Animal Nutrition-पशुपोषण

Turning Fiber into Milk: Technologies for improving fiber utilization in Rumen

May 23, 2023

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Turning Fiber into Milk: Technologies for improving fiber utilization in Rumen

Ruminant animal production systems are dependent on forage as the main nutritional components . Feed cost represents 40- 60% of the total cost of production in dairy farms . Thus, nutritionists are constantly looking for an efficient way of animals’ feed utilization particularly in terms of feed intake and digestibility. Increasing fiber digestibility is a common practice of reducing feed costs and ensuring profitability. Forages are ideal ruminant animal feed and will continue to be the most important components of their diets under any production system . In most tropical countries including Ethiopia, ruminant animals are fed on fibrous feed resources, high in cell wall content (40- 70%) and low in digestibility and productivity. At present, one of the major constraints to increased livestock production in developing tropical countries is availability and quality of feed resources. In the past, various physical, chemical and biological methods were developed to overcome the problems associated with livestock feed resource. With the emergence of concerns of food safety issues related to animal products, applications of biological treatment methods are very much appealing. As a biological treatment method, the utilization of exogenous enzymes has attracted the attention of researches and animal nutritionists . Significant attempts were made in the area of improving locally available low quality forage and roughages for ruminant animal feeding. The attempts made included plant breeding and management for improved digestibility and increase in feed utilization through physical, chemical and/or biotechnological treatments . Some of the recent advancements made in fermentation technology and biotechnology, led to the production of large quantities of low cost biologically active enzymes to be used as animal feed additives. It is acknowledged that enzyme preparations with specific activities could be used to enhance specific metabolic and digestive processes in the gastrointestinal tract, increase natural digestive processes and improve the availability of nutrients and feed intake . The improvement of forage quality, efficiency of utilization and increased productive efficiency of ruminants’ animals has been milestones of forage research. Recently, forage cell wall digestibility has undergone significant improvements through plant breeding, agronomic advancements and enzyme production technology. In terms of enzyme technology, the two most popular enzyme complexes are those of cellulase and hemicellulase families, generally known to be multicomponent enzymes, used as silage inoculant to enhance fermentation and preservation. It was reported that fibrolytic or cell wall degrading enzymes applied alone, or in combination with the other additives, may enhance preservation of forage within the silo by increasing the levels of lactic acid . According to enzyme treatments reduced the retention time of digesta in the rumen. In the fermentation proses, the enzymes acting on structures of the plant cell walls increased access of ruminal microbes to the potentially fermentable fiber for this case the objective of this review is the feasibility of improving the nutritive value of forage through the use of exogenous enzyme.

Current context of high price of feed raw materials is driving us to reconsider the importance farm-grown fibrous material in the ration of ruminant. Indeed, fiber is an essential component of plants which is resistant to degradation by the digestive enzymes of most monogastric animals. Ruminants, on the other hand, have the unique ability to release the energy from part of the fiber structure thanks to the fermentative activity of the rumen. Ruminant digestive system has the ability to degrade and ferment fiber through microbial activity. The fiber components, and the subsequent production of volatile fatty acids (VFAs), provide the majority of the energy for the ruminant. Hence, to optimize ration to maximize fiber digestibility to extract more energy from the cell wall components of the plant. Better understanding of how fiber is degraded in the rumen helps identify the levers that can help reach this goal and make sure fiber is no longer an untapped energy source.

From fiber to energy to milk

Fiber is slowly degraded in the rumen due to its physical structure and the lignin cross-linking that holds the fiber intact. Fiber degradation in the rumen is influenced by:

The anatomy of the fiber (pectin, hemicellulose and cellulose concentration), which is related to species
Lignin content and structure (maturity, species, stressors, etc.)
Particle size
Passage rate (highly influenced by particle size, uNDF, DMI) and its impact on rumen dynamics
Cud-chewing and ruminal contractions
Rumen microbial population (microbiome) influenced by several factors (diet, environment)

The ruminant reduces the particle size of the forage through the eating process via initial mastication (chewing). These particles are swallowed and float to the top of the rumen mass. The particles are then regurgitated and rechewed (cud-chewing) to increase moisture content and surface area of the material as well as to abrade the fibrous portion.

After initial mechanical abrasion of fiber through mastication, the feed is then exposed to the diverse population of microorganisms in the rumen. The first step in fiber degradation is the colonization in the rumen of the particle of fiber by fungi and bacteria. Fibrolytic microbiota are very sensitive to oxygen. Strict anaerobic conditions (measured though redox potential) are necessary to ensure the maximum colonization. Many species of bacteria can produce these enzymes and are broadly categorized as fibrolytic bacteria. Furthermore, other microorganisms can similarly degrade fiber including protozoa and fungi.

The extent of ruminal fiber digestion is influenced by the digestibility of the fiber (NDFd – see boxed text), the rate of degradation of the fiber (Kd of NDFd) and the passage rate (Kp) of the fibrous material from the rumen.

The digestibility (NDFd) of the forage is influenced by morphological factors such as maturity (leaf:stem ratio) and lignification, plant anatomy and plant species.
The rate of digestion (Kd of NDFd) is largely a function of species differences, lignin complexes and ratios, and maturity.
The passage rate (Kp) can be influenced by theoretical length of cut, rumen dysfunction (acidosis and SARA), moisture content and dry matter intake of the animal.

Fiber degradation in the rumen is leading to production of VFAs that represents up to 70% of the energy required for milk production. Thus, the efficacy of fiber degradation in the rumen is an important driver of milk production yield. Oba and Allen have determined that, for every 1% increase in NDF digestibility, milk production increases by 0.24 kg/d, and Fat Corrected Milk (FCM) increases by 0.25 kg/d (Oba and Allen, 1999).

Factors affecting fiber digestibility

There are several factors that can alter the population of the rumen microorganisms (rumen microbiome), including the influence of diet.

Ruminal pH and SARA

Since fibrolytic bacteria need a pH above 6.2, decreases in pH can inhibit their growth and performance. If rumen pH falls below 6.0, fiber digestion in the rumen begins to decline. When ruminal pH falls below 5.8 to 5.9, the rumen is mildly acidic, and fiber digestion in the rumen is disrupted.

Hence, any diet that can alter the pH can negatively impact fibrolytic species and result in reduced fiber degradation. This decreased pH can further lead to subacute rumen acidosis (SARA).

SARA can be influenced by a number of factors such as forage particle size, feeding behavior, starch content of the diet and grain level of the diet.

A meta-analysis by Ferraretto et al. (2012) examined factors that affected the digestibility of whole-plant corn silage. As starch levels increased in the diets, the digestibility of dietary NDF decreased by 0.61% units ruminally and experienced a 0.48% unit total-tract per %-unit increase in dietary starch content. The authors suggested this was due to a downward shift in ruminal pH.

Figure 3: Impact of the rumen pH on the NDF digestion rate of a raw material (Fox et al., 2003).

Impact of particle size

The particle size of the ingested forage can play a role in fiber digestibility. Longer particles may increase a lag to digestion due to a lag in hydration and a reduction in bacterial attachment. Bacterial attachment refers to the ability of the bacteria to start the digestion process by attaching to the cut end of the fiber. The bacteria digest the plant material from the inside out and require either a cut point or opening created by fungal digestion or abrasion to start this digestion process.

Feeding behavior

Dairy cattle are foragers. Over the millennia, cattle have grazed on fibrous pastures. Ruminants have the capacity to consume human inedible feed, including the digestion of cellulose, with forages as the main source thanks to grazing and foraging.

The grazing/foraging behavior would be spread out over a long period of time with frequent small meals. Considering the modern dairy cow now has access to a total mixed ration (TMR), they typically consume their daily DMI in three to five hours per day, spread between 6 to 10 meals with the largest meal occurring after the delivery of fresh feed (DeVries et al., 2016; DeVries and von Keyserlingk, 2005).

Rumen pH generally declines after each meal as rumen available carbohydrates are fermented and volatile fatty acids (VFAs) are produced. When VFA production exceeds the ability of the rumen environment to neutralize or absorb the acids, SARA occurs. The size of the meal and the amount of rapidly fermentable carbohydrates can have an impact on the decline in rumen pH. Having smaller and more frequent, meals reduces variability in rumen fermentation patterns as well as the rate of pH decline and the amplitude of the rumen pH. In consideration of these factors, it is safe to conclude that changes in feeding behavior as a result from TMR feedings can increase the risk of SARA. Changing feeding behavior can reduce the risk of cows experiencing SARA.

Ruminants however have the biggest capacity to consume human inedible feed, including the digestion of cellulose, with forages as the main source but also feed materials such as sugar beet pulp, citrus pulp and brewers’ grains. Their unique ruminant digestive system allows them to convert “low value” fiber-rich feed components into “high value” animal proteins (milk and meat) not in competition with human foods, goes largely unnoticed.

Rumen modifiers

Rumen specific live yeast Saccharomyces cerevisiae CNCM I-1077 (LEVUCELL SC) used as a feed additive, has the ability to enhance fiber degradation through its rumen modifier effects, translated into higher feed efficiency in dairy cows.

The effects and modes of action of this live yeast on rumen microbiota have been extensively studied. The main effects attributable to this strain include:

stabilization of ruminal pH
increase in fiber degradation and the subsequent improvement in digestibility

In sacco, trials demonstrate the positive effect of S. cerevisiae CNCM I-1077 on NDFd of more than 200 different forage samples, including: corn silage, straw, rye grass hay, alfalfa hay, annual rye grass (pasture), meadow hay, grass silage, etc. Saccharomyces cerevisiae CNCM I-1077 is found to increase NDF digestibility by 4 to 8 units, depending on the type of forage and on its own degradability (Guedes et al., 2008; Guedes et al., 2015; Chaucheyras-Durand et al, 2010, Ding et al, 2014).

Research studies have evaluated the possibility to model the effect of S. cerevisiae CNCM I-1077 on dynamic model. It clearly demonstrates that the effect of a rumen modifier based on its mode of action while well documented, can be integrated into a nutritional software and accurately predict the effect on animal performance.

Overall, combined data trials indicate a 3% improvement of feed efficiency with the live yeast supplementation, with higher effect under rumen challenged conditions (up to 7% increased feed efficiency, corresponding to a 6:1 up to 9:1 return on investment for the producer under these challenging situations .

Figure 4: Levucell SC effects of dairy cow feed efficiency (average of several trials).

Fiber represents the majority of milk energy for dairy cows. Fiber degradability is linked:

to the quality of the plant material, which depends on both the crop inherent characteristics and its growing environment, and
to the fiber digestion process once it is fed to the animal (mainly located in the rumen).

So, the degradation of fiber is influenced by farming practices and rumen dynamics. Indeed, the rumen can be pictured as an engine that, thanks to its unique microbiome, turns fibers into milk energy. Management and feeding practices that ensure optimal rumen environment (pH, microbial balance…) and function can help that improve the efficiency of the ‘rumen engine’ for optimal farm revenue.

Producers are experiencing skyrocketing prices of feed — up 20 to 30% worldwide compared to 2020. It’s driving the industry to find new and innovative ways to extract energy from the ration. This has a direct effect on farm revenue and income-over-feed costs. Given very high crude oil prices, this situation could last for a while because high fuel prices have a direct impact on the price of crops. High fuel prices also provide competition for raw materials that are resources for energy production, such as biofuel and biogas.

Ruminants have the unique ability to degrade and ferment fiber through microbial activity. Forage is a major fiber source and can be either grown on farm or available locally at a more competitive price than concentrates. Optimizing the ration to maximize fiber digestibility helps cattle extract more energy from forage and improves feed efficiency, income-over-feed costs and, finally, farm profitability. Profitability is one of the three pillars of sustainability, which is a growing concern for both consumers and producers.

A better understanding of how fiber is degraded in the rumen helps identify the changes that can help reach this goal and make sure fiber is no longer an untapped energy source.

FEED EFFICIENCY: THE KEYSTONE OF FARM PROFITABILITY

Feed efficiency measures the animal’s abilty to turn feed material into food product. Improving feed effiiciency is a way to optimize the quantity of food produced per kg of feed given to the animal (whether measured in milk or meat).

Ruminants have the unique ability to release the energy from part of the fiber structure thanks to the fermentative activity of the rumen. Nutritionists can take advantage of this unique and specific function that originates in the rumen. The ruminant digestive system has the ability to degrade and ferment fiber through microbial activity. The fiber components, and the subsequent production of volatile fatty acids (VFAs), provide the majority of the energy for the ruminant. A better understanding of how fiber is degraded in the rumen helps identify the levers that can help improve feed efficiency.

In addition, improving ruminant feed efficiency also means optimizing the quantity of food produced per hectare of arable land and offers a way to more sustainably meet the demands of an increasing world population. Improving the digestibility of locally available raw materials is a key driver of income-over-reed costs for the farm manager.

FEED EFFICIENCY STARTS AT THE FIBER SOURCE

From a fiber perspective, feed efficiency starts with forage management, from the field to the bunker. Optimal forage and fiber development starts with harvesting at the correct maturity and dry matter (DM) levels and is maintained with good storage management practices.

Producers can ensure optimal silage quality and digestibility by using a scientifically proven forage inoculant, such as MAGNIVA Forage Inoculants from Lallemand Animal Nutrition. Such forage inoculants preserve the forage’s nutritional potential, reduce DM losses and spoilage by limiting the growth of undesirable microorganisms. Taken together, this contributes to maximizing the energy available per kilogram of harvested forage .

SILAGE FERMENTATIONS OVER TIME HOW TO IMPROVE FIBER DIGESTIBILITY AND FEED EFFICIENCU THROUGH DIET FORMULATION?

Ruminant nutrition ration formulation is a compromise between raw materials, forage prices and nutrient availability of each of the feed components.

As energy is coming mainly from fiber degradation, one of the solutions is to optimize the rumen function, which leads to optimal digestion of fiber from all types of ruminant diets. This can be supported by the use of scientifically documented rumen modifiers such as the specific live yeast Saccharomyces cerevisiae CNCM I-1077.

The live yeast S. cerevisiae CNCM I-1077 acts as a real optimizer of the rumen engine. It helps boost the efficiency at which feed is transformed into energy, principally through improved degradation of fibrous material. This feed additive has a beneficial effect on microbial fiber degradation by stimulating the growth and fibrolytic activity of fiber degrading bacteria and fungi populations . Moreover, the live yeast promotes an optimal rumen environment, with a beneficial action on rumen pH. These effects and mechanisms of action are demonstrated through more than 100 scientific publications over the 30-plus years since this strain was discovered in partnership with the INRAE in France.

As a result, the live yeast is able to improve feed efficiency by 3 to 7% under standard or stress production conditions (figure 3). This represents a valuable tool that allows for the forage portion of the diet to be maximized and gives producers and nutritionists the possibility to increase milk or meat revenue per kilogram of feed — or allows them to optimize feed cost while maintaining similar revenue. Most importantly, this improved feed efficiency does not negatively impact animal welfare and many studies have shown benefits beyond farm economics on animal welfare through improved feeding behavior, reduced Sub Acute Ruminal Acidosis (SARA) risks, etc.

It gives producers and nutritionists the opportunity to switch from one ration to another depending on their specific situation — without compromising on feed efficiency, which supports greater flexibility and resilience.

HOW CAN NUTRITIONISTS MEASURE THE BENEFITS OF ADDING FEED ADDITIVE TO THE DIET?

Using a “precision-nutrition” tool can help nutritionists when formulating with live yeast. Lallemand Animal Nutrition has developed the “Levucell SC-submodel” with forage NDFd equations. Scientists conducted in vivo fiber digestibility assessment for a multitude of forages and feed ingredients, with and without the live yeast. These data allowed to model the live yeast’s effect in terms of increased energy value depending on the feed: +3% up to 8% depending on the ingredients and the forage characteristics (e.g., improvement obtained is higher for forages with lower intrinsic fiber degradability, Guedes, 2008) (Chaucheyras-Durand et al, 2010, Ding et al, 2014).

Thanks to this sub-model, the nutritionist can predict or model the effect that adding the feed additive to a ration will have on raw material digestibility, feed efficiency and income-over-feed cost. It contributes to precision feeding by providing different nutritional scenarios to answer farm managers’ needs (e.g., iso-cost for higher milk revenue or least cost formulations).

Recommendations-

Generally from this it is recommended that Forage should be treated by exogenous enzyme to improve the nutritive value for maximum production since exogenous enzymes are cell wall degrading and increase digestibility of low quality forages. § Enzyme application in liquid form that sprays to forage is important because uniform distribution through the forages. § Using enzyme technology should be expanded through the farmer level and the farmers should be promoted and educated by making awareness and through experiences sharing. § Generally, future studies are highly needed with the special emphasis on feed specific enzyme activity, method of extracting enzyme widely, method of application and optimum dosage of enzymes.

CONCLUSION

Improving feed efficiency while safeguarding animal welfare has always been an important objective for nutritionists. In the current context of raw material pricing, this goal continues to be a major priority.

Improving fiber degradation is one of the keys, which helps improve the environmental and economic sustainability of animal production. Getting every last nutrient out of the ration helps lessen its footprint in terms of land-use and greenhouse gas production and also helps protect the narrow margins of farm managers.

Ruminant animal productions are based on the available natural pastures and crop residues in developing countries. These feed resources are poor in nutritive value and consists of highly lignified stems. The opportunity of efficient forage utilization is subjected to seasonal variation. Improvement in nutritive value of the fibrous feed resource through the use of exogenous enzyme was reported to be appealing. In the past two decades, the application of exogenous fibrolytic enzymes (EFE) demonstrated to have the potential of increasing forage utilization. Supplementation of ruminant animal diets with exogenous enzymes showed beneficial effects on feed utilization, growth and production performance. The supplementary enzymes used were derived primarily from four bacterial (Bacillus subtilis, Lactobacillus acidophilus, L. plantarum and Streptococcus faecium, spp.), three fungal (Aspergillus oryzae, Trichoderma reesei and Saccharomyces cerevisiae) species and some yeasts. Enzymes have been applied to TMR, hay, ensiled forages, concentrate and premixes. Exogenous enzymes may be expected to be more effective when applied to high-moisture feeds (such as silages) compared to dry feeds. Enzyme application to diets at feeding is attractive because the fermentable substrates released by enzyme action could directly be fermented by ruminal bacteria. However care is needed to ensure an even distribution of the enzyme added