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Two experiments were conducted to assess the effects of porcine ST (pST) on the responses to a near-ideal blend of AA for pigs from 22 to 60 kg BW. Eighty Hampshire x Yorkshire gilts (40 gilts/experiment) were individually penned and assigned to a 4 x 2 factorial arrangement of treatments, consisting of 4 diets with and without pST injection. A fortified corn-soybean meal basal diet was formulated to contain 1.50% total Lys and Thr, Met, and Tip were added to obtain a near-ideal blend of these AA relative to Lys. In 3 additional diets, Lys was reduced to 1.25%, 1.00%, or 0.75% by diluting the basal diet with cornstarch, cellulose, and sand, such that the diets also contained the same ratios of AA. Pigs that received pST were administered a daily intramuscular injection of 2 mg of pST Data from the 2 experiments were pooled. Administration of pST increased ADG (P < 0.01), G:F (P < 0.01), and LM area (P < 0.01), and decreased ADFI (P < 0.03), last rib backfat (P < 0.01), and 10th rib backfat (P < 0.01). Also, estimated carcass muscle and calculated lean gain increased (P < 0.01) in pST-treated pigs. Administration of pST also increased (P < 0.01) the percentage, total gain and accretion rate of water, protein, and ash in the carcass, and decreased (P< 0.01) the percentage, total gain, and accretion rate of carcass fat. Growth rate, G:F, and carcass traits improved (P < 0.01), percentage of carcass proteinand water increased (P < 0.01 ), and carcass fat percentage decreased (P < 0.01) with increasing dietary Lys. The percentage, total gain, and accretion rate of carcass protein increased to a greater extent in pST-treated pigs than in untreated pigs, resulting in a pST x Lys interaction (P < 0.05). The results indicated that pST improves performance, leanness, and protein accretion in pigs from 22 to 60 kg BW, and that these responses to dietary Lys and a near-ideal blend of AA is greater in growing pigs treated with pST than untreated pigs. [ABSTRACT FROM AUTHOR]

Two 21-d experiments were conducted to determine the optimum standardized ileal digestible (SID) Trp:Lys in growing pigs fed corn-based diets compared with non-corn-based diets. The primary response variables in both experiments were ADG and plasma urea N (PUN) concentrations with the optimum SID Trp:Lys determined using broken-line analysis. Experiment 1 evaluated the optimum SID Trp:Lys in growing pigs fed corn-based diets consisting primarily of corn with minor inclusion of Canadian field peas and corn gluten meal to keep the SID Trp:Lys low. This experiment used 120 crossbred pigs (initial BW: 25.73 ± 2.46 kg) that were blocked by sex and initial BW and allotted to 5 SID Trp:Lys with 5 pens each for the first 4 treatments and 4 pens for the last treatment and 5 pigs/pen. Diets were formulated by the addition of supplemental Trp to create various SID Trp:Lys (12.77, 14.07, 15.50, 16.91, and 17.94%) with a constant SID Lys of 0.66%, which was determined to be 83% of the Lys requirement for pigs at this location. As the SID Trp:Lys increased from 12.77 to 17.94%, ADG increased (0.562, 0.648, 0.788, 0.787, and 0.815 kg/d) linearly (P < 0.001) and quadratically (P = 0.009), resulting in an optimum SID Trp:Lys of 15.73% (P < 0.001). Plasma urea N decreased (10.43, 9.30, 8.21, 8.55, and 9.25 mg/dL) linearly (P = 0.069) and quadratically (P = 0.015), resulting in an optimum SID Trp:Lys of 15.83% (P = 0.007). Experiment 2 evaluated the optimum SID Trp:Lys in growing pigs fed non-corn-based diets consisting primarily of barley and Canadian field peas, with smaller proportions of corn and wheat. Experiment 2 used 120 crossbred pigs (initial BW: 28.49 ± 2.92 kg) that were allotted to 5 increasing SID Trp:Lys (13.05, 14.32, 15.59, 16.85, and 18.11%; 0.66% SID Lys) in the same manner as Exp. 1. As SID Trp:Lys increased in Exp. 2, ADG increased linearly (P = 0.007) with the optimum SID Trp:Lys of 15.99% (P = 0.048). Plasma urea N concentrations decreased linearly (P = 0.056) and quadratically (P = 0.067) as SID Trp:Lys increased, resulting in an optimum SID Trp:Lys of 15.29% (P = 0.009). Averaging the break point values for ADG and PUN obtained from broken-line analysis for Exp. 1 and 2 produced optimum SID Trp:Lys of 15.78 and 15.64%, respectively. Based on the results from these 2 experiments, it seems that the optimum SID Trp:Lys is virtually unaffected by the dietary feedstuffs used as long as the diets are formulated on an SID AA basis. [ABSTRACT FROM AUTHOR]

An experiment involving 560 crossbred pigs (28 replications of 4 to 6 pigs per pen) was conducted at 9 research stations to assess the effects of dietary concentrations of corn distillers dried grains with solubles (DDGS) on pig performance and belly firmness. Fortified corn-soybean meal diets containing 0, 15, 30, or 45% DDGS were fed in 3 phases from 33 to 121 kg of BW. A common source of DDGS containing 90.1% DM, 26.3% CP, 0.96% Lys, 0.18% Trp, 9.4% crude fat, 34.6% NDF, 0.03% Ca, and 0.86% P was used at each station. Diets were formulated to contain 0.83, 0.70, and 0.58% standardized ileal digestible (SID) Lys during the 3 phases with diets changed at 60 and 91 kg of BW, respectively. The DDGS replaced corn and soybean meal, and up to 0.172% Lys and 0.041% Trp were added to maintain constant SID concentrations of Lys and Trp in each phase. At each station, 2 pigs from each pen in 2 replications were killed and a midline backfat core was obtained for fatty acid analysis and iodine value. In most instances, there were differences among stations (P < 0.01), but the station × treatment interactions were few. Body weight gain was linearly reduced in pigs fed the greater amounts of DDGS (0 to 45%) during phase I (950, 964, 921, and 920 g/d; P < 0.01) and over the entire experimental period (944, 953, 924, and 915 g/d; P = 0.03), but ADFI (2.73, 2.76, 2.68, and 2.70 kg) and G:F (347, 347, 345, and 341 g/kg) were not affected (P = 0.15 and P = 0.33, respectively) during the entire test. Backfat depth was reduced (linear, P < 0.02) by increasing amounts of DDGS (22.5, 22.7, 21.4, and 21.6 mm), but LM area (47.4, 47.4, 46.1, and 45.4 cm2) was not affected (P = 0.16) by treatments. Estimated carcass fat-free lean was 51.9, 52.2, 52.4, and 52.1% for 0 to 45% DDGS, respectively (linear, P = 0.06). Flex measures obtained at 6 stations indicated less firm bellies as dietary DDGS increased (lateral flex: 11.9, 8.6, 8.4, and 6.6 cm; linear, P < 0.001; vertical flex: 26.1, 27.4, 28.2, and 28.7 cm; linear, P < 0.003). Saturated and monounsaturated fatty acid concentrations in subcutaneous fat decreased linearly (P < 0.001) and PUFA concentrations increased linearly (P < 0.001) with increasing DDGS in the diet. Iodine values in inner (61.1, 68.2, 74.7, and 82.2) and outer (67.9, 73.6, 79.6, and 85.8) backfat increased linearly (P < 0.001) as DDGS in the diet increased. In this study, feeding diets with 30 or 45% DDGS did not have major effects on growth performance, but resulted in softer bellies. Regression analysis indicated that iodine values increased 4.3 units for every 10 percentage unit inclusion of DDGS in the diet. [ABSTRACT FROM AUTHOR]

A regional experiment was conducted to test the hypothesis that the concentration of dietary Ca does not affect the digestibility of Ca or P in diets fed to growing pigs. Six diets based on corn, potato protein isolate, cornstarch, and soybean oil were formulated. All diets also contained monosodium phosphate, crystalline AA, salt, and a vitamin-micromineral premix. The only difference among the diets was that varying concentrations of calcium carbonate were used to create diets containing 0.33, 0.46, 0.51, 0.67, 0.92, and 1.04% Ca. All diets contained between 0.40 and 0.43% P. Six universities participated in the experiment and each university contributed 2 replicates to the experiment for a total of 12 replicates (initial BW: 23.1 ± 4.4 kg). Pigs were placed in metabolism cages that allowed total, but separate, collection of feces and urine from the pigs. Pigs within each replicate were randomly allotted to the 6 diets and fed experimental diets for 14 d with urine and feces being collected over a 5-d period. Diets, feces, and urine samples were analyzed for Ca and P, and the daily balance, the apparent total tract digestibility (ATTD), and the retention of Ca and P were calculated. Results indicated that intake, fecal excretion, and urinary excretion of Ca increased (linear, P < 0.05) as dietary Ca concentration increased. The daily intake of P was not affected by the dietary concentration of Ca, but fecal excretion of P increased (linear, P < 0.05) as dietary Ca concentrations increased. In contrast, urinary P output was decreased (linear, P < 0.05) as dietary Ca increased. The retention of Ca increased (linear, P < 0.05) from 1.73 to 4.60 g/d, whereas the retention of P decreased (linear, P < 0.05) from 1.98 to 1.77 g/d as dietary Ca concentrations increased. However, if calculated as a percentage of intake, both Ca and P retention were decreased (linear, P < 0.05) as dietary Ca concentration increased (from 55.4 to 46.1% and from 48.4 to 43.5%, respectively). The ATTD of Ca was not affected by the dietary concentration of Ca, but the ATTD of P was decreased (linear, P < 0.05) from 56.9 to 46.2% as dietary Ca concentration increased. It is concluded that the dietary concentration of Ca does not affect the ATTD of Ca in calcium carbonate, but increased concentrations of dietary Ca may decrease the ATTD of P in diets based on corn, potato protein isolate, and monosodium phosphate. [ABSTRACT FROM AUTHOR]

Evaluations of the nutritional impact of antibiotics have largely centered on effects related to the digestibility and utilization of protein and energy. Recent research has demonstrated that virginiamycin increases P digestibility. Because of the importance of P in diet cost and in waste management plans, the present study evaluated the potential impact of 2 additional antibiotics, bacitracin methylene disalicylate (bacitracm) and tylosin, on P digestibility in swine. A total of 48 barrows (mean initial BW, 63.0 to 82.9 kg) were used in 2 nutrient balance experiments. A basal cornsoybean meal diet that was not supplemented with any inorganic source of P was used in each experiment. In Exp. 1, two diets were tested: basal vs. basal plus 33.1 mg of bacitracin/kg of diet. In Exp. 2, two diets were also tested: basal vs. basal plus 44.1 mg of tylosin/kg of diet. In both experiments, the pigs were fed their diets for a minimum of 12 d before fecal and urine collection, and pigs were fed the diet at 2.7% of BW during the adaptation and collection period. In Exp. 1, the apparent DM, Ca, and P digestibility values for the basal and bacitracin diets were 91.69, 65.96, and 43.03 vs. 91.47, 65.46, and 41.79%, respectively, and did not differ by diet. In Exp. 2, the DM, Ca, and P digestibility values for the basal and tylosin diets were 91.03, 62.17, and 38.80 vs. 91.11, 63.20, and 40.10%, respectively, and did not differ by diet. The effect of the antibiotics on gut microflora was also appraised but the evaluations failed to demonstrate an effect on the microflora ineasured, with the exception that tylosin decreased the number of phytate–utilizing bacteria (P = 0.05). Therefore, because these 2 antibiotics did not demonstrate an improvement in P digestibility, improvements in P digestibility seem to be an antibiotic–specific response rather than a generalized antibiotic response. [ABSTRACT FROM AUTHOR]

ABSTRACT: Three experiments were conducted to investigate the effects of thermal stress and dietary Cr on growth performance and physiological variables in weanling pigs. In Exp. 1, a total of 54 pigs (BW of 5.95 ± 0.84 kg) were allotted to a 2 x 3 factorial arrangement using 2 ambient temperatures (23.7 or 40.5°C during d 14 to 28 postweaning) and 3 dietary concentrations of Cr (0, 1,000, or 2,000 μg/kg) as Cr(III) picolinate. In Exp. 2, a total of 54 pigs (BW of 5.94 ± 1.29 kg) were allotted in the same treatment arrangement but with different ambient temperatures (26.5 or 16.0°C during d 14 to 26 postweaning). In Exp. 3, a total of 36 pigs (BW of 6.40 ± 0.72 kg) were allotted in the same treatment arrangement with ambient temperatures of 25.9 or 13.8°C during d 14 to 28 postweaning. During d 0 to 14 of all experiments, a neutral ambient temperature (NT) was maintained. In Exp. 1, pigs in high ambient temperature (HT) gained less BW (575 vs. 663 g/d; P < 0.001) and consumed less feed (926 vs. 1,074 g/d; P = 0.001) than pigs in NT during d 14 to 28. However, C:F was not affected by ambient temperature (0.623 vs. 0.618 g/g; P = 0.702). Dietary Cr had no effect on growth performance. Pigs in HT had less plasma cortisol (42.0 vs. 53.7 ng/mL; P = 0.012) and glucose (6.68 vs. 6.96 ng/mL; P = 0.018). Respiratory rate of pigs in HT was greater compared with the pigs in NT (114.6 vs. 65.0 breaths/mm; P < 0.001) on d 27. In Exp. 2 and 3 (pooled), pigs in low ambient temperature (LT) had decreased G:F (0.636 vs. 0.663 g/g; P < 0.01) associated with a tendency toward a greater ADFI (1,026 vs. 942 g; P = 0.079) during d 14 to 26 (28). Ambient temperature or dietary Cr supplementation had no effect on blood measurements. In Exp. 3, the respiratory rate measured on d 22 and 27 was less (43.2 vs. 54.2 breaths/mm and 42.2 vs. 57.0 breaths/mm, respectively; P < 0.001) in the pigs in LT than the pigs in NT with no effects of dietary Cr supplementation. These results indicate that growth performance is affected by thermal stress and plasma cortisol is decreased by heat stress, but these effects are not moderated by dietary Cr. [ABSTRACT FROM AUTHOR]

The concentration of Cr in several tissues in response to high-level, short-term supplementation was used to determine the relative bioavailability among 4 organic Cr sources and to assess the relative safety of high levels of supplementation. Crossbred pigs (n = 40; mean BW = 48.1 + 0.9 kg) were allotted to 5 diets: a control diet with no added Cr, or 5,000 µg/kg of Cr from Cr tripicolinate (CrTP), Cr propionate (CrPrp), Cr methionine (CrMet), or Cr yeast (CrY). Twenty guts were housed individually and barrows were housed in pairs. Average duration of feeding before slaughter was 75 d. For the total experiment, pigs fed the unsupplemented diet had less ADG than pigs fed CrY (P < 0.05). Serum clinical chemistry values, obtained during the final week of the experiment, demonstrated few effects with no responses that would raise concern about metabolic changes in response to the Cr sources. The effects of the forms of Cr fed on carcass measurements and meat quality were also minimal. All Cr sources reduced cooler shrink (P < 0.05) and most resulted in some meat color change on d 1 postslaughter. For tissue Cr content, 4 of 5 tissues (bone, kidney, liver, and ovary) were increased (P < 0.05) in Cr content by supplementation with CrTP and CrMet, whereas only 2 tissues (bone and kidney) were increased (P < 0.05) by CrY, and none were increased by CrPrp. In all tissues of response, CrTP exceeded CrMet and CrMet exceeded CrY. Comparing the relative increase in tissue Cr for all responsive tissues (bone, kidney, liver, and ovary) gave a range of responses, for which the mean bioavailability relative to CrTP across tissues was 13.1% for CrPrp (0.2 to 19.0%), 50.5% for CrMet (36.2 to 79.1%), and 22.8% for CrY (2.5 to 47.9%). In summation, these results show very clear Cr effects on multiple tissues, which is conclusive evidence of absorption and deposition. The lack of a negative response in growth performance, carcass measures, and clinical chemistry at the increased quantities used herein provides assurance that normal quantities of addition are extremely safe. [ABSTRACT FROM AUTHOR]

An experiment involving a total of 1,320 crossbred pigs was conducted at 3 universities to assess the effects of various levels of lactose in diets during phase 3 (wk 3 and 4 postweaning) of a 4-phase starter program. Pigs were weaned at 15 to 20 d (6.2-kg initial BW) and allotted to 5 treatments. All pigs were fed a complex phase 1 diet (20% lactose) the first week postweaning followed by a complex phase 2 diet (15% lactose) the second week postweaning. Phase 3 diets containing 0, 2.5, 5.0, 7.5, or 10.0% lactose were fed for wk 3 and 4, and then a common, corn-soybean meal diet was fed for an additional 1 to 2 wk (phase 4). The source of lactose was Dairylac 80, which contains 80% lactose. The phase 1, 2, and 3 diets were prepared at one site. Pigs were weighed, and feed intake was determined at weekly intervals. There were 8 replications at each station for a total of 24 replications per treatment with 5 or 23 pigs per pen. As expected, ADG, DFI, and G:F were not affected (P = 0.10) during the initial 2-wk period when all pigs received the same diet. During wk 3 and 4 (phase 3) when the 5 levels of lactose were fed, ADG and ADFI increased linearly (P < 0.01) with increasing levels of lactose, but G:F was not affected (P = 0.10). Although the quadratic component was not significant, ADG and ADFI reached a numerical plateau at the 7.5% inclusion level of lactose during phase 3. Compared with pigs fed the diet without lactose, the 7.5% level of lactose resulted in 350 g of additional BW gain coupled with 420 g of additional feed consumed per pig during phase 3, and most of the additional BW gain (294 g) was maintained through the end of the 5- to 6-wk study. These results suggest that pigs respond to dietary lactose during the mid to latter phase of the nursery period and that the response was obtained under different management and facility conditions. [ABSTRACT FROM AUTHOR]

Evaluations of the nutritional effect of antibiotics have largely centered on effects related to the digestibility and utilization of protein and energy. The current study evaluated the potential effect of virginiamycin (VTR) on P digestibility in swine. A total of 70 barrows (mean initial BW = 51 to 64 kg) were used in 4 nutrient-balance experiments. A basal, corn-soybean meal diet that was not supplemented with any inorganic source of P was used in each experiment. In Exp. 1, two diets were tested: basal vs. basal plus 11 mg/kg of VIR. In Exp. 2, four diets were used with a 2 × 2 factorial arrangement of 0 and 11 mg/kg of VIR and 0 and 750 phytase (PITY) units/kg of diet (PU/kg). Experiments 3 and 4 were the same as Exp. 2, except PITY was reduced to 300 PU/kg. For all experiments, VIR improved P digestibility (32.71 to 37.72%, P < 0.001) and Ca digestibility (54.99 to 58.30%, P = 0.002). The addition of PITY improved both P and Ca digestibility (P < 0.001); 750 PU/kg increased P digestibility 27.3% (from 34.6 to 61.9%, P < 0.001), whereas 300 PU in- creased it 13.8% (from 33.4 to 47.2%, P < 0.00 1). In an experiment conducted to evaluate the long-term effects of VIR on gut microbial profile, pigs (24 guts and 8 barrows; mean BW = 29.1 ± 0.50 kg) were fed a simple corn-soybean meal diet for 16 wk with a 2 × 2 factorial arrangement of VIR (0 and 11 mg/kg) addition and 0.15% dicalcium phosphate deletion. The long-term feeding of VIR in both the control diet and the diet with a marginally reduced P level resulted in a change in ileal microbial profile. A positive numerical increment in the number of phytate-utilizing bacteria was observed in both the normal and P-deleted diets (log unit increments of 12.4 and 17.2% over the respective controls, P = 0.13) when VIR was added. The addition of VIR also tended to affect lactobacilli populations (main effect, P = 0.11; interaction, P = 0.02); VIR decreased lactobacilli in the normal-P diet but did not affect this bacterial population in the P-deleted diet. In conclusion, the antibiotic VIR improves both Ca and P digestibility in pigs. The increase in digestibility is not as great as that provided by PHY, but because the potential mechanism of action (altered microbial populations) differs from that of PHY (direct addition of an enzyme), there can be a degree of additivity in P digestibility improvement when both products are used. [ABSTRACT FROM AUTHOR]

Split-sex feeding in the grow-finish period of swine production was an innovative technology of the last decade because of the different growth rates, feed efficiencies, and perhaps different nutrient needs between guts and barrows. However, due to various weaning strategies, split-sex feeding has not been adequately evaluated in the nursery. The objectives of our research were to determine 1) if gilts and barrows responded similarly to increased protein (Lys) after weaning, and 2) if the current NRC estimated requirements for Lys are adequate. Six experiment stations (KS, KY, MI, MN, OH, and SD) utilized 748 pigs (6.7 kg of BW; 19.4 ± 1.1 d of age). The pigs were allotted to 4 treatments in 32 replications (5 to 7 pigs/pen) in a randomized complete block design. Barrows and gilts were penned separately, and complex nursery diets were fed in 3 phases (d 1 to 7, 8 to 21, and 22 to 35). Lysine was provided at the NRC estimated requirements or at 0.20% greater (1.35 vs. 1.55%, 1.25 vs. 1.45%, and 1.15 vs. 1.35% for the 3 phases, respectively). Pigs and feed were weighed initially and at the end of each phase. The results demonstrated that sex did not affect ALDG, ADFI, or G:F in any phase or during the 35-d study (453 vs. 452 g/d, 674 vs. 675 g/d, and 0.673 vs. 0.671 for barrows and guts, respectively). The greater Lys concentration improved AIJG in phase 3 (628 vs. 589 g; P < 0.001) and overall (465 vs. 441 g; P c 0.001) compared with pigs fed the NRC-estimated Lys requirements. Increased Lys in the diet increased ADFI in phase 2 (P c 0.05), but not in the other phases or for the overall 35-d study. Gain:feed was improved by feeding greater Lys concentrations in phase 2 (0.785 vs. 0.704; P < 0.001) and in the overall 35-d experiment (0.695 vs. 0.649; P c 0.00 1). There was no evidence of a sex x Lys interaction (P = 0.33) for any of the response variables during any of the phases or overall. Our results demonstrate that increasing Lys concentrations in nursery diets results in improved pig performance of both sexes, and there appears to be no benefit to split-sex feeding when mixed genotypes are fed in the nursery. [ABSTRACT FROM AUTHOR]

Thirty-six barrows were used in a series of 3 P-balance experiments in which growing and finishing pigs were fed highly digestible, semi-purified diets at or below the dietary available P requirement to estimate the effect of BW on endogenous P loss. Experiments 1, 2, and 3 were conducted with pigs averaging 27, 59, and 98 kg of BW, respectively. In each experiment, pigs were placed in metabolism crates and allotted by weight and litter to 3 dietary treatments. The basal diet consisted of sucrose, dextrose, cornstarch, and casein fortified with minerals (except P) and vitamins. Diets 1, 2, and 3 in Exp. 1 were the basal diet with 0, 0.078, or 0.157% added P, respectively, from monosodium phosphate. In Exp. 2 and 3, diets 1, 2, and 3 were the basal diet with 0, 0.067, and 0.134% added P, respectively, from monosodium phosphate. Within replicate, pigs were fed equal amounts of feed twice daily. Pigs were adjusted to treatments for 7 d before a 6-d, marker-to-marker collection of feces and urine. Phosphorus intakes for pigs fed the 3 diets ranged from 1.73 to 3.91 g/d in Exp. 1, from 2.18 to 5.32 g/d in Exp. 2, and from 1.96 to 6.26 g/d in Exp. 3. Fecal P excretion and P absorption increased linearly (P < 0.05) with increasing P intake. In the 3 experiments, urinary P excretion (g/d) was low for pigs fed diet 1 (0.010, 0.011, 0.019) and diet 2 (0.013, 0.058, 0.084) and was low for pigs fed diet 3 in Exp. 1 (0.037); however, urinary P was greater in pigs fed diet 3 in Exp. 2 and 3 (0.550 and 0.486, respectively). When P absorption (Y, g/d) was regressed on P intake (X, g/d) in Exp. 1, 2, and 3, the relationships were linear (P < 0.01): Y = -0.110 + 0.97 1X (R2 = 0.999), Y = -0.156 + 0.939X (R2 = 0.998), and Y = -0.226 + 0.8919X (R2 = 0.982), respectively. Thus, our estimates of endogenous P loss at zero P intake were 110, 156, and 226 mg/d for 27-, 59-, and 98-kg pigs, respectively. When these Y-intercepts were regressed on BW, the relationship was Y = 63.06 + 1.632X (R2 = 0.996), where Y = endogenous P loss in mg/d and X = BW in kg. Based on these data, we estimate the endogenous P loss of pigs fed highly digestible, semi-purified diets to increase by approximately 1.632 mg for each 1-kg increase in BW from 25 to 100 kg. [ABSTRACT FROM AUTHOR]

Two experiments were conducted to evaluate the efficacy of dietary DL-methionine hydroxy analog-free acid (MHA-FA, 88%) compared with DL-me- thionine (DLM, 99%) as Met sources in pigs. In Exp. 1, a total of 245 crossbred pigs (initial BW of 6.4 kg [SD = 0.5]) were allotted to 7 treatments in 7 replicates for an experimental period of 28 d. The basal diet (BD) was formulated to contain 17.5% CP and 0.2 1% Met. Dietary treatments included 1) BD, 2) BD + 0.030% DLM, 3) BD + 0.060% DLM, 4) BD + 0.090% DLM, 5) BD + 0.034% MHA-FA, 6) BD + 0.068% MHA-FA, and 7) BD + 0.103% MHA-FA; the MHA-FA was supplemented on an equimolar basis to the DLM. Because of a nonlinear response, exponential regression analysis was used to evaluate the responses, and a comparison of the equations was then made to determine the relative effectiveness of the 2 Met sources. With increases in dietary Met, weight gain increased (P < 0.05). Compared with DLM on a product-to-product (wt/wt) basis, the relative effectiveness of MHA-FA was calculated to be 73% for increasing weight gain and 54% for decreasing the feed:gain. In Exp. 2, a total of 30 weanling barrows [initial BW of 16.8 kg (SD = 2.8)1 were used in a metabolism study to evaluate the relative value of MHA-FA to DLM. The BD was formulated to contain 16.9% CP and 0.21% Met. Dietary treatments included 1) BD, 2) BD + 0.030% DLM, 3) BD + 0.060% DLM, 4) BD + 0.046% MHA-FA, and 5) BD + 0.092% MHA-FA; the MHA-FA levels were chosen based on a pre-experiment estimate of bioequivalence in an attempt to provide approximately equal pig responses. There was no difference in fecal N output among the treatments; however, urine N linearly decreased with increasing concentrations of both sources (P = 0.034 for DLM, and P = 0.007 for MHA-FA), which resulted in a linear increase in retained N for both DLM (P = 0.012) and MHA-FA (P = 0.005). In addition, N retention (% of intake) linearly increased with increasing level of DLM (P = 0.0 14) and MHA-FA (P = 0.007). Using a slope-ratio procedure for comparison of the responses from the 2 sources, the relative biological equivalence value of MHA-FA to DLM in this experiment was 64.2% based on percent N retention and 66.3% based on the grams of N retained per day. Based on the results from both experiments, these data indicated that the mean relative bioequivalence of MHA-FA to DLM was 64% on a product-to-product (wt/wt) basis or 73% on an equimolar basis. [ABSTRACT FROM AUTHOR]

Five experiments were conducted to evaluate the effects of dietary spray-dried porcine plasma (SDPP) and spray-dried bovine plasma (SDBP) and their various molecular weight fractions on performance of pigs weaned at approximately 14 or 21 d of age. In addition, the efficacy of various levels of the immunoglobulin G (IgG)-rich fraction of SDPP and SDBP were evaluated. Experiment 1 evaluated the dietary addition of SDPP and three of its fractions (IgG- rich, albumin-rich, and low molecular weight fractions). Pigs fed SDPP grew faster and consumed more feed than the controls during the first week (P < 0.05). The IgG-rich fraction resulted in improvements in ADG and ADFI that were similar to those of pigs fed SDPP. The albumin-rich fraction had no effect on growth rate, but the low molecular weight fraction decreased feed intake as well as growth rate. Experiments 2 and 3 evaluated SDPP and graded levels of its IgG-rich fraction in pigs weaned at 21 or 14 d, respectively. In Exp. 2, pigs fed SDPP grew faster and consumed more feed than the controls during the first week (P < 0.05). Pig performance was enhanced with the addition of the IgG-rich fraction that provided 80% of the amount of IgG in the SDPP diet. In Exp. 3 there was no response to SDPP during the first week, but a positive growth response to SDPP (P < 0.01) occurred by the end of wk 2 (0 to 14 d). Feeding the IgG-rich fraction increased growth rate compared with controls (P < 0.05). Over the entire experiment, the greatest ADG occurred with the IgG-rich fraction that provided 128% of the amount of IgG provided by SDPP (quadratic; P < 0.05). Two additional experiments assessed feeding SDBP and bovine IgG-rich fractions to early weaned pigs. In Exp. 4, SDPP was superior to SDBP in stimulating growth and feed intake, but this difference did not occur in Exp. 5. In both experiments, the IgG fraction of bovine plasma seemed to be as effective at improving growth as SDPP and more effective than SDBP. The results indicate that both porcine and bovine plasma are beneficial to young pig performance during the first week after weaning and that the IgG fraction of plasma is the component that is responsible for the enhancement in growth rate and feed intake. [ABSTRACT FROM AUTHOR]

Five experiments were conducted to evaluate the effects of dietary spray-dried porcine plasma (SDPP) and spray-dried bovine plasma (SDBP) and their various molecular weight fractions on performance of pigs weaned at approximately 14 or 21 d of age. In addition, the efficacy of various levels of the immunoglobulin G (IgG)-rich fraction of SDPP and SDBP were evaluated. Experiment 1 evaluated the dietary addition of SDPP and three of its fractions (IgG- rich, albumin-rich, and low molecular weight fractions). Pigs fed SDPP grew faster and consumed more feed than the controls during the first week (P < 0.05). The IgG-rich fraction resulted in improvements in ADG and ADFI that were similar to those of pigs fed SDPP. The albumin-rich fraction had no effect on growth rate, but the low molecular weight fraction decreased feed intake as well as growth rate. Experiments 2 and 3 evaluated SDPP and graded levels of its IgG-rich fraction in pigs weaned at 21 or 14 d, respectively. In Exp. 2, pigs fed SDPP grew faster and consumed more feed than the controls during the first week (P < 0.05). Pig performance was enhanced with the addition of the IgG-rich fraction that provided 80% of the amount of IgG in the SDPP diet. In Exp. 3 there was no response to SDPP during the first week, but a positive growth response to SDPP (P < 0.01) occurred by the end of wk 2 (0 to 14 d). Feeding the IgG-rich fraction increased growth rate compared with controls (P < 0.05). Over the entire experiment, the greatest ADG occurred with the IgG-rich fraction that provided 128% of the amount of IgG provided by SDPP (quadratic; P < 0.05). Two additional experiments assessed feeding SDBP and bovine IgG-rich fractions to early weaned pigs. In Exp. 4, SDPP was superior to SDBP in stimulating growth and feed intake, but this difference did not occur in Exp. 5. In both experiments, the IgG fraction of bovine plasma seemed to be as effective at improving growth as SDPP and more effective than SDBP. The results indicate that both porcine and bovine plasma are beneficial to young pig performance during the first week after weaning and that the IgG fraction of plasma is the component that is responsible for the enhancement in growth rate and feed intake. [ABSTRACT FROM AUTHOR]

Evaluations of the nutritional impact of antibiotics have largely centered on effects related to the digestibility and utilization of protein and energy. Recent research has demonstrated that virginiamycin increases P digestibility. Because of the importance of P in diet cost and in waste management plans, the present study evaluated the potential impact of 2 additional antibiotics, bacitracin methylene disalicylate (bacitracm) and tylosin, on P digestibility in swine. A total of 48 barrows (mean initial BW, 63.0 to 82.9 kg) were used in 2 nutrient balance experiments. A basal cornsoybean meal diet that was not supplemented with any inorganic source of P was used in each experiment. In Exp. 1, two diets were tested: basal vs. basal plus 33.1 mg of bacitracin/kg of diet. In Exp. 2, two diets were also tested: basal vs. basal plus 44.1 mg of tylosin/kg of diet. In both experiments, the pigs were fed their diets for a minimum of 12 d before fecal and urine collection, and pigs were fed the diet at 2.7% of BW during the adaptation and collection period. In Exp. 1, the apparent DM, Ca, and P digestibility values for the basal and bacitracin diets were 91.69, 65.96, and 43.03 vs. 91.47, 65.46, and 41.79%, respectively, and did not differ by diet. In Exp. 2, the DM, Ca, and P digestibility values for the basal and tylosin diets were 91.03, 62.17, and 38.80 vs. 91.11, 63.20, and 40.10%, respectively, and did not differ by diet. The effect of the antibiotics on gut microflora was also appraised but the evaluations failed to demonstrate an effect on the microflora ineasured, with the exception that tylosin decreased the number of phytate–utilizing bacteria (P = 0.05). Therefore, because these 2 antibiotics did not demonstrate an improvement in P digestibility, improvements in P digestibility seem to be an antibiotic–specific response rather than a generalized antibiotic response. [ABSTRACT FROM AUTHOR]