Experiments were conducted to determine the tryptophan (Trp) requirement of 10- to 20-kg pigs. A Trp-deficient experimental diet (.11% total Trp, 18% CP, 3,320 kcal of ME/kg) was composed of corn, feather meal, corn gluten meal, soybean meal, and dried whey. True digestibility of Trp in the experimental diet was 70% (.077% digestible Trp) as established in a digestibility assay that involved cecectomized, adult cockerels (Exp. 1). An initial pig study (Exp. 2) verified that the experimental basal diet, when fortified with sufficient L-Trp, was capable of producing growth rate and feed efficiency similar to that of pigs fed a conventional corn-soybean meal-dried whey diet (18% CP, 3,320 kcal of ME/kg). In Exp. 3, crossbred pigs with an average BW of 10.9 kg were fed the Trp-deficient basal diet supplemented with 0, .015, .030, .045, .060, and .075% L-Trp. In Exp. 4, crossbred pigs that averaged 9.5 kg were fed the basal diet fortified with .030, .045, .060, and .075% L-Trp. By examining the data from Exp. 3 and 4 together, the digestible Trp requirement for maximum daily weight gain was estimated to be .14% of the diet. Assuming an 88% true digestibility of Trp in commercial diets based on corn and soybean meal (calculated from published data), the total Trp required in practice would be .16% (.89% of the dietary protein).

A proline-free, chemically defined amino acid basal diet was compared with this same diet fortified with 4g L-proline per kg when given to 5-kg pigs. During a 28-day feeding period, daily gain, food intake, and gain: food ratio of pigs given the proline-free diet were not different (P > 0·05) from those of pigs given the proline-supplemented diet. Young pigs can apparently synthesize adequate quantities of proline endogenously to meet their needs for both growth and maintenance.

An assay was conducted to determine the efficiency of dietary methionine retention for protein accretion in 14-kg pigs. During an 18-d feeding period, pigs were fed a chemically defined amino acid basal diet [147.7 g protein (N x 6.25)/kg, 14.43 MJ metabolizable energy/kg, 4000 mg L-cystine/kg] containing 1150, 1725 or 2300 mg L-methionine/kg. Linear (P less than 0.01) responses in daily gain, daily food intake, daily methionine intake, gain:food ratio and empty body weight gain were obtained as dietary methionine level increased. Representative pigs were killed at the beginning of the assay for whole-body compositional analysis, and the comparative slaughter technique was used to estimate methionine retention. Absolute retention of methionine, protein, water, fat and ash increased linearly (P less than 0.05) with dietary methionine supplementation. Regressing methionine retained on methionine intake resulted in an efficiency of methionine retention above maintenance of 71.7%. The maintenance requirement for methionine was estimated to be 57 mg/d (8 mg/kg body wt 0.75) in the presence of excess dietary cystine. Concentrations of most indispensable amino acids, including methionine, in whole-body protein increased linearly, although glycine and proline concentrations decreased as dietary methionine level increased. This suggests that the ratio of whole-body collagen protein to non-collagen protein decreases as dietary methionine is incremented from deficiency to near adequacy.

Three pig experiments were conducted using a chemically defined, amino acid diet under conditions in which all nutrients were 100% bioavailable to assess the maximal portion of the sulfur amino acid (SAA) requirement that could be furnished by cystine (Cys). In Exp. 1, a methionine (Met)-deficient diet containing .12% L-Met and .40% L-Cys was supplemented with graded levels of L-Met. Pigs weighing 10 kg initially responded quadratically (P < .05) to Met supplementation. A two-slope, broken-line regression model (weight gain regressed on percentage of dietary Met) estimated an inflection point at .23% dietary Met. A constant level of .46% dietary SAA with differing Met:Cys weight (wt:wt) ratios was used in Exp. 2. Pigs fed Met:Cys ratios of 60:40 and 50:50 had similar (P > .05) weight gains, but pigs fed a 40:60 Met:Cys ratio gained less (P < .05) than those fed the other diets. Maintaining dietary sulfur at .111% in Exp. 3, pigs fed Met:Cys ratios (wt:wt) of 100:0, 55:45, 50:50, and 45:55 gained weight at similar (P > .05) rates, but pigs fed the 45:55 Met:Cys ratio had a tendency to produce lower weight gains. Regardless of whether a constant dietary SAA or sulfur level was maintained, no more than 50% of the young pig's total SAA requirement (wt:wt) could be furnished by Cys.

Four nursery experiments were conducted using a methionine (Met)-deficient feather meal-corn-soybean meal-dried whey basal diet (20% CP; 3,250 kcal of ME/kg, .11% choline, .19% Met, 1.00% cystine) supplemented with lysine, tryptophan, and histidine to determine the Met requirement of 5- to 10- and 10- to 20-kg pigs. Based on a true Met digestibility value of 81.6% estimated by a pig ileal digestibility assay, the Met-deficient basal diet contained .155% of digestible Met. A preliminary experiment (Exp. 1) indicated that pigs fed the Met-deficient basal diet when fortified adequately with Met could produce weight gains similar to those of pigs fed a 20% CP practical corn-soybean meal-dried whey diet. In Exp. 2 and 3, crossbred pigs weighing 5.8 kg initially were fed diets containing graded levels of digestible Met between .195 and .355%. Average daily gain increased quadratically (P less than .05) as the level of Met increased. When the data of Exp. 2 and 3 were examined together, the digestible Met requirement of 5- to 10-kg pigs was estimated to be .255% of the diet. In Exp. 4 and 5, crossbred pigs averaging 10 kg were fed digestible Met concentrations ranging from .155 to .315%. Average daily gain increased quadratically (P less than .05). The digestible Met requirement of 10- to 20-kg pigs was estimated at .255% for maximal weight gain, which was similar to that of 5- to 10-kg pigs. Assuming an 89% digestibility of Met in practical corn-soybean meal diets, the total Met level needed in practice would be .29%.(ABSTRACT TRUNCATED AT 250 WORDS)

A total of 72 pigs averaging 9.6 ± 1.4 kg were used to evaluate the efficacy of supplemental L-methionine (Met), D-Met, DL-Met and DL-methionine hydroxy analog free acid (DL-HMB) when added to a Met-deficient feather meal-corn-soybean meal-dried whey diet. Growth performance was similar for all diets containing isomolar levels of Met isomers and analogs, and the pigs utilized L-Met, D-Met, DL-Met and DL-HMB with the same molar efficiency. Key words: Pigs, methionine isomers and analogs, growth performance

Two growth assays and one nitrogen balance experiment were conducted to develop an ideal amino acid pattern for 10-kg pigs. Crossbred pigs were fed chemically defined amino acid diets containing four indispensable amino acid (AA) patterns: 1) the Illinois final amino acid pattern (IFP), a recently developed AA profile for purified diets; 2) the Illinois ideal amino acid pattern (IIP), a modification of IFP; 3) the Wang and Fuller ideal amino acid pattern (WFIP); and 4) the 1988 National Research Council (NRC) amino acid requirement pattern for 10-kg pigs (NRCP). A mixture of dispensable AA consisting of glutamate, glycine, and proline that had been proven to be an efficient mixture of dispensable AA nitrogen was fed together with the indispensable AA patterns. Diets were made isonitrogenous and isoenergetic within experiments. In Exp. 1, pigs were given ad libitum access to experimental diets with AA levels set above the NRC AA requirements. Regardless of which AA pattern was fed, pigs had similar (P greater than .05) daily gains, daily feed intakes, and gain:feed ratios. In Exp. 2, all levels of indispensable and dispensable AA were reduced to 50% of levels present in Exp. 1. When pigs had ad libitum access to these diets, daily gains of pigs fed IIP were superior (P greater than .05) to those of pigs fed IFP or NRCP, but similar (P greater than .05) weight gains occurred in pigs fed IFP, WFIP, and NRCP. In Exp. 3, the efficiency of nitrogen utilization of the four indispensable AA patterns was evaluated by a nitrogen balance experiment in pigs equally fed the same experimental diets fed in Exp. 2. Pigs fed NRCP utilized nitrogen with an efficiency of 74%, which was less (P less than .001) than the efficiencies of 79 to 80% obtained in pigs fed IFP, IIP, and WFIP. Nitrogen retained (grams) per gram of nitrogen intake from indispensable AA was greater (P less than .01) for IIP than for either IFP or WFIP. The results of these experiments indicate that WFIP contains excesses of leucine, valine, phenylalanine plus tyrosine, methionine plus cystine, and threonine for pigs between 10 and 20 kg BW. Also, NRCP is probably first-limiting in leucine and also limiting in other AA, resulting in lower nitrogen utilization than IIP. The pattern of indispensable AA in IIP (grams of AA/100 g lysine) is as follows: lysine (100), methionine+cystine (60), threonine (65), tryptophan (18), phenylalanine+tyrosine (95), leucine (100), isoleucine (60), valine (68), arginine (42), and histidine (32).

Six ileal-cannulated pigs that averaged 100 kg BW and 16 adult cecectomized cockerels that averaged 2.35 kg BW were used to determine apparent and true digestibilities of amino acids (AA) in a complete crystalline AA mixture and in casein. A protein-free (PF) diet was included as a treatment to estimate endogenous AA losses. Fasted cockerels were compared to cockerels fed PF diets for calculation of true digestibility of AA in cockerels. For the AA diet, true digestibility of indispensable AA in the pig ranged from a low of 97.2% for leucine to a high of 100.5% for arginine (Arg). True digestibility of indispensable AA in casein ranged from a low of 93.5% for isoleucine (Ile) to a high of 99.9% for Arg. Correcting for endogenous losses increased digestibilities of lysine (Lys) and threonine (Thr) in pigs fed the AA diet by 2.4 and 7.1%, respectively, and increased Lys and Thr digestibility in pigs fed the casein diet by 1.8 and 6.1%, respectively. Feeding a PF diet to chickens to correct for endogenous losses resulted in higher true digestibility values for all AA with the exception of tryptophan, methionine, and Arg than those obtained using fasted animals. True digestibilities of Thr were 88.3 and 86.6% for AA and casein diets, respectively, using fasted controls but were 97.5 and 94.5% when the PF control was used. Proline digestibility was increased (P < .05) substantially in both pigs and cockerels when the PF control was used to correct for endogenous AA losses. Regardless of species, Ile in casein had a lower true digestibility value than any other indispensable AA. The results of this study indicated that true digestibilities of AA in a mixture of crystalline AA and in casein are essentially 100% in both pigs and cockerels.

Epidemic eosinophilia-myalgia syndrome (EMS) associated with excess L-tryptophan (Trp) consumption in humans has been declared a major public health problem. The EMS problem has not been observed in pigs, nor has comprehensive pathology associated with EMS in humans been described. Experiments were therefore conducted to evaluate the pathology and effects of excess dietary L-Trp for finishing (79 to 119 kg) pigs and to determine an LD50 of Trp for pigs. In Exp. 1, addition of .1 or 1% Trp to corn-soybean meal diets had no effect on growth performance or leukocyte and relative eosinophil counts or on plasma aspartate transferase, creatine phosphokinase, and lactate dehydrogenase activities. Likewise, untoward pathological effects of Trp feeding were not observed in the animals under study. In Exp. 2, supplementing the basal diet with 0, 2, and 4% Trp caused linear (P < .05) decreases in weight gain, feed intake, and gain:feed ratio. Mortality could not be produced by acute oral dosing in the LD50 study (Exp. 3), wherein Trp doses between 2.00 and 5.71 g/kg of BW were administered by stomach tube. Vomiting occurred at oral doses greater than 5.71 g/kg of BW. These results suggest that oral ingestion of Trp in pigs is safe and that pigs can tolerate considerable excesses of Trp.

Three growth assays and one balance experiment were conducted to determine the optimal mixture of dietary amino acids for 10-kg pigs fed a chemically defined diet. Pigs were meal fed at 0700 and 1700 h in all experiments. Increasing all indispensable amino acids by 20% from their original levels improved weight gain and gain:feed ratio to levels equivalent to those of pigs fed a 20% protein corn-soybean meal-dried whey positive control diet. Replacing the glutamateglycine-proline dispensable amino acid mixture with a complete mixture of dispensable amino acids (i.e., glutamate, glycine, proline, glutamine, serine, alanine, aspartate and asparagine) did not improve growth rate. A balance study showed that retention of nitrogen and energy (percentage of intake) from the final purified diet was superior to that of pigs fed the corn-soybean meal-dried whey diet. Metabolizable energy and metabolizable energy corrected for nitrogen retention of the final purified amino acid diet were determined to be 14.43 and 13.96 MJ/kg diet, respectively. The chemically defined diet developed here for young pigs provides a means of studying nutrient utilization in the pig under conditions in which all nutrients are essentially 100% bioavailable.

Three experiments were conducted to determine the riboflavin requirement for maximal growth of young chicks. Graded levels of crystalline riboflavin were added to either riboflavin-free, purified amino acid diets or corn-soybean meal diets. Chick growth responses were obtained upon adding riboflavin to both diets. Chicks fed the purified diet required 1.8 mg of riboflavin per kg of diet, but those fed the corn-soybean meal diet required 2.63 mg of riboflavin per kg of diet. Retarded growth and leg paralysis, rather than curled-toe paralysis, were the predominant signs of riboflavin deficiency. Calculations suggested that riboflavin bioavailability in the corn-soybean meal diet was 59.1%.

Chick and rat experiments were conducted to determine the efficacy of L-2-oxothiazolidine-4-carboxylate (OTC) as a cysteine (Cys) precursor for growth and hepatic glutathione (GSH) biosynthesis. Isosulfurous graded increments of OTC and Cys were added to Cys-free purified amino acid diets that were adequate in methionine. Curvilinear responses to both Cys and OTC for chicks and rats were obtained. Hepatic GSH accumulated in chicks only at dietary Cys levels above 0.10%. In rats, hepatic GSH increased linearly as dietary Cys content increased from deficient to adequate and from adequate to excessive. Utilization of OTC by chicks was as efficacious as isosulfurous levels of Cys for growth and hepatic GSH biosynthesis. In rats, OTC was slightly inferior to Cys for growth and hepatic GSH biosynthesis. Exponential regression slope-ratio growth efficacy values for OTC were 78.5% for chicks and 70.2% for rats; multiple linear regression slope-ratio GSH biosynthesis efficacy values were 80.3% for chicks and 83.7% for rats. It is concluded that orally administered OTC is active as a Cys precursor.

Oat flour, the by-product resulting from commercial production of oat bran, was analyzed to contain 7.7% moisture, 11% CP, 6% crude fat, 8.8% NDF, 1.56% ash (.10% Ca, .23% P), 4,265 kcal/kg GE, .41% lysine, .36% threonine, .17% tryptophan, .21% methionine and .34% cystine. Chick bioassays revealed that lysine and threonine were the first- and second-limiting amino acids in oat flour. Slope-ratio protein quality assessment indicated that the protein quality of oat flour was similar to that of dehulled soybean meal. True ME (corrected for N retention, i.e., TMEn) of oat flour for adult cockerels was 3,726 kcal/kg. A P bioavailability assay with chicks indicated that the P in oat flour was 59.7% bioavailable relative to a KH2PO4 standard. Oat bran was analyzed to contain 9.7% moisture, 15% CP, 6.2% crude fat, 19.2% NDF, 2.33% ash (.12% Ca, .41% P), 4,316 kcal/kg GE, .59% lysine, .47% threonine, .18% tryptophan, .24% methionine and .44% cystine. Protein quality assessment in chicks indicated that the protein quality of oat bran was similar to that of dehulled soybean meal. True MEn of oat bran was found to be 3,449 kcal/kg. Of the .41% total phosphorus in oat bran, 42.2% was bioavailable, relative to the KH2PO4 standard.

Two experiments were conducted to evaluate the effects of hydrated Na Ca aluminosilicate (HSCAS) on P utilization of young broiler chicks. Phosphorus-deficient corn-soybean meal diets containing .36% (.134% available) P and 1% Ca were fortified with 0, .05 and .10% P provided as KH2PO4 (22.8% P) or feed-grade dicalcium phosphate (18.9% P). Diets were available ad libitum to chicks receiving 0, .50 or 1.0% HSCAS during the period 8 to 22 d posthatching. Weight of tibia ash, percentage of tibia ash and bone-breaking force were regressed on supplemental P intake to assess P utilization in the absence or presence of HSCAS. Tibia parameters (ash weight, percentage of ash and bone-breaking force) responded linearly (P less than .01) to P supplementation. Regardless of P source (KH2PO4 or dicalcium phosphate), .5% or 1.0% HSCAS had no effect (P greater than .1) on P utilization. With no supplemental P, tibia parameters also were not affected (P greater than .05) by HSCAS. Phosphorus utilization from dicalcium phosphate was estimated to be 87% as efficient as that observed for KH2PO4. The results suggest that dietary HSCAS does not impair utilization of either phytate or inorganic P.

Three experiments were conducted to evaluate effects of hydrated sodium calcium aluminosilicate (HSCAS, a phyllosilicate) on Zn, Mn, vitamin A, and riboflavin utilization in young broiler chicks. In Experiment 1, addition of either .5% or 1.0% HSCAS to practical corn-soybean meal diets had no effect (P greater than .05) on total tibia Mn content or total liver vitamin A concentration. Total tibia Zn decreased slightly, but linearly (P less than .05), as level of HSCAS increased. Graded increments of riboflavin (0, .6 and 1.2 mg per kg of diet) were added to a riboflavin-free purified amino acid diet to assess riboflavin utilization as affected by HSCAS in Experiments 2 (.5% HSCAS) and 3 (1.0% HSCAS). Linear growth responses to riboflavin were obtained in the absence and presence of HSCAS. Common intercept multiple-linear regression indicated that riboflavin utilization was not affected (P greater than .05) by .5% or 1.0% HSCAS. The results suggest that .5% or 1.0% dietary HSCAS does not impair Mn, vitamin A, or riboflavin utilization, but that Zn utilization is reduced slightly as a result of HSCAS ingestion.

Two pig experiments were conducted using a methionine (Met)-deficient feather meal-corn-soybean meal basal diet (13% CP; 3,400 kcal ME/kg diet, .126% Met, 456% cystine) supplemented with an amino acid mixture (lysine, tryptophan, histidine, threonine and phenylalanine) to determine the Met requirement of finishing pigs between 50 and 80 kg live weight. Using young chicks in a Met bioavailability growth assay and cecectomized adult cockerels in a Met digestibility assay, the Met-deficient basal diet was found to contain .115% bioavailable and .110% digestible Met. These results gave a bioavailability estimate (relative to DL-Met set at 100%) of 91.3 +/- 2.5% and a true digestibility estimate of 87.0 +/- 2.2% for Met in the basal pig diet. In Exp. 1, 21 crossbred pigs averaging 61 kg initially were individually fed diets containing .115, .165 or .215% bioavailable Met for 21 d. Average daily gain and gain:feed ratio increased quadratically (P less than .05) as level of Met increased. In Exp. 2, 30 crossbred pigs averaging 53 kg were individually fed diets containing .115, .135, .155, .175 or .195% bioavailable Met for 27 d. Daily gain and gain;feed ratio responded linearly (P less than .01) as Met level increased. Based on the results of Exp. 2, the bioavailable Met requirement of finishing pigs in the weight range 50 to 80 kg was estimated to be .182% of the diet. Assuming an 88% bioavailability of Met in commercial diets based on corn and soybean meal, the total Met level needed in practice would be .207%. If 55% of the finishing pig's sulfur amino acid need can be furnished by cystine, the total sulfur amino acid requirement would be .45% of the diet.