Effects of porcine somatotropin administration on the responses to dietary lysine and a near-ideal blend of amino acids on the amino acid composition of whole-body protein and amino acid accretion rate in growing pigs.

An experiment was conducted to assess the effects of porcine somatotropin (pST) on the responses to a near-ideal blend of AA on the AA composition of empty, whole empty body (WEB) protein and WEB essential AA accretion rate in pigs from 22 to 60 kg BW. Forty Hampshire × Yorkshire gilts were individually penned and assigned to a 4 × 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 with Thr, Met, and Trp 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, and 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 i.m. injection of 2 mg of pST. At 60 kg BW, the WEB (carcass, head, viscera, blood, nails, and hair) was ground and analyzed for proximate and AA composition. Administration of pST increased (P < 0.001) accretion rates of WEB protein and essential AA. Increasing dietary essential AA increased (quadratic, P < 0.03) accretion rate of WEB protein, His, Leu, Trp, and Val in pST-treated pigs, but not in untreated pigs. Lysine composition in the accreted WEB protein was not affected (P > 0.05) by dietary Lys. The efficiency of Lys utilization for WEB Lys accretion was linearly affected (P < 0.01) by dietary Lys. These results indicated that the dietary Lys needed to achieve maximum WEB Lys accretion is markedly increased by pST administration.

Estimation of calcium and phosphorus content in growing and finishing pigs: whole empty body components and relative accretion rates.

Two comparative serial-slaughter experiments were conducted to determine whole empty body (WEB) composition and accretion rates of Ca and P in 18 to 109 kg BW pigs to provide information for modeling of these nutrients for growth. Both studies were conducted with 5 sets of 5 littermate barrows which were allotted to 5 slaughter groups in each study (Exp. 1: 18, 27, 36, 45, and 54 kg BW; Exp. 2: 36, 54, 73, 91, and 109 kg BW). Pigs were fed corn-soybean meal-based diets fortified with minerals and vitamins in 2 dietary phases in Exp. 1 (Phase 1: 18 to 36 kg BW; Phase 2: 36 to 54 kg BW) and 3 dietary phases in Exp. 2 (Phase 2: 36 to 54 kg BW; Phase 3: 54 to 78 kg BW; and Phase 4: 78 to 109 kg BW). At the predetermined BW, pigs were slaughtered and separated into body components of hair, hooves, blood, head, viscera, and carcass. The carcass was split along the dorsal midline and the left carcass side was ground for chemical analysis. Whole empty body weight averaged 93.6% and 94.0% of live BW in Exp. 1 and Exp. 2, respectively. As WEB weight increased in both experiments, the percentage carcass of the WEB linearly (P < 0.05) increased, the percentage viscera linearly (P < 0.05) decreased, and the mass (g) of N, ash, Ca, and P in the WEB increased linearly (R(2) = 0.98). The concentration (g/kg) of P in the WEB of 18 to 54 kg pigs increased from 4.30 to 4.57 (linear; P < 0.05) and for Ca increased from 5.13 to 5.66 (linear; P < 0.05). In Exp. 2, P concentration was not related to WEB weight and Ca concentration increased quadratically (P < 0.05). The relative accretion rate of N to P was 1.00 (R(2) = 0.99) in the pigs from 18 to 54 kg. In conclusion, these results indicate that compositional changes as BW increases are strongly related to P retention and that the quantification of WEB P and relationships of WEB P to other chemical components in the body may be useful for modeling purposes in growing and finishing pigs.

Effect of inorganic or organic selenium supplementation on reproductive performance and tissue trace mineral concentrations in gravid first-parity gilts, fetuses, and nursing piglets.

The objective of this experiment was to evaluate 2 supplemental forms of Se on reproductive performance and tissue trace mineral concentration in fetus and first-parity gilts during pregnancy and their progeny. Crossbred gilts (n=100) were selected at 183±2.7 d and 137±10 kg BW and fed a common diet. After 1 mo, 8 gilts were sacrificed to establish baseline liver Se concentration and the remaining 92 gilts allotted to receive Se (0.3 mg/kg diet) as inorganic Se (Na2SeO3) or a Se supplement that contains organoselenium compounds (Sel-Plex; Alltech Inc., Nicholasville, KY). At 267±5.7 d (171±11 kg), gilts were estrus-synchronized and bred. Gilts were then slaughtered at defined time points throughout gestation (d 0, 43, 58, 73, 91, 101, or 108 of gestation; n=6 to 12 gilts/time point). A week before the expected farrowing day, 10 pregnant gilts (5 from each treatment) were moved to farrowing crates and monitored. Two pigs from each litter were randomly selected and euthanized at d 0 (within 2 h after birth; nursing deprived), 7, 14, and 21 from each litter. During the gestation phase, maternal liver, and fetal body and liver were collected for determination of trace mineral concentration by inductively coupled plasma mass spectrometry. Total number of fetus, crown-rump length, and corpora lutea of gilts were recorded as well. During the lactation phase, pigs (without liver and gastrointestinal tract) and associated liver were analyzed for Se concentration. The results demonstrated that the source of Se generally did not affect the maternal reproductive traits and fetal characteristics. Also, the source of Se supplemented to the maternal diet did not, in general, affect Cu, Fe, Mn, or Zn concentrations in the tissues evaluated other than the observation of a greater maternal liver Mn content (P<0.01) in gilts fed Sel-Plex and a greater amount of Fe accumulated in the entire litter (P<0.01) in gilts fed Sel-Plex. However, with regard to Se concentrations, Se in fetal body, fetal liver, and maternal liver were greater (P<0.01) when Sel-Plex was fed. Postnatal pigs from gilts fed Sel-Plex had greater (P<0.05) Se retention in body and liver with similar growth performance during the 21-d period. The results demonstrate Se form differences wherein Sel-Plex is associated with greater Se accumulation in both maternal and fetal tissues.

Supplementation of organic and inorganic selenium to diets using grains grown in various regions of the United States with differing natural Se concentrations and fed to grower-finisher swine.

Grains grown in various regions of the United States vary in their innate or natural Se contents. A regional study evaluated the effects of adding inorganic Se (sodium selenite) or organic Se (Se yeast) to diets with differing innate Se contents. A 2 × 2 + 1 factorial experiment evaluating 2 Se sources (organic or inorganic) at 2 Se levels (0.15 or 0.30 mg/kg) in 18 total replicates (n = 360 total pigs). A basal diet was fed without supplemental Se and served as the negative (basal) control. The study was conducted as a randomized complete block design in 9 states (Georgia, Illinois, Kentucky, Nebraska, North Carolina, Ohio, South Dakota, Texas, and Wisconsin) with each station conducting 2 replicates. Pigs were fed from 25 to approximately 115 kg BW. Similar dietary formulations were used at each station, incorporating a common source of trace mineral and Se premixes. Three pigs per treatment in 16 replicates (n = 240) were bled at 55, 85, and 115 kg BW and serum Se and glutathione peroxidase (GSH-Px) activities were determined. Three pigs (n = 260) from each treatment pen were killed at 115 kg BW and issues (liver, loin, and hair) were analyzed for Se. The corn Se content from the various states ranged from 0.026 to 0.283 mg Se/kg while the soybean meal Se content ranged from 0.086 to 0.798 mg Se/kg. Tissue and serum Se concentrations were greater (P < 0.01) when supplemental organic Se was fed, whereas serum GSH-Px was greater (P < 0.01) as Se level increased. There were linear increases (P < 0.01) in loin and quadratic increases (P < 0.01) in liver and hair Se concentrations as dietary Se level increased within each state. There was a source × level interaction (P < 0.01) for each tissue resulting in a greater increase when organic Se was fed. Serum Se and GSH-Px activity increased (P < 0.01) when both Se sources were fed and plateaued at each state at 0.15 mg Se/kg. There was a high and significant correlation between each tissue Se, serum Se, and GSH-Px activity to dietary Se level indicating that those states having greater grain natural Se contents also had greater tissue Se concentrations. These results indicate that a large difference in corn and soybean meal Se concentrations exists between states, that the addition of organic or inorganic Se to these grains increased tissue and serum Se in each state, and that organic Se was incorporated at greater concentrations in the loin, liver, and hair tissues of grower-finisher pigs than inorganic Se.

Comparison of direct and indirect estimates of apparent total tract digestibility in swine with effort to reduce variation by pooling of multiple day fecal samples.

The intent of this study was to establish a fecal sampling procedure for the indicator method (IM) to provide digestibility values similar to those obtained by the total collection (TC) method. A total of 24 pigs (52.6 ± 1.5 kg) were fed 1 of 4 diets with a 2 × 2 factorial arrangement of virginiamycin and phytase (PHY) added to a corn-soybean meal diet with no inorganic P supplement. Pigs were housed in metabolism crates for a 5-d TC period after 7 d of adaptation. Immediately after the TC, a fecal collection period followed, using the IM by including 0.25% of Cr2O3 in the feed for 10 d. Fecal collection for the IM started the day after diets containing Cr2O3 were first fed, and continued for 9 consecutive days with a single grab sample per day. Similar portions of feces from d 5 to 9 were also composited into 4 samples to evaluate multi-day pooling combinations. Highly variable means and CV among samples for apparent total tract digestibility (ATTD) were observed at d 1 and 2 using the IM. The mean ATTD for DM, GE, and nutrients appeared to be stabilized by d 5 or 6 in all dietary treatments. The TC data seemed to have lower CV than the IM data for many components. Based on the linear broken-line analysis, fecal Cr concentration plateaued at d 3.75 (P < 0.001) after the first feeding of Cr. Mean ATTD values by the IM were lower than those by the TC method for DM (P < 0.05), GE (P < 0.01), P (P < 0.01), and Ca (P < 0.001). The PHY supplementation improved ATTD of P (P < 0.001) and Ca (P < 0.001) in both collection methods, whereas the PHY effect on ATTD of DM was observed only for the IM (P < 0.05). Differences related to PHY effect on ATTD were detected from d 4 to 9 in a single grab sample for P and DM but the ATTD of DM had inconsistent P-values by day. Fecal sampling after 4 d of initial feeding of marker always allowed detection of treatment effects on ATTD of P but not on ATTD of DM. Results indicated that the IM results in lower digestibility values than the TC method and does not provide the same treatment difference as the TC digestibility for energy and nutrients that are not highly impacted by the dietary treatment. For the IM, ATTD values and fecal Cr concentration stabilize at least on d 5 after initial feeding of diets containing Cr2O3. At least 2-d pooling of feces for the IM appears to be needed to provide greater accuracy and lower variations than a single grab sample.

Determining the optimal isoleucine:lysine ratio for ten- to twenty-two-kilogram and twenty-four- to thirty-nine-kilogram pigs fed diets containing nonexcess levels of leucine.

Three 21-d experiments were conducted to determine the optimum standardized ileal digestible (SID) Ile:Lys ratio in 10- to 22-kg and 24- to 39-kg pigs. In Exp. 1, 144 Yorkshire pigs (initial BW = 10.2 kg) were assigned to 6 diets with 6 pens per treatment. Diets 1 to 5 were formulated to contain 5 graded SID Ile:Lys (44, 51, 57, 63, and 70%), 1.18% SID Leu, and 0.90% SID Lys (second limiting). Diet 6 (diet 5 with added Lys) was formulated (1.06% SID Lys) as a positive control. Pigs fed diet 6 had higher (P < 0.05) ADG and G:F and lower (P < 0.05) plasma urea N (PUN) than pigs fed diet 5 (P < 0.02), indicating that Lys was limiting in diets 1 to 5. Final BW, ADG, and ADFI increased (linear and quadratic, P < 0.05) while G:F and PUN at d 21 were not affected (P > 0.10) by dietary Ile:Lys. Overall, ADG and ADFI were highest for pigs fed diet 2 (51% SID Ile:Lys). In Exp. 2, 216 Yorkshire pigs (initial BW = 9.6 kg) were assigned to 9 diets with 6 pens per treatment. Diets 1 to 4 contained 0.40, 0.47, 0.54, and 0.61% SID Ile, respectively, and 1.21% SID Lys; diets 5 to 8 contained 0.72, 0.84, 0.96, and 1.08% SID Lys, respectively, and 0.68% SID Ile. Diet 9 was high in both Ile and Lys (0.68% SID Ile and 1.21% SID Lys). All diets contained 1.21% SID Leu. The ADG and G:F increased (linear and quadratic, P < 0.05) as SID Ile:Lys increased (diets 1 to 4 and 9). The ADG and G:F increased (linear, P < 0.05) as SID Lys increased (diets 5 to 9). The PUN at d 21 decreased (linear, P < 0.05) by increasing dietary Ile:Lys. The SID Ile:Lys to optimize ADG was 46% by curvilinear plateau or exponential regression. For G:F, the optimal SID Ile:Lys was 47 and 51% by curvilinear plateau and exponential regressions, respectively. In Exp. 3, 80 pigs (PIC 327 × C23; initial BW = 24.0 kg) were allotted to 5 treatments with 4 pigs per pen. Diets 1 to 5 were formulated to contain 5 graded SID Ile:Lys (39, 46, 53, 61, and 68%), 1.17% SID Leu, and 0.91% SID Lys (second limiting). Final BW and ADG increased (linear and quadratic, P < 0.05) and ADFI increased (linear, P = 0.047) as SID Ile:Lys increased. Using ADG and G:F, the optimum SID Ile:Lys was 54 and 53%, respectively, by curvilinear plateau and exponential regression. The PUN was minimized at 53 and 59% SID Ile:Lys by curvilinear plateau and broken line regression. Overall, the average optimum SID Ile:Lys was approximately 51% for 10- to 22-kg pigs and 54% for 24- to 39-kg pigs fed diets containing nonexcess levels of Leu.

Dietary lipid sources and levels for weanling pigs.

Collaborative studies comprising growth performance and metabolism experiments were conducted to reevaluate growth performance and nutrient and energy utilization responses of nursery pigs to dietary lipid sources and levels. Two lipid sources (soybean oil or tallow) were included at the rate of 1%, 3%, or 5% at the expense of cornstarch in a 2 × 3 factorial arrangement for 6 diets, and Lys was added to maintain a constant calorie:Lys ratio. A growth performance experiment (d 0 to 7, d 7 to 21, and d 21 to 35 postweaning) involving a total of 822 crossbred pigs was conducted at 9 research stations. Each station contributed 2 to 7 replicate pens with 4 to 6 pigs per pen, resulting in a total of 28 replicate pens per diet. The initial BW ranged from 5.9 to 7.3 kg, and the final BW ranged from 20.9 to 28.9 kg. Diets fed during d 7 to 21 and d 21 to 35 were evaluated with 120 barrows in 2 metabolism experiments with 10 individually fed barrows per diet to determine digestibility and retention of nutrients and energy. Lipid source and the interaction between lipid level and source did not affect growth performance. Lipid did not affect growth performance from d 0 to 7. There was a quadratic decrease (P < 0.05) in ADG with increasing level of added lipid only during d 7 to 21 postweaning. The ADFI was decreased (P < 0.01) both during d 7 to 21 and d 21 to 35 postweaning with increasing level of lipid supplementation. A linear improvement (P < 0.001) in G:F with increasing level of lipid supplementation occurred during both d 21 to 35 and d 0 to 35 postweaning. There was a linear increase in DE, ME, and nitrogen-corrected ME (MEn) of diets fed during d 7 to 21 postweaning with increasing lipid level regardless of lipid source. For diets fed during d 21 to 35 postweaning, there were interactions (P < 0.05) between lipid source and level for digestibility of DM, N, lipid, and energy and for DE, ME, and MEn of diets. The improved feed efficiency was, perhaps, partly attributable to the increase in ME content of the diets with added lipids. There were interactions (P < 0.05) between lipid source and level for efficiency of energy use for BW gain for diets fed during d 21 to 35. The efficiencies of use of DE, ME, and NE for BW gain were not affected in pigs fed diets containing increasing levels of soybean oil; however, there were linear increases in these response criteria for pigs fed diets containing increasing levels of tallow. These results indicate that the energy values of soybean oil from the 2012 NRC study used in formulating these diets were fairly accurate.

Effect of dietary acids on growth performance of nursery pigs: a cooperative study.

An experiment involving 854 crossbred pigs (20 replicate pens of 4 to 8 pigs per pen) was conducted at 8 experiment stations to determine the effects of acids in nursery pig diets and their inclusion amounts on growth performance using diets and weaning ages typical of those used in the United States commercial pork industry. Diets were formulated to have constant a ME and contain 1.45, 1.45, and 1.30% standardized ileal digestible Lys for phases 1, 2, and 3, respectively. The basal diets were supplemented with various types and concentrations of acid at the expense of corn (Zea mays). Treatment diets included 0% acid (control), 0.1 or 0.2% phosphoric acid, 1 or 2% organic acids, and 0.1% phosphoric acid plus 1% organic acids with or without an antibiotic. The organic acids consisted of 50% citric acid and 50% fumaric acid by weight. All but the final diet contained the antibiotic carbadox. All diets contained 3,000 mg of Zn/kg diet from zinc oxide during phases 1 and 2 and had limited acid buffering capacity, ranging from 142, 127, and 122 mEq/kg of feed for phases 1, 2, and 3, respectively. At each participating station, pigs were randomly allotted to dietary treatments on the basis of their initial BW. Sex and ancestry were equally distributed across the treatments. Results indicated that treatment effects on pig performance were observed in phases 1 and 2 but not in phase 3. In phase 1, ADG of pigs fed 0.2% phosphoric acid was greater than that of pigs fed the combination of acids with no antibiotic (P = 0.041). In phase 2, pigs fed treatments containing an antibiotic had a greater ADG than those fed the combination of acids without antibiotic (P < 0.05). Addition of acids to diets did not affect growth performance during any phase or the overall period. Over the 4-wk study, growth rate was slowest on the treatment without antibiotic, with specific differences that were often statistically significant (P < 0.05). In summary, under the conditions of this experiment, the acid treatments had no effect but the antibiotic improved growth performance.

Effects of corn distillers dried grains with solubles on quality traits of pork.

The high cost of feed grains has led swine producers to seek alternative feedstuffs, such as distillers dried grains with solubles (DDGS). However, little is known about the effects of high levels of DDGS in swine diets on pork quality. The objective of this study was to evaluate belly processing and bacon, sausage, and loin quality of pigs fed high levels of DDGS. Sixty pigs averaging 34 kg BW were fed fortifi ed corn-soybean meal diets containing 0%, 15%, 30%, or 45% DDGS. At 120 kg BW, the pigs were humanely harvested and bellies, loins, and shoulders were removed from the left side of each carcass. Flex tests of bellies indicated that they became softer (linear, P < 0.03) as DDGS levels increased. The PUFA in backfat and belly fat increased linearly (P < 0.005), as did iodine values with increasing 0DDGS in the diet. Bellies were pumped to target 12% brine retention, cooked, and sliced at a commercial facility. Slicing yield was not affected by DDGS level fed. Fresh bacon slices were scored 1 to 6 with 1 representing no visible cracks in the fat and 6 representing a spider weblike shattering of the fat. Shatter scores decreased (linear, P < 0.001) with increasing dietary DDGS. Bratwurststyle sausage was produced by combining ground Boston butts and picnics to target 30% fat, blended with commercial seasonings, and stuffed into natural casings. Loose sausage was placed on trays, overwrapped with polyvinyl chloride wrap, and stored under constant, cool white fl orescent lighting (1,300 lx) at 4°C. Objective color values (L*, a*, and b*) were taken on loosepackaged sausage mix at 6 locations at the same time daily for 7 d. Sausage was also sampled for thiobarbituric acid reactive substances (TBARS) at the same time daily on d 0, 3, 5, and 7. Color scores of sausage were not consistently affected by DDGS level in the diet and the changes were slight. The TBARS in sausage from pigs fed the 30% and 45% DDGS diets increased to a greater extent from d 0 to 7 than in those fed the control or 15% DDGS diets. An 8-member, trained panel evaluated the sensory attributes of bacon slices, sausage, and loin chops. The DDGS resulted in a softer texture (P < 0.004) and increased juiciness (P < 0.04) in sausages, but no differences in sensory scores were found in bacon slices or loin chops. The results indicate that the softer bellies, greater concentrations of PUFA in carcass fat, and greater iodine values associated with feeding increased DDGS did not negatively affect slicing yield of cured bellies, quality of fresh bacon slices, or eating quality of bacon, sausage, or loin chops.

Effects of porcine somatotropin administration on the responses to dietary lysine and a near-ideal blend of amino acids for growing pigs.

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 × Yorkshire gilts (40 gilts/experiment) were individually penned and assigned to a 4 × 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 Trp 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 protein and 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 × 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.

Evaluation of trace mineral source and preharvest deletion of trace minerals from finishing diets for pigs on growth performance, carcass characteristics, and pork quality.

Weanling crossbred pigs (Sus scrofa; 72 barrows and 72 gilts; BW = 7.4 ± 1.1 kg) were used to evaluate dietary supplemental trace mineral (Cu, Fe, Mn, and Zn) source (inorganic vs. organic) and deletion (0, 2, 4, and 6 wk preharvest) on growth performance, carcass characteristics, and pork quality. Pigs were blocked by BW, ancestry, and sex, and randomly allotted to 24 pens, and fed a diet containing either inorganic or organic trace minerals supplemented at the 1998 NRC requirement estimates for each of 5 BW phases from 7 to 120 kg (equivalent to 14, 14, 42, 28, and 42-d periods, respectively). Two pigs were removed from each pen at the end of Phase IV (BW = 82.6 ± 6.0 kg), and 2 other pigs were removed at the end of Phase V (BW = 128.0 ± 8.3 kg) for collection of various tissues and for determination of carcass characteristics and pork quality. On d 1, 15, and 29 of Phase V, 3 pens within each source of minerals were switched to a common diet without supplemental trace minerals, whereas the remaining 3 pens within each source of minerals were fed diets containing trace minerals throughout the Phase V period. This resulted in 4 groups within each mineral treatment, in which trace mineral supplementation was deleted for 6, 4, 2, or 0 wk of Phase V. Trace mineral source (inorganic vs. organic) did not affect ADG, ADFI, and G:F (773 vs. 778 g/d, 1,680 vs. 1,708 g/d, and 461 vs. 456 g/kg, respectively) during the first 4 phases. During the mineral deletion period, ADG and G:F were not affected by the duration of trace mineral deletion, but ADFI increased when trace minerals were removed from the diet for 6 wk (6 vs. 0 wk, 3,393 vs. 3,163 g/d; P = 0.05). Hot carcass weight, cold carcass weight, carcass shrink, dressing percentage, LM area, 10th rib and midline average backfat, and carcass fat-free lean weight and percentage were not affected (P > 0.10) by the source of mineral or length of mineral deletion, but carcass length tended to decrease (P = 0.09) when time of trace mineral deletion increased. Increasing mineral deletion from 0 to 6 wk tended to reduce linearly (P = 0.08) Hunter a* scores on the day of carcass processing (24 h after slaughter), as well as 2 d after processing, and Hunter b* scores on d 2 and d 6 after processing. Results of this experiment indicate that use of organic trace minerals, rather than inorganic trace minerals, did not influence pig growth performance or carcass characteristics and quality; however, deletion of minerals during the last 6 wk before harvest increased ADFI and affected drip loss, some color scores of the LM, and carcass length.

Standardized ileal digestible tryptophan-to-lysine ratios in growing pigs fed corn-based and non-corn-based diets.

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.

Corn distillers dried grains with solubles in diets for growing-finishing pigs: a cooperative study.

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 cm(2)) 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.

Concentration of dietary calcium supplied by calcium carbonate does not affect the apparent total tract digestibility of calcium, but decreases digestibility of phosphorus by growing pigs.

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.

Evaluation of antibiotic effects on phosphorus digestibility and utilization by growing-finishing pigs fed a phosphorus-deficient, corn-soybean meal diet.

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 (bacitracin) 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 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 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 measured, 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.

The effects of dietary chromium(III) picolinate on growth performance, blood measurements, and respiratory rate in pigs kept in high and low ambient temperature.

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 degrees C during d 14 to 28 postweaning) and 3 dietary concentrations of Cr (0, 1,000, or 2,000 microg/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 degrees 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 degrees 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, G: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/min; 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/min and 42.2 vs. 57.0 breaths/min, 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.

The addition of ground wheat straw as a fiber source in the gestation diet of sows and the effect on sow and litter performance for three successive parities.

A regional experiment was conducted at 8 experiment stations, with a total of 320 sows initially, to evaluate the efficacy of adding 13.35% ground wheat straw to a corn-soybean meal gestation diet for 3 successive gestation-lactation (reproductive) cycles compared with sows fed a control diet without straw. A total of 708 litters were farrowed over 3 reproductive cycles. The basal gestation diet intake averaged 1.95 kg daily for both treatments, plus 0.30 kg of straw daily for sows fed the diet containing ground wheat straw (total intake of 2.25 kg/d). During lactation, all sows on both gestation treatments were fed ad libitum the standard lactation diet used at each station. Response criteria were sow farrowing and rebreeding percentages, culling factors and culling rate, weaning-to-estrus interval, sow BW and backfat measurements at several time points, and litter size and total litter weight at birth and weaning. Averaged over 3 reproductive cycles, sows fed the diet containing wheat straw farrowed and weaned 0.51 more pigs per litter (P

ASAS centennial paper: Landmark discoveries in swine nutrition in the past century.

During this centennial year of the American Society of Animal Science (ASAS), it is of interest to look back over the history of our Society and, in particular, to the many contributions made by researchers in the area of swine nutrition. A great number of basic and applied research studies involving the nutrition of weanling, growing, and finishing pigs, and gestating and lactating sows have been conducted by swine nutritionists during the past 100 yr. Most of these studies were conducted at universities by animal scientists or by the graduate students under their leadership. Others were conducted by nutritionists in the feed and pharmaceutical industries and government scientists at ARS/USDA research centers. Contributions were also made by animal scientists beyond our borders. Much of the research was published in the Journal of Animal Science during its 66 yr of existence. Before the first issue of the journal was published in 1942, some of the earlier studies were reported in the Proceedings of the Annual Meeting of the Society of Animal Production, the forerunner of ASAS. These research studies have progressively led to a better understanding of the role and utilization of dietary energy, protein, AA, carbohydrates, fats, minerals, and vitamins by pigs and have helped to quantify the nutrient requirements of pigs for various stages of growth, for sows during gestation and lactation, and to a limited extent, for boars. Determining the nutritional value of a wide array of feedstuffs, evaluating feeding strategies, and assessing the value of growth-promoting and carcass-enhancing agents have been important research contributions as well. To identify the particular studies that were among the most instrumental in contributing to our present knowledge of swine nutrition is, to say the least, a daunting assignment. To aid in this task, a survey of swine nutritionists was conducted in which they were asked to identify and rank the 10 most significant findings in swine nutrition during the past 100 yr. The results of that survey are presented in this paper.

Effect of chromium source on tissue concentration of chromium in pigs.

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 microg/kg of Cr from Cr tripicolinate (CrTP), Cr propionate (CrPrp), Cr methionine (CrMet), or Cr yeast (CrY). Twenty gilts 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.

Assessment of lactose level in the mid- to late-nursery phase on performance of weanling pigs.

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.