Dr. Muhammad Nadeem Sarwar
DVM, MSc. (Hons) Microbiology (UAF)
Poultry Disease Management, University of Arkansas, USA
CEO:
Sanna Laborateries
Zuram Brothers
Silantro Advance Care (Pvt) Ltd
In the last decades, many scientists and researcher are trying to exploring the opportunities to improve animal health, well-being, and performance through fermentation. In the last two decades, fermentation technology has gained good achievements in improving feed quality, feed utilization efficiency and promoting animal health. Fermentation technologies such as microbial-based fermentation and precision fermentation can improve feed digestibility by changing the physicochemical properties of the feed substrate, thus ensuring animal health and high quality production.
Metabolites produced during fermentation help in the breakdown of nutrients, improve their digestibility and bio-availability. This will result in efficient utilization of feed, reducing waste and improve feed conversion.
Fermentation plays an important role in the variety of livestock species which includes Cattles, Sheep,Goat, Horses, Poultry and Fisheries. What so ever is the specie, fermentation plays a crucial role in the improvement of animal health, well-being and performance by increasing digestibility and bioavailability of the feed ingredients.
1. FERMENTATION IN RUMINANTS
Ruminants have four compartments which include Rumen, Reticulum, Omasum and Abomasum.
Fermentation occurs in Rumen through microbes called ruminal fermentation. Rumen fermentation is a process that converts ingested feed into energy sources for the animals. Fiber scratches the rumen wall to start a series of contractions. These contractions lead to rumination, which is the process that physically breaks down the fiber source. Feed is then regurgitated, chewed and swallowed usually 50 to 70 times during rumination before passing through the next compartment of the stomach.
Microbial populations ferment feed and water into volatile fatty acids (VFA) i.e. Acetic Acid, Butyric acid and propionic acid and gases (methane and carbon dioxide). When fermentable carbohydrate in the diet is digested too rapidly, the bacteria will increase the production of both VFA and lactic acid. To sustain growth and the activity of fibrolytic microbes, it is crucial to maintain ruminal pH above 5.8, which will prevent the decline of fiber digestion and subsequent proble
Rumen Microbiota
Bacteria:
Rumen bacteria account for 1010 organism/ml of rumen fluid. By volume, they comprise up to 50% of the total microbial biomass. Bacteria species are an important source of microbial protein, which supply the ruminant with 75-80% of its metabolizable protein. Bacteria are also important for producing enzymes that digest fiber (cellulose, hemicellulose), starch and sugars.
Protozoa:
Ciliate protozoa are organisms larger than bacteria and account for 106 organisms / ml of rumen fluid. However, most of them degrade proteins very efficiently and release ammonia, so they can waste dietary protein. These proteins represent around 25% of the microbial protein available for the animal.
Fungi:
Rumen fungi comprise up to 8-10% of microbial biomass and are strictly anaerobic. They play an essential role in fiber digestion This physical action to plant cell walls, can facilitate access to more digestible tissues and help release polysaccharides, which are linked to lignin increasing the pool of digestible energy for the rumen microbiota.
Archaea:
This group of microorganisms is involved in methane (CH4) production from a limited range of substrates. They are thus called methanogenic Archaea are considered as very strict anaerobes and use some of the fermentation products, notably H2 and CO2, to form CH4 which is eructated by the ruminant animal.
2. FERMENTATION IN HORSES
Horses are single stomach (monogastric) herbivores that evolved to graze on fiber-rich roughage. Their unique digestive system consists of a foregut and hindgut, each with different functions for breaking down feed and absorbing nutrients. The stomach and small intestines, which make up the foregut, are responsible for digesting proteins, fats, and non-fibrous carbohydrates in the horse’s diet. This happens through mechanical action and chemical reactions facilitated by enzymes.
The hindgut, consisting of the cecum and colon, is where the digestion of fibrous carbohydrates takes place. Bacteria help synthesize nutrients and convert this fibre into usable energy through fermentation. The process of hindgut fermentation allows the horse to extract nutrients from plant material which are not digestible in the small intestine.
Because of their specialized digestive system, fibrous forages should comprise the largest percentage of your horse’s diet. Feeding horses too much sugar and starch from grain-based feeds can disrupt digestive
processes in the hindgut and cause gut problems.
What is Hindgut Fermentation in Horse?
The main purpose of the hindgut is to ferment the complex and structural carbohydrates found in the horse’s diet. Structural carbohydrates include fiber components in the plant cell wall, such as cellulose and hemicellulose. Complex but fermentable carbohydrates include pectin, beta-glucan, plant sugars and fructans, largely found within the plant cell.
In horses, fiber and complex carbohydrates from fresh grass and hay are digested via fermentation by microbes residing in the hindgut. Feeding a diet rich in structural and complex carbohydrates helps to promote optimal digestion and the transit of feed through the equine gastrointestinal tract (GIT). Hindgut fermentation produces volatile fatty acids (VFAs) that serve as a significant energy source for horses. Most of a horse’s energy requirements should be met through fiber fermentation in the hindgut.
Microbial fermentation also produces B-vitamins and amino acids. These B-vitamins can be absorbed and meet the horse’s requirements. Methane, carbon dioxide, and water are also produced by fermentation in the hindgut.
Fermentation Products
When the microorganisms in a horse’s hindgut ferment fiber and other complex plant carbohydrates, they produce substances such as volatile fatty acids, which are a source of energy for the horse. The most common VFAs produced in the equine gut are acetate, propionate, and butyrate. These fatty acids provide approximately 70% of the horse’s energy supply.
In addition to VFAs, the fermentation process also produces lactic acid, which can be used to make glucose as another energy source. While some lactic acid is normal, excessive amounts can lead to digestive issues and imbalances in the microbial populations. [3] The production of VFAs and lactic acid in the hindgut results in slower energy release than the rapid breakdown of soluble carbohydrates and
starch in the foregut.
Additional by-products of bacterial fermentation in the hindgut include B-vitamins (riboflavin, niacin, biotin, folate, B12, and B6) and amino acids (primarily used by microbes and not absorbed in significant quantities).
Composition of Hindgut Microbiota
The equine hindgut is home to a diverse community of microorganisms including bacteria, protozoa (single-celled organisms), and fungi. These microorganisms work together in a symbiotic relationship with the horse, aiding in the fermentation of fibrous materials. The activities of these
microorganisms allow horses to digest and extract energy and nutrients from fibrous feed in the hindgut.
The hindgut contains a more uniform range of bacteria compared to the stomach and small intestine, which host a more diverse bacterial population. The diversity of bacteria present in the foregut is due to the ingestion of a high volume of forage. Lactic acid bacteria comprise most of the microbiota in the large intestine. These bacteria produce the majority of volatile fatty acids (VFA) needed for energy.
Bacteria (Main Players)
Cellulolytic bacteria
- Fibrobacter succinogenes
- Ruminococcus flavefaciens
- Butyrivibrio fibrisolvens
Break down cellulose and hemicellulose into volatile fatty acids (VFAs)
Amylolytic bacteria
Streptococcus bovis, Lactobacillus spp.
Break down starches (from grains); can cause acidosis if starch overloads occur
Proteolytic bacteria
Break down proteins and amino acids
Lactic acid–utilizing bacteria
Megasphaera elsdenii, Selenomonas ruminantium
Help prevent acid buildup by converting lactic acid into less harmful VFAs
Fungi
-
Neocallimastix, Piromyces, Orpinomyces
Break down tough plant fibers (lignocellulose) and aid in physical disruption of plant cell walls - Less abundant than bacteria, but very important for digesting fibrous forage
Protozoa
- Ciliate protozoa like Entodinium spp. Contribute to starch digestion and help regulate bacterial populations
- Not essential for survival, but help balance fermentation dynamics
3. FERMENTATION IN POULTRY
In poultry, fermentation primarily occurs in the ceca, two pouches at the junction of the small and large intestines.
Functions:
- Microbial breakdown of fiber and undigested material.
- Production of short-chain fatty acids (SCFAs).
- Support for gut health and competitive exclusion of pathogens.
Step-by-Step Mechanism
| Step | Process |
| 1 | Arrival of Undigested Feed: Indigestible carbohydrates (fiber, NSPs), resistant starches, and some proteins reach the ceca and starts Fermentation. |
| 2 | Microbial Colonization: Anaerobic microbes (e.g., Lactobacillus, Bacteroides, Clostridium) dominate the ceca. |
| 3 | Fermentation Begins: Microbes break down the substrates through anaerobic fermentation. |
| 4 | Enzymatic Hydrolysis: Microbes secrete enzymes like cellulase, xylanase, protease, breaking down fiber and protein. |
| 5 | Production of Metabolites: Short-chain fatty acids (SCFAs) like acetate, propionate, and butyrate are produced, along with gases (CO₂, H₂). |
| 6 | Absorption: SCFAs are absorbed across the cecal epithelium and used as energy by the bird, Mainly butyrate |
| 7 | Microbial Balance: Probiotics and beneficial microbes crowd out pathogens (e.g., Salmonella, E.coli) via competitive exclusion. |
Key Microbial Products
| Product | Function |
| Acetate (Acetic Acid) | Used in energy metabolism throughout the body of birds |
| Propionate (Propionoic Acid) | Minor energy source; some gluconeogenesis potential |
| Butyrate (Butyric Acid) | Main fuel for cecal cells; enhances gut integrity and immune modulation |
| CO₂, H₂ | Excreted gases |
| Ammonia (NH₃) | Byproduct of protein breakdown; toxic in excess |
Why Fermentation Matters?
- Enhances nutrient utilization of otherwise indigestible materials
- Supports gut health and immune function
- Reduces pathogen load naturally (less need for antibiotics)
- Optimizes feed conversion ratio (FCR)
Positive Role of Fermentation in Poultry
| Benefit | Explanation |
| Improves gut health | Fermentation produces short-chain fatty acids (SCFAs) like butyrate,which nourish gut cells and strengthen the intestinal barrier. |
| Enhances nutrient digestibility | Microbes help break down non-starch polysaccharides (NSPs), fibers, and antinutritional factors, improving nutrient availability. |
| Reduces pathogenic bacteria | Beneficial microbes and SCFAs inhibit growth of harmful pathogens like Salmonella, E. coli, and Clostridium. |
| Boosts immunity | SCFAs and microbial metabolites excite local and systemic immune responses. |
| Decreases antibiotic use | Competitive exclusion by good microbes lowers disease risk, reducing the need for antibiotics. |
| Reduces feed cost (with fermented feed) | Fermenting agricultural by-products or low-cost ingredients improves their value and palatability. |
End Products of Fermentation in Poultry
- Short-Chain Fatty Acids (SCFAs): Acetate, Propionate, Butyrate
- Gases: CO2, Hydrogen, Trace Methane
- Ammonia (from protein breakdown)
- Lactic Acid (transitional)
- Small amounts of B-vitamins and bioactive compounds
Positive Effect of Acetic, Propionic & Butyric Acids in Poultry Feed:
| Effect | Explanation |
| Improved gut health | Butyric acid supports the health and re-formation of intestinal epithelial cells, mainly in the cecum. |
| Antibacterial action | Acetic and propionic acids lower gut pH, inhibiting harmful bacteria like Salmonella, E. coli, and Clostridium. |
| Better nutrient digestion | Acidification improves enzyme activity and nutrient absorption (mainly minerals like Ca, P). |
| Enhanced growth performance | Organic acids can improve feed conversion ratio (FCR) and weight gain by improving gut function. |
| Mold and fungal inhibition (feed preservation) |
Propionic acid is mainly effective at preventing mold growth in feed and increasing shelf life. |
Recommended Use (Guidelines):
| Acid | Recommended Level (in feed) |
| Acetic acid | 0.1%–0.5% (may vary depending on source and blend) |
| Propionic acid | 0.2%–0.5% (as preservative or gut acidifier) |
| Butyric acid | 0.05%–0.2% (often in protected/encapsulated form to reach intestine) |
4. FERMENTATION IN FISH
- Fermentation can occur throughout the fish’s body, but the gut and muscle tissues are particularly important sites. The gut contains a variety of microorganisms, and its enzymes can contribute to the initial breakdown of feed material.
- Fermentation itself does not directly promote fish growth when we’re talking about live fish in aquaculture. However, fermentation plays a powerful indirect role in supporting fish growth when used in fermented fish feed. Fermentation improves feed quality by enhancing its digestibility, nutrient availability, and safety, leading to better growth performance in farmed fish. Fermentation in fish is primarily an anaerobic process, meaning it occurs in the absence of oxygen.
Lactic Acid Fermentation
A common type of fermentation in fish is lactic acid fermentation, where lactic acid bacteria convert sugars into lactic acid. This process helps lower the pH of the fish, inhibiting the growth of harmful bacteria and contributing to the characteristic flavor of fermented fish product.
| Role of Fermentation | How It Helps Fish Growth |
| Improves digestibility | Fermentation breaks down complex proteins, carbs, and fats into simpler forms that are more easily absorbed by fish. |
| Enhances nutrient bioavailability | Releases amino acids, vitamins (especially B-vitamins), and minerals that support metabolic functions and muscle development. |
| Reduces anti-nutritional factors | Fermentation neutralizes substances like phytic acid and trypsin inhibitors, which otherwise block nutrient absorption. |
| Boosts gut health | Fermented feeds often contain beneficial microbes (probiotics) that improve gut microbiota balance, increasing nutrient uptake and immunity. |
| Stimulates appetite | Fermented feed often has better aroma and taste, encouraging fish to eat more consistently. |
| Increases feed conversion efficiency (FCR) | Fish gain more weight per unit of feed consumed when fed with fermented diets. |