017)..
In a study with broiler chickens and layers, steviosides were administered (0.6-1.1% via intubation) and no residues were recorded in meat or eggs.(Geuns, 2003).
These investigations helped to conclude that Stevia or its extracts can be used without genetically affecting tissues or the deposit of toxic residues in avian products. Due to the fact that it is quickly metabolized by the animal.
In other studies conducted in pigs, Stevia and its bioactive compounds were shown to have antimicrobial properties which could influence the intestinal microbiota possibly altering the activity of some digestive enzymes and their production of short-chain fatty acids.
It could also be inferred that steviosides do not influence the uptake of other essential nutrients such as amino acids, vitamins, minerals, etc. (Geuns et al., 2003). In addition to the previously mentioned properties, the Stevia plant has other advantages:
It is easy to grow
Does not require a large space to produce a great number of leaves.
The extraction of its compounds does not require great equipment nor is it very expensive (Grosso et al., 2012).
Use of Stevia in broiler chickens
A study was conducted with 15-day-old broiler chickens. It was observed that the administration of 0.13% ground Stevia leaves or 0.13% pure steviosides, for 4 weeks, improved the productive performance of the birds during the first weeks.
However, and in contrast to what was expected, at the end of the trial no changes were detected in the productive efficiency of the broiler chickens. On the contrary, a significant increase in abdominal fat was generated (Atteh et al. , 2008; Atteh et al., 2011).
In another study conducted with broiler chickens, the addition of Stevia (0-0.085%) during the finishing stage did not modify the feed conversion of the evaluated birds.(Wood et al., 1996).
The explanation possibly lies in the analytical composition of the leaves, the part of the plant that is most commonly used. The leaves (considering their dry weight) contain:
The oils extracted from Stevia leaves contain monounsaturated fatty acids, such as oleic acid (43 g/Kg-1) and polyunsaturated acids such as linoleic (90-120 g/Kg-1) and linolenic acid (200-250 g/Kg-1).
In addition, Stevia leaves contain functional saccharides such as fructooligosaccharides like inulin and dietary fibers which have been associated with prebiotic, antioxidant, anti-inflammatory and antimicrobial properties.(Christaki et al. , 2013).
The antioxidant properties of this phytogenic are due to the presence of phenols, flavonoids and other compounds such as vitamin C and Zn.
Stevia leaves also contain anti-nutritional agents such as oxalic acid (23 g/kg-1) and tannins (0.1 mg/kg-1) (Christaki et al. , 2013), which are undesirable components in bird diets. However they are found in a very low percentage and can be used in the diets of these animals for a short time.
Conclusions
Studies of natural growth promoter (NGPs) that improve intestinal health in the first days of life of birds are fundamental. Since good intestinal health can then manifest itself in the adult bird with an improvement in productive efficiency.
Possibly, the bioactive compounds obtained from Stevia increase intestinal absorption, influence the colonization of the intestinal microbiota and maintain the homeostasis of the intestinal mucosa.
Likewise, as it does not leave residues in meat or eggs and it is a natural product, stevia does not pollute the environment. Which meets the requirements of both current legislation and those of consumers who prefer products that are antibiotic free.
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