Probiotics are viable microorganisms with beneficial health effects for humans and animals. They are formulated into many functional foods and animal feed. There is a growing research interest in the application and benefits of probiotics in ruminant production. Several recent studies have evaluated the potential of probiotics in animal nutrition and health. In this chapter, we have reviewed current research on the benefits of probiotics on gut microbial communities in ruminants and their impact on ruminant production, health and overall wellbeing.
- ruminant health
- gut microbiota
- immune response
The gastrointestinal tract of domestic ruminant animals mainly cattle, sheep and goat are inhabited by diverse and complex microbial communities including bacteria, protozoa, fungi, archaea and viruses. In the last three decades, there have been numerous research studies to characterize the gut and rumen microbiota population and understand their importance on ruminant nutrition and health. In dairy cows, the rumen, which is the main fermentation chamber contains different microbial communities; about 100 billion bacteria, protozoa, methanogens and other anaerobic fungi [1, 2]. The major microbial groups in the rumen include
Probiotics are defined as “live microorganisms which, when administered in adequate amounts, confer a health benefit on the host” . Probiotics are widely recognized as non-pathogenic microbes with health benefits . The beneficial health effects of probiotics are related to their immunomodulatory activity in the gut by stimulating the secretion of immune modulators such as cytokines and IgA in intestinal mucosa . In ruminants, probiotics are administered to target the rumen (main site of feed digestion) where they have an effect on rumen fermentation especially on feed digestibility and degradability and rumen microbiota . Probiotic positively affect celluloysis and synthesis of microbial protein during digestion , and stabilizes rumen pH and lactate levels. In addition, probiotics are able to enhance nutrient absorption . Direct-fed probiotic have been shown to reduce ruminal acidosis .
Lactic-acid bacteria strains such as
Probiotics are typically used to improve gastrointestinal health, reduce diarrhea, bloating and protect against infectious diseases . Several researchers have reported the benefits of oral administration of probiotics to ruminants. Probiotics regulate and balance gut microbes, promote growth and development of animals, and improve the host resistance to diseases . Recent studies suggest that utilization of probiotics as feed supplement for ruminants improves growth performance, production, and enhance health and overall wellbeing of the animals. Applications of probiotics have been shown to reduce the negative environmental impact such as methane emission associated with ruminant production. In this chapter, we have reviewed current research on the benefits of probiotics on gut microbial communities in ruminants and their impact on ruminant production, health and overall wellbeing.
1.1. Selection of probiotic strain
It is important to select the suitable strain of a microorganism for use as probiotic. The suitable potential probiotic strain is considered as an inhabitant of the host organism and has the ability to adhere and colonize the epithelial cells of the gut. Also, the potential probiotic microbe should be able to grow and survive in the host . Microbial strains used as probiotics are required not to affect the indigenous gut microbiota population of the host. Other important requirement for the potential probiotic strain is to be able to adapt to the environment of the gut and locate a suitable niche in the rumen (such as epithelium, fluid or feed), and exerts positive effects on the host . Other Safety criteria and characteristic of probiotics to consider include, non-pathogenic, resistance to gastric juice and bile, anatgonize pathogenic bacteria, genetically stable, and exhibit stable qualities during processing, storage and delivery, viable at high populations . In the USA, there are regulatory considerations by the Food and Drug Authority for safety evaluation of microorganisms used as probiotic. The specific microorganism should have “Generally Regarded As Safe” (GRAS) status .
1.2. Different types of probiotic microorganisms
There are different microbial species used as probiotics in ruminants which include bacteria, yeast, etc. Table 1 presents a list of microorganism targets commonly used as probiotics in ruminants feeds and this includes bacteria species belonging to the genera
Prebiotic are defined as “non-digestible food ingredients that beneficially affect the host by selectively stimulating the growth/or activity of one or a limited number of bacteria in the colon” . Prebiotics are commonly dietary fiber and have effect on both the upper and lower GI tract. In the upper GI tract, prebiotics are able to withstand digestion, delay gastric removal, decrease glucose absorption and stimulate the release of intestinal hormonal peptides. The main prebiotics used in animal diet are carbohydrates and oligosaccharide. Non-digestible oligosaccharides used include oligofructose, inulin, lactulose, galactooligosaccharide, transgalactooligosaccharide [16, 32].
Synbiotics on the other hand are products that contain a mixture of probiotic and prebiotics. The host benefit from the synergistic effect of probiotic and prebiotic. Results from studies done have demonstrated the promising effect of synbiotics in reducing the numbers of food borne pathogens .
1.3. Administration of probiotics
There are different route of administration of probiotics. These sites include the oral cavity, intestines, vagina and the skin . In ruminants, probiotics are usually administered orally [35, 36, 37, 38, 39, 40, 41, 42, 43]. A study by Deng et al. [44, 45] utilized intravaginal infusion as mode of administering probiotics (containing a lactic acid bacteria mixture) to periparturient cows.
2. Probiotics and ruminant growth and production performance
2.1. Effect of probiotic on growth performance
Utilization of probiotics (either dry or live) as natural feed additives have been shown to favorably improve animal performance and welfare, via modulation of gut microbial community which is essential in ensuring host homeostasis . Probiotic have positive effect on growth rate and production performance of animals when administered as single or multi-strain feed supplement (Table 2). Oral administration of probiotic has been shown to improve feed intake, daily weight gain and overall weight gain in sheep, goats, and cattle [38, 39, 40, 41, 42, 43, 47, 49, 51, 52]. The population of beneficial microbes such as
|Probiotics type||Ruminant||Performance effect||References|
|Lactate-utilizing/or lactate-producing bacteria||Cattle||Improve feed efficiency, increase in daily gain (2.5%)|||
|Calf-specific probiotic (six ||Veal calves||Reduced diarrhea|
Decreased fecal coliform counts
|Live yeast||Beef cattle||Improve average daily gain, final weight, feed intake, feed to gain ratio|||
|Yeast||Dairy cows||Increased milk yield and quality|
Increase feed efficiency
Reduced ruminal acidosis
|Dairy cows||Improve quality and quantity of milk production|||
|FasTrack Microbial pack (||Dairy cows||Improve body weight||[42, 43]|
|Lactating cows||Increased milk production|||
|Sheep||Reduced lamb mortality rate|
Increased average daily milk yield per ewe
Improved fat and protein content of milk
|Probiotic mixture (||Goat||No effect on body weight, PCV, White blood cells differential count|||
|Mushroom-based probiotic (Coriolus versicolor)||Goats||No effect on body weight, PCV, White blood cells differential count|||
|Commercial probiotic||Meat Goats||Improved average daily gain|||
|Multi-strain Probiotic (||Goats||Improved Packed cell volume and FAMACHA scores|||
In small ruminants such as goats and sheep, treatment with commercial probiotic improved average daily gain . Gyenai et al. , Ekwemalor et al.  and Ekwemalor et al. , reported contrary results where there was no effect of probiotics on body weight. These different observations reported may be due to difference in the probiotic composition used, amount use, specific activity of the probiotic strains and variation in the breeds of goats used in their individual studies. This because studies have shown that different probiotic strains may have different effects depending on their capabilities and enzymatic activities different host species . In the study by Gyenai et al.  Spanish Boer kid-goats were drenched with a probiotic mixture consisting of
2.2. Effects of probiotics in milk
Use of probiotics as feed supplements for ruminants have beneficial influence on milk production, milk quality and functional components such as protein and fat content [24, 54]. Studies have shown that probiotic dairy products are safe for large-scale consumption . A study conducted by Yu et al.  showed that dairy cows treated with probiotic species
3. Molecular mechanism of action of probiotics
The mode of action of probiotics in the host organism include: regulation of intestinal microbial homeostasis, stabilization of the gastrointestinal barrier function, expression of bacteriocins enzymatic activity inducing absorption and nutrition, immunomodulatory effects, inhibition of procarcinogenic enzymes and interference with the ability of pathogens to colonize and infect the mucosa . In ruminants, the mechanism of probiotics metabolism is dependent on the strain of microorganism used. Probiotic bacteria can serve to decrease the severity of infection via a number of mechanisms including competition for receptors and nutrients, and/or the synthesis of organic acids and bacteriocins that create an environment unfavorable for pathogen development [49, 63, 64, 65, 66].
4. Probiotics and immunity
The beneficial health effect of probiotics have been partly attributed to the ability of probiotic bacteria to modulate the immune system, increasing both innate and adaptive immune response [67, 68]. Research evidence obtained from various in vivo and in vitro studies have demonstrated that probiotic promote gut health via stimulation of the innate immune response . Different probiotic bacteria including Lactobacillus casei,
The molecular impact of oral probiotic supplementation on systemic expression of genes associated with innate immune response in blood have been reported for ruminant species; cows [38, 42, 43], and goats  as shown in Table 3. Probiotics have been reported to activate pathways immunity and homeostasis including Toll-like receptor pathway, Wnt signaling pathway, innate and adaptive immune response pathway [38, 41, 42, 43]. A study by Ekwemalor et al.  showed that oral probiotic administration may exhibit systemic effect in goat blood, by modulating the expression of genes associated with immunity and homeostasis. In goats, probiotic treatments induced the expression of 32 innate immunity genes and 48 genes in the Wnt signaling pathway. Furthermore, treatment of goats with a mushroom based probiotic in an vivo study trial resulted in serum increase in pro-inflammatory cytokines such as interferon production regulator (IFNr), Rantes and Granulocyte-Colony Stimulating Factor (GCSF). But the level of granulocyte macrophage colony stimulating factor (GM-CSF) reduced .
|Innate immune response parameters||Genes||Ruminant type||References|
|[37, 42, 43]|
In dairy cows, oral probiotic supplementation had systemic effect on differential global gene expression. Probiotic treatment targeted 87 bovine pathways including Wnt signaling pathway, inflammatory response pathway, toll-like receptor signaling pathway, prostaglandin synthesis and regulation pathway and B cell receptor signaling pathway. Probiotic treatment modulated the expression of genes associated with innate immunity and homeostasis such as receptors TLR2, TLR6, TLR7, TLR8; cytokines, IL16, IL6, IL10RA; Wnt signaling genes Wnt8A, Wnt5A, Wnt10B, Kremens; and transcription regulators MAP4K3 and MAP3K8 [38, 42, 43].
5. Application of probiotic in ruminant
5.1. Probiotics and cattle
Probiotic have been widely used in cattle production for both dairy and beef cows at all developmental stages and growth. Studies have shown the beneficial effect of direct-fed microbials or probiotic bacteria including
Studies by Krehbiel et al.  have shown that probiotics are effective decreasing fecal shedding of Escherichia coli O157:H7 in infected calves. Research findings reported by Sherman et al. , demonstrated that treatment of intestinal cells with lactic acid producing bacteria reduced epithelial injury due to
5.2. Probiotics and goats
Utilizing probiotics as functional food supplement have been encouraged in goat production . Various commercial probiotic products consisting of either single strains or mixture of strains such as
There is an increasing market demand for nonfat goat milk and milk products such as yoghurt containing probiotics. A nonfat yoghurt has been developed from goat milk and is enriched with probiotic strains
5.3. Probiotics for sheep
In sheep production, probiotics have been applied to improve feed digestion and gut health. Two probiotics,
A study conducted in sheep showed that probiotic microorganisms are been used to improve food safety for consumers. Delcenserie et al. , found in their study that the presence of
Conflict of interest
The authors declare no conflict of interest.