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Solid state fermentation technology has proven to be a very efficient way to improve the nutritional value content of certain animal diets.
on April 8, 2008

The quest for improved fiber utilisation

Use of solid state fermentation can help create a positive bottom line for tomorrow's livestock industry.

The global demand for meat is growing at a significant rate, signaling with it a need to increase the rate of feed production. However, current feed production projections suggest that this rate will not be sufficient to meet the requirements for the extra production of meat. As we know, feed is the major production cost for swine and poultry, so it is essential to minimize feed cost. Although in the spotlight, the search for alternative sources of ingredients for corn and soybean is not a new concept as nutritionists have continually searched to reduce costs.

Additionally, the current situation has been aggravated due to the fact that much of the corn formerly used in animal diets will be siphoned to ethanol production and as we know, anything that competes for maize in the world marketplace will impact on cost of meat and egg production. Therefore, the alternative nutritionists have is to increase nutrient and energy availability of corn by-products (e.g. DDGS) and other feedstuffs fed to swine and poultry. Solid state fermentation (SSF) technology has proved to be a very efficient way to improve the nutritional value of corn-soybean meal based diets as well as those with high fibrous ingredient content.

Carbohydrates represent a major part of swine and poultry diets, with contents ranging from 40 to 70 percent. Cereal grains are major contributors of dietary carbohydrates. The function of their digestible fraction is to supply energy to the host. There is, however, a great variation among the different grains in the energy provided to the animal. Based on metabolisable energy (ME), grains can be ranked in the following order: corn>triticale>barley>oats>rye (Table 1). For many years, barley, oats and rye were not widely accepted as valuable components of poultry feeds due to poor flock performance and unmanageable litter conditions. In the past, the negative characteristics of these cereals were primarily attributed to their cellulose, hemicellulose and lignin content. Later, studies indicated that the inferior productive value of barley was related to beta-glucans (Hesselman and Aman, 1986) and to the water-soluble pentosans in rye (Fengler et al., 1988). The indigestible fractions of carbohydrates affect essentially the digestive tract, with effects which can be observed on its anatomy and histology, on the transit time, water losses, bacterial development, digestive efficiencies, etc., bringing about poor digestion in monogastric animals. These functions and effects of carbohydrates vary according to their chemical and physical properties (Carré, 2002).

Figure 1: The figure shows a schematic diagram outlining the production of Alltech's solid state fermentation.

SSF process

Recent reviews (Lyons, 2007, Filer, 2007) indicated that some 4,000 years ago, the Chinese faced similar problems to those found today: limited protein and poor digestibility of raw materials. In response, the Chinese developed the koji processor solid state fermentation (SSF), where the organism does the digesting for us. SSF also includes a number of well-known microbial processes such as soil growth, composting, silage production, wood rotting and mushroom cultivation. Today, many familiar western foods such as mold-ripened cheese and bread, and many Asian foods, are produced using SSF.

In 1995, Alltech began to revisit the technology and in 2000 opened a state-of-the art SSF plant in Serdan, Mexico. During the early stages of SSF development, researchers discovered that organisms would be effective on digesting the media on which they are grown. Through selection of specific strains and careful selection of growth media, an array of benefits were identified for improved energy, protein, and phytic acid that improve the digestibility of animal feeds containing larger amounts of by-products than routinely used. An example of this concept is the growth of organisms on wheat bran-rich media. This natural complex is extremely effective in releasing energy and reducing gut viscosity, both of which are important considerations when utilizing by-products such as wheat bran in animal diets. In effect, the organism responds to the substrate in order to grow and multiply. By combining the latest advances in microbiology and engineering, a revitalized SSF technology applicable to today's feed industry was created by the Alltech SSF process. The fungi Aspergillus and Rhizopus featured strongly.

According to Lyons (2007) and Filer (2007), the selected fungus is first propagated in liquid media to produce a large volume of inoculum which is mixed with pre-sterilized selected solid substrate (fiber) media to produce a mixture known as koji. Under strict aseptic conditions, the koji is then evenly distributed onto trays and introduced in environmentally controlled fermentation culture chambers. During this time, the fungus grows rapidly and breaks down the fiber to release nutrients it requires for continued growth. It is this release of nutrients and the conversion of cellulose to glucose that opens up the opportunity. The fungus is doing the digestion for us and by harvesting the kojithe complexwe can then transport that ability to the animal. By varying the raw materials, the fungi varies its response. The products generated during the SSF process allow for a more flexible approach to feed and diet reformulation through the inclusion of by-products or by reducing nutrient constraints in the diet, particularly energy, calcium and available phosphorus. It has also been shown, through animal performance, to remain effective over a wide range of feed processing conditions. SSF can be added directly to feed or via a premix with no special application systems required.

Table 1: Approximate composition of feed ingredients

SSF in poultry diets

The use of solid state fermentation in monogastric diets provides the opportunity for increasing the digestibility of energy, protein, phosphorus and calcium of dietary vegetable substrates. The results of its efficacy can be demonstrated by examining several poultry and swine trials conducted all over the world.

To introduce SSF technology to the market, a series of studies were run with animals. In broilers, the first studies with SSF technology were carried out throughout the Asia-Pacific region. A broiler trial conducted at the Queensland Poultry Research & Development Centre, Australia (2003), investigated the effect of supplementing SSF in wheat-soy diets. The negative control was formulated using 150 kcal/kg less metabolisable energy (ME) and included SSF in the treatment diet, which also had low ME. This resulted in an increase of over 60g in terms of improved body weight at 42 days with a feed conversion ratio maintained at 1.84.

In India, Ramesh and Devegowda demonstrated that SSF added on the top of the diet resulted in a significant improvement (P<0.05) in weight gain (79 g) over a 42-day period. The use of SSF maintained performance when reformulated in the diet with 75 kcal/kg less of ME and both the available phosphorus and calcium content reduced by 0.1 percent. Feed conversion ratio was also improved significantly (by 7 points, P<0.05; Figure 2) when SSF was added on the top and was maintained in the reformulated diet.

Due to the success of SSF in Australia, New Zealand and throughout Asia, Alltech decided to increase production and introduce the process to other regions of the world, in particular Latin America. To introduce SSF to that continent, a series of trials were conducted to revalidate the use of SSF under conditions where variations in climate, plant varieties, soil and other factors from different parts of the world were applicable and might interfere in the composition of feed ingredients.

The Universidade Federal de Pelotas, Brazil, Silveira et al. (2006) evaluated the interaction between different levels (0, 40, 80 and 120 kcal/ kg) of dietary formula, in order to overestimate metabolisable energy from SSF and amino acid (100 and 110 percent) content on broiler performance and carcass traits. They concluded that dietary ME could be reformulated in a range of 40 and 80 kcal less ME/kg by using SSF, without affecting performance and carcass traits. Similar energy release (60 kcal/ kg) with SSF was observed in an 83-day trial conducted with semi-intensive broiler chicks (Clave et al., 2007).

Figure 2: Feed conversion ratio was improved significantly in broilers when SSF was added on the top and was maintained in the reformulated diet.

Feed savings

Recent results from the Alltech-University of Kentucky Nutrition Research Alliance have shown the potential to release as much as an extra 200 kcal/kg of apparent metabolisable energy (AME), by using SSF in broiler chicken diets containing 25 percent DDGS. Results such as these, while preliminary, are extremely encouraging for the potential to allow nutritionists to consider adding DDGS to diets at levels previously unheard of. Consider that saving 200 kcal/kg is equivalent to 200,000 kcal/ton of feed. Assuming that, on average, fat has a value of 8500 kcal/kg, one could theoretically save up to 24 kg of fat per ton of feed.

Environmental pollution has become an important issue in many parts of the world. In a recent study run at the Research Institute of Biotechnology and Veterinary Medicine, Latvia, Vitina et al. (2007) evaluated the influence of SSF on the digestibility of nitrogen and phosphorus in the gastrointestinal tract of poultry and the excretion of nitrogen, phosphorus and microflora in manure. They concluded that adding fermented wheat bran SSF improved the digestive process in the GI tract of poultry and reduced pollution of the environment of undigested nitrogen compounds and harmful microflora.

In addition, SSF has proven thermo-stability across a range of diets. Silveira et al. (2006) examined the effect of pelleting (75 C) on diets containing SSF for broiler chickens. Birds were provided mash and pelleted diets, reformulated to energy (75 kcal/kg), calcium (0.1 percent) and phosphorus (0.1 percent). Birds fed pelleted diets showed better performance than those fed a mash diet. Bone (tibia) strength was not significantly affected by dietary treatments; however, a clear tendency towards higher bone resistance was observed in those birds fed reformulated mash or pellet diets supplemented with SSF as compared to those fed reformulated mash or pellet diets without SSF supplementation. As such, it was concluded that the SSF could tolerate pelleting temperatures. These results correspond with those observed at the Instituto Nacional de Tecnologia Agropecuaria (Argentina), in which Schang (Personal Communication) conducted a trial with broilers fed reformulated (75 kcal/kg, 0.1 percent Ca and 0.1 percent P) pelleted diets supplemented with SSF and confirmed the thermostability of SSF at up to 90 C.

The use of SSF has been shown to improve profitability in layer diets, both through improved performance, when added to low-density diets, and by maintaining performance in lower cost reformulated diets. In Asia, a layer trial conducted by Ji Cheng et al. (2005) demonstrated that SSF maintained performance in a corn-soy diet despite the removal of 100 kcal/kg from the diet. Egg quality (shell strength and thickness, Haugh units, egg yolk color and weight) was also maintained.

To revalidate the use of SSF under Latin America conditions, several trials were conducted to evaluate the effects of the enzymatic complex SSF for layers at the Universidade Federal de Pelotas poultry facilities. In the first experiment, a corn-soy-meat and bone meal diet was fed with performance and egg quality examined from 57 to 73 weeks (Nunes et al., 2007). In the second and third investigations, a corn-soy diet was offered from 26 to 42 weeks (Gentilini et al., 2007), and from 40 to 60 weeks of age to hens (Dallmann et al., 2006). In all trials, it was concluded that the use of this complex resulted in an energy release from 60 to 90 kcal ME/kg from the feed ingredients, without affecting the layer performance. Actually, a tendency to improve performance and maintain egg internal quality was observed. External egg quality numerically improved with the reformulated diets. In a similar study, 70 to 78 weeks of age hens were divided into light and heavy birds and fed corn-soy diets with or without addition of SSF. The addition of SSF improved the egg internal quality parameters, mainly the albumen height (Rossi et al., 2007).

Table 2: Effect of SSF supplementation on the performance of finisher pigs.

Improved gain in swine

SSF can be added on the top of existing diet or reformulated by reducing both the available phosphorus and calcium total diet content by 0.1 percent and DE content by 18 kcal/kg in corn-soy diets. In a grower pig study conducted at China Agricultural University (Qiang and Wang, 2004) SSF was added to a wheat soy diet formulated with 90 kcal of DE less per kg and 0.15 percent less available phosphorus. Feed conversion ratio and average daily gain were improved in the SSF supplemented diet.

A commercial trial was set up to examine the effect of SSF and a phytase enzyme on growing and fattening pigs, as presented in Table 2. Pigs fed SSF showed daily weight gain (27g). Carcasses for the SSF group were 5.0 kg heavier than those from the other enzyme-fed group. This difference may be attributed to increased energy availability from SSF-supplemented diet (Taylor-Pickard and Suess, 2007).

Feed is the major cost of production for swine and poultry, so it is essential to minimize its cost. The use of the solid state fermentation technology allows for a more flexible approach to feed formulation through the inclusion of fibrous by-products or by reducing nutrient constraints in the diet, particularly energy, calcium and available phosphorus. It has also been shown to remain effective over a wide range of feed processing conditions.

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