Sunday, 20 October 2019



The two main classes of enzymes used in animal nutrition are non-starch polysaccharide degrading enzymes (NSPases) and phytases, with significant but lesser use of amylases and proteases. Phytases, for example, are almost ubiquitous in the diets of non-ruminant product species. although Sumner was yet to describe the true nature of an enzyme, the use of additive enzymes in poultry feeding was first suggested in the mid-1920s. In 1925 1], described the use of Protozyme, an enzyme which he suggested had multiple amylolytic and proteolytic activities, which improved leghorn performance. In 926, the same year as Sumner published his work on the nature of enzymes, Lickner and Follwell described Protozyme as having multiple activities, with the major activity appearing to be that an amylase with a broad pH optimum.

The early development of xylanases for animal feeding is described in Masey t al. and readers are directed there. In short, by the 1950s and 1960s, the area f enzymes in animal nutrition had become a hot topic. Teams in the United States showed that adding an amylolytic enzyme preparation to barley-based broiler diets could reduce sticky droppings and improve growth. It was not until the late 1960s that the specific activities and substrates were described. Bell and Burnett attributed the effect of an amylolytic product to a contaminating side activity—endo-β-glucanase—which shortened soluble glucan chains, resulting in reductions in viscosity and improved nutrient digestibility. Association of a response from an enzyme preparation to the wrong activity is an issue even today, despite the use of recombinant “mono-component” enzymes. Even relatively mall amounts of a contaminating activity may be responsible in part or in total or the response observed, and unfortunately, journals are ineffective in demanding wide-ranging analysis of all potential activities in a product claiming to be single activity.

The first commercial application of feed enzymes was in Finland in 1984 hen a feed company took advantage of the fact that it happened to have a sister company that produced β-glucanases for use in the brewing industry. The application of the β-glucanases in diets based principally on barley was very successful, reducing viscous droppings which resulted in far drier litter and better animal performance, but it still took 5 years for this practice to expand outwards to other U countries. Concurrently, work showed the negative effects of rye on the digestibility of various nutrients and animal performance. This was attributed, similarly, to the viscosity induced by soluble pentosans and as such attenuated by the specific use of Pentosanases for broilers and pigs. Australian work later that showed the negative effects of adding extracted pentosans from wheat to broiler diets could be overcome by the inclusion of a Pentosanase, subsequently improving apparent metabolizable energy and nutrient digestibilities.

Expanding on the successful use of β-glucanases in barley-based rations, the feed enzyme industry which had consolidated in Northern Europe as a result of the use f barley in these regions, turned its focus to wheat and xylanases to address similar, albeit lesser, viscosity problems of poor performance and litter quality. It was fortunate for the emergent European feed enzyme industry that the varieties of heat endemic at the time tended to be relatively high viscosity, hence the problems were quite apparent and easily seen to be solved. The almost miraculous uring of wet litter was probably the biggest selling point of these enzymes at this point in time.

In the late 1990s and early 2000s, the use of NSPases became more and more common and work began to understand the mechanism of action in animals and also to further develop the products themselves. The viscosity effect was well understood and it was certainly clear that a diet containing high levels of soluble SP reduced performance and this was ameliorated with the use of space. he functions of NSP in cereal grains are in the formation and integrity of the cell wall. It follows that they are implicated in encapsulating the nutrients within the cell. In a cereal endosperm cell, this is starch and protein. As such, since animals o does not possess any NSPase activity, there is potential for nutrients to be completely inaccessible without exogenous enzymes. Thus, the “cell-wall” theory s conceivable. In fact, using microscopy, it has been shown that cereal cell walls appear to be broken during the digestive process when NSPases are included in the animal’s diet. However, in order to mimic this effect in vitro, the dose of SPase required to affect cell wall rupture is in vast excess to that used commercially. Moreover, the conditions needed during the in vitro process are quite different from those the enzyme would encounter during the digestive process. Taking his into consideration, and the fact that NSPases continue to be effective despite the fact that through cereal breeding, cereals are far less viscous than they are once ere, there must also be other mechanisms to explain their efficacy. More recently, the concept of space acting as a pseudo or pre-prebiotic has been proposed. This centers on the value of the product of enzyme activity rather than solely the benefit of removing a substrate. For example, when arabinoxylan, a complex xylose and arabinose polysaccharide found in cereal cell walls, is broken down by the action of xylanase, short xylooligosaccharides are produced.

These oligosaccharides are known to exhibit many of the characteristics of the classic prebiotic, namely that they are not digestible by animal’s endogenous enzymes, not directly absorbed, and most importantly, will promote the growth of considered as beneficial species of bacteria, such as bifidobacteria and lactobacilli. This clearly has benefits in terms of the promotion of host gut health.



Whereas most enzymes used in the feed industry have been leveraged from other industrial platform uses, be it food, textiles or industrial use, phytase stands alone n that it was developed exclusively for the animal feed industry. Phytase degrades phytic acid, or inositol hexaphosphate, to inositol monophosphate and in the process releases five phosphate moieties. In the form of phytic acid, the phosphate is largely unavailable to the monogastric as it lacks sufficient phytase activity to enable consistent release. As a result, most monogastric animal feed has to e supplemented with inorganic phosphates to meet the requirements of the animal as there is insufficient available phosphorus, P, in the diet to satisfy their needs. Two elements of this problem contributed to the development of the phytase industry. The first was that this supplementation of inorganic phosphate resulted in n diets containing high levels of total P simply to meet the digestible P contents f the diet. The result is that the undigested P is excreted in the manure which ultimately adds to the phosphate loading of the land on which the manure was distributed. Such P loading became critical in the Netherlands in the early 1990s. his was due to the concentration of a significant poultry and pig industry in a relatively small landmass, which resulted in the accumulation of P in the soil over time with the threat of eutrophication of waterways increasing as a result.

Legislation was introduced which limited the amount of P that could be spread per hectare of land, which in effect forced the industry to consider reducing the population of animals by 25%?30% (which was economically inviable for many producers) or consider a technological solution to enhance the availability of the available phosphate from phytic acid. Thus, the phytase industry was born, albeit in a limited way in that its use was restricted to geographies where the penalty for P pollution drove the economics for inclusion, which for several years restricted use to the Netherlands and some parts of northern Germany. In the mid o, the late 1990s the Delmarva area in the United States also started using phytase as the art of a P pollution abatement program. If it were not for the penalties for excess manure P the use of phytase was not economical and thus its use was limited.

Up until the late 1990s, phytase was a relatively minor player in the feed enzyme industry but this changed with the development of the second problem noted in the previous paragraph, namely that of supply of inorganic phosphate. P is the third most expensive nutrient in monogastric feeds and the cost of the phosphates was subject to global supply and demand. The vast majority of rock phosphate is used in fertilizer manufacture with approximately 3% being used in animal feed. This source is finite and supply and demand were such that prices started to increase at the same time that prices of the phytase fell, resulting in the enzyme costing in too many diets and thus usage increased. At the outset, there was only one supplier of phytase on the market which was derived from Aspergillus niger, ut, as it grew a second product derived from Peniophora Lycii entered the market and competition, drove prices down further. Nevertheless, the costs per tonne treated were still five to ten times what they are today. In the mid-2000s several Escherichia coli variants entered the market and today there are additional products derived from Citrobacter, Yersinia, Hafnia, Butiauxella, and further evolved E. coli products.

These newer phytases are more biologically effective per molecule and hence much more cost-efficient, resulting in the use of higher dosages at much ower inclusion costs. Whereas phytases were used originally to extract 30%?40% f the phytate phosphorus in a typical diet, they are commonly used today to extract 50%?75%. Moreover, the recent recognition that phytate (IP6) and it's ower esters (IP5,4,3) are antinutrients in their own right, has to lead to a completely different use of this enzyme in monogastric nutrition, namely phytate destruction or maximum animal growth efficiency. Usage rates, as a result, are increasing significantly, as much as two to four times the normal commercial usage for simple a and P release. Moreover, more widespread use in this new application has resulted in increased consequential benefits in animal products that were not overseen, for example, antioxidant status, semen quality, and shifts in the microbiome. The latest findings suggest that we have much to learn if we are to use this enzyme class optimally in sustainable animal production.



Amylase, or an amylolytic activity, was possibly the first documented enzyme sed in broiler feeding. Whether or not the amylolytic activity was the main benefit of the product is impossible to tell. There are currently several amylase products on the animal feed market, originating from Bacillus spp. They are com- only presented as part of a combination product. That is, they have produced an individual activity and blended with others produced elsewhere. It is generally understood that the production of amylase by the pancreas of animals is an extremely efficient process and does not limit the digestion of starch. However, there re circumstances where it is conceivable that this is not correct. For example, in the very young chick, while the gastrointestinal tract is still developing, it is likely hat amylase production and secretion are sub-optimal. Classen suggested that young turkeys and piglets may be most likely to need exogenous amylase. The act that products are often presented as combinations means that the true benefit f an amylase, when provided singularly, is difficult to ascertain from the literature. As these products were beginning to become established, Mahagna et al.
showed that an amylase-containing product gave a significant performance benefit to 7-day-old chicks, but not beyond that point. Around the same time, Stella et al. demonstrated that such products, containing amylase, improved leal starch, protein and fat digestibility in broilers. Recently, authors have demonstrated the benefit of a combination product containing three activities, over the Individual activities. In that case, of the single enzymes, only the xylanase ad an impact on 42d FCR but the combination of xylanase, amylase, and protease was better again. This implies that amylase (and indeed protease) work better n the presence of xylanase.



As the pressure in world protein supply increases, producers are looking to reduce protein in their diets. Proteases are gaining momentum as a category for this season, as they are seen as able to support reduced protein in the diet. Protease enzymes are usually derived from and produced using the expression in, Bacillus pp. Like amylase, protease is often used as part of a combination product and the efficacy of the singular enzyme is often difficult to assess in the literature.

A greater number of protease-specific products and literature do exist, but the evidence for their value is equivocal. Simbaya et al. demonstrated that protease had an impact on broiler Feed Conversion Ratio (FCR) in that responsive manner and that the effect may be dependent on the protein meal used in the diet. It has been suggested that protease is particularly effective in reduced-protein diets. However, Ding et al. did not find an interaction between protein content and protease, but increasing protease dose improved broiler feed conversion ratio and increased protein digestibility. Most recently, there has been more focus on investigating the varying properties of different classes of protease, which may impact performance in the animal. Strategies have been suggested to include protease and synthetic amino acids, to reduce crude protein in the diet.

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