INDUSTRIAL USE OF ANIMAL BY-PRODUCTS

INTRODUCTION

The terms by-products and coproducts as they relate to animal production are often used interchangeably. The need to debate, which is most appropriate or descriptive, is not extremely important, except to draw attention to one fact. By-product is defined as a secondary product obtained during the manufacture of a principal commodity. Co-product possesses the meaning of being together or joined. Thus, the important facts for the animal production and processing industries are the utilization and opportunities that exist for the by-products that are produced ancillary to the production of meat, milk, and eggs for human food consumption.
The actual value of animal by-products in comparison to the food components has not been determined in composite, nor have published economic projections for the alternative uses for animal derived tissues, when used as biological and industrial products, been made available. But as one reviews the array of significant products that are derived from animal production and the technical opportunities that exist, one acquires a greater appreciation for their contributions to society.

BIOLOGICALS

Thymus

Serum, vaccines, antigens, and antitoxins are derived from many food-animal tissues acquired both during the slaughter and processing of and by primary extraction from hyperimmunized animals. The true biologicals serve as preventive and treatment regimes in both humans and animals and are primarily derived from blood. Other animal tissues have been primary for the replication of cell-culture vaccines. Biotechnology continues to alter vaccine production processes, but animal by-products and their extractions are still important components. Purified animal blood is fractionated into many vital end products for numerous medical applications.
Examples include thrombin, which is used for blood coagulation agents and skin graft procedures, fibrin used in surgical repair of internal organs, and fibrinolysin, an enzyme used to assist digestive and vaginal infections, as well as for wound cleaning agents. Biological applications extend into uses for numerous pharmaceuticals, neutraceuticals, nutritional supplements, glandular extracts, and enzymes. Tissue implants, hormones, organs, glands, and tissue meats are considered to possess specific custom or health benefits. Other than heart, tongue, liver, kidney, pancreas/thymus (sweetbread), brain, stomach (tripe), and intestines that are used as food, all other noncarcass material, though edible biologically, is generally referenced as by-product tissue.

GLANDULAR EXTRACTS, HORMONES, AND ENZYMES

Glandular extracts, hormones, and enzyme collections are specific to the species, age, and sex of respective animals. Major products such as pepsin, rennin and other digestive enzymes, lipase and trypsin enzymes extracted from the pancreas, bile from the liver, adrenocortical steroids from the adrenal glands, and female reproductive hormones from the ovary are all medically significant products. Though insulin has been referenced as one of the prime pharmaceutical products derived from animal by-products, it is now synthesized by other procedures. This is true  for a number of other pharmaceuticals, but reliance on the natural production and extraction is still an important source of medical treatment and prevention compounds.

IMPLANTS AND GRAFTING

Tissue transplants and grafting with animal tissues are routine human treatment regimes. Of particular note are the use of skins for initial treatment of burn patients and arteries, heart values, bone cartilage, and bone fragments, which are used as substitutes for diseased or damaged human tissue parts. In many of these treatment areas, there are no synthetic products that function or perform equally well. Historically, animal by-products have been used for these pharmaceutical and biological medical treatments for centuries. Rather crude applications based primarily on folklore preceded the extensive medical research and technology that guided their use in more modern times.
The biological properties of the component tissues and their extracts of animal by-products have provided the scientific basis for the development of synthetic substitutes. Many of the animal by-products are still indispensable as treatment regimes and research assets for the development of new and improved applications. A significant market has accompanied the biotechnical age in research work related to cell media, bioactive peptides, immunochemicals, molecular biology, tissue culture media, and reagents.

NEUTRACEUTICALS

Bovine Trachea

Much has been referenced recently regarding various neutraceutical effects from a variety of foodstuffs that include those derived from animal by-products. A neutraceutical is vaguely defined. Though not defined as a specific required nutrient, the effects of identified compounds in specific tissues and their alleged benefit to certain health conditions is an expanding market. The majority of the neutraceuticals do not possess FDA approval for specific indications, but are marketed over the counter as nutritional supplements. Though the health food shelves are laden with products for nearly all ailments, an exemplary example of the product types are glucosamine hydrochloride and chondroitin sulfate.
The supplements are labeled as an aid to the promotion of healthy cartilage and joint support. These supplements are extracts from animal by-product cartilage such as bovine trachea. There are numerous such supplements extracted or processed from animal by-products and made available for domestic and international markets. The Asian market has traditionally used and continues to expand its usage of nutritional supplements.

GELATIN

Gelatins obtained from both inedible and edible tissues are water-soluble protein derived from collagen extracted from animal connective tissues such as bone, cartilage, skin, and tendons. A variety of uses have been made of the various grades and types of gelatin. These include the primary use as food from edible processes and glue from inedible processes. Other significant uses are photographic film, adhesives, and gelatin coatings for pharmaceutical products. To dispel past beliefs, the only protein tissue that can yield gelatin or animal glue is collagen. Therefore, animal parts such as horns, hair, and hooves, which are composed of distinctly different proteins, cannot be used to make gelatin.

HIDES, SKIN, AND WOOL/HAIR

Bovine Hide

The largest component, based on value and volume, of animal by-products derived from the slaughter of food animals is the hide, in particular the hides derived from cattle. The skin of virtually every animal can be used to produce leather. Animal skins have been the source of clothing attire for man since historical times. Leather is used in a remarkable number of applications, including automobile and furniture upholstery, shoes, sporting goods, luggage, garments, gloves, and purses. A representative of the leather industry categorized leather utilization as 40% for upholstery, 50% for shoes and shoe leather, and 10% for other uses. Leather garments are again increasing in vogue around the world.
A very high percentage of hides, especially from cattle, produced in the United States are currently exported to China and Korea and, in lesser volume, to Mexico. Pork skins are likewise a popular tissue used for garments and footwear, as are other skins from a number of minor species. Similarly, wool and hair have multiple uses based on their fiber properties. These qualities guide their usage into fabric, building insulation, and absorptive products. Synthetically derived products have challenged hide, skins, wool, and hair in nearly all of their traditional uses and will undoubtedly continue to do so in the future.

INDUSTRIAL USE

Tallow

Certain animal by-products have found complementary outlets in many industrial niche markets, but with the exception of tallow and other species fat, animal byproduct protein factions have been processed for their utilization as livestock, poultry, companion animal, and aquaculture feed ingredients. Tallow gained its prominence as an industrial ingredient for the soap, candle, cosmetic, and oleochemical industries. Animal fat utilization typically involves the production of lubricants, fatty acids, and glycerol. These fatty acids have primary industrial manufacturing uses for surfactants, soaps, plastics, resins, rubber, lubricants, and defoaming agents. Actual volume utilization for industrial uses of animal fats is not available.
Worldwide, all the animal fats represent approximately 15% of the total production of all fats and oils. Tallow and grease are important commodities, and when lard is added to the total volume, rendered meat fats constitute the third largest commodity after soybean oil and palm oil.[3] The United States produces in excess of 50% of the world’s tallow and grease. Tallow has been the primary animal fat for soap making, as lard and grease yield lower-quality soap. The USDA estimate of the current usage of tallow in producing soap is now less than 6% of domestic production, compared to 72% in 1950 and 27% in 1965. Thus, the usage in soap is still an important volume, but its use as feed ingredients both domestically and as a product for export now commands its largest utilization.

BIOENERGY USES

Renewable and recyclable sourced fuels are now recognized as being an important part of U.S. as well as global energy plans. As such, fats, oils, and recycled greases are feedstocks now used as biofuels. Biodiesel is defined as a monoalkyl ester of long-chain fatty acids that are derived from animal fats, vegetable oils, and recycled cooking oils/restaurant grease. Production by the reaction of a fat or oil with an alcohol in the presence of a catalyst results in an alternative or additive fuel to petroleum diesel. The methyl esters produced by this same process are used in a broad area of industrial chemicals for use as solvents and cleaners.
The use of rendered animal fats as burner fuel resources that are alternatives to natural gas, #2 fuel oil, and #6 fuel oil has now evolved as a viable and often economical use of feedstocks for energy alternatives. Both the protein and fat fractions from rendered animal byproducts have potential for generation of captured energy. The lipid factions, however, have many more opportunities for use of this resource.

CONCLUSIONS

Animal by-products are the direct result of the production and processing of animals for food. Providing meat, milk, and eggs for the global table results in the ancillary production of inedible by-products. The total volume of such by-products approximates the total volume of edible meat when these animals are processed. This volume is increasing annually as the trend for more table-ready meat preparations increases. The utilization and the exploration for new utilizations as biological, industrial, and other value-added products must remain a priority in concert with the most economical, environmentally friendly, biosecure, and ecologically appropriate production of animal-derived foods.

By Gary G. Pearl (Fats and Proteins Research Foundation, Inc., Bloomington, Illinois, U.S.A.) in the book "Encyclopedia of Animal Science", edited by Wilson G. Pond & Alan W. Bell, published by Marcel Dekker, New York, 2005, excerpts from pages 19 to 21. Adapted and illustrated to be posted by Leopoldo Costa.