Nutrient Requirements for Swine 10th Edition: Was It Worth the Wait?

Nutrition Update
Volume 9 No.2, August 1998

In April of 1998, the National Research Council (NRC) held a satellite conference to announce the launch of the Nutrient Requirements for Swine - 10^th Revised Edition. The NRC began publishing its Nutrient Requirements of Swine series in 1944, with subsequent updates published every 4 to 6 years until 1988. The ten year gap between the last two publications is much longer than average. Was it worth the wait?

The current edition marks a significant change in approach from earlier editions. Previously, an animal's requirements were dependent only on age and weight. In the 10^th Edition, the Aone-size-fits-all approach@ used in earlier editions has been replaced by estimates that are now based on a modeling procedure that takes into account genotype, performance and production conditions. Each copy of the requirements' publication is offered with a compact disk so that users can run the program on their own computers and process data from individual farms into specific rations to suit the operation and its pigs.

Three modeling programs, describing gestation, growth and lactation, have been produced especially for the 10^th Edition. Since commercially available models could not be used due to the proprietary nature of their inner workings, the NRC Committee developed totally new models. This information was then contracted out and the necessary software was developed in a menu-driven format using a Microsoft Windows environment.

The models are fairly simple, straightforward and initial attempts to run the program would indicate that it is quite Auser-friendly.@ Each model was built to be as solid as possible from the best data available. One could question whether the Committee correctly assigned the coefficient for the growth model, such as how well dietary lysine is converted into lean tissue. In addition, more research is still needed to address the issues of how crowding and/or environmental temperature effect lean gain.

According to Dr. G.L. Cromwell, U. of Kentucky and Chair, NRC Swine Nutrition Committee, work on the growth model began in 1994. The swine nutrient requirements were estimated by determining the protein accretion rates of pigs together with their maintenance requirements. This allowed for the derivation of the estimate of the total available lysine necessary for an animal to incorporate into whole-body protein. The committee then had to decide on the efficiency of lysine utilization, ie efficiency of digestion, absorption and deposition into body protein. With this information, the dietary level of lysine could be calculated. The other amino acids are expressed as a ratio of lysine. Requirements are presented not only as total amino acids, but also include apparent and true digestibility values. Thus, the requirements indicated should be applicable for the use of ingredients other than corn in the diets.

The models estimate the energy requirements in both digestible and metabolizable terms. In the gestation model, the user can enter either daily energy intake or weight gain. The model will then estimate either a weight gain on a given level of intake or estimate the energy requirement to reach a target weight gain. Similarly for the lactation model, either energy intake or weight change can be entered, however litter size and piglet average daily gain must be known. If energy intake is inputted, the model estimates weight change. If the estimated weight change is entered, the model estimates the amount of energy need to support the weight change along with the milk production needed to support the specified piglets' growth rate.

Committee member Dr. J.E. Pettigrew, Pettigrew Consulting International, suggests that the introduction of modeling into the current NRC edition is a huge advance. Nutrient requirements can change with different on-farm circumstances. The 10^th Edition allows these circumstance to be taken into account when developing feeding programs. The growing pig and sow models provide a greater opportunity for nutritionists to estimate the minimum requirements of different animals. However, the models are sometimes limited by the shortage of definitive data about certain amino acids or other nutrients. Where there was not an abundance of data, such as for valine, the NRC committee provided an estimate that is somewhat higher than previously reported. Pettigrew suggests that valine could be very important in the diets of breeding animals; possibly second or first limiting for sows. In nursery diets, valine will probably be only the 5^th or 6^th limiting amino acid depending on the protein source used.

The feedstuffs composition tables in the 10^th edition are expanded from earlier versions, with more ingredients and more data listed for the ingredients. The energy value of feedstuffs in expressed as DE, ME or NE. Estimated of apparent and true amino acid digestibility are presented, along with the amino acid composition of the feedstuffs.

In summary, the 10^th edition of the NRC Nutrient Requirements for Swine has been significantly changed from previous editions. It is somewhat more difficult to use than previous versions, however the additional information provided makes this edition much more powerful than previous editions. The modeling approach systematically and quantitatively allows the users of edition to address variations in requirements from one situation to another. No model is absolutely perfect, however the NRC model does make an effort to address the issue of variations that exist among operations. It was worth the wait.

References:
Minimum requirements for swine: New NRC reference closes a 10-year gap. Feed Management. 49 (5).
1998. Nutrient Requirements for Swine. 10^th ed. Washington, DC: NRC/NAS.
1998. NRCs address energy, amino acid requirements, vitamins, minerals. Feedstuffs. 70 (21).

Prepared by: Ian R. Seddon, Ph.D.

Contact:	David Hunt or Ron Bazylo
	Farm Production Extension Specialist - Swine
	Livestock Knowledge Centre
	Manitoba Agriculture, Food and Rural Initiatives