Benefits of Probiotics in Animal Health

Introduction

• In the modern animal nutrition, probiotics are included in the group of feed additives; for stabilizing the intestinal microflora. They are also known as bioregulators, intestinal microflora stabilizers or direct-fed microbials (DFMs). Probiotics can confer a health benefit for the host when administered in appropriate and regular quantities.
• Once ingested, the probiotic microorganisms can modulate the balance and activities of the gastrointestinal microbiota, whose role is fundamental to gut homeostasis. It has been demonstrated that numerous factors, such as dietary and management constraints, can strongly affect the structure and activities of the gut microbial communities, leading to impaired health and performance in ruminants and monogastric animals (equines, pigs, poultry and fish); as well as their implications in terms of animal nutrition and health.
• Probiotics belongs to the group of lactic acid bacteria, bacillus spores and yeast. The dynamic equilibrium of the microflora is regulated by the co-existence of the various bacterial species in the open ecosystem of the gastrointestinal tract. The composition of the intestinal microflora changes with the ambient conditions in the intestine.
• When the microflora is in equilibrium, the proportion of the main flora is over 90 percent. It is composed mainly of anaerobic species (Bifidobacteria, Lactobacillae, Bacteroides, Eubacteria) which produce lactic acid and other short-chain fatty acids. The satellite flora represents approximately 1 percent and consists mainly of enterococci and E.coli. The residual flora is below 0.01% and is composed mainly of harmful microorganisms such as Proteus, Staphylococci and Pseudomonas. The state when the main, satellite and the residual flora form a ratio of >90:1:0.01 is called eubiosis (good co-existence). In this situation, the host and the microflora live together in symbiosis, meaning with mutual benefit. If the relationship is severely disrupted, the condition is called dysbiosis (bad co-existence).
• The host provides ideal living condition such as constant temperature, regulated pH, supply of nutrients and removal of metabolites. In exchange, the intestinal microflora, when in the state of eubiosis, supports the host with essential activities such as :
• Probiotic bacteria modulate the metabolic activity of the gut flora.
• Probiotics, being able to lower the pH in the intestinal tract, may thus be able to interfere with the enzymatic activity of the flora.
• Protection of the intestinal mucous membrane against invading microorganisms.
• Antagonistic action against invading microorganisms or against non-desirable microorganisms.
• Contribution to the maturation and stimulation of the host’s immune system, for instance by production of immunoglobulin A.
• Improved digestion and absorption capacity of nutrients.
• Detoxification of toxic molecules.
• Influence on the metabolism of bile acids and thus promoting the absorption of fat.

Potential beneficial effects of probiotics in animals

• Greater resistance to infectious diseases
• Increased growth rate
• Improved feed conversion.
• Improved digestion.
• Better absorption of nutrients
• Provision of essential nutrients
• Improved milk yield
• Improved milk quality.
• Increased egg production.
• Improved egg quality
• Improved carcass quality and less contamination
• Avoid hindgut disorders (acidosis, colic etc.) and increase digestibility of diet.
• Limit stress (transportation, race etc.)
• Limit occurence of constipation
• Increase litter size and vitality

Probiotics in Poultry Nutrition

• Growth rate – Probiotics have enhanced the growth rate in broilers better than Antibiotics Growth Promotor (AGP) (avilamycin) and other substitutes for AGP, such as phytochemicals (e.g. essential oils). Many strains of probiotic microbes improve the growth rate of poultry, but results can be inconsistent.
• Feed intake and feed efficiency – The effect of probiotics on feed intake and feed use efficiency may be growth phase dependent. Many probiotics have positive effects on feed intake and feed use efficiency. However, as with other effects of probiotics, the impact on feed intake and feed use efficiency has not been consistent across studies or with different probiotics.
• Carcass yield and quality – Few studies have seen the positive effects of probiotics on carcass yield and quality in poultry, growth rate and feed use efficiency (FCR) of poultry. Tenderness & Water holding capacity of poultry meat was increased (reduced drip loss) in birds fed with the probiotic coagulans. The intramuscular fat content in breast muscle was increased in birds treated with probiotic C. butyricum, while there was no effect with the probiotic E. faecium. So, the effects of probiotics on carcass quality and yield are inconclusive.
• Nutrient Digestibility – Probiotics can improve nutrient digestibility in poultry since strains of probiotic microbes produce enzymes, but the interaction with different feedstuffs used in poultry diets is little understood at present.
• Intestinal histomorphology- Probiotics in poultry diets can affect the histology of the intestinal mucosa. The villus height and the villus : crypt ratio in the intestinal mucosa were increased by use of probiotics results in increase absorption of nutrients due to a larger surface area.
• Control or prevention of enteric pathogens – Probiotics could be a potential alternative to antibiotic feed additives to manage the enteric pathogen like salmonellosis, campylobacteriosis, coccidiosis, clostridium caused necrotic enteritis etc. load in poultry, by reducing intestinal colonization and spread of common zoonotic and other enteric pathogens.
• Egg production and quality – While probiotics can affect the production, feed use efficiency and quality of eggs in laying hens, these effects have been very inconsistent. One of the most promising effects of probiotics on egg quality is the consistent reduction of cholesterol in egg yolk. Yolk cholesterol has been reduced by lactic acid bacteria, Bacillus spores and yeast.

Probiotics in Pig Nutrition

• Growth rate and feed use efficiency – Probiotics can enhance the growth of pig but with less consistent results than for poultry.
• Health – Probiotics can be effective in reducing post-weaning diarrhoea in piglets and morbidity and mortality in pigs.
• GIT microbial population – In pigs, probiotics increased lactic acid bacteria and decreased Clostridium, E. coli and Enterobacterium spp. in the GIT.

Probiotics in Ruminant Nutrition

• Milk yield – Probiotics can improve the milk yield in dairy animals. Increased feed intake together with improved microbial digestion of feed could be the possible mode of action for improved animal performance.
• Growth – Probiotics can increase the weight gain of ruminants. Probiotics feeding to pregnant animal results in increase dry matter (DM) intake and live weight gain during pregnancy, followed by better performance of the young ones during early lactation.
• Nutrient digestibility -The improvement in performance by ruminants is often associated with improvement in nutrient digestibility. Probiotics feeding improves the digestibility of crude protein (CP), neutral detergent fibre (NDF) and acid detergent fibre (ADF) in lactating cows; resulting in increase milk production per day without increase in dry matter intake (DMI) due to a change in the rumen microbial ecosystem. Therefore probiotic feeding improve productivity, increase milk yield, induce better nutrient digestion and enhance growth rate in ruminants.
• Health – Probiotics can reduce diseases of ruminants particularly those related to the disturbance of rumen pH (e.g. acidosis), calf scours and pathogenic E. coli. Probiotics are believed to stabilize ruminal pH by modulating rumen microbes. Lactate utilizing bacteria (e.g. Megasphaera elsdenii ) could potentially be used to prevent the accumulation of lactic acid in the rumen. However, the establishment of such micro-organisms in the rumen is difficult. Similarly, probiotics are effective in reducing the incidence of calf scours by preventing ruminal dysbiosis. Probiotics are also effective in reducing the faecal shedding of the shiga-toxin producing E. coli O157:H57. However, these responses to use of probiotics are highly variable and reflect differences in micro-organisms (species, strains) used as probiotics and differences in animal husbandry practices (nutrition, housing etc.).
• Rumen fermentation – It has been postulated that yeast-based probiotics in ruminants increase the number of cellulolytic bacteria, which affects the microbial fermentation, resulting in higher cellulose degradation and increased microbial protein production. Although probiotics, especially Saccharomyces cerevisiae can improve digestibility of low quality roughage by ruminants, the results are inconsistent.

 Conclusion

In general, higher concentration of probiotics are recommended in animal feed during the following conditions:

1. The intestinal microflora is not yet established, e.g. in young animals.
2. The intestinal microflora is disturbed by stress factors such as change of feed, transportation and climate.
3. An increased infection pressure is expected (mixing animals of different origin, climatic influences).
4. The feed composition encourages the proliferation of pathogenic microorganisms in the digestive tract (increased content of buffer ingredients such as proteins, phosphorus, calcium and low crude fiber content).
5. The intestinal microflora is compromised by the use of therapeutics, especially antibiotics.