Nonlinear analysis of heart rate variability for evaluating the growing pig stress response to an acute heat episode.

Heart rate variability (HRV) is a proxy measure of autonomic function and can be used as an indicator of swine stress. While traditional linear measures are used to distinguish between stressed and unstressed treatments, inclusion of nonlinear HRV measures that evaluate data structure and organization shows promise for improving HRV interpretation. The objective of this study was to evaluate the inclusion of nonlinear HRV measures in response to an acute heat episode. Twenty 12- to 14-week-old growing pigs were individually housed for 7 days and acclimated to thermoneutral conditions (20.35°C ± 0.01°C; 67.6% ± 0.2% RH) before undergoing one of the two treatments: (1) thermoneutral control (TN; n = 10 pigs) or (2) acute heat stress (HS; n = 10 pigs; 32.6°C ± 0.1°C; 26.2% ± 0.1% RH). In Phase 1 of the experimental procedure (P1; 60 min), pigs underwent a baseline HRV measurement period in thermoneutral conditions before treatment [Phase 2; P2; 60 min once gastrointestinal temperature (Tg) reached 40.6°C], where HS pigs were exposed to heated conditions and TN pigs remained in thermoneutral conditions. After P2, all pigs were moved back to thermoneutral conditions (Phase 3; P3; 60 min). During each phase, Tg data were collected every 5 min and behavioural data were collected to evaluate the amount of time each pig spent in an active posture. Additionally, linear (time and frequency domain) and nonlinear [sample entropy (SampEn), de-trended fluctuation analysis, percentage recurrence, percentage determinism (%DET), mean diagonal line length in a recurrence plot] HRV measures were quantified. Heat stressed pigs exhibited greater Tg (P = 0.002) and spent less time in an active posture compared to TN pigs during P2 (P = 0.0003). Additionally, low frequency to high frequency ratio was greater in HS pigs during P3 compared to TN pigs (P = 0.02). SampEn was reduced in HS pigs during P2 (P = 0.01) and P3 (P = 0.03) compared to TN pigs. Heat stressed pigs exhibited greater %DET during P3 (P = 0.03) and tended to have greater %DET (P = 0.09) during P2 than TN pigs. No differences between treatments were detected for the remaining HRV measures. In conclusion, linear HRV measures were largely unchanged during P2. However, changes to SampEn and %DET suggest increased heat stress as a result of the acute heat episode. Future work should continue to evaluate the benefits of including nonlinear HRV measures in HRV analysis of swine heat stress.

Short communication: Assessment of disbudding pain in dairy calves using nonlinear measures of heart rate variability.

The purpose of this study was to evaluate whether pain-related stress caused by disbudding could be detected using nonlinear measures of heart rate variability (HRV). Twenty-five female Holstein calves (4-7 wk of age) were randomly assigned to 1 of 3 treatments: (1) sham disbud (SHAM; n = 9), (2) disbud with lidocaine-meloxicam pain mitigation (MED; n = 8), or (3) disbud without pain mitigation (NoMED; n = 8). Heart rate variability (sample entropy, percentage determinism, percentage recurrence, or mean length of diagonal lines in a recurrence plot) was recorded on d -1, 0, 1, 3, and 5 relative to the experimental procedure, with disbudding taking place on d 0. The short-term detrended fluctuation analysis scaling exponent was greater in MED calves than in SHAM calves, indicating a greater stress response to the disbudding procedure regardless of pain mitigation. These results indicate that calves in the MED group may have experienced pain-related stress as a result of the disbudding procedure. The remaining nonlinear HRV measures did not differ by treatment. Future research on this topic should address additional potential confounding factors, such as the effect of pain-mitigating drugs on autonomic function or the influence of the autonomic nervous system on wound healing, that may prohibit HRV measurement as an indicator of disbudding pain severity.

Effects of dirty housing and a Typhimurium DT104 challenge on pig growth performance, diet utilization efficiency, and gas emissions from stored manure.

The objectives of this study were to elucidate the effects of a dirty environment and a challenge plus associated environmental contamination on pig growth performance, diet utilization efficiency, and gas emissions (CO, NH, CH, NO, and HS) from stored manure. Twenty-four weaned barrows, aged 31 d at initiation of the trial, were randomly allotted to 3 different treatments in a completely randomized design. Treatments were: pigs housed in cages with manure removed and cages washed daily (Clean); pigs housed in cages sprayed daily with manure slurry mixtures (Dirty); or pigs challenged with Typhimurium DT104 and housed in cages that were not washed, but manure was removed daily ( challenge). Rectal temperature, body weight, daily feed intake, manure output, manure composition, and gas emissions from stored manure were measured throughout the 24-d animal phase. The Dirty and challenge treatments were statistically compared to the Clean treatment to evaluate individual effects. Dirty housing tended to decrease ADG from d 1 to 24 ( = 0.06) but there were no other effects on pig performance compared with the Clean treatment. In contrast, a challenge was associated with a marked reduction in each of the measured indicators of pig performance. challenge increased the carbon to nitrogen ratio, ether extract, and lignin concentrations in excreted manure ( = 0.02, 0.01, 0.003, respectively), and increased manure and head space temperatures in manure tanks ( < 0.0001). Gas emissions from stored manure of pigs on the Dirty or treatments were increased for each of the measured gases as compared to the Clean treatment ( < 0.01) when expressed per unit of BW gain. When gas emissions from manure of pigs housed in the Dirty treatment were expressed per unit of manure volatile solids (VS), they were increased for NH, CH, and HS ( < 0.02). challenge was associated with increased emissions of CO, and NO and decreased emissions of HS per kilogram manure VS compared to the Clean treatment ( = 0.06, 0.03, 0.04, respectively). Collectively, these results indicated that a challenge and associated housing contamination caused depressed growth rate and increased manure gas emissions, while exposure to a Dirty environment slightly reduced growth performance and clearly increased manure gas emissions per unit of BW gain as compared to Clean control.

Effects of porcine reproductive and respiratory syndrome virus on pig growth, diet utilization efficiency, and gas release from stored manure.

The objectives of this study were to examine the effects of porcine reproductive and respiratory syndrome virus (PRRSV) infection and vaccination on pig growth, dietary nutrient efficiency of utilization, manure output, and emissions of CO, CH, HS, NO, and NH gases from stored manure. Forty-eight pigs, aged 21 d at the start of the study, were subjected to 1 of 4 treatment combinations arranged in a 2 × 2 factorial design with main factors of PRRSV vaccination and PRRSV infection. Body weight, ADFI, manure output, and nutrient efficiency of utilization were assessed and gas emissions from stored manure were determined daily from 50 to 78 d of age and for 24 d after completion of the animal phase. Infection with PRRSV markedly reduced final BW, ADG, and ADFI ( < 0.01) and reduced efficiencies of ADF and ether extract utilization ( = 0.05 and = 0.02, respectively) regardless of vaccination status. No significant treatment effects were found on manure output, manure pH, efficiencies of lignin utilization, and N retention. Infecting pigs with PRRSV increased daily manure CO emission per pig ( = 0.01). There was an interaction between immunization and infection for NO per pig with manure from uninfected, vaccinated pigs producing as much as the manure from infected, vaccinated pigs whereas there was a difference by PRRSV infection state for nonvaccinated pigs. There were also interactions between treatments for HS and NO emissions per kilogram of manure volatile solids excreted ( = 0.01 and = 0.0001, respectively) with the same pattern as for NO per pig; that is, the vaccinated pigs had similar rates of emission regardless of infection state. Pigs infected with PRRSV increased NO nitrogen per kilogram of total N excreted compared with noninfected groups ( = 0.03). Collectively, these results indicated that PRRSV infection caused decreased growth rates and nutrient utilization efficiency and increased gas emissions from stored manure.

Controlling Salmonella infection in weanling pigs through water delivery of direct-fed microbials or organic acids: Part II. Effects on intestinal histology and active nutrient transport.

The objective of this study was to evaluate the effects of water-delivered, direct-fed microbials (DFM) or organic acids on intestinal morphology and active nutrient absorption in weanling pigs after deliberate Salmonella infection. Pigs (n = 88) were weaned at 19 ± 2 d of age and assigned to 1 of the following treatments, which were administered for 14 d: 1) control diet; 2) control diet + DFM (Enterococcus faecium, Bacillus subtilis, and Bacillus licheniformis) in drinking water at 10(9) cfu/L for each strain of bacteria; 3) control diet + organic acid-based blend (predominantly propionic, acetic, and benzoic acids) in drinking water at 2.58 mL/L; and 4) control diet + 55 mg/kg carbadox. Pigs were challenged with 10(10) cfu Salmonella enterica var Typhimurium 6 d after commencement of treatments. Pigs (n = 22/d) were harvested before Salmonella challenge and on d 2, 4, and 8 after challenge. Duodenal, jejunal, and ileal mucosal tissues were sampled for measurement of villus height and crypt depth. Jejunal tissue was sampled for determination of active nutrient absorption in modified Ussing chambers. Duodenal villus height was greater in pigs fed in-feed antibiotic before infection (P < 0.05). Jejunal crypts were deeper in DFM- and acid-treated pigs on d 4 after infection compared with all other treatments (P < 0.05). Salmonella infection resulted in a linear decrease in phosphorus (P < 0.001) and glucose (P < 0.05) active transport, and an increase (P < 0.001) in glutamine uptake immediately after challenge. Salmonella infection reduced basal short-circuit current (I(sc)); however, water-delivered DFM or organic acid treatments caused greater basal I(sc) on d 2 after challenge than did carbadox. Carbachol-induced chloride ion secretion was greatest in negative control pigs before infection (P < 0.01) and DFM-treated pigs (P < 0.05) after infection. In conclusion, both the DFM and acidification treatments induced increases in basal active ion movement and jejunal crypt depth, which could be interpreted as responses consistent with increased Salmonella pathology, but none of the additives markedly affected intestinal absorptive and secretory function in response to Salmonella challenge.

Controlling Salmonella infection in weanling pigs through water delivery of direct-fed microbials or organic acids. Part I: effects on growth performance, microbial populations, and immune status.

Pigs (n = 88) weaned at 19 ± 2 d of age were used in a 14-d study to evaluate the effects of water-delivered direct-fed microbials (DFM) or organic acids on growth, immune status, Salmonella infection and shedding, and intestinal microbial populations after intranasal inoculation of Salmonella Typhimurium (10(10) cfu/pig). Pigs were challenged with Salmonella 6 d after commencement of water treatments. Treatments were 1) control diet; 2) control diet + DFM (Enterococcus faecium, Bacillus subtilis, and Bacillus licheniformis) in drinking water at 10(9) cfu/L for each strain of bacteria; 3) control diet + an organic acid-based blend (predominantly propionic, acetic, and benzoic acid) in drinking water at 2.58 mL/L; and 4) control diet + 55 mg/kg of carbadox. Serum samples were taken on d 6, 8, 10, and 14 for determination of tumor necrosis factor α (TNFα) concentrations. Fecal samples were taken on d 0, 5, 7, and 11 for determination of Salmonella shedding and enumeration of coliforms. Pigs were euthanized on d 6, 8, 10, and 14. Intestinal and cecal tissue and digesta and mesenteric lymph nodes were sampled and analyzed for Salmonella. Duodenal, jejunal, and ileal mucosal scrapings were sampled for measurement of mucosal TNFα concentrations. Water delivery of DFM prevented a decline in ADG on d 2 to 6 postchallenge compared with the negative control (P < 0.05). Coliform counts tended to be greater (P = 0.09) in the cecum of the DFM treatment group on d 2 postinfection compared with the negative control and acid treatment groups. However, Salmonella prevalence in the feces, gastrointestinal tract, or lymph nodes was not affected by water delivery of acids or DFM. Serum and mucosal TNFα concentrations were not affected by treatment throughout the study with the exception of ileal concentrations on d 4 postchallenge, which were greater in the negative control group compared with all other treatments (P < 0.05). The in-feed antibiotic was the only treatment that reduced Salmonella prevalence and this was localized to the cecum on d 8 postinfection. In conclusion, the DFM and organic acid treatments used in this study offered little or no benefits to pigs infected with Salmonella and should not be considered under the constraints of this study as viable alternatives to in-feed antibiotics in a pathogen challenge situation.

Effect of feeding reduced crude protein and phosphorus diets on weaning-finishing pig growth performance, carcass characteristics, and bone characteristics.

Two experiments were conducted to determine the effects of feeding a corn- and soybean meal-based diet (control) or a low nutrient excretion (LNE) diet, formulated with reduced dietary CP and additional synthetic AA, low phytic acid corn, and phytase, on pig growth performance during the grower (BW=32 to 77 kg) and finisher (BW=78 to 126 kg) periods and on carcass and bone characteristics at slaughter. Pigs (32+/-1.3 kg of BW, Exp. 1; 6.7+/-0.27 kg of BW, Exp. 2) were blocked by sex and BW and randomly allotted to a control or LNE diet. Pigs were housed in 4 rooms during the nursery period and in 2 rooms during the grower and finisher periods, with individual and identical ventilation systems. Pigs were phase fed 3 nursery diets for 5 wk (Exp. 2) and phase fed 2 grower and 2 finisher diets for 16 wk (Exp. 1 and 2). Pigs were housed 4 or 5 pigs/pen with 9 pens x sex(-1) x treatment(-1) during the nursery period and 4 or 5 pigs/pen with 5 pens x sex(-1) x treatment(-1) in the grower phase and 2 or 3 pigs/pen in the finisher phase. Individual BW and pen feed disappearance were recorded weekly in the nursery period and every 2 wk in the grower-finisher period. Pigs were scanned ultrasonically at d 34 of the nursery period and wk 8 and 16 of the grower-finisher period to determine backfat depths and LM area. Ten pigs x sex(-1) x treatment(-1) were slaughtered at wk 16 of each experiment to determine carcass characteristics. Overall growth performance was not different during each experiment. However, nursery G:F (control=0.65; LNE=0.60), grower ADG (Exp. 1 and 2), and grower G:F (Exp. 2) were reduced (P<0.05) when the LNE diets were fed. Diet had no effect on 10th-rib carcass data in either experiment. Metatarsal bone ash percentage was reduced (P<0.05) when the LNE diets were consumed in both experiments. Feeding LNE diets resulted in the maintenance of overall growth performance, bone variables, and carcass characteristics. However, further refinements are still required in the nursery and grower phases of pig production to optimize LNE diet use by the swine industry.

Feeding conjugated linoleic acid partially recovers carcass quality in pigs fed dried corn distillers grains with solubles.

Dried corn distillers grains with solubles (DDGS) fed to swine may adversely affect carcass quality due to the high concentration of unsaturated fat. Feeding CLA enhances pork quality when unsaturated fat is contained in the diet. The effects of CLA on growth and pork quality were evaluated in pigs fed DDGS. Diets containing 0, 20, or 40% DDGS were fed to pigs beginning 30 d before slaughter. At 10 d before slaughter, one-half of each DDGS treatment group was fed 0.6% CLA or 1% choice white grease. Carcass data, liver- and backfat-samples were collected at slaughter. Longissimus muscle area, 10th-rib back-fat depth, last rib midline backfat depth, LM color, marbling, firmness and drip loss, and bacon collagen content were not altered by DDGS or CLA. Outer layer backfat iodine values were increased (P 0.05) for pigs fed DDGS. Feeding CLA decreased (P

Effects of water and diet acidification with and without antibiotics on weanling pig growth and microbial shedding.

Two 5-wk experiments were conducted to determine the effects of water and diet acidification with and without antibiotics on weanling pig growth performance and microbial shedding. In Exp. 1, 204 pigs (19.2 d of age) were used in a 3 x 2 factorial, with 3 dietary treatments fed with or without water acidification (2.58 mL/L of a propionic acid blend; KEM SAN, Kemin Americas, Des Moines, IA). Dietary treatments were: 1) control, 2) control + 55 ppm of carbadox (CB), and 3) dietary acid [DA; control + 0.4% organic acid-based blend (fumaric, lactate, citric, propionic, and benzoic acids; Kemin Americas)] on d 0 to 7 followed by 0.2% inorganic acid-based blend (phosphoric, fumaric, lactic, and citric acids; Kemin Americas) on d 7 to 34. In Exp. 2, 210 pigs (average 18.3 d of age) were fed 1 of 3 dietary treatments: 1) control, 2) control + 55 ppm of CB, and 3) control + 38.6 ppm of tiamulin + 441 ppm of chlortetracycline on d 0 to 7 followed by 110 ppm of chlortetracycline on d 7 to 35 (TC) with or without dietary acidification (same as Exp. 1) in a 3 x 2 factorial arrangement of treatments. For both experiments, the pigs were allotted based on genetics, sex, and initial BW [5.5 kg (Exp. 1) or 5.6 kg (Exp. 2)]. Pigs were housed at 6 or 7 (Exp. 1) and 7 (Exp. 2) pigs/pen. Treatments were fed in 3 phases: d 0 to 7, 7 to 21, and 21 to 35 (34 d, Exp. 1). Fecal grab samples were collected from 3 pigs/pen on d 6, 20, and 33 for measurement of pH and Escherichia coli. During phase 3 and overall in Exp. 1, pigs fed CB had greater (P < 0.001) ADG (overall ADG, 389 vs. 348, and 348 g/d, respectively), ADFI (P < 0.007, 608 vs. 559, and 554 g/d, respectively), and d 34 BW (P < 0.001, 18.8 vs. 17.3, and 17.3 kg, respectively) than pigs fed NC and DA. Phase 3 ADG was improved (P < 0.01) by water acidification across all diets. In Exp. 2, pigs fed CB and TC had greater ADG (P < 0.004; 315 and 303 vs. 270 g/d, respectively), ADFI (P < 0.01), and d 35 BW (P < 0.002; 16.7 and 16.2 vs. 15.1 kg, respectively) than pigs fed NC. There was a tendency (P < 0.08) for an improvement in ADG when DA was added to the NC or TC, but decreased ADG when DA was added to CB.

Effects of Acid LAC and Kem-Gest acid blends on growth performance and microbial shedding in weanling pigs.

Weanling pigs with mean initial BW of 6.04 kg (Exp.1) and 5.65 kg (Exp. 2) and mean age at weaning of 18.2 d (Exp. 1) and 17.7 d (Exp. 2) were used in two 5-wk experiments (Exp. 1, n = 180; Exp. 2, n = 300) to evaluate the effects of an organic acid blend (Acid LAC, Kemin Americas Inc., Des Moines, IA) and an inorganic/organic acid blend (Kem-Gest, Kemin Americas Inc.) on weanling pig growth performance and microbial shedding. In Exp. 1, the 5 dietary treatments were 1) negative control, 2) diet 1 + 55 ppm carbadox, 3) diet 1 + 0.4% Acid LAC, 4) diet 1 + 0.2% Kem-Gest, 5) diet 1 + 0.4% Acid LAC and 0.2% Kem-Gest. In Exp. 2, the 6 dietary treatments were diets 1 through 4 corresponding to Exp. 1, plus 5) sequence 1: 0.4% Acid LAC for 7 d followed by 0.2% Kem-Gest for 28 d, and 6) sequence 2: 0.2% Kem-Gest for 7 d followed by 0.4% Acid LAC for 28 d. Pigs were housed at 6 (Exp. 1) or 10 (Exp. 2) pigs/pen. Treatments were fed throughout the experiment in 3 phases: d 0 to 7, d 7 to 21, and d 21 to 35. In Exp. 1, there were no differences (P > 0.05) in ADG, ADFI, or G:F among the dietary treatments at any time during the study. In Exp. 2, throughout the study, pigs fed carbadox (diet 2) and sequence 1 (diet 5) diets had the greatest ADG (d 0 to 35; 262, 294, 257, 257, 292, and 261 g/d, diets 1 through 6, respectively; P < 0.05), greater ADFI than all other acid treatments (P < 0.05), and tended to have greater ADFI than diet 1 (P < 0.10). Fecal pH, Escherichia coli concentrations, and Salmonella presence were determined at d 6, 20, and 34 for Exp. 1, and on d 32 for Exp. 2. For both experiments, there was no effect of treatment on the presence of fecal Salmonella (P > 0.10) at any sampling time. In Exp. 1, fecal E. coli concentrations for pigs fed the carbadox (P < 0.05) diet were greater than for pigs fed the combination diet with 0.4% Acid LAC and 0.2% Kem-Gest on d 34, and the pigs fed the negative control diet tended (P < 0.10) to have greater fecal E. coli concentrations than those fed the combination diet on d 34. In Exp. 2, fecal pH of pigs fed sequence 1 tended to be greater than fecal pH of pigs fed diet 1, diet 4, or sequence 2 (P < 0.10), but there was no dietary effect on fecal E. coli. In Exp. 1, growth performance of pigs fed the Acid LAC and Kem-Gest diets was similar to each other and to that of the carbadox-fed pigs. Adding the combination of 0.4% Acid LAC and 0.2% Kem-Gest to nursery pig diets reduced ADFI and pig growth rate. In Exp. 2, pigs fed the acid sequence of Acid LAC-Kem-Gest had similar growth performance to pigs fed carbadox, and this novel dietary acid sequence may have merit as a replacement for antibiotics in the nursery phase.

Estimating equivalency values of microbial phytase for amino acids in growing and finishing pigs fitted with steered ileo-cecal valve cannulas.

Ten crossbred barrows (48.3 +/- 2.3 kg of initial BW) fitted with steered ileo-cecal valve cannulas were used to investigate the effects of supplemental microbial phytase on the apparent ileal digestibilities (AID) of AA, Ca, P, N, and DM, and the apparent total tract digestibilities of Ca, P, N, and DM. All diets were corn-soybean meal-based, and contained 0.44% Ca and 0.40% total P. Diets 1, 2, and 3 contained 12.0, 11.1, and 10.2% CP, respectively. Diets 4 and 5 had the same ingredient composition as diet 3, plus 250 and 500 U/kg phytase (Natuphos), respectively. Pigs were randomly allotted to 1 of 5 dietary treatments in a paired 5 x 5 Latin square with an extra period to test for carryover effects. Each 14-d period consisted of a 7-d adjustment followed by a 3-d total collection, a 12-h ileal digesta collection, a 3-d readjustment, and a second 12-h ileal digesta collection. Pigs were housed individually in metabolism pens (1.2 x 1.2 m). Water was supplied ad libitum, and feed was supplied at a level of 9% of the metabolic BW (BW(0.75)) per day in 2 equal daily feedings. As the dietary CP concentration increased, the AID of CP and all AA measured increased linearly (P < 0.05) with the exception of proline. In addition, the apparent total tract digestibilities (grams per day) and retention of N (grams per day) increased linearly (P < 0.01) with increasing CP levels. Supplementing diets with phytase increased the AID of Ca (P < 0.01), P (P < 0.001), CP (P = 0.07), and the AA (P < 0.10) Gly, Ala, Val, Ile, Thr, TSAA, Asp, Glu, Phe, Lys, and Arg. Protein and phytase response equations were generated for those AA affected (P < 0.10) by both CP level and phytase supplementation. Based on these equations, 500 U/kg of phytase can replace 0.52 percentage units of the dietary CP, which includes a 0.03 percentage unit improvement in Lys AID. The results of this study show that supplementing pig diets with microbial phytase improves CP and AA digestibilities in addition to Ca and P digestibilities.

The digestive fate of Escherichia coli glutamate dehydrogenase deoxyribonucleic acid from transgenic corn in diets fed to weanling pigs.

Corn containing genetically engineered plasmid DNA encoding an Escherichia coli glutamate dehydrogenase (gdhA) was fed to 19-d-old weanling swine to trace the digestive fate of the transgenic DNA. Eight pens of 8 pigs were fed a commercial (nongdhA) starter for 2 wk. One pig was randomly selected from each pen for 0-h control samples. The remaining 56 pigs were transitioned onto a corn-soybean meal diet and fed a diet containing 58% gdhA corn for approximately 1 wk; immediately thereafter, liver, 10th rib muscle, white blood cells, and plasma from the hepatic portal vein and ingesta from the stomach, distal ileum, and large intestine were collected. The DNA was extracted and the concentration determined via spectrophotometry. Polymerase chain reaction and gel electrophoresis were performed with primers designed to amplify 490 bp that included the plasmid's ligation site between the maize ubiquitin and the gdhA genes. The gdhA corn-derived DNA and diet served as positive assay controls, and conventional corn DNA and distilled water acted as negative assay controls. Detection limits were 0.99 fg of target DNA confounded with 500 ng of conventional corn DNA per each 20 &L reaction. Transgenic DNA was detected in 71.43% of the stomach and 1.79% of the ileal ingesta samples from treatment animals but was not detected in the large intestine, white blood cells, plasma, liver, or muscle samples. Transgenic DNA was not detected in any sample from 0-h control animals. Stomach and ileal ingesta samples were further analyzed using real-time PCR. With an estimated limit of detection of 1.049 ag/microL, 89.29% of the stomach ingesta samples were positive (average 1.56 fg target DNA). The proportion of transgenic DNA to total DNA differed between diet and stomach ingesta samples (P < 0.001). Despite the greater sensitivity of real-time PCR, target DNA was detected in only 1.79% of ileal ingesta. These data suggest that the gdhA transgene began degradation in the stomach and was nondetectable in the large intestine.

Technical Note: Improved technique for fitting pigs with steered ileocecal valve cannulas.

Collection of ileal digesta to evaluate AA digestibilities has become increasingly important in swine nutrition research. Steered ileocecal valve cannulation of pigs permits total collection of ileal digesta, while still allowing normal digesta flow during noncollection periods. This technique was modified and used with 64 crossbred barrows in five trials. Our procedural changes included preoperative i.v. administration of a broad-spectrum antibiotic and nonsteroidal antiinflammatory drug, sharp incision through the muscle layers of the laparotomy wound, use of a heparinized saline lavage solution, replacement of the guide ring with a stylette, and fixing the outer cannula barrel in place with a hose clamp. The current technique involves a right flank laparotomy, parallel and distal to the last rib, with the pig under general anesthesia. A stainless-steel ring (inner ring = 2.0 mm thick, 35.0 mm i.d.) is introduced into the ileal lumen through an enterotomy proximal to the origin of the ileocecal fold. A nylon string attached to this ring is threaded through the ileum and ileocecal valve into the cecum using a silastic stylette, which encases the string. A second stainless-steel ring (outer ring = 2.0 mm thick, 34 mm o.d.) is fixed in place around the ileum, distal to the inner ring and just proximal to the ileocecal valve. A polyurethane cannula barrel (barrel = 100 mm long, 26 mm i.d., 32 mm o.d.; flange = 70 mm o.d.) is introduced into the cecal lumen via an enterotomy through the lateral cecal band and secured in place with two purse-string sutures. The cannula is exteriorized through an incision caudal and proximal to the intial laparotomy site, where it is plugged using a cylindrical stopper (26 mm o.d., 55 mm long) and held in place by a second cannula barrel (barrel = 43 mm length, 33 mm i.d., 41 mm o.d.; flange = 80 mm o.d.). Procedural changes decreased postsurgical complications, as evidenced by decreased seepage around the cannula and fewer and less severe adhesions noted at necropsy. Based on five trials, this technique is a reliable means of collecting ileal digesta for nutrient analyses.

Animal management to reduce phosphorus losses to the environment.

Water quality in the United States is threatened by contamination with nutrients, primarily nitrogen and phosphorus. Animal manure can be a valuable resource for farmers, providing nutrients, improving soil structure, and increasing vegetative cover to decrease erosion potential. At the same time, application of manure nutrients in excess of crop requirements can result in environmental contamination. Environmental concerns with P are primarily associated with pollution of surface water (streams, lakes, rivers). This pollution may be caused by runoff of P when application to land is in excess of crop requirements. Increased specialization and concentration of livestock and crop production has led to the net export of nutrients from major crop-producing areas of the country to areas with a high concentration of animal agriculture. Concentrated animal agriculture has been identified as a significant source of P contamination of surface water. Areas facing the dilemma of an economically important livestock industry concentrated in an environmentally sensitive area have few options. If agricultural practices continue as they have in the past, continued damage to water resources and a loss of fishing and recreational activity are inevitable. If agricultural productivity is decreased, however, the maintenance of a stable farm economy, a viable rural economy, and a reliable domestic food supply are seriously threatened. Decreasing the P content of manure through nutrition is a powerful, cost-effective approach to reducing P losses from livestock farms and will help farmers meet increasingly stringent environmental regulations. This paper reviews opportunities available to reduce the P content of livestock manure, including more accurate interpretation of the published P requirements of animals, improved diet formulation and group-feeding strategies to more precisely meet requirements, and approaches to improve availability of feed P for monogastric and ruminant species.

Nutritional value of a corn containing a glutamate dehydrogenase gene for growing pigs.

Eight female PIC Line 42 pigs (initial BW = 47.5 +/- 1.8 kg) were used in a two-period switchback design (n = 4 per treatment per period) to evaluate the nutritional difference between a genetically modified corn and a similar nontransgenic corn. The genetically altered corn (gdhA+) contained a glutamate dehydrogenase gene isolated from Escherichia coli. The non-transgenic corn was the same variety lacking the transgenic cassette, grown at the same two locations. Pigs were surgically fitted with steered ileocecal valve cannulas for collection of ileal digesta. Diets were made up of primarily one of the two corn sources. Dietary AA profiles were adjusted using crystalline AA to match Illinois Ideal Protein Ratios. Pigs were limit-fed at 8% of metabolic body weight (BW0.75) in two equal feedings at 0600 and 1800 daily throughout the experiment. The study consisted of two 15-d periods. Each period consisted of a 7-d acclimation period, a 3-d total collection of feces and urine, two 12-h ileal collections, and a 3-d adjustment period between ileal collections to ensure adequate hydration. Crude protein, leucine, methionine, alanine, aspartic acid, glutamic acid, and tyrosine concentrations were greater (P < 0.05) in the gdhA+ corn than in the nontransgenic variety. The presence of the gene did not alter (P > 0.17) BW gain. Similarly, DM digestibility, fecal N excretion (grams per day), apparent total-tract N digestibility, N balance, net protein utilization, and N retained as percentages of absorbed were not affected (P > or = 0.32) by the gene modification. Apparent ileal AA digestibility values did not differ (P > 0.31) between the two dietary treatments. Results of this study suggest corn that contains the E coli. gene for glutamate dehydrogenase was nutritionally equivalent to the unaltered variety.

Comparison of phytase from genetically engineered Aspergillus and canola in weanling pig diets.

Ninety-six crossbred pigs with an average weight of 9.0 kg were used in a 5-wk trial to compare the efficacy of genetically engineered Aspergillus ficuum phytase, expressed in Aspergillus niger (Natuphos) or in canola seed (Phytaseed), for enhancing the utilization of phytate P in corn-soybean meal-based diets fed to young pigs and to evaluate the safety of Phytaseed phytase. Three levels of the two sources of phytase (250, 500, or 2,500 U/kg of diet) were added to a corn-soybean meal basal diet containing .35% total P, .09% available P, and .50% Ca. There were six pens per treatment (one barrow and one gilt/pen), except that the diet without added phytase was fed to 12 pens of pigs. Pen feed consumption and BW were recorded weekly. During wk 5, pen fecal samples were collected for determination of apparent digestibilities of DM, Ca, and P. At the end of wk 5, all barrows were killed, and the 10th rib on both sides was removed for determination of shear force and energy. Thirty pigs (six from the diet without added phytase and the diets with 500 and 2,500 U/kg phytase from both sources) were randomly selected for gross necropsy and histologic evaluation of liver, kidney, and bone tissues. Both sources of phytase were equally effective in increasing (P < .05) daily gain, gain:feed, apparent digestibilities of DM, P, and Ca, and 10th rib measurements. Fecal P excretion was reduced with phytase addition. Feed intake was increased by phytase levels during wk 4 to 5. No significant abnormalities were seen in any of the 30 pigs necropsied. The fit of a nonlinear function revealed that most measurements were reaching a plateau at 2,500 U/kg phytase. In summary, based on performance, bone measurements, and digestibilities of P, Ca, and DM of young pigs, the efficiency of Phytaseed was similar to that of Natuphos for enhancing the utilization of phytate P in corn-soybean meal-based diets. General necropsy and histologic examination of tissues indicated no toxic effect of phytase.

Comparison of genetically engineered microbial and plant phytase for young broilers.

This study was conducted to compare the efficacy of genetically engineered microbial (Natuphos) and plant (Phytaseed) phytase for enhancing the utilization of phytate P in corn-soybean meal-based diets fed to young broilers and to evaluate the safety of Phytaseed phytase. Three levels of each of the two sources of phytase (250, 500, and 2,500 U/kg of diet) were added to a corn-soybean meal basal diet containing 0.46% total P, 0.21% nonphytate P, and 0.92% Ca. There were eight cages per treatment (eight birds per cage for Weeks 2 to 3 and seven birds for Weeks 4 to 5), except for the basal diet without added phytase that had 16 cages. Cage BW and feed consumption were recorded weekly. During Week 5, cage excreta samples were collected for determination of apparent retention coefficients of DM, Ca, and P. At the end of Week 5, all birds were killed, and the left and right toes were removed for determination of toe ash weight and percentage. Forty birds (one per cage from the diet without added phytase and diets with 500 or 2,500 U phytase/kg from both sources) were randomly selected for gross necropsy and histologic evaluation of liver, kidney, and bone tissues. Addition of both sources of phytase resulted in similar increases (P < 0.05) of BW gain; feed intake; gain:feed; apparent retention of DM, P and Ca; and toe measurements. Phosphorus excretion decreased as phytase addition increased. No significant abnormalities were seen in any of the 40 broilers necropsied. Further, the fit of a nonlinear function revealed that most measurements reached a plateau at 2,500 U/kg. Based on performance, bone characteristics, and retention of P, Ca, and DM of young broilers, the efficacy of Phytaseed phytase was similar to that of Natuphos phytase for enhancing the utilization of phytate P in corn-soybean meal-based diets. General necropsy and histologic examination of liver, kidney, and tibial tissues revealed no adverse effects of phytase source or level.