Starter Pig Amino Acid Requirements in Relation to Gut Health Concerns

Gut remodeling after weaning

Heo et al. (2012) provide an excellent review of the gastrointestinal changes that occur in weaned pigs after weaning. As a brief summary of their review, the gastrointestinal changes at weaning include:

Increased stomach gastric pH because of decreased acid secretion capacity and decreased lactic acid production due to lowered lactose intake. These changes may increase susceptibility of piglets to enteric infections at weaning
Gastric motility is reduced which reduces stomach emptying. The lower motility may allow for pathogenic bacteria to proliferate in the intestinal tract.
Decreased villus height (due to villus atrophy) and increased crypt depth. (hypertrophy of crypt cells) in the small intestine (partly, but not entirely due to decreased intake at weaning) results in decreased digestive capability.
Decreased lactase (and other pancreatic enzyme) secretion for first 3 to 5 days after weaning.
Reduction in net absorption of fluid and electrolytes and malabsorption of nutrients in small intestine immediately after weaning. The low ileal digestive capability could lead to osmotic diarrhea by increasing the quantity of nutrients presented to the hindgut.
In the large intestine, crypt cell number is decreased, which lowers absorptive capacity of large intestine. This reduced absorptive capability can lead to diarrhea when there is excessive fluid loss from the small intestine.

Minimizing challenge to the gut

The changes in the gastrointestinal tract mean that the gut is compromised at weaning and time is required for the pig to fully recover their digestive and absorptive capacities. The goal of nutritionists is to help the pig transition through this phase without incurring excessive diet cost. Some ingredients and diet formulation techniques help the pig counteract some of the normal gut changes that occur at weaning. For example, adding lactose to the diet increases lactic acid production, which lowers gastric pH. Reducing the acid binding capacity of the diet decreases the requirement for acid to buffer the pH. Decreasing the soybean meal level in the diet decreases the challenge that an immature digestive tract has in dealing with legume proteins. High levels of soybean meal can cause transient hypersensitivity when the immune system reacts to an unfamiliar protein source (Engle, 1994).

Another method to decrease the challenge that the diet poses to the gastrointestinal system is to lower the crude protein level in the diet. Reducing the crude protein content lowers the need for soybean meal or other protein sources. Presenting the large intestine with a large quantity of undigested nitrogen appears to be a factor in postweaning diarrhea (Heo et al., 2012). Lowering the quantity of protein in the diet decreases the ammonia concentration in the small intestine (Bikker et al., 2006) and urea nitrogen and volatile fatty acids in the ileum (Nyachoti et al., 2006). It is thought that the decreased nitrogen concentrations are due to reduced protein fermentation by the bacteria (De Lange et al., 2010).

Until recently, lowering the crude protein level in the diet usually corresponded with reduced growth performance because the minimum requirement for the fourth, fifth, or sixth amino acids (often tryptophan, valine, or isoleucine) or nonessential amino acids that have a role in gut development (arginine, glutamine, or glycine) were not met. Numerous recent research trials have demonstrated that performance can be maintained when the crude protein level in the diet is reduced by using crystalline amino acids to replace intact protein sources (Heo et al., 2009; Lordelo et al., 2008; Nemechek et al., 2011a).

In order to lower the crude protein level in the diet, we need to first ensure that we are not formulating the diets above the lysine requirement. The requirements for other essential amino acids in relation to lysine must also be known to allow crude protein to be lowered to minimal levels.

Lysine requirements for nursery pigs

Numerous research trials have explored the SID lysine requirement of nursery pigs in recent years. Researchers at Kansas State University and the University of Missouri conducted a series of experiments under field and university conditions to determine the lysine requirement from 5 to 10 and 10 to 25 kg. For the lighter weight range, the requirement estimate was found to be between 1.35 and 1.40% SID lysine (4.0 to 4.2 g/Mcal ME; Gaines el al., 2003; Nemechek et al., 2011b). This requirement was similar to the estimate found by Dean et al. (2007) of 1.4% SID lysine or 18.9 g of lysine per kg of gain for 6 to 12 kg pigs.

For 10 to 25 kg pigs, Kendall et al. (2008) conducted 5 experiments with 3,628 pigs and found the SID lysine requirement to be 1.30% SID lysine (3.80 g/Mcal ME). This was equivalent to 19 g of SID lysine per kg of gain. Schneider et al. (2010) titrated energy and lysine levels simultaneously in two separate trials with different genotypes. With one genotype, the optimal SID lyine:ME ratio was approximately 3.4 to 3.6 g/Mcal ME, while the optimal ratio was 3.9 to 4.2 g/Mcal ME for the other genotype. However, when expressed relative to gain, the requirement was approximately 19.0 g of SID lysine/kg of gain for both genotypes. In another large field study, Lenehan et al., (2003) found the SID lysine requirement for 10 to 20 kg pigs was 1.40%; however, when calculated on a g/kg of gain basis, the optimal level was again 19 g of SID lysine/kg of gain. In a cooperative study involving several universities in the United States, Hill et al. (2007) confirmed that the lysine requirement of nursery pigs of modern genotypes was higher than recommendations of NRC (1998).

Although lysine requirements of nursery pigs have increased in recent years and vary with environmental conditions and genotype, when expressed relative to growth rate, empirical studies in recent years have consistently found the requirement to be 19 g per kg of gain.

Threonine:lysine ratio

The large difference between apparent and standardized digestibility values for threonine has caused some confusion by nutritionists with this amino acid over the years. Deficiencies of threonine cause real, but relatively small reductions in growth and efficiency as compared to deficiencies of the other major amino acids. This has led to an underestimation of requirements and under-formulation for threonine by many nutritionists.

Van Milgen and Le Bellego (2003) conducted a meta-analysis of 22 different studies and found the optimal threonine:lysine ratio increased from 58% at 15 kg to 65% at 110 kg using a linear-plateau model. Use of curvilinear models resulted in higher requirement estimates. In two separate experiments, Lenehan et al. (2003, 2004) found an optimal threonine:lysine level of 64 to 66% for 10 to 20 kg pigs. James et al. (2003) also found the optimal threonine:lysine ratio to be 60 to 65% for 10 to 20 kg pigs. Although Wang et al. (2006) did not report a SID threonine:lysine ratio, the growth rate of pigs in their study can be used to estimate the SID lysine requirement (19 g/kg of gain) to calculate an SID threonine:lysine ratio. Their data would suggest the ratio is at least 60% of lysine for growth and 67% for immunity. Li et al. (1999) also demonstrated that the threonine requirement for immunity was higher than the requirement for growth.

TSAA:lysine ratio

Considerable research has been conducted in recent years on the total sulfur amino acid requirement and individual requirements for methionine and cystine. It is generally assumed that methionine must constitute at least 50% of the TSAA ratio (NRC = 48% on weight basis); however, recent data (Gillis et al., 2007) suggests that methionine may need to be slightly greater (55% on weight basis; 50% on molar basis) than cystine in the ratio.

For nursery pigs, Dean et al., 2007 suggested that the requirement for total sulfur amino acids was 10.1 g/kg gain or 54% of lysine for 6 to 12 kg pigs. Gaines et al. (2005) found a slightly higher ratio of 57 to 61% depending on the response criteria and method of assessing the breakpoint with 8 to 26 kg pigs. Yi et al. (2006) found a similar TSAA:lysine ratio of 58% for optimal ADG with 12 to 24 kg pigs. In a series of experiments, Kansas State University researchers found a similar range of SID TSAA:lysine ratios of 57 to 60% for 10 to 20 kg pigs with Genetiporc (Schneider et al., 2004) and PIC (Schneider et al., 2006) pigs.

Tryptophan:lysine ratio

Research on the optimal tryptophan to lysine ratio is difficult to conduct. Because of the relatively small inclusion rates and small differences in range of tryptophan levels tested (ex. 14 to 22% of lysine), diet manufacturing is a challenge to ensure the very low additions are thoroughly mixed. Also, tryptophan is a difficult amino acid to analyze and different analytical techniques yield different results adding to the confusion. There is also disagreement in the quantity of tryptophan present in key basal ingredients used in many of the research trials, which can dramatically impact the projected ratios because the basal ingredients make up such a large proportion of the tryptophan in test diets. Finally, the level of other large neutral amino acids in the diet may influence the response to increasing tryptophan levels. The optimal tryptophan:lysine ratio suggested by most researchers ranges from 16 to 20%. Although this range is relatively small, the difference can lead to large changes in diet formulation and cost and inclusion of other crystalline amino acids in the diet.

On the low end of the recommended range for nursery pigs, Ma et al. (2010) suggested that the SID tryptophan:lysine requirement may be as low as 15% for 11 to 22 kg pigs; however, data from Nemechek et al. (2011a) demonstrates that 15% SID tryptophan:lysine results in lower ADFI and ADG than a ratio of 20%. Guzik et al. (2002) estimated the SID tryptophan requirement for nursery pigs at 0.21, 0.20, and 0.18% of the diet for 5.2 to 7.3 kg, 6.3 to 10.2 kg, and 10.3 to 15.7 kg pigs, respectively. Using the SID lysine levels suggested above, these ratios would all be less than 16% of lysine. Jansman et al. (2010) found higher estimates for SID tryptophan for 10 to 20 kg pigs, both as a percentage of the diet (0.22%) and as a ratio to lysine (21.5%). In a review of 33 experiments, Susenbeth (2006) summarized that the SID tryptophan:lysine requirement is below 17.4% and likely near 16.0%. Susenbeth (2006) also concluded that feeding at 17% would include a safety margin to cover most of biological variations and that the tryptophan:lysine ratio seemed to be unaffected by body weight, growth rate, lysine and protein concentration in the diet, or genetic improvement of the animals.

There is conflicting data on the impact of sanitary conditions on the tryptophan requirement of nursery pigs. Le Floc’h et al. (2007) found that the requirement to pigs in low sanitary conditions may have a higher response to tryptophan due to the increased requirement of the immune system. However, Frank et al (2010) found the opposite response with pigs having a greater response to increasing trp:lys in clean environment than in a dirty environment.

Valine:lysine ratio

Although there are some differences in the estimates for the optimal valine:lysine ratio, we believe that much of the difference may be in the basal valine and lysine levels used in diet formulation. If you formulate the same corn-soybean meal diets with crystalline amino acids using NRC (1998) and INRA or Brazilian (Rostagno, 2005) amino acid values for the corn and soybean meal, a diet containing 65% SID valine:lysine with NRC values will contain 68% SID valine:lysine with INRA values and 69% with values from Rostagno (2005). These differences are minor, but may explain much of the difference between the valine:lysine estimates of 70% from Europe (Barea et al., 2009a) compared with 65% from the United States (Gaines et al., 2010)

Numerous valine trials have been published in the last 10 years. Mavromichalis et al. (2001) was one of the first publications to suggest that the valine requirement of nursery pigs was greater than the level suggested by NRC (1998). Their data suggested that 10 to 20 kg pigs required 12.5 g of SID lysine per kg of gain. Gaines et al. (2010) found a similar requirement of 12.3 g of SID lysine/kg of gain for 13 to 32 kg pigs. Using the requirement of 19 g of SID lysine per kg of gain for nursery pigs found by several researchers and discussed earlier in this paper, a SID Val: SID Lys of 66% can be calculated, which is similar to the 65% reported by Gaines et al. (2010) for 13 to 32 kg pigs and 65 to 67% reported by Wiltafsky et al. (2009b) for 8 to 25 kg pigs. The 65% SID valine:lysine ratio was recently confirmed by Nemechek et al. (2011a) using 7 to 12 kg pigs. A ratio of 65% using NRC (1998) ingredient nutrient values is equivalent to a ratio of 69% using Brazilian ingredient nutrient values of Rostagno (2005).

Isoleucine:lysine ratio

Similar to other amino acids, our understanding of the optimal ratios of isoleucine to lysine has increased greatly in the last 10 years. The main confusion in understanding the optimal isoleucine to lysine ratio is the interaction between isoleucine and other branch chain amino acids, in particular leucine. Excess leucine in the diet increases branch chain keto dehydrogenase levels which leads to catabolism of all branch chain amino acids, leading to increased requirement for isoleucine due to the increased breakdown of circulating levels.

Spray dried blood cells have been used in several isoleucine studies to create a basal diet with a low isoleucine:lysine ratio (Parr et al., 2003, 2004; Kerr et al., 2004). The problem is that blood cells contain high leucine levels, which later were determined to increase the isoleucine:lysine recommendation. Subsequently, Fu et al (2005a,b), Fu et al (2006a,b,c), Dean et al. (2005), and Wiltafsky et al (2009a) demonstrated that the SID isoleucine:lysine requirement was 60% or greater in diets containing blood meal or blood cells and closer to 50% for diets without high levels of blood cells. The requirement of 50% or less for SID isoleucine:lysine when blood cells are not included in the diet was confirmed by Barea et al. (2009b) for 11 to 23 kg pigs. Lindemann et al. (2010) also found the SID isoleucine:lysine requirement to be between 48 and 52% for ADG. Norgaard and Fernandez (2009) found that increasing the isoleucine:lysine ratio from 53 to 62% did not influence performance of 9 to 22 kg pigs. It appears that the SID isoleucine:lysine is less than 52% for diets don’t contain a protein source that provides excess leucine in relation to the isoleucine level, such as blood products. Caution is advised with all branch chain amino acids; however, as feeding as little as 5% below the minimum ratio (ex. 45 vs 50% of lysine) will greatly reduce feed intake and daily gain.

Nonessential amino acid requirement

Although the order can vary with different dietary ingredient mixtures, typically the first 5 limiting amino acids for most practical diets are lysine, threonine, methionine, tryptophan, and valine. However, formulating diets with high levels of synthetic amino acids to the optimal ratio for the first 5 limiting amino acids often has resulted in poorer performance than diets with higher levels of intact protein sources. Kendall et al. (2004) found that certain nonessential amino acids (Ex. glycine) were required in corn-soybean meal diets with high levels of synthetic lysine and that the nitrogen could not be provided by nonprotein nitrogen. In a series of experiments, Powell et al. (2009a,b) and Southern et al. (2010) found that glycine and another amino acid to provide nitrogen were required in diets formulated to the fifth or sixth limiting amino acid in order to maintain feed efficiency at similar levels to control diets.

Another method to ensure that the diet contains enough nonessential amino acids is to place a maximum on the total lysine to total crude protein ratio in diet formulation. The biological basis for a lysine:CP ratio originates from the level of total lysine as a percentage of crude protein in muscle, which ranges from 6.5 to 7.5% (NRC, 1998). Although an average lysine:CP ratios of 6.8% is often cited, a higher lysine:CP ratio can be used in the diet because the lysine released during normal muscle protein breakdown is conserved and recycled with greater efficiency than other amino acids. Ratliff et al. (2005) suggested that the total lys:CP ratio should not exceed 7.1%. Nemechek et al (2011b) found that feed efficiency was only poorer when the total lysine:CP ratio exceeded 7.35%. More research is clearly needed to continue to improve our understanding of nonessential amino acid needs of the pig.

Nonessential amino acids appear to play a particularly important role immediately after weaning due to their high requirement for intestinal growth. Glutamine serves as a primary fuel for the intestinal mucosa. Glutamine and glycine stimulate polyamine synthesis. Arginine is the precursor for polyamines and nitric oxide which is important for regulation of intestinal blood flow and migration of intestinal epithelial cells. Numerous other roles of the nonessential amino acids are reviewed by Wu (2011).

Table 1. Suggested minimum SID amino acid ratios for growing swine^a

Starter Pig Amino Acid Requirements in Relation to Gut Health Concerns - Image 1

^aAdapted from Shannon and Allee, 2010 with updates by authors. Ratios are based on NRC (1998) nutrient levels for ingredients. Nutritionists should review their ingredient nutrient values relative to NRC (1998) to apply these ratios to their diets.
^bTryptopan:lysine ratio appears to be increased when the diet contains large excesses of large neutral amino acids (leucine, isoleucine, valine, phenylalanine, and tyrosine)
^cRatio is at least 60% when high levels of blood meal or cells are included in the diet. Ratio may be lower than 52% when blood cells are not included, but more research is required to verify and to determine the optimal ratio of isoleucine to leucine.

Citation

Tokach, M.D., R.D. Goodband, J.M. DeRouchey, and S.S. Dritz. 2012. Starter pig requirements in relation to gut health concerns. Proceedings of 2012 Eastern Nutrition Conference. Pp 9-18. Kitchner, Ontario.

References

Barea, R., L. Brossard, N. Le Floc'h, Y. Primot, D. Melchior, and J. van Milgen. 2009a. The standardized ileal digestible valine-to-lysine requirement ratio is at least seventy percent in postweaned piglets J Anim Sci, 87:935-947.

Barea, R., L. Brossard, N. Le Floc'h, Y. Primot, and J. van Milgen. 2009b. The standardized ileal digestible isoleucine-to-lysine requirement ratio may be less than fifty percent in eleven- to twenty-three-kilogram piglets. J. Anim. Sci. 87:4022-4031.

Bikker, P. A. Dirkzwager, J. Fledderus, P. Trevisi, I. le Huerou-Luron, J. P. Lalles, and A. Awati. 2006. The effect of dietary protein and fermentable carbohydrates levels on growth performance and intestinal characteristics in newly weaned piglets. 84:3337-3345.

Dean, D. W., L. L. Southern, B. J. Kerr, and T. D. Bidner. 2005. Isoleucine requirement of 80- to 120-kilogram barrows fed corn-soybean meal or corn-blood cell diets. J. Anim. Sci. 83:2543-2553.

Dean, D. W., L. L. Southern, B. J. Kerr, and T. D. Bidner. 2007. The lysine and total sulfur amino acid requirements of six- to twelve-kilogram pigs. Prof. Anim. Sci. 23:527-535.

De Lange, C.F.M., J. Pluske, J. Gong, and C. M. Nyachoti. 2010. Strategic use of feed ingredients and feed additives to stimulate gut health and development in young pigs. Livest. Sci. 134:124-134.

Engle, M. 1994. The role of soybean meal hypersensitivity in postweaning lag and diarrhea in piglets. J. Swine Health Prod. 2: 7-10.

Frank, J.W., C.L. Bradley, B.E. Bass, C.V. Maxwell, R.D. Boyd, and J.L. Usry. 2010. Effect of environment on the tryptophan:lysine ratio in nursery pigs. J. Anim. Sci. 88 (E-Suppl. 3): 148 (Abstr.)

Fu, S.X., R.W. Fent, P. Srichana, G.L. Allee, and J.L. Usry. 2005a. Effects of protein source on true ileal digestible (TID) isoleucine:lysine ratio in late-finishing barrows. J. Anim. Sci. 83 (Suppl. 2): 149 (Abstr.).

Fu, S.X., D.C. Kendall, R.W. Fent, G.L. Allee, and J.L. Usry. 2005b. True ileal digestible (TID) isoleucine:lysine ratio of late-finishing barrows fed corn-blood cell or corn-amino acid diets. J. Anim. Sci. 83 (Suppl. 2): 148 (Abstr.).

Fu, S.X., R.W. Fent, G.L. Allee, and J.L. Usry. 2006a. Branched chain amino acid interactions and isoleucine imbalance in late-finishing pigs. J. Anim. Sci. 84 (Suppl. 1): 371 (Abstr.).

Fu, S.X., R.W. Fent, G.L. Allee, and J.L. Usry. 2006b. Branched chain amino acid interactions increases isoleucine requirement in late-finishing pigs. J. Anim. Sci. 84 (Suppl. 1): 372 (Abstr.).

Fu, S.X., A.M. Gaines, R.W. Fent, G.L. Allee, and J.L. Usry. 2006c. True ileal digestible isoleucine requirement and ratio in 12 to 22 kg pigs. J. Anim. Sci. 84 (Suppl. 1): 370 (Abstr.).

Gaines, A.M., D.C. Kendall, G.L. Allee, M.D. Tokach, S.S. Dritz, and J.L. Usry. 2003. Evaluation of the true ileal digestible (TID) lysine requirement for 7 to 14 kg pigs. J. Anim. Sci. 81(Suppl. 1):139(Abstr.).

Gaines, A. M., D. C. Kendall, G. L. Allee, J. L. Usry, and B. J. Kerr. 2010. Estimation of the standardized ileal digestible valine to lysine ratio in 13 to 32 kg pigs. J. Anim. Sci. 89:736-742.

Gaines, A. M., G. F. Yi, B. W. Ratliff, P. Srichana, D. C. Kendall, G. L. Allee, C. D. Knight, and K. R. Perryman. 2005. Estimation of the ideal ratio of true ileal digestible sulfur amino acids:lysine in 8- to 26-kg nursery pigs. J. Anim. Sci. 83: 2527-2534.

Gillis, A. M., A. Reijmers, J. R. Pluske, and C. F.M. de Lange. 2007. Influence of dietary methionine to methionine plus cysteine ratios on nitrogen retention in gilts fed purified diets between 40 and 80 kg live body weight. Can. J. Anim. Sci. 87:87-92.

Guzik, A. C., L. L. Southern, T. D. Bidner, and B. J. Kerr. 2002. The tryptophan requirement of nursery pigs. J. Anim. Sci. 80:2646-2655.

Heo, J. M.; J.C. Kim, C.F. Hansen, B.P. Mullan, D.J. Hampson, and J.R. Pluske. 2009. Feeding a diet with decreased protein content reduces indices of protein fermentation and the incidence of postweaning diarrhea in weaned pigs challenged with an enterotoxigenic strain of Escherichia coli. J. of Anim. Sci. 87:2833–2843.

Heo, J. M., F. O. Opapeju, J. R. Pluske, J. C. Kim, D. J. Hampson, and C. M. Nyachoti. 2012. Gastrointestinal health and function in weaned pigs: a review of feeding strategies to control post-weaning diarrhoea without using in-feed antimicrobial compounds. J. Anim. Physiol. Nutr. 2012 Mar 14. doi: 10.1111/j.1439-0396.2012.01284.x.

Hill, G. M., S. K. Baido, G. L. Cromwell, D. C. Mahan, J. L. Nelssen, H. H. Stein, and NCCC-42 Committee on Swine Nutrition. 2007. Evaluation of sex and lysine during the nursery period. J Anim Sci. 2007; 85:1453-1458.

James, B.W., M.D. Tokach, R.D. Goodband, S.S. Dritz, J.L. Nelssen, and J.L. Usry. 2003. The optimal true ileal digestible threonine requirement for nursery pigs between 11 to 22 kg. J. Anim. Sci. 81(Suppl. 1):42(Abstr.).

Jansman, A.J.M., J. Th. M. van Diepen, and D. Melchior. 2010. The effect of diet composition on tryptophan requirement for young piglets. J. Anim. Sci. 88:1017-1027.

Kendall, D.C., R.W. Fent, J.L. Usry, and G.L. Allee. 2004. The essentiality of nonessential amino acids in low protein diet formulations for 11 to 30 kg barrows. J. Anim. Sci. 82 (Suppl. 2): 125 (Abstr.).

Kendall, D. C., A. M. Gaines, G. L. Allee, and J. L. Usry. 2008. Commercial validation of the true ileal digestible lysine requirement for eleven- to twenty-seven-kilogram pigs. J. Anim. Sci. 86: 324-332.

Kerr, B. J., M. T. Kidd, J. A. Cuaron, K. L. Bryant, T. M. Parr, C. V. Maxwell, and J. M. Campbell. 2004. Isoleucine requirements and ratios in starting (7 to 11 kg) pigs. J. Anim. Sci. 82:2333–2342.

Le Floc’h, N., D. Melchoir, L. Le Bellego, J. J. Matte, and B. Seve. 2007. Le statut sanitaire affecte-t-il le besoin en tryptophane pour la croissance des porcelets après sevrage? 39^th J. Recherche Porcine. 39:125-132.

Lenehan, N.A., S.S. Dritz, M.D. Tokach, R.D. Goodband, J.L. Nelssen, and J.L. Usry. 2003. Effects of lysine level fed from 10 to 20 kg on growth performance of barrows and gilts. J. Anim. Sci. 81(Suppl. 1):46(Abstr.).

Lenehan, N.A., M.D. Tokach, S.S. Dritz, R.D. Goodband, J.L. Nelssen, J.L. Usry, J.M. DeRouchey, and N.Z. Frantz. 2004. The optimal true ileal digestible lysine and threonine requirement for nursery pigs between 10 and 20 kg. J. Anim. Sci. 82(Suppl. 1):293(Abstr.).

Li, D., X. Changting, Q. Shiyan, Z. Jinhui, E. W. Johnson, and P. A. Thacker. 1999. Effects of dietary threonine on performance, plasma parameters and immune function of growing pigs. Anim. Feed Sci. Technol. 78:179–188.

Lindemann, M.D., A.D. Quant, J. H. Cho, B.J. Kerr, G.L. Cromwell, and J.K. Htoo. 2010. Determining the optimium ratio of standardized ileal digestible (SID) isoleucine to lysine for growing pigs fed wheat-barley based diets. J. Anim. Sci. 88 (E-Suppl. 3): 43 (Abstr.).

Lordelo, M. M., A.M. Gaspar, L. Le Bellego, and J.P. B. Freire. 2008. Isoleucine and valine supplementation of a low-protein corn-wheat-soybean meal-based diet for piglets: growth performance and nitrogen balance. J. Anim. Sci. 86:2936–2941.

Ma. L. Z.P. Zhu, R.B. Hinson, G.L. Allee, J.D. Less, D.D. Hall, H. Yang, and D.P. Holzgraefe. 2010. Determination of SID Trp:lysine ratio requirement of 11- to 22-kg pigs fed diets containing 30% DDGS. J. Anim. Sci. 88 (E-Suppl. 3): 151. (Abstr.)

Mavromichalis, I, B. J. Kerr, T. M. Parr, D. M. Albin, V. M. Gabert, and D. H. Baker. 2001. Valine requirement of nursery pigs. J. Anim. Sci. 79:1223-1229.

Nemechek, J.E., M.D. Tokach, S.S. Dritz, R.D. Goodband, J.M. DeRouchey, and J.L. Nelssen. 2011a. Effects of deleting crystalline amino acids from low-CP, amino acid-fortified diets and dietary valine:lysine ratio of for nursery pigs from 6.8 to 11.3 kg. J. Anim. Sci. 89(Suppl. 3):(Abstr).

Nemechek, J.E., M.D. Tokach, S.S. Dritz, R.D. Goodband, J.M. DeRouchey, J.L. Nelssen and J.L. Usry. 2011b. Evaluation of SID lysine level, the replacement of fish meal with crystalline amino acids, and lysine:CP ratio on growth performance of nursery pigs from 6.8 to 11.3 kg. J. Anim. Sci. 89(Suppl. 3):(Abstr).

Nørgaard, J.V., and J.A. Fernández. 2009. Isoleucine and valine supplementation of crude protein-reduced diets for pigs aged 5–8 weeks. Anim. Feed. Sci. Tech. 154:248-253.

NRC. 1998. Nutrient requirements of swine: 10th revised edition. Natl. Acad. Press, Washington, DC.

Nyachoti, C.M., F.O. Omogbenigun, M. Rademacher, and G. Blank. 2006. Performance responses and indicators of gastrointestinal health in early-weaned pigs fed low-protein amino acid-supplemented diets. J. Anim. Sci. 84:125-134.

Parr, T. M., B. J. Kerr, and D. H. Baker. 2003. Isoleucine requirement of growing (25 to 45 kg) pigs. J. Anim. Sci. 81:745-752.

Parr, T. M., B. J. Kerr, and D. H. Baker. 2004. Isoleucine requirement for late-finishing (87 to 100 kg) pigs. J. Anim. Sci. 82:1334-1338.

Powell, S. T. Bidner, L. Southern, and R. Payne. 2009a. Growth performance of 20- to 50-kilogram pigs fed low crude protein diets supplejmented with Glycine and L-Arginine. J. Anim. Sci. 87 (E-Suppl. 3):153 (Abstr.).

Powell, S. J. Greely, T. Bidner, L. Southern, and R. Payne. 2009b. Growth performance of 20- to 50-kilogram pigs fed low crude protein diets supplemented with L-Histidine, L-Cystine, and Glycine. J. Anim. Sci. 87 (E-Suppl. 3):152 (Abstr.).

Ratliff, B. W., A. M. Gaines, P. Srichana, G. L. Allee, and J. L. Usry. 2005. Evaluation of high synthetic amino acid inclusion and supplemental arginine in starter diets. J. Anim. Sci. 83(Suppl. 2):69(Abstr.).

Rostagno, H. S. 2005. Brazilian Tables for Poultry and Swine: Composition of Feedstuffs and nutrient requirements. 2^nd Edition.

Schneider, J. D., M. D. Tokach, S. S. Dritz, J. L. Nelssen, J. M. DeRouchey, and R. D. Goodband. 2010. Determining the effect of lysine:calorie ratio on growth performance of ten- to twenty-kilogram of body weight nursery pigs of two different genotypes. J. Anim. Sci. 88:137-146.

Schneider, J.D., M.D. Tokach, S.S. Dritz, R.D. Goodband, J.L. Nelssen, J.L. Usry, J.M. DeRouchey, C.W. Hastad, N.A. Lenehan, N.Z. Frantz, B.W. James, K.R. Lawrence, C.N. Groesbeck, R.O. Gottlob, and M.G. Young. 2004. The optimal true ileal digestible lysine and total sulfur amino acid requirement for nursery pigs between 10 and 20 kg. J. Anim. Sci. 82(Suppl. 1):293(Abstr.).

Schneider, J.D., M.D. Tokach, S.S. Dritz, R.D. Goodband, J.L. Nelssen, J.M. DeRouchey, G.F. Yi, K.R. Perryman, and C.D. Knight. 2006. The optimal true ileal digestible lysine and sulfur amino acid requirement for nursery pigs between 10 and 20 kg. J. Anim. Sci. 84 (Suppl. 1):63 (Abstr.).

Shannon, M. C., and G. L. Allee. 2010 Protein and amino acid sources in swine diets. In: National Swine Nutrition Guide. Ed. D.J. Meisinger.

Southern, L.L., M.L. Ross, A.M. Waguespack, S. Powell, T.D. Bidner, and R.L. Payne. 2010. Developing low protein amino acid supplemented diets for swine. J. Anim. Sci. 88 (E-Suppl. 3): 42 (Abstr.).

Susenbeth, A. 2006. Optimum tryptophan:lysine ratio in diets for growing pigs: Analysis of literature data. Livest. Sci. 101:32-45.

Van Milgen, J. and L. LeBellego. 2003. A meta-analysis to estimate the optimum threonine to lysine ratio in growing pigs. J. Anim. Sci. 81 (Suppl. 1):553 (Abstr.).

Wang, X., S.Y. Qiao, M. Liu, Y.X. Ma. 2006. Effects of graded levels of true ileal digestible threonine on performance, serum parameters and immune function of 10–25kg pigs. Anim. Feed. Sci. Tech. 129:264-278.

Wiltafsky, M. K., J. Bartelt, C. Relandeau, and F. X. Roth. 2009a. Estimation of the optimum ratio of standardized ileal digestible isoleucine to lysine for eight- to twenty-five-kilogram pigs in diets containing spray-dried blood cells or corn gluten feed as a protein source J Anim Sci 87: 2554-2564.

Wiltafsky, M. K., B. Schmidtlein, and F. X. Roth. 2009b. Estimates of the optimum dietary ratio of standardized ileal digestible valine to lysine for eight to twenty-five kilograms of body weight pigs. J. Anim. Sci. 87:2544-2553.

Wu, G. 2011. Importance of intestinal amino acid metabolism in nutrition and health: Thinking outside the box. Proceedings of Gentech’s First International Nutrition Forum. Pages 2-32.

Yi, G. F., A. M. Gaines, B. W. Ratliff, P. Srichana, G. L. Allee, K. R. Perryman, and C. D. Knight. 2006. Estimation of the true ileal digestible lysine and sulfur amino acid requirement and comparison of the bioefficacy of 2-hydroxy-4-(methylthio)butanoic acid and DL-methionine in eleven- to twenty-six-kilogram nursery pigs. J Anim Sci 84:1709-1721.

Starter Pig Amino Acid Requirements in Relation to Gut Health Concerns

Specialty Nutrition portfolio for monogastrics

How to train the first line of defence for better immunity in pigs