Triennial Growth Symposium: important roles for L-glutamine in swine nutrition and production.

L-Glutamine (Gln) has traditionally not been considered a nutrient needed in diets for livestock species or even mentioned in classic animal nutrition textbooks. This is due to previous technical difficulties in Gln analysis and the unsubstantiated assumption that animals can synthesize sufficient amounts of Gln to meet their needs. Consequently, the current (1998) version of NRC does not recommend dietary Gln requirements for swine. This lack of knowledge about Gln nutrition has contributed to suboptimal efficiency of global pig production. Because of recent advances in research, Gln is now known to be an abundant AA in physiological fluids and proteins and a key regulator of gene expression. Additionally, Gln can regulate cell signaling via the mammalian target of rapamycin pathway, adenosine monophosphate-activated protein kinase, extracellular signal-related kinase, Jun kinase, mitogen-activated protein kinase, and nitric oxide. The exquisite integration of Gln-dependent regulatory networks has profound effects on cell proliferation, differentiation, migration, metabolism, homeostasis, survival, and function. As a result of translating basic research into practice, dietary supplementation with 1% Gln maintains gut health and prevents intestinal dysfunction in low-birth-weight or early-weaned piglets while increasing their growth performance and survival. In addition, supplementing 1% Gln to a corn- and soybean-meal-based diet between d 90 and 114 of gestation ameliorates fetal growth retardation in gilts and reduces preweaning mortality of piglets. Furthermore, dietary supplementation with 1% Gln enhances milk production by lactating sows. Thus, adequate amounts of dietary Gln, a major nutrient, are necessary to support the maximum growth, development, and production performance of swine.

Amino acid and energy digestibility of protein sources for growing pigs.

Two experiments were conducted to determine the apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of AA and DE, and to estimate ME and NE of rice protein concentrate, salmon protein hydrolysate, whey protein concentrate, and spray-dried plasma protein. In Exp. 1, 6 barrows (initially 29.5 +/- 2.5 kg of BW) were fitted with ileal T-cannulas and fed each of 5 cornstarch-based diets in a balanced crossover design over 35 d. During a given week, there were either 1 or 2 replications of each treatment, resulting in 6 total replications over 5 wk. The 4 test diets (fed from d 0 to 28) were formulated to contain 12.5% CP by using analyzed nutrient compositions of rice protein concentrate, salmon protein hydrolysate, whey protein concentrate, or spray-dried plasma protein. The fifth (N-free) diet was fed from d 28 to 35 to estimate basal endogenous losses of CP and AA, which were used to calculate SID. Ileal digesta were collected and analyzed, and AID and SID values were calculated. Apparent ileal digestible Lys, Met, and Thr values were 80.0 +/- 3.3, 65.6 +/- 3.1, and 68.4 +/- 4.5% for rice protein concentrate; 85.6 +/- 4.8, 85.5 +/- 4.3, and 69.8 +/- 8.5% for salmon protein hydrolysate; 93.3 +/- 1.4, 89.9 +/- 5.8, and 83.6 +/- 5.3% for whey protein concentrate; and 92.8 +/- 0.9, 85.7 +/- 2.1, 86.5 +/- 2.3% for spray-dried plasma protein, respectively. In Exp. 2, 6 barrows (initially 37.6 +/- 1.7 kg of BW) were fed each of 5 corn-based diets in a balanced crossover design over 35 d. During a given week, there were either 1 or 2 replications of each treatment, resulting in 6 total replications over 5 wk. The 4 diets containing the test ingredients were formulated to contain approximately 20% CP by using their analyzed nutrient compositions. The fifth (corn control) diet containing 8.2% CP was also used to calculate energy values by difference. Feces were collected to determine DE. The ME and NE contents were estimated using published regression equations. The DE, ME, and NE (as-fed) values were 4,724 +/- 461, 4,226 +/- 437, and 3,235 +/- 380 kcal/kg for rice protein concentrate; 4,173 +/- 1,052, 3,523 +/- 1,002, and 2,623 +/- 872 kcal/kg for salmon protein hydrolysate; 4,949 +/- 1,002, 4,352 +/- 955, and 3,344 +/- 831 kcal/kg for whey protein concentrate; and 4,546 +/- 673, 3,979 +/- 652, and 3,020 +/- 567 kcal/kg for spray-dried plasma protein, respectively. The excellent AA digestibility and relatively high DE, ME, and NE values indicate that these protein sources warrant further investigation as ingredients for growing pig diets.

Use of carbohydrases in corn-soybean meal-based nursery diets.

Three experiments were conducted to test the hypothesis that supplementing nursery pig diets with a mixture of carbohydrases (CS) will improve pig performance and nutrient digestibility. The CS used in these experiments contained 7 units/g of alpha-1,6-galactosidase, 22 units/g of beta-1,4-mannanase, beta-1,4 mannosidase, and trace amounts of other enzymes. In Exp. 1, 108 pigs weaned at d 21 of age were fed one of three diets containing 0 (control), 0.1, or 0.2% CS for 5 wk, based on a three-phase feeding program (1, 2, and 2 wk). Over the entire 35-d period, ADG was not affected (P > 0.05) by treatment, but supplementing 0.1% CS increased (P < 0.05) gain:feed by 9%. Experiment 2 used 10 gilts fitted with simple T-cannula in the terminal ileum at 3 wk of age. After cannulation, pigs were fed the same control Phase I and II diets, but the Phase III diet contained either 0 or 0.1% CS. Ileal samples were collected for the 3 d following the 5-d adjustment period during Phase III. Apparent ileal digestibility of GE, lysine, threonine, and tryptophan was greater (P < 0.05) in the CS diet. In Exp. 3, 90 pigs weaned at 21 d of age were fed the same control Phase I and II diets, but the Phase III diet contained either 0 or 0.1% CS. Phase III diets were fed for 3 wk. Average daily gain of the CS group was greater (P < 0.05) than the control group during wk 3. Gain:feed ratio was greater (P < 0.05) for the carbohydrase group during the entire Phase III period. Four pigs per treatment were killed at the end of Exp. 3 to measure villus height and to determine the concentration of raffinose and stachyose in different parts of the gastrointestinal tract. Average villus height was greater (P < 0.05) in pigs fed the CS diet. Carbohydrase supplementation decreased (P < 0.05) the concentration of stachyose in freeze-dried digesta from the proximal and distal small intestine. Raffinose concentration, on the other hand, was decreased (P < 0.05) by CS supplementation only in the distal small intestine. These lower concentrations suggest that CS improved the digestibility of carbohydrate in soybean meal. In conclusion, the addition of CS to Phase I and Phase II nursery diets containing low levels of soybean meal did not improve pig performance, but its addition to corn-soybean meal-based Phase III nursery diets improved gain:feed ratio and energy and AA digestibility.

Variability in mixing efficiency and laboratory analyses of a common diet mixed at 25 experiment stations.

An experiment involving 25 experiment stations in the North Central and Southern regions (NCR-42 and S-288, respectively) was conducted to assess the degree of uniformity of diet mixing among stations and to assess the variability among station laboratories in chemical analysis of mixed diets. A fortified corn-soybean meal diet was mixed at each station using a common diet formula (except for vitamin and trace-mineral additions). The diet was calculated to contain 14% crude protein (CP), 0.65% Ca, 0.50% P, and 125 ppm Zn (based on 100 ppm added Zn). After mixing, samples were collected from the initial 5% of feed discharged from the mixer, after 25, 50, and 75% was discharged, and from the final 5% of discharged feed. The five samples were sent to the University of Kentucky, finely ground, and divided into subsamples. Each set of five subsamples from each station was distributed to three randomly selected stations for analysis of CP, Ca, P, and Zn (i.e., each station analyzed five diet sub-samples from three other stations). In addition, two commercial and two station laboratories analyzed composites of the five subsamples from each of the 25 mixed diets. Based on the laboratories that analyzed all diets, means were 13.5, 0.65, and 0.52%, and 115 ppm for CP, Ca, P, and Zn, respectively. Ranges of 11.8 to 14.6% CP, 0.52 to 0.85% Ca, 0.47 to 0.58% P, and 71 to 182 ppm of Zn were found among the 25 diet mixes. The coefficients of variation among the 25 diet samples for CP, Ca, P, and Zn were 4.3, 9.3, 4.1, and 17.4%, and among the 25 laboratories were 3.6, 12.5, 10.7, and 11.1%, respectively. Overall analyses of the five sub samples were, respectively, CP: 13.4, 13.6, 13.4, 13.5, and 13.4% (P < 0.06); Ca: 0.66, 0.67, 0.67, 0.66, and 0.67%; P: 0.50,0.51,0.51,0.50, and 0.50%; and Zn: 115, 116, 112, 113, and 120 ppm (P < 0.001). Diets were not uniformly mixed at all stations (station x sample No. was P < 0.08 for Ca and P < 0.01 for CP, P, and Zn). Among stations, the range of the five samples, expressed as a percentage of the mean and averaged for CP, Ca, P, and Zn, varied from +/- 1.1% (i.e., 98.9 to 101.0%) to +/- 12.9% (84.6 to 110.4%), with an overall average of +/- 5.2%. Neither type nor volume of mixers was related to mixing uniformity. The results suggest that uniformity of diet mixes varies among experiment stations, that some stations miss their targeted levels of nutrients (especially Zn), and that the variability among experiment station laboratories in analysis of dietary Ca, P, and Zn in mixed diets is quite large.

Arginine catabolism in lactating porcine mammary tissue.

In vivo studies have shown that the uptake of plasma arginine by the lactating porcine mammary gland greatly exceeds the output of arginine in milk, but little is known about the metabolic fate of arginine in this organ. The objective of this study was to quantify arginine catabolism via arginase and nitric oxide synthase pathways in the mammary tissue of sows on d 28 of lactation. Mammary tissue slices (approximately 60 mg) were incubated at 37 degrees C for 1 h in 2 mL of Krebs bicarbonate buffer containing 0.5 or 2 mM L-[U-14C]arginine, and arginine metabolites were measured using HPLC and radiochemical techniques. Rates of arginine utilization were similar to rates of urea production. Proline, ornithine, urea, glutamate, glutamine, CO2 and polyamines (putrescine + spermidine + spermine) were formed from arginine, accounting for 46, 31, 17, 2.3, 1.5, 0.22, and 0.30%, respectively, of the metabolized arginine carbons. Relatively small amounts of arginine were utilized for nitric oxide and citrulline synthesis, with citrulline accounting for 2% of the metabolized arginine carbons. Production of all arginine metabolites increased with increasing extracellular arginine concentrations from 0.5 to 2 mM, indicating a high capacity for arginine degradation. Consistent with the metabolic findings, the activities of arginases, ornithine aminotransferase, and pyrroline-5-carboxylate reductase were high, whereas those of pyrroline-5-carboxylate dehydrogenase, ornithine decarboxylase, and nitric oxide synthases were relatively low, and there was no proline oxidase, ornithine carbamoyltransferase or pyrroline-5-carboxylase synthase activity in the mammary tissue. Our results demonstrate for the first time that proline, ornithine, and urea were the major products of arginine catabolism via the arginase pathway in lactating porcine mammary tissue and provide a biochemical basis to explain a relative enrichment of proline but a relative deficiency of arginine in sow's milk.

Effects of level of supplemental phytase on ileal digestibility of amino acids, calcium, and phosphorus in dehulled soybean meal for growing pigs.

Ileally cannulated pigs were used to assess the effects of four dietary levels of microbial phytase (Natuphos) on the apparent and true digestibility of Ca, P, CP, and AA in dehulled soybean meal. Fourteen pigs (25 kg initial BW) were surgically fitted with T-cannulas at the terminal ileum and assigned to diets in a replicated 7 x 7 Latin square design. Following a 14-d recovery, four diets consisting of 30.5% soybean meal with 0, 500, 1,000, or 1,500 units of phytase/kg of diet were fed. Diets 5 (1.05% lysine, 0.90% Ca, and 0.75% P) and 6 (1.05% lysine, 0.90% Ca, and 0.75% P) contained 35.25% soybean meal and 27.0% soy protein concentrate, respectively. Diet 7 (0.37% lysine, 0.03% Ca, and 0.05% P) was a low-CP, casein-based diet used to estimate the nonspecific endogenous losses of Ca, P, CP, and AA in order to estimate the true digestibility of these nutrients. All diets contained cornstarch and dextrose and were fortified with vitamins and minerals. Chromic oxide was used as an indigestible indicator. The diets were fed daily at 9% of metabolic BW (BW0.75). Apparent and true ileal digestibility of P increased quadratically (P < 0.01) and true digestibility of Ca increased linearly (P < 0.07) with increasing levels of phytase. Apparent digestibility of Ca was unaffected (P = 0.15) by phytase level. Apparent and true ileal digestibility of CP and most AA increased slightly with the addition of 500 units of phytase/kg of diet, but not at higher levels of phytase supplementation (in most cases, cubic effect, P < 0.05). Apparent and true ileal nutrient digestibility coefficients were unaffected by soybean meal source (Diet 1 vs Diet 5), except for arginine and Ca. The apparent and true digestibility coefficients for most of the AA tended (P < 0.10) to be lower in diets containing soy protein concentrate vs the common source of soybean meal used in Diet 5, but ileal digestibilities of Ca and P were unaffected (P = 0.15). In this study, supplemental microbial phytase did not improve the utilization of AA provided by soybean meal but was an effective means of improving Ca and P utilization by growing swine fed soybean meal-based diets.

Apparent ileal digestibility of amino acids and the digestible and metabolizable energy content of dry extruded-expelled soybean meal and its effects on growth performance of pigs.

We conducted three experiments to determine the apparent ileal digestibility of amino acids (Exp. 1), metabolizable and digestible energy (Exp. 2), and feeding value (Exp. 3) of dry extruded-expelled soybean meal with (DEH) or without (DENH) hulls compared with solvent-extracted soybean meal with hulls removed (SBMNH). Soybeans used to produce DEH were unadulterated prior to extrusion, but those used for DENH were dehulled prior to extrusion. In Exp. 1, six nonlittermate barrows (initially 39 kg) were fitted with ileal T-cannulas and used in a replicated 3 x 3 Latin square design digestion trial. Experimental diets (0.80% total lysine) were cornstarch-based and contained soybean meal from one of the three different sources as the sole source of lysine. Apparent ileal digestibilies of nutrients were similar (P > 0.10) for DEH and DENH. Apparent ileal digestibilies of CP, Lys, Ile, Leu, Arg, Phe, and Val were greater (P < 0.05) for DEH and DENH than for SBMNH. In Exp. 2, six barrows (initially 41 kg) were fed three corn-based diets containing 25% of one of the three soybean meal sources. A fourth diet was fed at the end of the trial containing all ingredients except soybean meal, so that energy values of the soybean meal could be determined by difference. Digestible energy and ME contents were similar (P > 0.10) for DEH and DENH and both had greater (P < 0.05) DE and ME contents than SBMNH. In Exp. 3, pigs (n = 216, initially 10.6 +/- 1.3 kg and 35 +/- 3 d of age) were blocked by weight and allotted to six dietary treatments. Corn-soybean meal-based diets (0.95% digestible lysine and 3.44 kcal/g ME) containing DEH or DENH were compared with similar diets containing SBMNH or solvent-extracted soybean meal with hulls (SBMH). In addition, a diet containing a second expelled soybean meal with hulls (ESBM) was compared with a diet containing SBMH and soy oil. Growth performance of pigs fed diets containing DEH or DENH was not different (P > 0.10) than that of pigs fed corresponding diets containing SMBH or SBMNH. Pigs fed ESBM had lower (P < 0.05) ADG and G/F compared with its corresponding SBMH and soy oil diet. In conclusion, DEH and DENH are more digestible than conventional soybean meal and can be successfully used in swine diets.

Postnatal changes of plasma amino acids in suckling pigs.

Amino acids, ammonia, urea, orotate, and nitrate plus nitrite (stable oxidation products of nitric oxide) were determined in plasma of 1- to 21-d-old suckling pigs. Jugular venous blood samples were obtained from pigs at 1, 3, 7, 14, and 21 d of age for analysis of plasma amino acids and metabolites by HPLC and enzymatic methods. Plasma concentrations of arginine and its immediate precursors (citrulline and ornithine) decreased (P < 0.01) progressively (20 to 41%) with increasing age from 3 to 14 d. Plasma concentrations of glutamine declined (P < 0.01) progressively (10 to 31%) during the 1st wk of life. Plasma concentrations of branched-chain amino acids, threonine, and alanine decreased (P < 0.01) (5 to 12%) in 14- and 21-d-old pigs, compared with 1- and 3-d-old pigs. There were no postnatal changes (P > 0.05) in plasma concentrations of other amino acids. Plasma concentrations of ammonia increased (P < 0.01) by 18 and 46%, whereas those of nitrate plus nitrite decreased (P < 0.01) by 16 and 29%, in 7- and 14-d-old pigs, respectively, compared with 1- to 3-d-old pigs. Because arginine plays a crucial role in ammonia detoxification via the hepatic urea cycle and is the physiological substrate for nitric oxide synthesis, our results of the decreased plasma concentrations of arginine and nitrate plus nitrite, as well as the increased plasma ammonia concentration, indicate a hitherto unrecognized deficiency of arginine in 7- to 21-d-old suckling pigs. Arginine is an essential amino acid for piglets and has a great potential to enhance neonatal growth; therefore, further studies are necessary to elucidate the mechanism responsible for arginine deficiency in sow-reared piglets and to identify hormonal and metabolic means for improving neonatal arginine nutrition and growth.

Nutritional value of a genetically improved high-lysine, high-oil corn for young pigs.

Two experiments were conducted to compare the nutritional adequacy of a genetically improved high-lysine, high-oil corn (HLHOC; .408% lysine, 6.21% fat, as-fed basis) and a high-oil corn (HOC; .289% lysine, 5.97% fat, as-fed basis) for young growing pigs. Experiment 1 used four non-littermate barrows (initially 20.0 kg BW) fitted with ileal T-cannulas in a crossover-designed digestion study. The .75% total lysine diets contained 8.5% casein and an equal amount of lysine (.25%) from the test corn. Apparent ileal digestibilities of amino acids, GE, DM, and CP were similar (P > .10) between diets. Apparent ileal lysine digestibilities were 65 and 71% for the HOC and HLHOC, respectively, assuming the lysine in casein to be 100% digestible. Experiment 2 used 100 barrows reared in a segregated early-weaning environment (initially 8.3 kg BW and 27 d of age) to evaluate five corn-soybean meal-based diets in a 2 x 2 factorial arrangement with main effects being corn type and dietary lysine (.80 or 1.15% digestible lysine). The fifth diet consisted of the .80% digestible lysine HOC diet supplemented with .23% additional L-lysine x HCl (.975% digestible lysine) to verify that lysine was the limiting amino acid in the low-lysine diets. Increasing digestible lysine from .80 to 1.15% increased (P < .001) ADG and gain/feed (G/F) regardless of corn variety. Combined ADG and G/F were .347 kg and .641 and .443 kg and .790 for the .80 and 1.15% digestible lysine diets, respectively. Within lysine level, corn type did not affect ADG, ADFI, or G/F (P > .10). The results of these studies indicate that the lysine in HLHOC is as available as the lysine in HOC and that HLHOC can be used successfully in swine diets.

A cortisol surge mediates the enhanced polyamine synthesis in porcine enterocytes during weaning.

This study was conducted to determine whether a cortisol surge mediates the enhanced expression of intestinal ornithine decarboxylase (ODC) in weanling pigs. Piglets were nursed by sows until 21 days of age, when 40 pigs were randomly assigned into one of four groups (10 animals/group). Group 1 continued to be fed by sows, whereas groups 2-4 were weaned to a corn and soybean meal-based diet. Weanling pigs received intramuscular injections of vehicle solvent (sesame oil), RU-486 (a potent blocker of glucocorticoid receptors; 10 mg/kg body wt), and metyrapone (an inhibitor of adrenal cortisol synthesis; 5 mg/kg body wt), respectively, 5 min before weaning and 24 and 72 h later. At 29 days of age, pigs were used to prepare jejunal enterocytes for ODC assay and metabolic studies. To determine polyamine (putrescine, spermidine, and spermine) synthesis, enterocytes were incubated for 45 min at 37 degrees C in 2 ml Krebs-bicarbonate buffer containing 1 mM [U-(14)C]arginine, 1 mM [U-(14)C]ornithine, 1 mM [U-(14)C]glutamine, or 1 mM [U-(14)C]proline plus 1 mM glutamine. Weaning increased intestinal ODC activity by 230% and polyamine synthesis from ornithine, arginine, and proline by 72-157%. Arginine was a quantitatively more important substrate than proline for intestinal polyamine synthesis in weaned pigs. Administration of RU-486 or metyrapone to weanling pigs prevented the increases in intestinal ODC activity and polyamine synthesis, reduced intracellular polyamine concentrations, and decreased villus heights and intestinal growth. Our results demonstrate an essential role for a cortisol surge in enhancing intestinal polyamine synthesis during weaning, which may be of physiological importance for intestinal adaptation and remodeling.

Enhanced intestinal synthesis of polyamines from proline in cortisol-treated piglets.

This study was conducted to determine a role for cortisol in regulating intestinal ornithine decarboxylase (ODC) activity and to identify the metabolic sources of ornithine for intestinal polyamine synthesis in suckling pigs. Thirty-two 21-day-old suckling pigs were randomly assigned to one of four groups with eight animals each and received daily intramuscular injections of vehicle solution (sesame oil; control), hydrocortisone 21-acetate (HYD; 25 mg/kg body wt), RU-486 (10 mg/kg body wt, a potent blocker of glucocorticoid receptors), or HYD plus RU-486 for two consecutive days. At 29 days of age, pigs were killed for preparation of jejunal enterocytes. The cytosolic fraction was prepared for determining ODC activity. For metabolic studies, enterocytes were incubated for 45 min at 37 degrees C in 2 ml of Krebs-bicarbonate buffer (pH 7.4) containing 1 mM [U-(14)C]arginine, 1 mM [U-(14)C]ornithine, 1 mM [U-(14)C]glutamine, or 1 mM [U-(14)C]proline plus 1 mM glutamine. Cortisol administration increased intestinal ODC activity by 230%, polyamine (putrescine, spermidine, and spermine) synthesis from ornithine and proline by 75-180%, and intracellular polyamine concentrations by 45-83%. Polyamine synthesis from arginine was not detected in enterocytes of control pigs but was induced in cells of cortisol-treated pigs. There was no detectable synthesis of polyamines from glutamine in enterocytes of all groups of pigs. The stimulating effects of cortisol on intestinal ODC activity and polyamine synthesis were abolished by coadministration of RU-486. Our data indicate that an increase in plasma cortisol concentrations stimulates intestinal polyamine synthesis via a glucocorticoid receptor-mediated mechanism and that proline (an abundant amino acid in milk) is a major source of ornithine for intestinal polyamine synthesis in suckling neonates.

Salivary and plasma cortisol response to adrenocorticotropin administration in pigs.

Two experiments were conducted to determine the responsiveness of salivary and plasma cortisol to acute (i.v.), depot (i.m.) and chronic (repeated i.m.) adrenocorticotropin (ACTH) administration in swine. In Experiment 1, barrows (castrated pigs) were assigned to one of three injection treatments: (1) saline i.m. (SHAM1, n=2); (2) 0.75 IU/kg BW ACTH in saline i.v. (ACUTE, n=2); (3) 2.25 IU/kg BW ACTH in gel i.m. (DEPOT, n=3). Total cortisol concentrations were determined for concurrent saliva and blood samples. Correlations between salivary and plasma cortisol within treatments were: SHAM1, r=0.60; ACUTE, r=0.58; DEPOT, r=0.79. In Experiment 2, barrows were assigned to one of two injection treatments: (1) gel i.m. (SHAM2, n=3); (2) 2.25 IU/kg BW ACTH in gel i.m. (CHRONIC, n=4). The injections occurred every 6 h for a total of eight injections. Concurrent saliva and blood samples were obtained every 3 h for 72 h followed by an increasing sampling interval until day 6. Overall correlations between salivary and plasma cortisol were: SHAM2, r=0.30 and CHRONIC, r=0.61. Experiment 1 found that the relationship between salivary and plasma cortisol was stronger during longer (DEPOT) than shorter (ACUTE) ACTH stimulation. Experiment 2 found a strong relationship between the two measurements during chronic ACTH stimulation, but that relationship weakened after ACTH stimulation ceased.

Growth promotion effects and plasma changes from feeding high dietary concentrations of zinc and copper to weanling pigs (regional study).

An experiment was conducted to determine the effect of high dietary intakes of Zn and Cu and their combination on growth performance of weanling pigs with diverse health status and management strategies. Twelve experiment stations cooperated and used a total of 1,356 pigs that averaged 6.55 kg BW and 22.2 d age at weaning. The four dietary treatments, all of which met or exceeded NRC requirements, were 1) control, 2) 3,000 ppm Zn (from Zn oxide), 3) 250 Cu ppm (from Cu sulfate), or 4) 3,000 ppm Zn and 250 ppm Cu. The diets were fed as a complex Phase I diet (1.4% lysine) for 7 d followed by a Phase II diet (1.2% lysine) for 21 d. Chlortetracycline (220 ppm) was added to all diets. Fecal color (1 = yellow to 5 = black) and consistency (1 = very firm to 5 = very watery) were scored daily for 3 wk. At the end of the 28-d study, 412 pigs were bled at five stations, and plasma Cu, Zn, and Fe concentrations were determined at one station with atomic absorption spectrophotometry. Average daily gain (375, 422, 409, 415 g/d), feed intake (637, 690, 671, 681 g/d), and gain/feed (586, 611, 611, 612 g/kg) were improved (P < .01) by the addition of Zn and(or) Cu. Significant Cu x Zn interactions imply that the responses to Zn and Cu were independent and not additive. There were significant (P < .01) Zn and Cu effects and a Zn x Cu interaction on fecal color (3.17, 3.24, 4.32, 3.57) and consistency (2.39, 2.14, 2.14, 2.13). Dietary additions of Cu and Zn resulted in elevated plasma concentrations of Cu and Zn, respectively. These data indicate that pharmacological additions of 3,000 ppm Zn (oxide) or 250 ppm Cu (sulfate) stimulate growth beyond that derived from intakes of Zn and Cu that meet nutrient requirements. However, the combination of Zn and Cu did not result in an additive growth response.

Perinatal ontogeny of brain growth in the domestic pig.

The perinatal development of the brain is highlighted by a growth spurt whose timing varies among species. The growth of the porcine cerebrum was investigated from the third trimester of gestation (70 days postconception) through the first 3.5 weeks of postnatal life (140 days postconception). The shape of the growth curves for cerebrum weight, total protein mass, total cell number (estimated by DNA content), and myelination (estimated by cholesterol accretion) were described. The growth velocity of cerebrum weight had two peaks, one at 90 days and the other at 130 days postconception, whereas that of total protein was greatest from 90 to 130 days postconception, and that of total DNA was greatest between 90 and 110 days and again at 130 days postconception. The growth velocity for total cholesterol continued to increase during the entire period, suggesting that myelination continued after the growth spurts for cells (protein and DNA). The growth velocity patterns observed in these contemporary pigs suggest that this species may be an appropriate model for human brain development, not only in the perinatal pattern of increase in mass of the cerebrum, as established previously, but also with regard to the patterns of cellular development and myelination.

Arginine nutrition in development, health and disease.

As a precursor of nitric oxide, polyamines and other molecules with enormous biologic importance, L-arginine plays versatile key roles in nutrition and metabolism. Arginine is an essential amino acid in the fetus and neonate, and is conditionally an essential nutrient for adults, particularly in certain disease conditions. L-Arginine administration is beneficial in improving reproductive, cardiovascular, pulmonary, renal, gastrointestinal, liver and immune functions, and in facilitating wound healing. The effect of L-arginine in treating many common health problems is unique among amino acids, and offers great promise for improved health and well-being in the future.

Amino acid composition of the fetal pig.

Amino acid composition and accretion were determined in fetal pigs obtained from gilts by hysterectomy at d 40-114 of gestation. The whole homogenate of the fetal pig was used for analysis of dry matter, nitrogen and amino acids. Uterine uptake of amino acids was estimated at d 110-114 of gestation on the basis of uterine arteriovenous concentrations. Nitrogen and amino acid accretion in fetal pigs increased more rapidly with gestation than non-nitrogen dry matter. Amino acid nitrogen represented 83-88% of total nitrogen, and arginine was the most abundant nitrogen carrier in fetal pigs at all gestational ages. Amino acid composition changed with gestation, with glycine and hydroxyproline increasing (P < 0.05) markedly and other amino acids (except ornithine and tryptophan) decreasing (P < 0.05) to a lesser extent. Amino acid concentrations in fetal pigs increased (P < 0.05) progressively from d 60 to 114 of gestation. Uterine uptake of arginine and proline plus hydroxyproline met requirements for fetal growth during late gestation only marginally, and uterine uptake of aspartate/asparagine and glutamate was only 9-29% of fetal accretion. In contrast, uterine uptake of citrulline and ornithine was 55- and 15-fold greater (P < 0.05) than fetal accretion, respectively. On the basis of hydroxyproline content, collagen was estimated to represent approximately 7, 15, 25, 28 and 29% of total body protein at d 40, 60, 90, 110 and 114 of gestation, respectively. Amino acid composition of the fetal pig is similar to that for the human fetus, indicating that the pig is an excellent model for studying amino acid nutrition and metabolism in the human preterm neonate and infant.

Lactate inhibits citrulline and arginine synthesis from proline in pig enterocytes.

Hypocitrullinemia and hypoargininemia but hyperprolinemia are associated with elevated plasma concentration of lactate in infants. Because the small intestine may be a major organ for initiating proline catabolism via proline oxidase in the body and is the major source of circulating citrulline and arginine in neonates, we hypothesized that lactate is an inhibitor of intestinal synthesis of citrulline and arginine from proline. To test this hypothesis, jejunum was obtained from 14-day-old suckling pigs for preparation of enterocyte mitochondria and metabolic studies. Mitochondria were used for measuring proline oxidase activity in the presence of 0-10 mM L-lactate. For metabolic studies, enterocytes were incubated at 37 degrees C for 30 min in Krebs bicarbonate buffer (pH 7.4) containing 5 mM D-glucose, 2 mM L-glutamine, 2 mM L-[U-14C]proline, and 0, 1, 5, or 10 mM L-lactate. Kinetics analysis revealed noncompetitive inhibition of intestinal proline oxidase by lactate (decreased maximal velocity and unaltered Michaelis constant). Lactate had no effect on either activities of other enzymes for arginine synthesis from proline or proline uptake by enterocytes but decreased the synthesis of ornithine, citrulline, and arginine from proline in a concentration-dependent manner. These results demonstrate that lactate decreased intestinal synthesis of citrulline and arginine from proline via an inhibition of proline oxidase and provide a biochemical basis for explaining hyperprolinemia, hypocitrullinemia, and hypoargininemia in infants with hyperlactacidemia.

Efficacy of Natuphos in sorghum-based diets of finishing swine.

The efficacy of a recombinantly derived microbial phytase (Natuphos 5000, BASF Corp.) was evaluated in sorghum-soybean meal-based diets of finishing swine. During the 50- to 80- and 80- to 118-kg BW intervals, diets contained .40 and .39% plant P, respectively; control diets fed during the two weight intervals were supplemented with .08 and .04% inorganic P from dicalcium phosphate. The all plant-P diets were supplemented with 0, 300, or 500 phytase units (FTU) per kilogram of diet. Supplemental P (P = .09) and phytase (linear, P = .01) increased growth rate but did not affect feed efficiency. Dietary treatment did not affect quantitative carcass traits, CP, fat, or moisture content of the loin or taste panel scores of the cooked loin other than a quadratic decrease (P = .02) in connective tissue amount as phytase supplementation increased. Apparent ileal and total tract digestibilities of DM, GE, and N were not affected (P > .25) by phytase supplementation, whereas ileal and total tract digestibilities of Ca and P increased (P < .05 or P < .01) with increasing phytase supplementation. Ultimate load and ash content of the third and fourth metacarpals and metatarsals and serum P levels increased in response to inorganic P and phytase supplementation. Pig performance, carcass traits, and bone traits were essentially equal for the 300 and 500 FTU/kg treatments. These results show that phytase effectively liberates P in sorghum-based diets, and that 300 FTU/kg (or less) will optimize performance and carcass merit of finishing swine.

Digestible phosphorus needs of terminal-cross growing-finishing pigs.

Growth and digestion experiments were conducted to estimate the digestible P needs of terminal-cross growing-finishing pigs fed sorghum-soybean meal-based diets from 25 to 118 kg. Dietary available P levels approximated the levels recommended by the NRC (1988) or were approximately 25% above or below those levels. Up to 80 kg, dietary treatment did not affect performance; from 80 to 118 kg, the lowest P level (no inorganic P) reduced (P = .03) feed efficiency. Carcass leanness, subjective quality scores for the loin, chemical content of lean, and sensory evaluation of cooked lean were not adversely affected by decreasing P. As dietary P decreased, connective tissue amount in the lean decreased (P = .06). Ash content (P < .01) and peak load (P < .05) of metacarpals and metatarsals decreased as dietary P decreased, but structural soundness scores in the live pig were unaffected by treatment. Apparent digestibility of P decreased (P = .08 to P < .01) as dietary P decreased in the diets. Estimated P excretions per pig decreased with decreasing dietary P up to 80 kg; during the 80-to-118-kg interval, P excretions were similar for pigs fed the two lowest P diets due to reduced feed efficiency of pigs fed the lowest P diet. Dietary digestible P contents maximizing performance and carcass merit were .21, .19, and .16% for pigs fed from 25 to 50, 50 to 80, and 80 to 118 kg, respectively. The results suggest that P excretions of terminal-cross pigs can be reduced by feeding less than current NRC recommendations for P without reducing performance, carcass merit, or structural soundness of live pigs.

Nutritional value for swine of soybean meal produced by isopropyl alcohol extraction.

Three experiments were conducted to compare the nutritional value of soybean meal produced by extraction with 95% isopropyl alcohol (IPA) or hexane (HEX) for swine. The same batch of soybeans and the same processing equipment were used to produce both soybean meals. Analyzed contents of the IPA and HEX meals were, respectively: CP, 48.7, 47.0%; lysine, 3.11, 3.06%; urease, .24, .13 delta pH. In Exp. 1, two soybean meals and dietary lysine at .90 or 1.25% were used in a 2 x 2 factorial arrangement of treatments. Corn-based diets were fed to 32-d-old pigs for 26 d. There were no dietary lysine x soybean meal interactions (P > or = .35). Increasing dietary lysine increased (P < .001) ADG and gain/ feed, but soybean meal source did not affect performance. In Exp. 2, the nutritional value of HEX and IPA meals were evaluated in a N balance study using 34-kg barrows and isonitrogenous corn-based diets containing equal N from either HEX or IPA. Apparent total tract N and DM digestibility were similar for both diets. Nitrogen retention (14.4 vs 13.7 g/d, P < .10) and apparent biological value (56.5 vs 54.5%, P < .05) were slightly higher for HEX than for IPA. The effect of feeding HEX and IPA meals on morphological changes of small intestine in pigs weaned at 21 d of age was investigated in the last experiment. At 28 d of age, weaned pigs that were fed diets containing either HEX or IPA and unweaned control pigs were killed for the examination. Villus height and lamina propria depth at the duodenum were similar among all treatments. At the jejunum, weaned pigs had smaller (P < .05) villus height and greater lamina propria depths (P < .001) than unweaned pigs. Dietary soybean meal source did not affect villus height, but lamina propria depth was less (P < .10) for pigs fed IPA. The results of these experiments indicate that soybean meals produced using IPA or HEX as the solvent have equal nutritional value for swine.