Investigating the effect of β-mannanase enzyme feed additive on broiler performance.

World’s population is growing faster than the production of food to meet its needs. It is therefore necessary to improve the effective use of available food resources. One way to achieve this is to improve digestibility and assimilation of foodstuffs, through the use of enzymes as feed additives in the production of animal feed.
Currently four enzyme types are established on the market and proven their significance in animal nutrition:

• The enzyme xylanase has proven its effectiveness in wheat, rye and triticale based rations that are known to contain large amounts of non-starch polysaccharides, mainly arabinoxylans in endosperm cell walls. The latter are not assimilated by monogastric animals, but is hydrolysed by microbial xylanase and made available for pigs and poultry, which do not produce this enzyme.

• Another enzyme widely used in the feed industry is β-glucanase – it is particularly useful in barley and oats based rations that contain significant amounts of glucans – a substance that is known to decrease nutrient assimilation in addition to increasing fecal water content, deteriorate bedding quality and cause the formation of breast blisters and pododermatitis in poultry.

• Phytase is the third type enzyme widely used in feed formulation – It acts on phytic acid and releases inorganic phosphorous. Phytase is added to the rations of pigs and poultry in order to improve the animals` phosphorous utilization rate. Phytates in their different forms take up 50 to 80% of the phosphorous in different feedstuffs. The phytase enzyme degrades phytates – complexes of phosphorous, calcium, amino acids and microelements and releases phosphorous, that otherwise remains unassimilated by simple stomach animals, such as pigs and poultry.

• Mannanase is another type of enzyme that applied to rations based on corn and soybean meal or other legumes has demonstrated an unexpected effect in terms of reducing feed consumption per unit gain and increase in animal growth.

In compound feed based on barley or oats, the β-glucan contents, and in rations based on wheat, rye or triticale, the arabinoxylan contents, the anti-nutritional polymers represent a large portion of the grain`s endosperm. By contrast in conventional fodders – based on corn and soybean meal, the mannans contents is negligible. The main source of galactomannans in a typical corn-soybean meal feed is the soybean meal with amounts around 1.3%. A ration with 30% soybean meal shows only about 0.4% mannan polymers. The additional energy that is released from the full utilization of this insignificant share of the ration cannot explain the significant improvement of livestock performance indicators as observed by Fodge W. et al., 2008.

This can be explained through the difference in the mechanism of the enzyme compared to other enzymes. While they release energy from the feed, β-mannanase is an energy saving enzyme. The innate immune system of the animals detects and perceives β-mannans as a pathogen, due to the similar molecular pattern. This entails an immune response, consuming energy and nutrients. It is a known fact that even in small amounts β-mannans can trigger an immune response. Consequently, a part of the energy for growth is used for the immune response, reducing nutrient absorption and decreasing insulin secretion. These events can consume about 3 – 5% of the total metabolic energy of the feed. β- mannanase degrades β-mannans in the feed and minimizes this immune response, while the saved energy is redirected for growth and productivity. Therefore, the principal mode of action of β-mannanase is to reduce the immune response through reducing the β-mannan content in the feed. (Stahl, P. and Ezekowitz, R.,1998,Klasing, K., 2007).

According to Dierick (1989) and ChemGen Corp. the content of β-mannans in different feed materials in percentage of dry matter is as follows:

In typical compound feed for broiler, the β-mannans content is in the range of 0.3 – 0.5%.

Low metablolizable energy compound feeds are used in many parts of the world. In these countries, they do not add fat during the production of animal feed. Consequently, there is a need for increasing the efficiency of energy in low-energy rations. At the same time, in developed or developing countries the added fat is excluded due to health concerns. In addition, there are numerous problems associated with the addition of fat to increase the metabolizable energy in feed, such as cardiac dysfunction and / or ascites in broiler chickens, influencing meat and eggs taste. Therefore, the possibility to reduce the use of fat without sacrificing animal productivity is of common interest.
In addition, the use of high-energy compound feeds with increased fat content, to facilitate growth in poultry is not always feasible or desirable due to the high cost of fat and vegetable oils, or the limited quantities available in some densely populated regions of the world such as China and India.
US patent number 5.429.828, Hemicell^® includes a method for improving the energy efficiency of compound feed rich in hemicellulose by the addition of hemicellulase enzymes and especially β- mannanase.
Hemicell^® is a fermentation product from Bacillus lientus – genetically modified microorganism strains and is the first product registered based on β-mannanase. It contains large amounts of β-mannanase that digests the β-mannan in feeds and side activities such as α-amylase 65 – 95 U/kg, β-glucanase 32 – 55 U/kg, xylanase 2 – 10 U/kg and cellulase 2 – 10 U/kg.

It was established that Hemicell^® improved significantly the energy assimilation from 80 to 150 kcal/kg feed, protein digestibility from 2 to 2.5% and raw fiber digestibility from 5 to 10%.
A good example of the effect of Hemicell^® on productive performance of broiler chickens provide the data from the eight field tests, the results of which are shown in the following table:

Field-tests results with Hemicell^® on broiler chickens -ChemGen Corp., 2008

In 2002, the ChemGen corporation, the manufacturer of Hemicell^®, conducted a series of experiments aimed to investigate the enzyme`s effect on a control of coccidiosis in broiler chickens. The first experiment tested five different variants, where a part of the test animals at 7 days of age were orally infected with 70 000 oocysts of E. acervulina and 1 250 oocysts of E. maxima, in addition at 11, 12 and 13 days these birds were infected with a culture of C. perfringens. Some of the groups were subsequently treated with β-mannanasse, others with salinomycin and bacitracin. Best results in terms of growth, feed conversion and survivability were observed in the group treated with salinomycin and bacitracin, followed by β-mannanasse. It is important to emphasize that under the influence of β-mannanase was achieved 11% higher growth rate, 10% better feed conversion and a six-point decrease in mortality as compared to the untreated group.

The second experiment studied the effect of β-mannanase application to uninfected and infected birds with the same microbial cultures and strains, untreated and treated with medications, while each variant was compared with and without the addition of β-mannanase. The obtained results with the enzyme are not unidirectional. In the infected but untreated chicks, a noticeable effect of the enzyme is achieved. In two of the infected and medication treated groups there was no effect of the addition of β-mannanase, while in one group there is an effect on the live weight at 21 day and feed utilization.

In broiler chicks administered with Coccivac B vaccine, two of the groups received β-mannanase, while the other two did not. At 18-th day of age the number of oocysts in the feces of chickens that received β- mannanase was between 0 – 6 250 number per gram, while in the control these numbers are from 16 326 to 29 851 numbers per gram.

After infecting three groups of 8 day old chickens with 75 000 oocysts of E. acervulina and 5 000 oocysts of E. maxima per bird, in addition at 11, 12 and 13 days these birds were infected with a culture of C. perfringеns 108 CFU. The first group was not treated, the second group was treated only with β- mannanase and the third group was treated only with medications. For the period from 8 to 21 days, the growth was respectively 258.1g, 324.4g and 345.6g, the feed conversion ratio was 2.44, 2.036 and 1.866, while mortality was 42.71%, 20.83% and 5.21%. The data shows a very good therapeutic effect of the medication used, however the very good influence of β-mannanase should not be neglected - β- mannanase facilitated 25% better growth, FCR improved by 17% and the mortality rate has decreased by 50% compared to the negative control group with the untreated birds.

In 2015, Khaksarzareha and Hashemipour tested the effect of VemoZyme^® M, an enzyme feed additive produced by VEMO 99 Ltd, Bulgaria with main active ingredient β-mannanase and the related side activities of xylanase, β-glucanase, cellulase, amylase, etc. The experiment was conducted with 250 male day-old broiler chickens of the Ross 308 breed and lasted six weeks. The positive control group received combined feed in accordance with the recommendations for the breed. The birds from the negative control group were fed with compound feed with 5% decreased metabolizable energy, compared to the positive control. The experimental group chickens received the same compound feed as the negative control with the addition of VemoZyme® M. The obtained results show that the addition of VemoZyme^® M to combined feed with reduced metabolizable energy helps achieve end live weight, mean daily gain and feed conversion ratio comparable to the productivity parameters of the positive control group and confirm the effect of the application of Hemicell^®.

A review of the available literature concerning the application of the enzyme β-mannanase to compound feed for broilers provides grounds to summarize the effects of using the following guidelines:

• Saves about 3 – 5% of the feed`s metabolic energy through degradation of β-mannan contained in soybean meal and legume feedstuffs by reducing the immune response of birds and energy spent on its course
• Shows a positive impact on control coccidiosis in poultry
• Helps improve intestinal tract stability
• Stimulates the immune system in young birds
• Provides for uniformity in the bird flock
• Reduces fecal water content and thereby improves litter quality
• Reduces the cases of pododermatitis
• It is compliant with other enzymes and / or feed additives