Disease resistance and immune responsiveness have been traits generally ignored by animal breeders. Recent advances in immunology and molecular biology have opened new avenues towards our understanding of genetic control of these traits. The major histocompatibility gene complex (MHC) appears to play a central role in all immune functions and disease resistance. The need to understand the relationship between immune responsiveness, disease resistance and production traits is discussed in this review. Antagonistic relationships might prevent simultaneous improvement of all of these traits by conventional breeding methods. It is suggested that genetic engineering methods may allow the simultaneous improvement of disease resistance and production traits in domestic animals. Genes of the MHC will be especially good candidates for genetic engineering experiments to improve domestic species.

The rendering industry collects and safely processes approximately 25 million t of animal byproducts each year in the United States. Rendering plants process a variety of raw materials from food animal production, principally offal from slaughterhouses, but include whole animals that die on farms or in transit and other materials such as bone, feathers, and blood. By recycling these byproducts into various protein, fat, and mineral products, including meat and bone meal, hydrolyzed feather meal, blood meal, and various types of animal fats and greases, the sustainability of food animal production is greatly enhanced. The rendering industry is conscious of its role in the prevention of disease and microbiological control and providing safe feed ingredients for livestock, poultry, aquaculture, and pets. The processing of otherwise low-value OM from the livestock production and meat processing industries through rendering drastically reduces the amount of waste. If not rendered, biological materials would be deposited in landfills, burned, buried, or inappropriately dumped with large amounts of carbon dioxide, ammonia, and other compounds polluting air and water. The majority of rendered protein products are used as animal feed. Rendered products are especially valuable to the livestock and pet food industries because of their high protein content, digestible AA levels (especially lysine), mineral availability (especially calcium and phosphorous), and relatively low cost in relation to their nutrient value. The use of these reclaimed and recycled materials in pet food is a much more sustainable model than using human food for pets.

-One third to one half of each animal produced for meat, milk, eggs, and fiber is not consumed by humans. These raw materials are subjected to rendering processes resulting in many useful products. Meat and bone meal, meat meal, poultry meal, hydrolyzed feather meal, blood meal, fish meal, and animal fats are the primary products resulting from the rendering process. The most important and valuable use for these animal by-products is as feed ingredients for livestock, poultry, aquaculture, and companion animals. There are volumes of scientific references validating the nutritional qualities of these products, and there are no scientific reasons for altering the practice of feeding rendered products to animals. Government agencies regulate the processing of food and feed, and the rendering industry is scrutinized often. In addition, industry programs include good manufacturing practices, HACCP, Codes of Practice, and third-party certification. The rendering industry clearly understands its role in the safe and nutritious production of animal feed ingredients and has done it very effectively for over 100 years. The availability of rendered products for animal feeds in the future depends on regulation and the market. Regulatory agencies will determine whether certain raw materials can be used for animal feed. The National Renderers Association (NRA) supports the use of science as the basis for regulation while aesthetics, product specifications, and quality differences should be left to the market place. Without the rendering industry, the accumulation of unprocessed animal by-products would impede the meat industries and pose a serious potential hazard to animal and human health.Key Words: feed, ingredients, manufacturing practices, rendering North American Rendering -processamento de proteínas e gorduras de alta qualidade para alimentos para animais RESUMO -De um terço a metade da produção animal para carne, leite, ovos e fibra, não são consumidos pelos seres humanos. Estes materiais não consumidos são sujeitos a processamento em graxarias e indústrias de alimentos de origem animal, resultando em uma série de produtos úteis. Entre estes produtos incluem-se farinha de carne e ossos, farinha de carne, farinha de co-produtos de abatedouros de aves, farinha hidrolisada de penas, farinha de sangue, farinha de peixe, e gorduras animais são os produtos primários resultantes dos processos de graxarias. O mais importante e valoroso uso para estes co-produtos de origem animal é a utilização como ingredientes alimentares para compor dietas e rações para bovinos, suínos, aves, peixes e animais de companhia. Há numerosas referências científicas validando as qualidades nutricionais destes produtos, e não há razões científicas para alterar a prática de uso destes co-produtos para os animais. As agências governamentais regulam o processamento de alimentos tanto para animais como para humanos, e a indústria de alimentos de origem animal é monitorada frequentemente. Além disso, os programas destas indústrias adotam as boa...

As part of the Pork Chain Quality Audit, pork manufacturing companies were surveyed to identify and quantify factors influencing pork quality. Surveys were designed to evaluate the quality of pork at the slaughter and fabrication segments of the chain. Meat firms provided information based on 57% of the 88 million barrows and gilts slaughtered in federally inspected plants in 1992. All major hog‐producing areas of the U.S. were represented. Results of the survey indicated that the primary concerns about the quality of pork at the packing level were: (1) excessive fat; (2) inadequate muscle‐color/water‐holding‐capacity; (3) inconsistent live weights; (4) too many abscesses; and (5) excessive bruising. The results of the survey were used to determine costs associated with quality deficiencies. It was determined that $10.10 or approximately 10% of the live‐animal value is lost per slaughter barrow/gilt due to quality nonconformities.

Rendering recycles animal and poultry by‐products such as fat, bones, hide, offal, feathers, hoofs, horns, hair, and blood. The by‐products represent from 37% to 50% of the live weight of the various meat animals and as much as 57% of the live weight of many fish species. The current annual global production of meat and poultry is 325 million metric tons (MMT), and the resulting raw material for rendering would be 217 MMT per year if rendering was used everywhere. Rendered proteins and fats compete on the world commodity market with plant‐based products. Rendered protein products are primarily used in food for poultry, pigs, ruminants, pets, and fish. Fat products are used for animal food, oleochemicals, and biofuels. Rendering meat by‐products into animal food ingredients improves the sustainability of both the meat production industry and the users of the by‐products. Composting or anaerobic digestion of these by‐products is less environmentally impactful than landfills but results in more GHG production than feed ingredient use. Reducing food waste will improve global sustainability when otherwise wasted animal by‐products are put to the highest value use. The future of rendering will depend on the industry adapting to the ever‐changing environmental, social, health, and sustainability challenges.