Source: SOUTH DAKOTA STATE UNIVERSITY submitted to
FACTORS AFFECTING NUTRIENT UTILIZATION AND -EXCRETION BY GROWING SWINE
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
TERMINATED
Funding Source
HATCH
Reporting Frequency
Annual
Accession No.
0190004
Grant No.
(N/A)
Project No.
SD00131-H
Proposal No.
(N/A)
Multistate No.
(N/A)
Program Code
(N/A)
Project Start Date
Oct 1, 2001
Project End Date
Sep 30, 2006
Grant Year
(N/A)
Project Director
Stein, H. H.
Recipient Organization
SOUTH DAKOTA STATE UNIVERSITY
PO BOX 2275A
BROOKINGS,SD 57007
Performing Department
ANIMAL & RANGE SCIENCES
Non Technical Summary
Nutrients wasted from intensive animal production are a major environmental concern. Nitrogen, phosphorus, and micro-minerals that are excreted by the animals may end up in the water supply, and thus pollute drinking water for human consumption and cause damage to aquatic species. It is the purpose of the current research to identify nutritional factors that can decrease nutrient excretion and ammonia emission from swine production.
Animal Health Component
(N/A)
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
30235101010100%
Knowledge Area
302 - Nutrient Utilization in Animals;

Subject Of Investigation
3510 - Swine, live animal;

Field Of Science
1010 - Nutrition and metabolism;
Goals / Objectives
It is the objective of the experiments proposed to identify factors that can improve nutrient utilization and contribute to a reduction in nutrient output of nitrogen, phosphorus, and micro-minerals from growing swine. To reduce nitrogen excretion, factors affecting protein digestibility in pigs pigs will be identified by conducting the following experiments: Additivity of digestibility coefficients; Effects of feeding level on endogenous amino acid losses and digestibility coefficients; Effect of body weight on amino acid digestibility coefficients. Factors influencing Phosphorus digestibility and -excretion will be addressed by investigating the effect of using phytase and low phytate corn. The effects of using different chemical forms of micro-minerals on micro-mineral excretion and pig performance will be investigated by measuring digestibility and excretion of various chemical forms of micro-minerals, and the requirements of digestible microminerals will be calculated. The net energy of low-protein diets will be measured, and diets based on net energy will be formulated.
Project Methods
For the digestibility experiments, a common protocol will be used. Growing pigs will be equipped with a T-cannula in the distal ileum and housed in 1 x 1.2 m pens in the Animal Science Complex swine facility. Experimental diets will be prepared and 0.25% chromium oxide will be included in all diets as an inert marker. Pigs will be fed their respective diets for 7-9 days with ileal digesta being collected from the cannulas in 12-hour periods during the final two days of each feeding period. Samples will be analyzed for their nutrient content and digestibility coefficients will be calculated. In some experiments, fecal and urine samples will be collected to analyze the excretion of nutrients from the pigs. In these experiments, pigs will be placed in metabolism cages allowing for the collection of fecal and urinary excretions. Total tract digestibility coefficients will be calculated using procedures as described above. Work to reduce the excretion of micro minerals will be conducted by determining micro-mineral absorption, digestibility, and excretion of organic and inorganic forms of zinc, copper, iron, and manganese. Diets will be formulated using different chemical forms of these minerals, and the digestibility and excretion of the minerals will be determined. Based on this information, the most digestible forms will be identified and diets based on digestible amounts of the minerals will be formulated and the reduction in mineral excretion compared to conventionally used forms of the minerals will be calculated. To evaluate the effect of the energy system on protein utilization, the net energy value of corn and soybean meal will be determined using an open circuit calorimeter and conventional energy balance techniques. Subsequently, diets will be formulated on a net energy basis and amino acids will be included in these diets based on their standardized digestibility coefficients. The diets formulated will vary in their content of crude protein, and fed to growing pigs in balance studies as well as performance experiments. Nitrogen excretion, nitrogen accretion, body composition, and pig performance will be determined for pigs fed diets containing between 10 and 18% crude protein. The hypothesis that growing pigs fed low protein diets will perform equally as well as pigs fed conventional diets if diets are formulated based on net energy and standardized ileal amino acid digestibility coefficients will be tested. In all the above experiments, emphasis will be placed on nutrient excretion and animal performance. At the end of the period covered by this proposal, factors that can contribute to a reduction in nutrient excretion without compromising pig performance have been identified. Animals used in the above experiments will be cared for according to "Guide for the Care and Use of Agricultural Animals in Agricultural Research and Teaching" (Federation of Animal Societies, 1999). Prior to the initiation of each experiment, the experimental protocol will be submitted to The Animal Care and Use Committee at SDSU for approval.

Progress 10/01/01 to 09/30/06

Outputs
Dr. Stein left SDSU for the University of Illinois in August 2006, and this is a general summary of his efforts. The majority of his work has been with determining the amino acid and phosphorus digestibilites of various ethanol co-products. His work has shown a wide range in digestbilities between co-product sources. Also, Dr. Stein was working on a system to more rapidly determine the AA availability in DDGS. One of his MS students is finishing up her research on the use of phytase in DDGS-based diets to enhance P utilization.

Impacts
This research has a very large impact on water quality since by determining the AA and P in DDGS, diets can be prpoerly formulated, resulting in less N and P making it into ground and surface waters. As the ethanol industry continues to rapidly expand, more and more DDGS must be incorporated into livestock diets. However, in commercial feed mills, they do not have the time to take DDGS samples and have them analyzed before they are used. With the large varibiality in DDGS content, many mills end up using average AA and P values for DDGS, which results in either over-feeding or under-feeding AA and P most of the time. When Dr. Stein completes his procedures, it will allow nutritionists to use actual values, resulting in better balanced diets with less N and P being excreted.

Publications

  • Petersen, G. I., and H. H. Stein. 2006. A novel procedure for estimating endogenous losses and measuring apparent and true digestibility coefficients of phosphorus by growing pigs. J. Anim. Sci. 84:XXXX (Submitted).


Progress 01/01/05 to 12/31/05

Outputs
Two experiments were conducted to investigate factors that may effect the utilization of nitrogen and phosphorus in pigs. In Exp. 1, the effect of using the newly developed corn hybrid called NutriDense corn was investigated. NutriDense corn has a greater concentration of Lys and ether extract than yellow dent corn. The apparent and standardized ileal digestibility of AA in NutriDense corn was measured in an experiment involving ileal cannulated pigs. The digestibility of all AA in NutriDense corn was compared to the digestibility of AA in yellow dent corn, wheat, barley and sorghum. Results of this experiment showed that the digestibility for most indispensable AA is greater (P < 0.05) in NutriDense corn and wheat than in the other cereal grains. The SID for Lys in NutriDense corn (77.6%) was greater (P < 0.05) than in yellow dent corn (68.5%), and sorghum (56.9%), but not different from wheat (75.1%) and barley (71.7%). The SID for Arg and Met in NutriDense corn also were greater (P < 0.05) than in yellow dent corn (88.1 and 87.2% vs. 84.5 and 82.8%, respectively). For the remaining indispensable AA, no differences in SID between NutriDense corn and yellow dent corn were observed. In Exp. 2, the effect of including different levels of a newly developed phytase enzyme in diets fed to weanling pigs was investigated. Five diets (i.e., a positive control, a negative control, and the negative diet supplemented with graded levels of phytase) were formulated and fed to pigs during a 28-day period that started two weeks post-weaning. The ADG was lower (P = 0.03) for pigs fed the negative control diet compared with pigs fed the positive control diet for the d 15 to 28 day period. However, there were no differences in the average daily gain (ADG) between the positive control diet and the phytase supplemented diets, but there was a tendency for a linear increase in ADG with increasing phytase inclusion in the diet (P = 0.10, 0.18, and 0.11 for day 0 to 14, day 14 to 28, and day 0 to 28, respectively). The gain to feed ratio (G:F) ratio was similar for pigs fed the positive and the negative control diets during the initial 2 weeks of the experiment. However, as phytase was added to the negative control diet, the G:F improved (linear effect, P = 0.004). During the final 2 weeks of the experiment, the G:F was lower (P = 0.01) in pigs fed the negative control diets compared with pigs fed the positive control diet, but pigs fed the phytase supplemented diets had a G:F that was similar to pigs fed the positive control diet. For the entire experimental period, the G:F for the negative control diet tended (P = 0.06) to be lower than for the positive control diet. However, the G:F increased linearly (P = 0.04) with increasing inclusion rates of phytase to the negative control diet. By adding phytase to the negative control diet, values for G:F that were similar to the G:F for the positive control diet was obtained.

Impacts
Results of Exp. 1 demonstrate that if NutriDense corn is included in diets fed to swine, the excretion of nitrogen will be reduced because of the higher digestibility of AA in NutriDense corn than in yellow dent corn. With an estimated usage of 25 mill metric ton of corn in the US swine industry, the potential reduction of excreted N is significant. The results of Exp. 2 demonstrated that by including phytase in the diets fed to weanling pigs, the dietary concentration of phosphorus may be reduced from 0.60 to 0.40% without reducing performance of the pigs. Such a reduction in the dietary phosphorus concentration will reduce the excretion of phosphorus from the pigs by approximately 50%. The total annual reduction in phosphorus excretion will be approximately 5,000 metric tons if all diets fed to weanling pigs are fortified with phytase.

Publications

  • Bohlke, R. A., R. C. Thaler, and H. H. Stein. 2005. Calcium, phosphorus, and amino acid digestibility in low-phytate corn, normal corn, and soybean meal by growing pigs. J. Anim. Sci.83:2396-2403.
  • Stein, H. H., C. Pedersen, M. L. Gibson, and M. G. Boersma. 2006. Amino acid and energy digestibility in ten samples of dried distillers grain with solubles by growing pigs. J. Anim. Sci. 84:XXXX (In Press).
  • Chastanet, F., A. A. Pahm, C. Pedersen, and H. H. Stein. 2006. Effect of feeding schedule on apparent energy and amino acid digestibility by growing pigs. Anim. Feed Sci. and Technol. XX:XXXX (In Press).
  • Fan, M. Z., L. I. Chiba, P. D. Matzat, X. Yang, Y. L. Yin, and H. H. Stein. 2006. Measuring nitrogen-containing polymer synthesis rates by using stable isotope tracers. J. Anim. Sci. 84:XXXX (In Press).
  • Petersen, G. I., and H. H. Stein. 2006. A novel procedure for estimating endogenous losses and measuring apparent and true digestibility coefficients of phosphorus by growing pigs. J. Anim. Sci. 84:XXXX (In Press).
  • Mahan, D. C., E. P. Berg, J. H. Brendemuhl, S. D. Carter, L. I. Chiba, T. D. Crenshaw, G. L. Cromwell, C. R. Dove, A. F. Harper, G. M. Hill, G. R. Hollis, S. W. Kim, M. D. Lindemann, C. V. Maxwell, P. S. Miller, J. L. Nelssen, B. T. Richert, G. C. Shurson, L. L. Southern, T. S. Stahley, H. H. Stein, E. van Heugten, and J. T. Yen. 2005. Comparison of dietary selenium fed to grower-finisher pigs from various regions of the United States on resulting tissue Se and loin mineral concentrations. J. Anim. Sci. 83:852-857.
  • Hollis, G. R., S. D. Carter, T. R. Cline, T. D. Crenshaw, G. L. Cromwell, G. M. Hill, S. W. Kim, A. J. Lewis, D. C. Mahan, P. S. Miller, H. H. Stein, and T. L. Veum. 2005. Effects of replacing pharmacological levels of dietary zinc oxide with lower dietary levels of various organic zinc sources for weanling pigs. J. Anim. Sci. 83: 2123 - 2129.
  • Stein, H. H., C. Pedersen, A. R. Wirt, and R. A. Bohlke. 2005. Additivity of values for apparent and standardized ileal digestibility of amino acids in mixed diets fed to growing pigs. J. Anim. Sci. 83:2387-2395.


Progress 01/01/04 to 12/31/04

Outputs
Factors Affecting Nutrient Utilization and Excretion by Growing Swine Four experiments were conducted to identify factors that may affect P and N utilization and excretion by growing pigs. In Exp. 1, the apparent and standardized ileal digestibility coefficients of amino acids (AA) in dried distillers grain with solubles (DDGS) was measured. Results of this experiment showed that there is a great variation in AA digestibility among sources of DDGS. The most variable AA are Lys and Trp, where digestibility coefficients ranged from 44 to 78% and from 46 to 80%, respectively. A variation of this magnitude was also reported in a previous experiment and represents a big concern for the swine industry. It is, therefore, necessary that a rapid and inexpensive in vitro procedure be developed to allow the feed industry to screen qualities of DDGS. Current work in our laboratory is addressing this question. In Exp. 2, the effects of soaking or fermenting corn-soybean meal based diets were investigated. Feed was fed in a dry form or after soaking with water in a 1:1 ratio or a 1:3 ratio or after fermenting the feed for 24 h prior to feeding. Results from this experiment documented that the mixing of feed with water in a 1:3 ratio or fermentation may reduce the quantities of digestible AA that are absorbed by the pigs, and therefore, increase the quantity of N that is excreted. These feeding practices are, therefore, not recommended. In Exp. 3, the apparent and true digestibility of P in field peas was measured in diets without or with microbial phytase. Results of this experiment showed that the apparent digestibility of P in field peas is 55 and 70% in diets without and with microbial phytase, respectively. The corresponding numbers for true total tract digestibility are 61 and 76%, respectively. Values for the digestibility of P in field peas have never previously been published in North America, but they are higher than in other vegetable feed ingredients. As a consequence, the excretion of P from pigs fed field peas is lower than from pigs fed diets containing other feed ingredients. Because of the high digestibility of P, less inorganic P is needed in diets containing field peas which will help lower the costs of diets containing field peas. Exp. 4 was conducted to identify the site in the GI-tract of pigs that is most important for the digestion of P. A new technique involving double cannulation of pigs was developed, and samples were taken from the duodenum, the ileum, and the rectum of the pigs. It was possible to calculate the digestibility in three compartments of the GI-tract; i.e., the mouth and stomach, the small intestine, and the large intestine. Results of this experiment revealed that the digestibility of P is relatively low in the mouth and the stomach (20.9 and 23.0% for diets without or with microbial phytase, respectively). However, the majority of the P is digested in the small intestine (39.3 and 56.1% for diets without and with microbial phytase, respectively). The results provide basic information about the mechanics of P digestion in pigs. This information will increase the understanding of P digestion in pigs.

Impacts
Results of Exp. 1 will help the swine industry utilize DDGS in their rations. In addition, this research has highlighted the need for further research in this area. The results of Exp. 2 demonstrates that feed fed in a dry form or mixed with water in a 1:1 ratio will give a better utilization and a lower excretion of N compared to feed mixed with more water or fermented. Such data have not previously been available to the swine industry. The data obtained in Exp. 3 and 4 will help the swine industry find feeding practices that will reduce the excretion of P from growing swine.

Publications

  • Stein, H. H., G. Benzoni, R. A. Bohlke, and D. N. Peters. 2004. Assessment of the feeding value of South Dakota grown field peas (Pisum Sativum L) for growing pigs. J. Anim. Sci. 82:2568-2578.
  • Moter, V., and H. H. Stein. 2004. Effect of feed intake on endogenous losses and amino acid and energy digestibility by growing pigs. J. Anim. Sci. 82:3518-3525.
  • Kim, I.B., P. R. Ferket, W. J. Powers, H. H. Stein and T. A. T. G. van Kempen. 2004. Effects of different dietary acidifier sources of calcium and phosphorus on ammonia, methane and odorant emission from growing-finishing pigs. Austral. J. Anim. Sci. 17:1131-1138.
  • Nyachoti, C. M., and H. H. Stein. 2004. Bioavailability: Amino Acids. P. 108 - 110 in Encyclopedia of Animal Science. Marcel Dekker Inc.
  • Petersen, G. I., M. R. Smiricky-Tjardes, and H. H. Stein. 2005. Apparent and standardized ileal digestibility of amino acids in gelatin-based diets by growing pigs. Anim. Feed Sci. Technol. 119:107-115.


Progress 01/01/03 to 12/31/03

Outputs
Four experiments were conducted to identify factors that may affect P and N utilization and excretion by growing pigs. Two experiments were conducted to investigate how dietary phosphorus is utilized by growing pigs. In exp. 1, the effects of adding microbial phytase to diets for weanling, growing, and reproducing swine were investigated. Results of this experiment confirmed that the addition of phytase to diets for growing pigs and lactating sows increases the absorption of dietary phosphorus by 60 to 80%, which reduces the excretion of phosphorus from these animals by 40 to 50%. However, this research also revealed that gestating sows are not capable of utilizing microbial phytase. Therefore, microbial phytase should not be used in diets for gestating sows. This finding has never previously been reported in North America and will impact the future use of microbial phytase by the swine industry. In exp. 2, a novel procedure for measuring the digestibility of P in feed phosphates was developed using a new P-free diet. This diet may also be used to estimate the endogenous loses of P from pigs which allow researches to calculate the true phosphorus digestibility of P in feed phosphates. The procedure was successfully used to measure the apparent (ATTD) and the true (TTTD) digestibility coefficients of five feed phosphates. It was found that dicalcium phosphate and two sources of monocalcium phosphates (MCP) have ATTD that are similar (81 to 83% ATTD and 88 to 89% TTTD). However, the ATTD and the TTTD for monosodium phosphate (91 and 98%, respectively) were higher (P < 0.05) than for the other sources. A purified sample of MSP had ATTD and TTTD of 88 and 94%, respectively. These values were not different from any of the other sources. The data from this experiment provide digestibility coefficients for all the feed phosphates that are commonly used in the swine industry. Such values have never before been available, but they allow swine producers and feed companies to formulate diets based on the digestible contents of phosphorus and choose feed phosphates that will result in the lowest excretion of phosphorus from the animals. Two experiments were conduced to investigate opportunities for reducing the excretion of N from growing pigs. In exp. 3, the protein and AA digestibility coefficients in four sources of dried distillers grain with solubles (DDGS) were measured. Results from this experiments revealed that the digestibility of AA in different sources of DDGS is highly variable (between 50 and 75% for total nitrogen). Future research is directed at identifying the exact causes for this variation, and thus, provide the industry with recommendations to be followed in the production of DDGS. This will ensure that DDGS with the highest possible digestibility is produced which will lower the excretion of N from pigs fed DDGS-based diets. In exp. 4, the effect of the level of feed intake on the digestibility of AA in growing pigs was investigated. It was found that the digestibility increases as feed intake goes up. Therefore, the lowest excretion of N from pigs will be obtained if pigs are fed on an ad libitum basis.

Impacts
The results obtained in exp. 1 and 2 allow nutritionist to formulate diets for growing and reproducing swine that will reduce the excretion of P from swine to the greatest extend. Based on our findings, it is possible to reduce the P excretion by at least 50% by using available technologies in feed formulation. The results of exp. 3 will be utilized by the ethanol industry to adjust the processing procedures to produce DDGS with the higest possible digestiblity. This will increase the utilization of DDGS by the swine industry and at the same time, the excretion of N from pigs fed diets based on DDGS will be reduced.

Publications

  • Sulabo, R. 2003. Effect of body weight and reproductive status on phosphorus digestibility and efficacy of phytase in pigs. MS Thesis. South Dakota State University.
  • Snow, J. L., Stein, H. H., Ku, P. K., and Trottier, N. L. 2003. Amino acid digestibility and nitrogen utilization of high oil, high lysine, and waxy corn fed to growing pigs. Anim. Feed Sci. Technol. 113:113 - 126.
  • Stein, H. H., and M. Nyachoti. 2003. Animal effects on Ileal Amino Acid Digestibility. P. 223 - 241 in R. O. Ball (Ed.): Proc. 9 th Intl. Symp. Digest. Phys. in Pigs, Vol. 1. Banff, Canada.
  • C. M. Nyachoti and H. H. Stein. 2003. Bioavailability: Amino Acids. Encyclopedia of Animal Science. Marcel Dekker Inc. (In Press).
  • Stein, H. H. 2003. Digestible Amino Acids: Determination and use. Proc. 64th Minnesota Nutr. Conf., p 231 - 257.
  • V. Rayadurg, and H. H. Stein. 2003. The effect of feed intake on amino acid digestibility in growing pigs. J. Anim. Sci 81(Suppl. 2):45 (Abstr.).
  • M. R. Smiricky-Tjardes, D. M. Albin, J. E. Wubben, V. M. Gabert, and H. H. Stein. 2003. Estimating the true ileal digestibility of soy products using the homoarginine technique. Proc. 9th Intl. Symp. Digest. Phys. in Pigs, p.25 - 27.
  • R. A. Bohlke, H. H. Stein, A. R. Wirt, and R. C. Thaler. 2003. Differences in total tract and ileal digestibility coefficients of calcium and phosphorus in growing pigs fed low phytate corn, normal corn, soybean meal, and corn soybean meal based diets. J. Anim. Sci. 81(Suppl. 1):100. (Abstr.).
  • Thaler, R. A., and H. H. Stein. 2003. Using South Dakota Grown Field peas in swine diets. Extension Extra 2041, South Dakota State University.


Progress 01/01/02 to 12/31/02

Outputs
Nine growing barrows were used to determine apparent ileal digestibility coefficients (AID) and apparent total tract digestibility coefficients (ATTD) of calcium (Ca), and phosphorus (P) in low phytate corn (LPC), normal corn (NC), and soybean meal (SBM). The AID and the standardized ileal digestibility coefficients (SID) of CP and AA were also determined for these feedstuffs. Nine diets were formulated and fed to ileal cannulated growing barrows (initial average BW: 29.3) in a 9 x 9 Latin Square design. Diets 1 and 2 contained LPC and NC, respectively, as the sole source of CP, AA, Ca, and P. Diets 3 and 4 were identical to diets 1 and 2 with the exception that limestone (iCa) and monosodium phosphate (iP) were added to these diets. Diet 5 contained SBM as the sole source of CP, AA, Ca, and P. Diet 6 was based on SBM with iCa and iP added. Diet 7 contained LPC, SBM, iCa, and iP, likewise, diet 8 contained NC, SBM, iCa, and iP. Diet 9 was a protein-free diet, which allowed for the calculation of endogenous losses of CP and AA. Diets 3, 4, 6, 7, and 8 were formulated to contain similar Ca:digestible P ratios. Results of the experiment showed that the AID and the ATTD (70 and 69%, respectively) of Ca in LPC were higher (P < 0.05) than in NC (47 and 50%) and SBM (51 and 47%). The addition of iCa did not affect (P > 0.05) the AID or the ATTD of Ca for any of the three feed ingredients. No differences (P > 0.05) in the AID of Ca were found between the LPC-SBM and NC-SBM diets (63 and 63%, 43 and 46%, and 57 and 50% for LPC, NC, and SBM, respectively). The AID and the ATTD of P in the LPC diet were higher (P < 0.05) than that of the NC and SBM diets (57 and 55% vs. 28 and 29% and 37 and 38%). When iP was added to NC and SBM, the AID and the ATTD of P increased (P < 0.05) to 45 and 50% and 50 and 46%, respectively. However, the addition of iP did not (P > 0.05) improve the AID or the ATTD of P in LPC (50 and 51%, respectively). For both Ca and P, there were no differences (P > 0.15) between the AID and the ATTD in any of the feed ingredients. The AID of CP in SBM was higher (P < 0.05) than in LPC and NC (79% vs 68 and 64%). The same was the case for all of the indispensable amino acids except leucine and methionine. The AID of Arg, Ile, Lys, Phe, Thr, and Val were higher (P < 0.05) in LPC than in NC. Likewise, the SID of Lys, Phe, and Thr were higher (P < 0.05) in LPC than in NC and the SID of Arg, His, and Lys were higher (P < 0.05) in SBM compared to both corns. In conclusion, LPC has a higher digestibility of Ca and P than NC. Therefore, less inorganic Ca and P need to be supplemented when feeding diets based on LPC rather than NC. The AA digestibility in LPC is at least as high as in NC. There appears to be no net absorption or excretion of Ca and P in the large intestine of growing pigs fed corn or soybean meal based diets.

Impacts
Because of the improved digestiblity coefficients of P and AA in low-phytate corn, the excretion of P and N from growing pigs can be reduced if swine producers use low phytate corn rather than normal corn in their formulations for growing pigs. By doing so, the amount of P and N released into the environment can be reduced.

Publications

  • Bohlke, R. A., 2002. Calcium, phosphorus, and amino acid digestibility coefficients in low phytate corn by growing pigs. MS Thesis. South Dakota State University.
  • Bohlke, R. A., H. H. Stein, A. R. Wirt, and R. C. Thaler. 2002. Differences in apparent and standardized crude protein and amino acid digestibility coefficients between low phytate corn, normal corn, and soybean meal in growing pigs. J.Anim. Sci. 80 (Suppl. 2): 42. (Abstr.).