Enzymes for feed

Animal feed

Global meat consumption is estimated at 285 million tons, and is expected to increase to over 400 million tons by 2030. Highest growth worldwide is expected in poultry production followed by pork production. This was echoed in a presentation by Dr. Henning Steinfeld from the U.N. F.A.O. at the World Pork Conference, who predicted between 70 and 80 per cent more meat would be needed to feed the world population in 2050 (http://www.thepigsite.com/articles/3664/meeting-global-demand-for-more-meat). Again, most of the growth in meat consumption and production is predicted to come from monogastric animals, chickens and hogs. In the United States, per capita meat consumption is 51 lbs. of pork and 83.6 lbs. of chicken. Growth of pork and chicken consumption is predicted to continue to increase by the USDA, while beef consumption is expected to drop.  A huge meat-production industry is needed to meet this demand; currently there are over 60 million hogs and 8.6 billion broilers in the U.S. production system.  The major cost of producing meat is the cost of feed for the animals.   Traditionally, corn and soybeans have been used to feed hogs and chickens. The recent rise in corn and soy prices has had a significant impact on the profitability of production of hogs and broilers.

The rising cost of soy and corn has led to the use of other energy and protein sources in both hog and chicken feeds. A wide variety of materials can be utilized as energy feeds including barley, flax, oats, oat bran, rye, sorghum, triticale, and wheat.  A problem common to many of these energy sources is the high level of soluble fiber present in the materials; this soluble fiber is primarily composed of xylan and beta-glucan. Xylan is a complex polymer with a beta- (1,4) xylose backbone that can be substituted with a number of sugars including arabinose and alpha-glucuronic acid. The beta-glucan content in whole grain oats ranges from 2 to 8% of dry weight; the beta-glucan content of oat bran concentrate is higher, between 15 and 35% of dry weight. Other grains, especially barley, also possess significant amounts of beta-glucan (Figure 1).

Figure 1

beta-glucan graph

Present in a number of grains, β-glucan is a homopolymer of glucose with predominantly β-1,4 linkages interspersed with β-1,3 linkages. The molecular weight of barley β-glucan has been reported as 175,000 daltons and 250,000 daltons. The molecular weight of oat β-glucan has been reported to be much higher, with molecular weights of soluble and insoluble forms at 1,100,000 and 1,600,000 daltons, though another report gives a value of 88,000. Cellotriose and cellotetraose units make up approximately 90% of the β-glucan in barley flour; these cellotriose and cellotetraose units are linked to each other by a single β-1,3-linkage.  The anti nutritive effects of β-glucan appear related to the same properties that have gained β-glucan interest over its ability to improve glucose and insulin regulation and to lower blood cholesterol levels. Pigs fed diets high in fiber had higher maintenance energy requirements due the nutrient needs for increased viscera. Fiber was not degraded by the pig in the small intestine, but partially digested in the large intestine by microbes, resulting in increased formation of volatile fatty acids.

The use of enzymes in improving non-ruminant nutrition has been recently reviewed, showing the benefits of enzyme supplementation under certain conditions.  Addition of xylanase to wheat-based diet for chickens resulted in improved feed utilization, however addition of xylanase, phytase and protease had little or negative effects when chickens were fed a corn-based diet.  Similarly, addition of commercial enzymes did not decrease the amount and stickiness of the manure produced or improve Foot Pad Dermatitis in chickens fed a corn-soy feed.  The use of enzymes in improving pig nutrition has also been recently reviewed, and a number of benefits have been observed with enzyme supplementation. Addition of enzymes to feed results in improved utilization of nutrients as well as improving the gut microbiota of pigs.   In addition to improving nutrition, addition of xylanase to pig diets results in lower odor from volatile fatty acids in manure and lower ammonia emissions.

Xylan contains a backbone of  β-1,4 linked xylose residues.  Depending on the source, the backbone can be substituted with α-1,2 linked glucuronic acid (glucuronoxylan, GX), α-1,2 and  α-1,3 linked arabinose (arabinoxylan, AX) or α-1,2 linked glucuronic acid and  α-1,3 linked arabinose (glucuronoarabinoxylan, GAX) (Figure 2).  Additional substitutions such as acetyl and methyl groups can be present, and the material can be crosslinked to components of lignin such as ferrulic acid.  Xylanases (technically endoxylanases) cleave β-1,4 xylose linkages in the backbone.  β-xylosidases cleave xylose from the nonreducing end of the xylan chain.  α-Glucuronidases cleave the α-1,2 linked glucuronic acid from the backbone and α-arabinosidases (arabinofuranosidases) cleave the α-1,2 and  α-1,3 linked arabinose from the backbone.

Figure 2  

Xylan

 

 C5-6 supplies a complete set of xylan-degrading activities to advance your research.  Xylanases from C. thermocellumD. turgidum, and Geobacillus sp. all possess the stability to withstand the high temperatures encountered in feed production.   All these enzymes can be easily scaled-up for pilot and production testing. 

Enzymes for mixed-linkage glucan (β-glucan) degradation

β-Glucanases cleave either β-1,4 linkages in mixed-linkage glucans containing  β-1,4 and β-1,3 linkages.  β-Glucanases cleave β-1,4 linkages in mixed-linkage glucans but not in crystalline cellulose, while endocellulases β-1,4 linkages in mixed-linkage glucans and crystalline cellulose.   (This also explains why both cellulase and β-glucanase activities are measured using β-glucan as substrate.)  β-Glucanases cannot cleave the β-1,3 linkages in mixed-linkage glucans, these can only be cleaved by curdlanases or lichenases (Figure 3).

Figure 3  

GLucan

 C5-6 supplies a complete set of mixed-linkage glucan-degrading activities to advance your research. β-glucanases and endocellulases from C. thermocellumD. turgidum, A. cellulolyticus, and Geobacillus sp. all possess the stability to withstand the high temperatures encountered in feed production.   All these enzymes can be easily scaled-up for pilot and production testing. Other β-glucanases, endocellulases, and curdlanases are available from a diverse range of organisms including B. cellulosilyticus, F. succinogenes, and T. reesei.  β-glucosidases are available from all these organisms, allowing you to match activity profiles of endo-activities and exo-activities.