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The results from computer simulations and phantom experiments to evaluate DAX performance in the presence of phase aberration and noise are described. The data obtained suggested that the aberration occurring in the breast with weak to hard aberrators could be modeled with 3 mm FHWM.

To alleviate the need for daily injection of porcine somatotropin (pST), a sustained-release implant (pSTSR) was devised that continuously delivers a daily dose of 2 mg of pST for 42 d. Ninety-six white composite (Large White x Landrace) finishing barrows (83.6 [+ or -] 1.2 kg BW) were assigned to receive zero or two pSTSR implants (4 mg pST/d) and to consume one of six diets differing in total Lys concentration (0.29, 0.52, 0.75, 0.98, 1.21, or 1.44%, as-fed basis). Diets were formulated to be isocaloric and based on the ideal protein concept. Pigs were housed individually, allowed ad libitum access to feed and water, and slaughtered at 112 kg of BW. The pSTSR affected neither ADG (P = 0.88) nor 10th rib LM area (LMA; P = 0.51), but it decreased (P < 0.01) ADFI, average backfat thickness, 10th rib fat depth, weights of leaf fat and ham fat, improved (P < 0.05) G:F, and increased (P < 0.01) weights of four trimmed lean cuts (T-cuts), and percentages of ham lean and bone. Increasing total Lys increased ADG (quadratic; P < 0.05) and ADFI (linear; P < 0.01). The G:F, plasma urea N concentrations (PUN), and T-cuts were affected by the interaction pSTSR x dietary Lys (P < 0.01). Without pSTSR, the G:F did not differ (P -0.37) among pigs fed 0.52% and greater total Lys. With pSTSR, the G:F was less (P < 0.05) for pigs fed 0.52% than 0.98 and 1.44% total Lys. Increases in dietary total Lys resulted in increased PUN (P < 0.01), and incremental increases were less in pSTSR-implanted pigs. Maximal yield of T-cuts was at 0.98% dietary total Lys in nonimplanted pigs and 1.21% total Lys in pSTSR-implanted pigs. Estimates of total Lys requirements of pigs without and with pSTSR, respectively, were 0.52 and 0.86% for growth (ADG and G:F) and 0.73 and 0.88% for lean production (LMA and T-cuts). Equivalent apparent ileal digestible Lys requirements of pigs without and with pSTSR, respectively, were 0.44 and 0.68% for growth, and 0.62 and 0.75% for lean production. With ADFI of 3.5 kg daily, an intake of approximately 26.1 g of total daily Lys (0.75%) or 22.4 g of apparent ileal digestible Lys is needed to maximize lean production in finishing barrows receiving 4 mg pST/d via sustained-release implant. Key Words: Finishing Pig, Lysine Requirement, Porcine Somatotropin, Sustained-Release Implant

A study was conducted to evaluate the mineral content of pork tissue with particular emphasis on Se between various states (regions) having different diet (grain) indigenous Se concentrations. The study involved 19 states in the north, central, and southern regions of the United States, with committee members of NCR-42 and S-1012 (formerly S-288). A total of 62 pigs were used, with collaborators sending 100-g samples each of loin, heart, and liver, and a 3- to 4-g sample of hair (collected along the topline) from two to five market-weight pigs to a common laboratory for analysis. Diets at each station were formulated with locally purchased soybean meal and grain that was either grown or normally fed to pigs within their state. Tissues were analyzed for Se, but only the loin was analyzed for the macro- and micromineral elements. Correlation of dietary minerals to the tissue element was determined. The results demonstrated differences in tissue Se among states (P < 0.01), with high correlations of dietary Se to loin (r = 0.86; P < 0.01), heart (r = 0.84; P < 0.01), liver (r = 0.83; P < 0.01), and hair Se (r = 0.90; P < 0.01) concentrations. The correlation of hair Se to the Se concentration of loin, heart, and liver tissues was high (r > 0.90; P < 0.01). States in the west-central region of the United States and west of the Mississippi river had higher dietary Se and tissue Se concentrations than states in the eastern section of the Corn Belt, east of the Mississippi river, and along the East Coast. Generally, states did not differ greatly in their loin macro- and micromineral concentrations. The simple correlation of dietary minerals to their corresponding loin mineral concentration was generally nonsignificant, but most macrominerals had decreasing mineral concentrations when the dietary mineral level was higher. These results indicate that regional differences in tissue Se were influenced more by the indigenous Se content of the diet (grain) fed to the pigs than from sodium selenite. Key Words: Geographical Region, Pigs, Selenium

Two trials were conducted to determine the replacement nutritive value of dried skim milk for growing-finishing pigs. In a three-phase feeding trial, 180 growing composite barrows (40.8 [+ or -] 2.9 kg BW) were allotted to three dietary treatments. Each phase lasted 28 d. Treatment 1 comprised a basal corn-soybean meal diet supplemented with crystalline AA to contain true ileal digestible concentrations (as-fed basis) of 0.83, 0.66, and 0.52% Lys; 0.53, 0.45, and 0.40% Thr; and 0.51. 0.45, and 0.42% sulfur amino acids (SAA; Met + Cys) in Phases 1, 2, and 3, respectively. Treatments 2 and 3 were the basal diets with 5 and 10% (as-fed basis) dried skim milk added. The three diets at each phase were formulated to have the same quantities of DE, true ileal digestible Lys, Thr, Trp, SAA, Ca, and available P. Pigs were housed 10 per pen (six pens/treatment), allowed ad libitum access to feed, and slaughtered at 121.6 [+ or -] 9.3 kg BW. No differences were detected between pigs fed the basal diet and the dried skim milk diets of between pigs fed the 5 and 10% dried skim milk diets, respectively, in 84-d ADG (P = 0.84 or P = 0.71), ADFI (P = 0.54 of P = 0.91), and G:F (P = 0.80 or P = 0.97), in hot carcass weight (P = 0.66 or P = 0.74), 45-min postmortem LM pH (P = 0.90 or P = 0.53), 10th-rib backfat thickness (P = 0.24 or P = 0.77), LM area (P = 0.13 or P = 0.63), weights of belly (P = 0.43 of P = 0.70), trimmed wholesale cuts (P = 0.18 to 0.85 or P = 0.06 to 0.53), and ham components (P = 0.25 to 0.98 of P = 0.32 to 0.63). In the N balance trial, four littermate pairs of finishing gilts (82.9 [+ or -] 2.0 kg BW) were assigned within pair to the basal or the 10% dried skim milk (asfed basis) finishing diet. Daily feed allowance was 2.6 x maintenance DE requirement and was given in two equal meals. Total fecal collection from eight meals and a 96-h urine collection began on d 14 when gilts weighed 92.1 [+ or -] 2.2 kg BW. No differences were found between dietary treatments in gilt's daily N intake (P = 0.33) and the daily output of urinary urea (P = 0.88), urinary N (P = 0.97), fecal N (P = 0.69), and total manure (P = 0.62), as well as apparent total-tract N digestibility (P = 0.84) and N retention (P = 0.84). It is concluded that growing-finishing pigs fed diets containing 10% dried skim milk would have growth performance, carcass traits, and N digestibility and use similar to those red typical corn-soybean meal diets. Key Words: Carcass Traits, Dried Skim milk, Growing-Finishing pigs, Growth, Nitrogen Digestibility, Urinary Nitrogen Excretion

Four Duroc x White composite crossbred (21.8 [+ or -] 1.0 kg BW) and four 12-wk-old Meishan purebred (20.7 [+ or -] 1.6 kg BW) growing barrows were used to determine the relative breed differences in metabolic and microbial responses to a high-fiber diet. The pigs were trained to consume 700 g of a diet containing 35% (as-fed basis) dehydrated alfalfa meal once daily. The pigs' daily intakes of DM, N, GE, NDF, and ADF were 610 g, 16.6 g, 2.64 Mcal, 150 g, and 88 g, respectively. On d 12 after surgical catheterization of the portal vein, ileal vein, and carotid artery, a 3-d total urine and feces collection was conducted. On d 24 after surgery, each pig was placed in an open-circuit calorimeter, and its catheters were connected to a system for simultaneous measurements of oxygen consumption by portal-drained viscera and by whole body, and the net portal absorption of VFA after a 24-h fasting and during a 5-h postprandial period. The VFA measured included acetic, propionic, isobutyric, butyric, isovaleric, and valeric acids. A second 3-d total urine and feces collection was conducted on d 30 after surgery. There were no differences (P = 0.13) between the first and second collections in apparent total-tract digestibility coefficients for nutrients and N retention of pigs. Compared with Duroc x White composite crossbred pigs, Meishan pigs had lower (P = 0.05) apparent digestibility coefficients for DM, N, NDF, hemicellulose, and N retention, but their portal-drained viscera used a greater (P = 0.05) fraction of whole-body oxygen consumption. No differences (P = 0.12) were found between Duroc x White composite crossbred and Meishan pigs in total viable bacteria and cellulolytic bacteria from fecal samples, in vitro digestibility of alfalfa NDF fractions by fecal inocula, whole-body oxygen consumption, net portal absorption of VFA, total energy of absorbed VFA, and the potential of absorbed VFA for meeting the energy needs for whole-body heat production. These results indicate that, in contrast to previous beliefs, the ability of Meishan growing pigs to utilize a high-fiber diet is not superior to that of Duroc x White composite crossbred growing pigs. Key Words: Energetics, High-Fiber Diet, Microbial Fiber Degradation, Nutrient Utilization, Pigs, VFA Absorption

Net portal absorption of AA during the 6-h postprandial period was measured in eight gilts (48.5 [+ or -] 1.6 kg BW) in a crossover design. The pigs had chronic catheters placed in the portal vein, carotid artery, and ileal vein, and were trained to consume 1.2 kg of a standard grower diet once daily. Blood samples were taken every 30 min for 4 h and then hourly until 6 h after feeding. The first set of blood samples was taken after pigs were fed a meal of the test 16% CP corn--soybean meal diet (16% CP) or the test 12% CP corn--soybean meal diet supplemented with crystalline lysine, threonine, and tryptophan (12% CP + AA) to equal the three AA levels in the 16% CP diet. Pigs were then fed the standard diet for 2 d. Following that, blood samples were again taken after the pigs were fed a meal of the test diet that was not given to them at the first sampling period. Net portal AA absorption was calculated by multiplying porto-arterial plasma AA concentration difference by portal vein plasma flow rate (PVPF), estimated by an indicator-dilution technique employing p-aminohippuric acid as the indicator infused into the ileal vein. Plasma concentrations of lysine and threonine of pigs were affected by the diet x time interaction (P < 0.01). Portal and arterial plasma lysine and threonine concentrations in pigs attained the maximal level by 1 h postprandial when the 12% CP + AA diet was fed, but reached the peak level at 2.5 h postprandial when the 16% CP diet was given. The PVPF of pigs over the 6 h postprandial was less (P < 0.01) when the 12% CP + AA diet was given than when the 16% CP diet was fed. Net portal absorptions of lysine and threonine also were affected (P < 0.05) by time x diet interaction. The peak portal absorption of both lysine and threonine in pigs appeared at 0.5 h postprandial when the 12% CP + AA diet was given, but at 2.5 h postprandial with the feeding of the 16% CP diet. The early appearance of peak portal absorption of lysine and threonine from feeding the 12% CP + AA compared with the 16% CP diet indicates that crystalline lysine and threonine are absorbed more rapidly than protein-bound lysine and threonine in pigs fed once daily. Key Words: Crystalline Amino Acids, Lysine, Pigs, Portal Absorption, Protein-Bound Amino Acres, Threonine

The study was conducted to determine the effects of feeding a 16% CP diet, a 12% CP diet, or a 12% CP diet supplemented with crystalline Lys, Trp, and Thr (12% CP + AA diet) in a thermal-neutral (23[degrees]C) or heat-stressed (33[degrees]C) environment on various body and physiological measurements in growing pigs. Heatstressed pigs were given a 15% lower daily feed allowance than thermal-neutral pigs to remove the confounding effect of feed intake caused by high temperature. No diet x temperature interaction was observed for any variables (P [greater than or equal to] 0.09) except for pig activity and pancreas weight. At 33[degrees]C, pig activity and pancreas weight did not differ among dietary treatments (P > 0.05). In contrast, at 23[degrees]C, pigs fed the 12% CP diet had greater activity than those fed the 16% CP diet or the 12% CP + AA diet (P < 0.05). Pancreas weight was greater for pigs fed the 12% CP + AA diet than those fed the 12% CP diet (P < 0.05) when maintained at 23[degrees]C. Compared with 23[degrees]C, the 33[degrees]C temperature decreased pig activity, heat production, daily gain, feed efficiency, and affected the concentration and accretion of empty body protein and ash, as well as weights of heart, pancreas, stomach, and large intestine (P < 0.05). Pigs fed the 12% CP + AA diet attained similar levels of performance and rates of empty body water, protein, lipid, and ash deposition as pigs fed the 16% CP diet (P [greater than or equal to] 0.10). Pigs fed the 12% CP + AA diet had lower serum urea plus ammonia nitrogen concentrations (P < 0.01) and total heat production (P < 0.05) compared with those fed the 16% CP diet or the 12% CP diet. These results confirm that, with crystalline AA supplementation, growing pigs fed a 12% CP diet will perform similar to pigs fed a 16% CP diet. The data further indicate that lowering dietary CP and supplementing crystalline AA will decrease total heat production in growing pigs whether they are housed in a thermal-neutral or heat-stressed environment. Key Words: Amino Acids, Growth, Heat Production, Pigs, Temperature

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 subsamples 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 subsamples 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. Key Words: Chemical Analysis, Feed Mixing

A cooperative research study involving members of a regional committee (North Central Regional Committee on Swine Nutrition [NCR-42]) was conducted to assess the variability in nutrient composition (DM, CP, Ca, P, Se, and amino acids) of corn and soybean meal from 16 sources (15 states, mostly in the Midwest) and to assess the analytical variability in nutrient assays among 22 laboratories (labs; 16 experiment station labs and six commercial labs). Corn samples were obtained from each participating station's feed mill during a 3-yr period (1989, 1990, and 1992), as were soybean meal samples during a 2-yr period (1989 and 1990). Both regular soybean meal (with hulls) and dehulled soybean meal were represented in the study. Samples were analyzed for DM and CP by all 22 labs, for Ca and P by 15 labs, for amino acids by 10 labs, and for Se by 6 labs. Each lab used its own analytical procedures. Samples of corn and soybean meal varied in their nutrient composition depending on the area of origin. The greatest variation among sources was in Se concentration, ranging from .02 to .29 mg/kg in corn and .08 to .95 mg/kg in soybean meal. Crude protein and lysine in corn were positively correlated, but the regression coefficient was low (r(super 2) = .49). The relationship between CP and lysine for the two soybean meals combined was considerably stronger (r(super 2) = .81). Lysine in corn increased by .018 percentage point and lysine in soybean meal (regular and dehulled combined) increased by .063 percentage point for each 1 percentage point increase in CP. Except for CP and Se, the analytical variability among labs was as great as, and in some cases greater than, the variability in nutrient composition among sources of corn and soybean meal. Within-lab analytical variability tended to be less than among-lab variability. Some labs performed certain analyses with considerably less variability and more accuracy than others. Key Words: Chemical Analysis, Maize, Soybean Oilmeal

Two experiments were conducted to evaluate the effect of excess protein on growth performance, carcass characteristics, organ weights, plasma urea concentration, and liver arginase activity of finishing barrows and gilts. In Exp. 1, 35 barrows and 35 gilts with an initial BW of 51 kg were used. Five pigs of each sex were slaughtered at the start of the study to determine initial body composition. The remaining 60 pigs were allotted to a randomized complete block (RCB) experiment with a 2 x 5 factorial arrangement of treatments (two sexes x five protein levels: 13, 16, 19, 22, and 25% CP). The experiment continued until the average BW was 115 kg, at which time three blocks of pigs (30 total) were selected randomly and slaughtered. Feed intake decreased with increasing protein concentration (linear, P < .05), and the reduction was greater in gilts than in barrows (P < .05). There was a trend toward a linear negative effect of dietary protein on ADG (P < .10) and also a quadratic effect of protein on protein accretion (P < .10). Fat accretion decreased linearly as protein level increased (P < .05). Increased protein concentrations increased liver, kidney, and pancreas weights (linear, P < .05). Plasma urea concentration increased with each protein concentration, with the exception of the 25 vs 22% CP treatment in gilts. In Exp. 2, 18 barrows and 18 gilts (BW 63 kg) were allotted to an RCB design consisting of a 2 x 2 factorial arrangement of treatments with two sexes and two dietary protein concentrations (16 and 25% CP). The experiment was terminated when the average BW of pigs reached 105 kg. Average daily feed intake was greater (P < .10) in barrows than in gilts. Average daily gain was reduced by 18% in grits when dietary protein was increased from 16 to 25% but was only reduced 3% in barrows (sex x protein, P < .10). Barrows had lighter livers (P < .005), greater arginase activities (P < .05), and greater plasma urea concentrations (P < .005) than did gilts. Increasing dietary protein concentration from 16 to 25% increased liver weight, arginase activity, and plasma urea concentration (P < .005). These data suggest that gilts are more sensitive than barrows to excessive intakes of protein. The more negative effects in gilts may be related to liver metabolic capacity and activity of urea cycle enzymes. Key Words: Pigs, Protein Excess, Sex Differences, Growth

Three experiments were conducted to evaluate the relationship between feed intake and plasma urea concentration. In Exp. 1, six gilts (BW 53 kg) with catheters in their venae cavae were used in a 5 x 5 + 1 Latin square design to determine the amount of infused urea needed to mimic the plasma urea concentration of pigs fed a 25% CP diet. Five gilts were fed a 16% CP corn-soybean meal diet and were infused continuously with either saline or one of four doses of urea (6, 12, 18, and 24 g/d) during each of five periods (12 h/period). Between periods, infusions were stopped for 36 h. The sixth pig was fed a 25% CP diet and infused with saline during each of the experimental periods. Venous blood samples were obtained at 1-h intervals starting 1 h before infusion. As expected, plasma urea concentration increased with increasing amount of urea infused. A daily infusion of 24 g of urea resulted in a plasma urea concentration similar to that of the pig fed the 25% CP diet with saline infusion. In Exp. 2, 12 gilts (BW 60 kg) were used in a crossover design. Pigs received a 16% CP diet and a different treatment (saline or 24 or 30 g/d of urea) in each of three infusion periods. Each infusion period lasted 2 wk. Infusions were stopped for 2 d between periods. Blood samples were obtained before infusion and daily after infusions started. Feeders were weighed daily to determine ADFI. Experiment 3 was similar to Exp. 2, except that only two treatments (saline and 30 g/d of urea) were used. Data from Exp. 2 and 3 were combined for statistical analysis. Plasma urea concentration increased linearly (P < .001) with increasing amount of urea infused. Overall, there was a trend (P < .10) for urea infusion to decrease ADFI, and pigs infused with 30 g/d consumed less (P < .05) feed than pigs infused with saline. Therefore, plasma urea concentration may play a role in regulating feed intake in gilts consuming excess protein. Key Words: Pigs, Infusion, Plasma, Urea, Feed Intake

The effect of prepubertal feed level on growth and reproductive development of gilts was investigated. At 13 wk of age, white crossbred gilts were penned individually and assigned to the following treatments: Ad lib, ad libitum intake from 13 to 25 wk of age (n = 64); Control, ad libitum intake from 13 wk of age until 100 kg BW and then 90% of ad libitum intake until 25 wk of age (n = 65); and Restricted, 74% of ad libitum intake from 13 wk to 25 wk of age (n = 64). Feed was formulated to primarily restrict energy intake. The study was replicated in two seasons. At 25 wk of age, gilts were moved to group pens, approximately 16 gilts/pen, allowed ad libitum access to feed, and estrus detection was initiated. Gilts were mated at first estrus and those recycling were remated. After mating, gilts were moved to gestation stalls and fed 1.5x maintenance. At 30 d of gestation, reproductive tracts were harvested, and numbers of corpora lutea (CL) and live embryos were recorded. From 13 to 25 wk of age, feed consumption was 258 for Ad lib, 251 for Control, and 189 kg/gilt for Restricted, and, from 13 wk of age until 30 d of gestation, total feed consumption was 367 for Ad lib, 356 for Control, and 299 kg/gilt for Restricted gilts. Age at puberty (196 d) and pregnancy (200 d) was not affected (P > .18) by treatmentu However, the rate at which gilts attained puberty (e.g., percentage pubertal at 28 d) was greatest in Ad lib (7 5) and least in Control (61) gilts. Number of CL and live embryos at 30 d of gestation/gilt assigned to the study was unaffected (P > .21) by treatment. Quantity of feed consumed from 13 wk of age to 30 d of gestation per live embryo in gilts assigned to the study was 40.0 for Ad lib, 39.8 for Control, and 30.6 kg/gilt for Restricted gilts. These results indicate that moderate feed restriction of gilts during prepubertal development may increase efficiency of swine production without negative impact on reproductive performance through 30 d of gestation. Key Words: Gilts, Puberty, Growth, Pregnancy

A regional study involving a total of 618 nursery pigs with 468 continuing through the grower-finisher period evaluated the feeding duration of a Phase 1 starter diet (1, 2, or 3 wk) to 23-d old weanling pigs of two weaning weights (5.5 or 7.5 kg). The study was a 3 x 2 factorial arrangement of treatments in a randomized complete block design conducted in 19 replicates during the nursery period, with 14 replicates continuing through the grower-finisher period. Upon completion of feeding the Phase i diet for the experimental period, pigs were fed a Phase 2 diet (total of 5 wk for both Phases), whereupon a corn-soybean meal mixture formulated to .80% lysine was fed during the grower (to 56 kg BW) and a .65% lysine diet to a final body weight of 105 kg. Station effects were significant (P < .05) but station x treatment responses were not (P > .15). Pigs with heavier weaning weights gained faster (P < .01) and consumed more feed (P < .01) during each week of the nursery period. Nursery pig gains (P < .06) and gain: feed ratios improved (P < .01) when the Phase 1 diet had been fed for either 2 or 3 wk for both pig weight groups. There was no interaction response during the nursery period between weaning weight or duration of feeding the Phase I diet on daily gains or feed intake measurements; however, pigs in the heavier weight group were more efficient (P < .05) in feed utilization when fed the Phase 1 diet for 2 or 3 wk. During the grower-finisher period, gains were higher (P < .01) with the heavier pig group. When the Phase 1 diet had been fed for either 2 or 3 wk to the pigs of either weight group, gains (P < .01) and feed efficiency (P < .05) were improved. There was no evidence of compensatory growth for the lower weight pig group during the subsequent grower or finisher periods. Pigs with heavier weaning weights reached 105 kg BW approximately 8 d sooner (P < .01) and consumed less total feed (P < .05) from weaning to 105 kg than those in the lower weight group. Feeding the Phase 1 diet for 2 wk to pigs of either weight group reduced the time from weaning to 105 kg BW, but weaning heavier pigs seemed to have a greater effect on postweaning performance than the feeding duration of a Phase 1 diet. Key Words: Weaning, Diets, Nutrition Programs, Pigs

Dietary fiber may contribute up to 30% of the maintenance energy needs of growing pigs. Higher energy contributions may be obtained from dietary fiber fed to sows, along with some improvements in reproduction, health, and well-being. As long as cereal grain supplies and high-quality protein supplements are abundant, the use of fibrous feeds for swine most likely will be limited. However, as the human demand for cereal grains increases, swine producers, especially those with reproductive animals, may be economically forced to incorporate alternative feedstuffs. These feedstuffs might include lignified plant cell wall material such as grasses and legumes, and feed-milling and distillery by-products that contain a high level of fiber residues. The microflora in swine large intestine will be able to adapt to these lignified forages and by-product feeds much better than the microflora in humans. Swine microflora contain highly active ruminal cellulolytic and hemicellulolytic bacterial species, which include Fibrobacter succinogenes (intestinalis), Ruminococcus albus, Ruminococcus flavefaciens, Butyrivibrio spp., and Prevotella ruminicola. Additionally, a new highly active cellulolytic bacterium, Clostridium herbivorans, has been recently isolated from pig large intestine. The populations of these microorganisms are known to increase in response to the ingestion of diets high in plant cell wall material. The numbers of cellulolytic bacteria from adult animals are approximately 6.7 times greater than those found in growing pigs. None of these highly active cellulolytic bacterial species are found in the human large intestine. Thus, the pig large intestinal fermentation of fiber seems to more closely resemble that of ruminants than that of humans. Key Words: Fiber, Intestinal Microorganisms, Cellulose, Sows

We evaluated the combined use of 0 or 4 mg/d of recombinant porcine somatotropin (pST) and 0 or 2.75 ppm salbutamol in three genotypes of growing barrows (139 d old) differing in lean and lipid accretion potential. Treatments were in a 2 x 2 x 3 factorial arrangement, and the three genotypes tested were Meishan (M, n = 32, 49 kg), Duroc x White composite (D x Wc, n = 31, 62 kg), and Meishan x White composite (M x Wc, n = 31, 64 kg) pigs. Growth performance was evaluated over 28 d for individual pigs, and 20-h feed-deprived heat production was measured before slaughter (d 34). Daily pST injection increased ADG (+70 g/d) and reduced ADFI (-.61 kg/d) across genotypes (P < .05). Salbutamol increased (P < .05) ADG in M x Wc pigs (+146 g/d) but not in M pigs (-60 g/d) or D x Wc (+80 g/d) pigs. However, M pigs had the lowest ADG and ADFI, and M x Wc pigs not treated with salbutamol grew slower than D x Wc pigs (P < .05). Carcass protein and moisture accretion were additively (P < .05) increased by pST and salbutamol for D x Wc and M x Wc pigs. Meishan pigs had increased carcass protein and moisture accretion from pST, whereas only moisture accretion was increased by salbutamol (P < .05). The longissimus muscle area and semitendinosus weight increased as the percentage of M in the genotype decreased (P < .05), and both were increased by pST or salbutamol treatment (P < .001). Leaf fat was decreased more (P < .05) in M pigs than in D x Wc or M x Wc pigs with pST injection. The similar magnitude of leaf fat reduction between D x Wc and M x Wc pigs resulted in a mean genotype difference (P < .05), and salbutamol decreased leaf fat across genotypes. Oxygen consumption and heat production were increased by pST in M pigs more than in the crossbred genotypes, but C[O.sub.2] production was reduced by similar magnitudes across genotypes, and salbutamol only tended to reduce C[O.sub.2] production in D x Wc pigs. In general, these data indicate that pST and salbutamol result in additive increases in carcass lean composition; however, growth rate, carcass accretion, and various organ weights may vary among genotypes with salbutamol and pST treatment. Key Words: Pigs, Somatotropin, [Beta]-Adrenergic Agonists, Performance, Calorimetry, Carcasses

We evaluated the effects of recombinant porcine somatotropin (pST) and the [Beta]-adrenergic agonist salbutamol on plasam endocrine and metabolite profiles and muscle chemistry in three genotypes of growing barrows (n = 96, 139 d old). Treatments were in a 2 x 2 x 3 factorial arrangement, and main effects were pST (0 or 4 mg/d) and salbutamol (0 or 2.75 ppm); the three genotypes including purebred Meishan (M), 1/4 Duroc, 3/4 White composite (D x Wc), and 1/4 Meishan, 3/4 White composite (M x Wc). Individual pigs were injected daily with buffer or pST at 0700 and allowed ad libitum access to a corn-soybean meal diet (1.2% lysine) and water for 33 d. Plasma was obtained 4 h after injection and 3 h postprandially on d 0, 14, and 28 for determination of growth hormone (GH), insulin, IGF-I, glucose, urea N (PUN), NEFA, triglycerides, and cholesterol. Longissimus and semitendinosus samples were obtained, and protein, RNA, and DNA were quantified and loin chop shear force was measured. In general, plasma hormones and metabolites on d 14 and 28 were not affected by salbutamol in the absence of pST, although salbutamol tended to increase d 14 and 28 GH concentrations. Salbutamol lowered plasma IGF-I (d 14 and 28,P < .05), insulin (d 14, P < .01), and NEFA (d 28, P = .07) when pST was administered, although concentrations still exceeded those for control pigs. Salbutamol reduced (P < .05) IGF-I in M and M x Wc pigs, and GH was not changed in M pigs. Meishan pigs had a greater increase in glucose with pST than M x Wc or D x Wc pigs, although the effect was not consistent over time. Individual treatment with pST caused GH, insulin, IGF-I, glucose, NEFA, and triglycerides to be increased and PUN to be decreased on d 14 and 28. Cholesterol on d 14 and 28 was decreased by pST in M pigs, whereas no effects were found in the other genotypes. Muscle protein and RNA were increased by salbutamol and were consistently lowest for M pigs. Furthermore, pST did not affect muscle protein, but it increased RNA more in M pigs than in the others. Overall, pST and salbutamol seemed to act separately and by different mechanisms to alter muscle composition, but blood criteria generally representing fat metabolism (insulin, glucose, NEFA, triglycerides) were interactively affected. Meishan pigs tended to have greater changes in muscle and plasma composition with pST treatment than did M x Wc or D x Wc pigs. Key Words: Pigs, Genotypes, Somatotropin, [Beta]-Adrenergic Agonists, Hormones, Muscles

We hypothesized that much of the positive effect of porcine somatotropin (pST) on the immune system would be offset by the pST/IGF stimulation of gonadal function and that there would be negative effects on thymic weight and function from increased androgens in males. Male and female hogs (78 boars, 90 gilts) representing three genetic lines (lean, obese, and crossbred meat type) received 0, 2, or 4 mg of recombinant pST/d via implant for 42 d. Blood samples were collected on 0, 7, 14, 28, and 42 d of the trial for changes in pST, IGF-I, IGF-II, thymosin [Beta]4, dehydroepiandrosterone/dehydroepiandrosterone sulfate (DHEA/DHEAS[O.sub.4]), and testosterone concentrations. Thymic, splenic, gonadal, and adrenal weights were collected at slaughter (d 42). Thymic weights increased with dose of pST in both sexes (P < .01), but splenic weights were unaltered. Adrenal weights increased with dose of pST (P < .01), but gonadal weights showed no response to pST in either sex or any line. Overall, concentrations of pST, IGF, and thymosin [Beta]4 increased with dose of pST. Serum testosterone concentrations in boars declined with dose of pST in lean and obese lines, and DHEA/ DHEAS[O.sub.4] declined in all lines with pST treatment. Testicular testosterone concentrations were not different among lines or doses of pST, indicating no stimulatory effect of increased pST/IGF-I on Leydig cell function. Although pST and its effects through increased circulating IGF are thought to be overall stimulants of growth and protein accretion, the actions on the tissues of the immune system (thymus/spleen) and steroidogenic tissues (adrenal/gonadal) can be selective. Increases in thymic weights and thymosin [Beta]4 concentrations from pST treatment in boars were partially due to the pST-induced decline in circulatory androgens, and the responses found in this in vivo model do not support pST/IGF effects documented in in vitro systems on Leydig cell function. Key Words: Pigs, Thymus, Testes, Testosterone, Thymosin

We investigated the effect of sustained-release implant administration of porcine somatotropin (pST) (4 mg/d) to male pigs for different lengths. of time before slaughter. Crossbred white boars were assigned to six groups (n = 10/group); B0, non-implanted boars; B6, boars implanted from 22 to 28 wk of age; B12, boars implanted from 16 to 28 wk of age; B18, boars implanted from 10 to 28 wk of age; C0, non-implanted castrates; and C18, castrates implanted from 10 to 28 wk of age. Castration was at 65 d of age. All pigs were slaughtered at 28 wk of age, and measures of offal and carcass components were recorded. Loin chops were collected for sensory evaluation. During the trial the pigs were maintained in individual pens with ad libitum access to water and a 19% CP corn-soybean meal diet containing 1.08% calculated lysine. Although pST reduced feed intake in castrates (P < .01), the effect in boars was nonsignificant. Slaughter weight was increased in a linear (P < .04) manner with length of pST treatment of boars, and slaughter weights of castrates given pST were greater (P < .01) than those of Control castrates. The product of the changes in feed intake and gain resulted in greater efficiency of gain in pST-treated pigs than in control pigs (P < .01). A linear effect (P < .06) of length of pST treatment on trimmed lean cut weights of boars was noted. The weights of trimmed lean cuts produced by castrates treated for 18 wk with pST and boars treated for 12 or 18 wk were similar. Boars given pST for 18 wk had improved (P < .10) boar taint scores compared with untreated boars. Boars and castrates given pST for 18 wk had similar rates of gain and weights of trimmed lean cuts. Efficiencies of gain were greater in pST-treated boars and castrates than in untreated boars, which were superior to untreated castrates in efficiency of gain. Key Words: Somatotropin, Boars, Boar Taint, Growth, Carcass Composition

This experiment was conducted to determine the relationship between 3-methylhistidine (3MH) production and proteinase activity in skeletal muscles of growing barrows. Barrows at 13 wk of age were randomly assigned to either control diet available on an ad libitum basis (21% of ME consisted of protein; control group), control diet fed restricted (pair-fed with barrows in protein-free group; intake-restricted group), or protein-free diet available on an ad libitum basis (protein-free group) for 14 d. During the last 3 d, blood samples were collected for determination of 3MH production rate, which is a measure of myofibrillar protein breakdown. At slaughter, two muscles were taken: masseter (M) and longissimus (L) muscles. The muscle samples were analyzed for calpastatin, [micro]-calpain, m-calpain, multicatalytic proteinase (MCP), cathepsin B, cathepsins B+L, and cystatins activities. Both muscles were also analyzed for amounts of DNA, RNA, total protein, and myofibrillar and sarcoplasmic proteins. Growth rate (kilograms/day) was influenced by dietary treatments (P < .05). Fractional breakdown rate (FBR, percentage/day) of skeletal muscle, as calculated from 3MH production rate (micromoles.[kilogram.sup.-1].[day.sup.-1]), was 27% higher for the protein-free group than for the control group. However, no differences in proteinase activities were observed, except for lower MCP activity in the M muscle of the protein-free group than in that of the other groups (P < .05). In the present study, no direct relation was observed between myofibrillar protein degradation rate and proteinase activities in skeletal muscle during a protein-free feeding strategy. Key Words: Pigs, Dietary Protein, Methylhistidine, Proteinases, Growth, Skeletal Muscle

Experimental studies to identify conditions to introduce intestinal cellulolytic bacteria into bovine rumen and pig large intestine reveal that a competition should be overcome for efficient introduction of these organisms into an intestinal ecosystem. In bovine rumen Clostridium longisporum exists as a transient organism, while C. herbivorans is part of the pig large intestine.

The objective of this study was to compare techniques for measuring whole-body |O.sub.2~ uptake of steers. Oxygen uptake provides a basis for evaluating metabolic energy expenditure. We measured |O.sub.2~ uptake as the product of the difference in |O.sub.2~ contents of incoming and exhaust air times air flow through a respiration calorimeter (head box). Additionally, we used catheters and thermistors placed into the blood vessels near the heart to measure cardiac output and whole-body |O.sub.2~ uptake. The cardiac output measurement system used thermodilution to measure the blood flow rate through the pulmonary artery. Catheters placed in the pulmonary artery and in the aorta provided respective samples of oxygen-depleted and oxygen-enriched blood. The product of blood flow rate times blood oxygenation by the lungs provided the basis for calculating total |O.sub.2~ uptake. Four sets of simultaneous measurements with the two techniques were made on eight steers weighing from 272 to 528 kg. Oxygen uptake was not different (P |is greater than~ .20) for the two techniques. Overall (mean |+ or -~ SEM) |O.sub.2~ uptake measured by cardiac output (117.2 |+ or -~ 7.0 L/h) was 97 |+ or -~ 3% of |O.sub.2~ uptake measured by respiration calorimetry.

Growing gilts that had catheters inserted into the portal vein, ileal vein, and carotid artery and that were trained to consume 1.2 kg of a 16% CP corn-soybean meal basal diet once daily were used. In Trial 1, hourly simultaneous measurements of the O2 consumption by portal vein-drained organs (PVDO) and by the whole animal during the 24- to 30-h postprandial period were conducted in eight pigs (33.8 + or - .6 kg). After initial measurements, four pigs continued to receive the basal diet and four pigs were fed a basal diet + 250 ppm of Cu. Following a 7-d acclimation period, the second series of measurements were made. In pigs fed the diet supplemented with Cu, the PVDO and whole-animal O2 consumptions and the fraction of whole-animal O2 consumption used by PVDO were not different (P > .05) between the initial and second series. In Trial 2, seven gilts (38.5 + or - .9 kg) were used for measurements of net portal NH3 absorption and the O2 consumption by PVDO and by the whole animal during the 0- to 6-h postprandial period. The second series of measurements were made 7 d after four pigs were fed the diet supplemented with Cu. For pigs fed the diet supplemented with Cu, during the second series of measurements, the net portal NH3 absorption was lowered (P < .05). No differences (P > .05) in PVDO and whole-animal O2 consumptions and the fraction of whole-animal O2 consumption used by PVDO were found between the initial and second series. These results indicate that mechanisms other than reduced oxidative demand by PVDO may be responsible for the growth-stimulating effect of high dietary Cu on pigs.

Two identical trials, each with 128 crossbred weanling barrows (6.8 + or - .2 and 7.6 + or - .2 kg for Trials 1 and 2, respectively), were conducted. In each trial, pigs were allowed to consume ad libitum a 16% CP corn-soybean meal basal diet (B), B + 55 ppm of carbadox, B + 250 ppm of copper (Cu), or B + 125 ppm of Yucca shidigera extract for 56 d (four pens/diet; eight pigs/pen). At d 56 of the test, eight pigs/diet (two pigs/pen) were slaughtered for carcass and viscera measurements. Data of carbadox treatment in Trial 1 are excluded from this paper because of an error in mixing of the diet. In Trial 1, during the test period from d 0 to 28, pigs fed Cu had greater (P < .05) ADG and ADFI than those fed B, whereas pigs fed yucca extract had higher ADFI (P < .05) but similar ADG (P > .05) compared with those fed B. During the period from 29 to 56 d, ADG was similar among pigs fed different diets (P > .05) but ADFI was affected (P < .05) by diet (yucca extract > Cu > B). No differences (P > .05) among diets were detected for gain/feed (G/F) and visceral weights expressed as a percentage of slaughter BW. In Trial 2, during the first 28 d, the ADG, ADFI, and G/F responses of pigs to Cu, yucca extract, and B were similar to those observed in Trial 1. The ADG and ADFI of pigs fed carbadox were not different (P > .05) from those of pigs fed Cu, but they were greater (P < .05) than those of pigs fed B or yucca extract. During the period from d 29 to 56, pigs fed carbadox also had greater (P < .05) ADG than those fed B or Cu. At slaughter, pigs fed carbadox had smaller (P < .05) small intestinal mass than those fed B, Cu, or yucca extract. It is concluded that, in weanling pigs, the growth-promoting action of carbadox is related to the change in small intestinal mass; Cu increases daily gain for a shorter duration than does carbadox and has no effect on small intestinal mass, and neither growth rate nor small intestinal mass is affected by yucca extract.

Previous studies have documented the effectiveness of porcine somatotropin (pST) administered by daily injection in promoting lean tissue growth in lean and obese pigs and the influence of sex and genotype. The present study examined the accretive responses in pigs of different lines and sexes to a slow release formulation of pST (pST-SR). Implants that deliver 2.0 mg of pST/d were implanted in genetically lean and obese barrows and gilts at 65 plus or minus .7 kg BW (mean plus or minus SE). Pigs received no, one, or two implants (i.e., doses of 0, 2.0, and 4.0 mg of pST/d). Pigs (four per line x sex x dose) were housed individually and continuously supplied with fresh water and a 19% CP diet containing 1.08% lysine. Pigs were slaughtered on d 0 (four per line x sex) and at the end of the trial (approximately 42 d after implantation) for estimation of initial composition and calculation of accretion rates. Blood samples were collected at d 0, 7, 14, 28, and 42 to measure endocrine and metabolite responses to pST-SR. Sustained-release pST elevated (P < .05) circulating pST throughout the trial with peak concentrations at d 7. On d 7, serum pST concentrations in the pigs given 2.0 mg of pST-SR per day were 16-fold greater than those in control pigs, and in pigs given 4.0 mg of pST-SR per day pST concentrations were 33-fold greater than in controls. Elevated serum pST resulted in increased (P < .05) serum concentrations of insulin-like growth factor (IGF)-I, IGF-II, insulin, and glucose and in reduced (P < .05) concentrations of urea nitrogen and IGF binding protein (IGFBP)-2. Gain was not influenced by pST-SR dose; however, feed consumption was reduced (P < .05) and efficiency of gain was increased (P < .05). Accretion of all body components except cold carcass weight, cecum, and untrimmed Boston butt and ham were changed (P < .05) with pST-SR administration. Heart and stomach were the only components of the carcass and offal whose accretion was not affected by line or sex. Increases in accretion of carcass components (< 75%) induced by sustained-release pST were considerably less than those measured in the organs (liver, 157%; lungs, 748%). The pST-SR treatment resulted in elevated serum concentrations of pST and its mediators and improved efficiency and composition of gain. Thus, pST-SR seems to be an effective method of pST administration; however, the response is influenced by genotype and sex of the treated pig.

Prepubertal gilts of obese (n = 24) or lean (n = 24) genetic lines were injected (s.c.) daily with 0, 2, or 4 mg of porcine somatotropin (pST) for 6 wk starting at 160 d of age to determine whether pST affects follicular function. Blood and ovaries were collected at slaughter 24 h after the last injection. Surface follicles is greater than or equal to 1.0 mm in diameter were counted, and pools of follicular fluid (FFL) and granulosa cells were collected from 1.0- to 3.9-mm (small) and 4.0- to 6.9-mm (medium) follicles. Oocytes were collected from small and medium follicles and evaluated for maturational stage and viability. Porcine somatotropin increased (P < .08) the numbers of small but not the numbers of medium follicles per gilt (P > .10). Oocyte maturation and viability were not affected by pST or genetic line. Porcine somatotropin increased (P < .05) concentrations of insulin-like growth factor I (IGF-I) in serum and FFL of both obese and lean gilts; IGF-I was lower (P < .01) in lean gilts. Treatment with pST decreased (P < .05) IGF-II in FFL of lean but not in that of obese gilts. Dose of pST and line had no effect on concentrations of progesterone in FFL of small or medium follicles or on concentrations of estradiol in FFL of small follicles. Concentrations of estradiol in FFL of medium follicles were decreased (P < .05) by pST (2 and 4 mg/d) in obese gilts, but estradiol was lower (P < .01) and unaffected (P > .10) by pST in lean gilts. The numbers of LH/hCG binding sites in granulosa cells were decreased (P < .05) by pST (4 mg/d) in medium follicles. The 4 mg/d dose of pST increased (P < .05) IGF-I binding protein activity only in serum of obese gilts. We conclude that 2 and(or) 4 mg/d of pST can increase concentrations of IGF-I in serum and FFL and stimulate growth of small follicles in two genetically divergent lines of gilts without affecting oocyte viability.

Fasting [O.sub.2] consumption by the whole animal W) and by portal vein-drained organs (PVDO) during the 24- to 30-h postprandial period were measured in seven growing pigs (36.1 [+ or -] 2.3 kg) with catheters chronically placed in the hepatic portal vein, ileal vein, and carotid artery trained to consume 1.2 kg of a 16% CP corn-soybean meal basal diet (B) once daily. The pigs were placed individually into an open-circuit, indirect calorimeter and connected to an arteriovenous (A-V) [O.sub.2] difference analyzer for hourly simultaneous measurements of [O.sub.2] consumption by W and PVDO. The PVDO [O.sub.2] consumption was calculated by multiplying the A-V [O.sub.2] difference by the portal vein blood flow rate derived from constant infusion of a p-aminohippuric acid solution into the ileal vein. After the initial series of hourly measurements, four pigs remained on the B diet and three pigs were fed a B + 55 ppm carbadox diet. Seven days later, the second series of measurements was made. In pigs fed the diet with carbadox added, the hourly W [O.sub.2] consumptions were not different (P > .05) between the initial and second series and averaged 7.5 mL. [min.sup.-1].kg of [BW.sup.-1]. However, the A-V [O.sub.2] differences (mL/dL) were reduced (P < .05) from 4.6 to 4.0 at 24 h, 4.8 to 4.0 at 25 h, and 4.6 to 4.0 at 29 h postprandial and the fractions of W [O.sub.2] consumption used by PVDO (percentage) were reduced (P < .05) from 28.6 to 21.6 at 26 h and 25.2 to 18.2 at 27 h postprandial. These results suggest that the growth-promoting effect of carbadox, a synthetic antimicrobial agent, in growing pigs may be associated with reduced oxidative demand by the PVDO, which includes digestive tract, pancreas, and spleen. Key Words: Pigs, Growth Promoters, Oxygen Consumption, The influence of carbadox on fasting oxygen consumption by portal vein-drained organs was determined by putting chronic catheters into the portal vein, ileal vein and carotid artery of ten pigs. Oxygen consumption was measured by indirect calorimeters. Carbadox was supplemented in the diet of some pigs and assays show that it reduces the energetic requirements of the gastrointestinal tract, spleen and pancreas. The energy spared by the process is diverted to other growth needs of the animal.