My name is Dr. Ameer Pahm, and I work as a postdoctoral researcher in the lab of Dr. Hans Stein. Today I would like to talk about feeding wheat to pigs. Just a brief introduction: Wheat is a major crop grown in the U.S. and approximately 10% of the annual wheat production of over 2 billion bushels is used for livestock. The major classes of wheat are hard red winter, hard red spring, soft red winter, white, and durum wheat. While corn is the dominant grain source for pigs in most of the regions in the U.S., the greater concentration of amino acids can make the use of wheat more attractive than corn, particularly in wheat-producing areas or in areas where corn is scarce. In the next few minutes, I will talk about the concentration and digestibilities of energy and nutrients in wheat. The U.S. wheat grain can be classified into U.S. Grade #1 to 5, depending on the test weight, the amount of damaged kernels, and the concentration of foreign materials. It is expected that lower grades of wheat will have a lower concentration of energy and nutrients as a result of the diluting effect of the non-nutritive contaminants in wheat. Wheat contains slightly lower concentration of starch and crude fat, but greater concentration of acid detergent fiber (or ADF) and neutral detergent fiber (or NDF) compared with corn. Wheat also has a slightly greater concentration of crude protein and amino acids than corn, while lysine and tryptophan are the two most limiting amino acids in corn-based diets fed to pigs, lysine, threonine, and tryptophan are the first and second limiting amino acids in pigs fed wheat-based diets. In terms of energy, wheat has a lower concentration of digestible energy (or DE), metabolizable energy (or ME), and net energy (or NE) compared with corn. Relative to corn, wheat is 91 to 97% of the value of the corn in terms of energy contribution to pigs. The slightly lower concentration of crude fat, greater concentration of NDF, and the presence of variable amounts of non-starch polysaccharides (or NSP) may be partly responsible for the lower concentration of energy in wheat relative to corn. In terms of digestible nutrients, the concentration of standardized ileal digestible amino acids is generally greater in wheat than in corn. The concentration of indispensable standardized ileal digestible amino acids is at least 5 percentage points greater in wheat relative to corn, mainly due to the greater concentration of standardized ileal digestible tryptophan, lysine, and threonine in wheat. Thus, less amount of soybean meal is needed when formulating wheat-based diets, and the economics of the use of wheat will partly depend on the prevailing costs of soybean meal and other protein sources. Wheat contains 0.35 to 0.39% total phosphorus, but 65 to 70% is in the form of phytic acid. Wheat has a greater phytase activity than corn, which may be partly related to the greater utilization of phosphorus in wheat than in corn when fed to pigs. Despite this, utilization of phytate phosphorus in wheat is still low at 45%. Thus, the use of exogenous enzymes such as microbial phytase to improve phosphorus availability in wheat may be considered. I will move now on the consideration on the use of wheat as feedstuffs for pigs. First is the performance of pigs fed wheat. Pigs fed wheat-based diets can gain as fast and as efficiently as pigs fed corn-based diets. Wheat can be used in diets for young pigs without affecting subsequent performance, and from starter to finisher phase without affecting carcass quality, fatty acid characteristics of pork fat, and meat color. Thus, performance and meat quality of pigs fed wheat-based diet is expected to be similar to pigs fed corn-based diet when both diets are formulated to contain the same concentration of digestible energy and other nutrients. Second consideration in using wheat is the variation in energy concentration. The coefficient of variation in the concentration of digestible energy in wheat is low at 2.6% based on 16 separate studies that were summarized by Wu and Ewan in 1979. However, based on 17 more recent studies from 1974 to 2004 that were summarized by Kim and his coworkers in 2005, the concentration of digestible energy ranged from 3177 to 4761 kcal/kg dry matter, warranting a careful assignment of energy value to wheat. The relatively wide range of digestible energy in wheat may be partly attributed to differences in growing conditions and season, and the presence of variable amounts of total non-starch polysaccharides in wheat. Physical damage to wheat can reduce its bushel weight, thus the latter is commonly used to grade different qualities of wheat; however, bushel weight does not always correlate to the concentration of digestible energy according to Wiseman in 1980. The concentration of digestible energy appears to be more related to the concentration of specific non-starch polysaccharide components in wheat, such as xylose, according to Zijlstra in 1999. Another consideration is processing. Grinding of wheat improves the digestibility of energy and amino acids, and may improve animal performance. However, no single and definite grind size of wheat for different classes of pigs has been established. A grind size of 860 to 1710 microns did not show differences in weight gain when fed to nursery and grower pigs, whereas 400 microns and 1710 microns have been shown to be suitable for finisher pigs. In one study, performance was similar among pigs fed wheat-based diets that contained particle sizes that ranged from 500 to 3350 microns. Nevertheless, finely ground wheat-based diets may increase the risk of gastrointestinal lesions, and may reduce the feed intake as a result of increased dustiness. Fine grinding of wheat would require additional electrical power, and based on these data, a grind size of 500 to 1000 microns may be acceptable for pigs. Another consideration is the use of enzymes. Wheat contains about 11% total non-starch polysaccharides, 80% of which is insoluble non-starch polysaccharides. While non-starch polysaccharides limit the use of wheat in poultry rations, the negative effects of non-starch polysaccharides in wheat on the digestibility of energy and nutrients and on the growth of pigs are currently not clear. The amount of soluble non-starch polysaccharides is not well correlated with the concentration of digestible energy in pigs according to Zijlstra and coworkers in 1999. The effect of feeding wheat on digesta viscosity is also not a limiting factor in pigs, as it is in poultry. This may be a consequence of the greater fermentative capacity of the pig compared with poultry. Pigs also have a longer retention time of digesta, allowing for better fermentation of non-starch polysaccharides. The phytase phosphorus in wheat is poorly available to the pig because the latter does not produce sufficient intestinal phytase, and though wheat has endogenous phytase activity in the aleurone level of the kernel, it is relatively inefficient in cleaving the phosphorus bond to phytic acid. Phosphorus utilization in wheat can be influenced by concentration of phytate phosphorus and the effects of specific wheat varieties on digesta viscosity. Improvement in phosphorus utilization in wheat-based pig diets supplemented with microbial phytase have been reported, and up to 1000 phytase units of exogenous phytase may be used. However, the effect of the exogenous phytase supplementation on pig performance is currently not well established. The last consideration in feeding wheat to pigs is the physical quality of wheat. The expected test weight of wheat can range from 50 to 60 pounds/bushel, or 66 to 70.9 kg/hectaliter based on U.S. grade standards. Damage to wheat kernels reduces the digestibility of energy and nitrogen, and feeding weather-damaged wheat may reduce pig performance. However, it is difficult to estimate the amount of digestible energy in wheat with varying amounts of damaged kernels. A safe limit for wheat intended for livestock would be that no more than 20% of the total weight of the lot should be comprised by the sum of the damaged kernels, foreign materials, shrunken and broken kernels, which would corresponse to U.S. Grade #5. When using out-of-grade wheat that is 20% damaged grain and foreign materials on a weight basis, it is advisable to analyze for chemical components that is indicative of its energy concentration such as gross energy and DF, and adjust the digestible energy accordingly using prediction equations.