The NRC - A Culmination of 54 Years of Swine Nutrition Research

Since 1944, the National Research Council (NRC) has published 9 editions of Nutrient Requirements of Swine. It has been a long time coming but the latest edition has finally arrived. The publication, prepared by the Sub-Committee on Swine Nutrition, replaces a 10-year-old document, the 1988 edition. The NRC launched the new publication via an international satellite symposium on April 14th -15th. The conference was attended by 673 participants in 21 locations across North America, seven of which were in Canada.

The Nutrient Requirements of Swine serves as a guideline to nutritionists and feed industry to aid in the development of feeding programs for swine. The NRC is a bible of sorts for the swine nutrition industry because it provides a set of standards, or benchmarks, that the entire industry can follow. Even though many feed companies have developed their own models for nutrient requirements, the NRC provides a basis to which all can measure and compare.

The authors of the new NRC are leaders in the field of swine nutrition, who came together from universities across North America to develop a compendium of current, up-to-date and accurate information about swine nutrition. Their challenge was to translate all of that information into nutrient requirements that would apply to all pigs under all situations. The process, which lasted three years, involved a thorough review of all swine nutrition research carried out since the last version was published and the interpretation of the results to recommend any changes to the requirements for each individual nutrient.

Ten years is a long time to wait for such an important publication in an industry that is changing as rapidly as the swine industry, but as the authors themselves will admit, this is not a static document. The publication stands only for a moment in time and will serve as the basis on which the research community can build for another committee's work 10 years from now.

The changes to the NRC are not vast and sweeping, but instead focus on a number of key areas, where research has proven that the requirements in the previous NRC were inadequate. In many cases there is conflicting information or a lack of information on which to base conclusions. As a result, there is still much that we do not know about pig nutrition. An important result of the background work that goes into the preparation of the NRC is that the committee identifies important areas of research that may be lacking and in need of attention in the future.

This version of the NRC has brought with it a change in philosophy. The nutrient requirements are no longer presented to the industry in tables that are set in stone. The single biggest change in this new NRC is the introduction of a computer program, which is included on CD-ROM. The program uses models to generate estimates of energy and amino acid requirements. With the program, nutritionists can estimate individual requirements for a specific pig at a particular stage of development - growing, gestation or lactation - using parameters specific to that situation. The computer program allows users to pose hypothetical situations by changing those parameters to reflect their individual conditions, e.g. adjusting lean growth curves, temperature and spacing.

Nutrient requirement tables, generated by the computer program, have been provided in the publication to serve as a reference. The tables list ranges of "typical" growing, gestating and lactating pigs similar to past versions. For growing pigs, the tables have been expanded to separate barrows and gilts at 50 - 120 kg to address split-sex feeding. This edition also features, for the first time, a separate table for sexually active boars, which are not included in the computer program.

Knowledge of the underlying principles and assumptions being used in the model is essential to understanding the nutrient requirements that are generated. This also applies to the use of the nutrient requirement tables supplied in the publication. Producers are encouraged to only use the program and tables in concert with a knowledgeable swine nutritionist. It is important to note that the NRC only estimates minimum nutrient requirements without safety allowances. They should NOT be considered recommended allowances. Nutritionists may choose to increase the levels of some of the more critical nutrients to include safety margins in some instances (except in the case of selenium).

When comparing the 1998 to the 1988 estimates, lysine requirements for growing and gestating pigs are generally higher as a result of improvements in genetics, health and environmental conditions. Lysine requirements for lactating sows have increased considerably from 1988 in response to research showing that lactating sows nursing large litters produce more milk and lose less maternal body weight when fed higher levels of lysine.

Some interesting changes can be noted in mineral and vitamin requirements. Chromium is now recognized as an essential trace mineral, although no exact estimate of requirement has been determined. As a result of new research findings, the sodium and chlorine requirements of the young pig were increased. The manganese requirement of the gestating and lactating sow were increased from 10 mg/kg to 20 mg/kg in response to research that showed that higher levels result in higher birth and litter weights.

Vitamin E and folacin requirements of gestating and lactating sows were also increased based on recent research findings. Vitamin E was increased from 22 IU/kg to 44 IU/kg as a result of research that showed that higher levels maximized both litter size and immunocompetency. Folacin requirement was increased from 0.30 mg/kg to 1.30 mg/kg in response to results that showed that higher levels resulted in larger litter birth weights and increased litter growth rate.

There is still conflicting, incomplete or a total lack of information on several nutrients at different stages of the pig's life cycle. This is particularly true of the vitamins and trace minerals for the young pig and the gestating and lactating sow. These areas require further research.

There have been other changes in the publication itself. The nutrient composition tables have been greatly expanded to include 23 new ingredients that were not available 10 years ago, e.g. spray-dried plasma, to bring the total to 79 feed ingredients. New tables include the fatty acid composition of fat sources and estimates of the four most limiting amino acids in feedstuffs, based on their crude protein content. This new edition also devotes a chapter to examining the issue of minimizing nutrient excretion and expands further on the topic of non-nutritive feed additives.

This publication will be with us for the next 10 years or maybe even longer, but the swine industry will not stop growing and changing. The Nutrient Requirements of Swine, 10th Revised Edition will serve as a standard as genetics, research and biotechnology continue to take the industry in new directions and change the rules.