Binaural summation of amplitude modulation involves weak interaural suppression.

The brain combines sounds from the two ears, but what is the algorithm used to achieve this summation of signals? Here we combine psychophysical amplitude modulation discrimination and steady-state electroencephalography (EEG) data to investigate the architecture of binaural combination for amplitude-modulated tones. Discrimination thresholds followed a 'dipper' shaped function of pedestal modulation depth, and were consistently lower for binaural than monaural presentation of modulated tones. The EEG responses were greater for binaural than monaural presentation of modulated tones, and when a masker was presented to one ear, it produced only weak suppression of the response to a signal presented to the other ear. Both data sets were well-fit by a computational model originally derived for visual signal combination, but with suppression between the two channels (ears) being much weaker than in binocular vision. We suggest that the distinct ecological constraints on vision and hearing can explain this difference, if it is assumed that the brain avoids over-representing sensory signals originating from a single object. These findings position our understanding of binaural summation in a broader context of work on sensory signal combination in the brain, and delineate the similarities and differences between vision and hearing.

The in vitro cytotoxicity, antioxidant and antibacterial potential of Satureja hortensis L. essential oil cultivated in Egypt.

This study was designed to evaluate the antioxidant, antibacterial and cytotoxicity effects of Satureja hortensis (S. hortensis) essential oil (EO). The GC-MS analysis of S. hortensis EO (SEO) has identified seven compounds, representing 96.84% of the oil. The two main constituents of the oil were; carvacrol (48.51%) and γ-terpinene (36.63%). The total phenolics and flavonoids contents of SEO were 199.1 ± 0.5 µg GAE/mg (GAE-gallic acid equivalent) and 161.5 ± 0.9 µg CE/mg (CE-catechin equivalent), respectively. SEO showed superior antioxidant potential (ABTS, 1038.66 and DPPH, 12.679 mg Trolox/g), and exhibited antibacterial activity against five food born bacterial strains, exerting the minimum inhibitory concentration (MIC) ranging from 2 to 4 mg/mL. On the other hand, using of SEO at inhibiting concentrations for pathogenic bacteria can affect the beneficial bacteria negatively. Moreover, SEO showed toxicity on normal cells (WI-38, THLE2, and phoenx-eco) and consequently, it is worthwhile for extensive toxicity studies in normal cells and animal models. As our-knowledge, this is the first study on antioxidant, antimicrobial and cytotoxicity of Egyptian S. hortensis.

Interocular interaction of contrast and luminance signals in human primary visual cortex.

Interocular interaction in the visual system occurs under dichoptic conditions when contrast and luminance are imbalanced between the eyes. Human psychophysical investigations suggest that interocular interaction can be explained by a contrast normalization model. However, the neural processes that underlie such interactions are still unresolved. We set out to assess, for the first time, the proposed normalization model of interocular contrast interactions using magnetoencephalography (MEG) and to extend this model to incorporate interactions based on interocular luminance differences. We used MEG to record steady-state visual evoked responses (SSVER), and functional magnetic resonance imaging (fMRI) to obtain individual retinotopic maps that we used in combination with MEG source imaging in healthy participants. Binary noise stimuli were presented in monocular or dichoptic viewing and were frequency-tagged at 4 and 6 Hz. The contrast of the stimuli was modulated in a range between 0 and 32%. Monocularly, we reduced the luminance by placing a 1.5 ND filter over one eye in the maximal contrast condition. This ND filter reduces the mean light level by a factor of 30 without any alteration to the physical contrast. We observed in visual area V1 a monotonic increase in the magnitude of SSVERs with changes in contrast from 0 to 32%. For both eyes, dichoptic masking induced a decrease in SSVER signal power. This power decrease was well explained by the normalization model. Reducing mean luminance delayed monocular processing by approximately 38 ms in V1. The reduced luminance also decreased the masking ability of the eye under the filter. Predictions based on a temporal filtering model for the interocular luminance difference prior to the model's binocular combination stage were incorporated to update the normalization model. Our results demonstrate that the signals resulting from different contrast or luminance stimulation of the two eyes are combined in a way that can be explained by an interocular normalization model.

Effect of dietary protein and lysine fluctuations in the absence and presence of ractopamine on performance and carcass quality of late-finishing pigs.

Two experiments with finishing pigs were conducted to evaluate the effects of fluctuating dietary CP levels and ractopamine on performance and carcass traits. In Exp. 1, a total of 408 finishing pigs (mixed sex) were assigned to 1 of 4 protein regimens. Average initial and final BW were 89 and 123 kg, respectively. Pigs on treatments 1 to 4 were fed 16, 11, 16, and 13% CP from wk 0 to 2, respectively. From wk 2 to 5, the pigs on regimens 1 to 4 were then fed 15, 18.33, 18, and 20% CP, respectively, with regimens 3 and 4 also containing supplemental ractopamine (9.9 mg/kg) from wk 2 to 5. Overall (wk 0 to 5), BW gain, G:F, loin depth, percentage of lean, and dressing percentage were improved (P < 0.05) in pigs on regimens 3 and 4 compared with those on regimens 1 and 2. No statistically significant overall (wk 0 to 5) protein sequence regimen differences occurred between the standard regimens (1 and 3) and the low-high CP regimens (2 and 4). Experiment 2 involved 172 finishing pigs (mixed sex) in 2 protein regimens. Average initial and final BW were 91 and 136 kg, respectively. The diets consisted of 1) a control (16% CP from d 0 to 14, 18% CP + 4.95 mg of ractopamine/kg from d 14 to 24, and 18% CP + 9.9 mg of ractopamine/kg from d 24 to 35; 2) a low-high CP regimen (12.5% CP from d 0 to 14, 20.33% CP + 4.95 mg of ractopamine/kg from d 14 to 24, and 20.33% CP + 9.9 mg of ractopamine/kg from d 24 to 35. From d 0 to 14, pigs fed the low CP diet (12.5% CP) had reduced (P < 0.05) BW gain and G:F compared with those fed the control diet (16% CP). In contrast, from d 14 to 35, pigs on the low-high regimen had improved (P < 0.08) BW gain and G:F compared with pigs on the control regimen. Despite the wide dietary CP fluctuations for pigs in Exp. 2, performance and carcass traits were similar for both regimens over the 35-d test period. These data indicate that pigs fed deficient levels of CP and Lys for 14 d, followed by increased levels of CP and Lys during a subsequent 21-d period can recover and achieve growth performance and carcass merit equal to that achieved with a conventional protein feeding regimen.

Standardized amino acid digestibility in cecectomized roosters and lysine bioavailability in chicks fed distillers dried grains with solubles.

This study was conducted to compare the concentration of standardized digestible (SDD) Lys and relative bioavailable Lys in 7 sources of corn distillers dried grains with solubles (DDGS). A second objective was to evaluate 2 in vitro methods, reactive Lys and color score, to predict the concentration of SDD Lys and bioavailable Lys in DDGS. Seven sources of DDGS were fed to cecectomized roosters, and digestibility of amino acids was measured using the total excreta collection method. To measure the relative bioavailable Lys in DDGS, a standard curve (r(2) = 0.96, P < 0.01) was constructed from 9-d weight gain of young chicks fed a Lys-deficient basal diet or diets containing increasing concentrations of l-Lys-HCl. Seven additional diets were formulated by adding each of the 7 sources of DDGS to the basal diet, and total weight gain of chicks was measured. Weight gain of chicks fed each DDGS-containing diet was then compared with the standard curve to calculate the bioavailable Lys and bioavailability of Lys in each source of DDGS. All DDGS sources were analyzed for reactive Lys using the guanidination procedure, and a Hunterlab color score was used to measure the degree of lightness (L), redness (a), and yellowness (b). Results showed that the mean SDD Lys values and the mean relative bioavailability of Lys were 61.4 and 69.0%, respectively. Differences between the concentration of SDD Lys and the concentration of bio-available Lys were not observed in 5 of 7 sources of DDGS. The concentration of SDD Lys was correlated (r(2) = 0.84, P < 0.05) with the concentration of reactive Lys in DDGS. Greater Hunterlab L scores were associated with a greater (r(2) = 0.90, P < 0.05) concentration of bioavailable Lys in DDGS. In conclusion, the concentration of SDD Lys in DDGS does not overestimate the concentration of bioavailable Lys for poultry. Values for reactive Lys may be used to estimate the concentration of SDD Lys, whereas Hunterlab L may be used to estimate the concentration of bioavailable Lys in DDGS.

Cyst(e)ine imbalance and its effect on methionine precursor utilization in chicks.

Five 9- or 12-d chick growth bioassays were done in batteries using 2 Met-deficient diets: a purified AA-based diet containing (by analysis, as-fed) 20.3% CP, 0.12% Met, and 0.05% cyst(e)ine; and an AA-fortified corn-peanut meal diet containing (by analysis, as-fed) 19.0% CP, 0.22% Met, and 0.23% cyst(e) ine. Feed-grade DL-Met (dl-M; 99%) was compared with feed-grade DL-OH-Met, Ca (OH-M; 84%). When the purified diet was modified to contain 0.12% Met and 0.20% or greater cyst(e)ine, slope-ratio assays involving graded dosing of DL-M (0, 404, 808, and 1,212 mg of DL-M/kg) or isosulfurous levels of OH-M resulted in linear (P < 0.01) BW gain and G:F responses. Multiple linear regression analysis (BW gain vs. supplemental sulfur intake, R(2) = 0.98) resulted in a mean bioefficacy estimate of 78.1% for OH-M vs. DL-M (equivalent to 65.6% on a supplemental compound basis). In assay 3, the purified diet was modified to be equally deficient in Met and cyst(e)ine [i.e., 0.12% Met, 0.12% cyst(e)ine]. When this diet was supplemented with either 404 mg of DL-M/kg or 476 mg of OH-M/kg, BW gain and G:F responded (P < 0.01) markedly to either compound, and differences between DL-M and OH-M were not significant (P > 0.10). Assays 4 and 5 used the corn-peanut meal basal diet containing 0.22% total Met and 0.23% total cyst(e)ine. In both assays, addition of either 465 mg of DL-M/kg or 554 mg of OH-M/kg resulted in increased (P < 0.01) BW gain and G:F, regardless of dietary cyst(e)ine concentration. In the absence of excess cyst(e)ine, BW gain responses to DL-M and OH-M were similar, but when 0.10% excess cyst(e)ine was provided as L-cystine or feather meal, DL-M responses tended to exceed those of OH-M. Moreover, this small excess of dietary cyst(e)ine, regardless of source, depressed (P < 0.01) feed intake and BW gain when added to the basal diet. Overall, these results suggest that excess dietary cyst(e)ine, when included in Met-deficient diets, has the potential to be both anorexigenic and pernicious to OH-M utilization.

DL-Methionine is as efficacious as L-methionine, but modest L-cystine excesses are anorexigenic in sulfur amino acid-deficient purified and practical-type diets fed to chicks.

Three bioassays were conducted to elucidate the effects of dietary cystine on the efficacy of L-Met and DL-Met fed to chicks. In assay 1, a purified diet markedly deficient in Met (0.12%) and cyst(e)ine (0.05%) was used to compare the relative effectiveness of L-Met and DL-Met in the presence of graded levels of dietary cystine. Addition of 0.05% Met improved (P < 0.01) weight gain when added to diets with 0 or 0.07% added L-cystine, but weight gain decreased linearly (P < 0.01) with greater cystine supplementation up to 0.35%, regardless of Met supplementation. There were no differences in growth performance due to supplementation of L-Met vs. DL-Met. In assay 2, a corn-soybean meal-peanut meal diet (0.25% Met and 0.25% cyst(e)ine) was supplemented with 0, 0.025, 0.05, or 0.075% L-Met plus 0 or 0.2% added L-cystine. Supplemental Met improved (P < 0.01) growth performance, but weight gain and feed intake were depressed (P < 0.01) by cystine supplementation. Whereas 0.2% added L-cystine depressed feed intake 6.9%, weight gain was reduced only 3.6%. Thus, cystine supplementation actually improved (P < 0.01) gain:feed. In assay 3, the corn-soybean meal-peanut meal diet was supplemented with 0 or 0.03% L-Met or DL-Met in the absence or presence of 0.2% added L-cystine. Again, Met supplementation improved (P < 0.01) growth performance, whereas supplemental cystine reduced (P < 0.05) weight gain and feed intake, but increased (P < 0.01) gain:feed. From these bioassays, it may be concluded that there is no evidence to suggest differences in effectiveness between L-Met and DL-Met in purified or practical-type low-protein diets of varying sulfur amino acid (SAA) content fed to chicks from 8 to 20 d of age. However, supplemental cystine has a negative impact on voluntary feed intake when supplemented in diets markedly deficient in SAA. This effect is evident with minimal SAA intake and when greater than 50% of SAA intake is provided by cyst(e)ine, rather than Met.

Psychophysical evidence for two routes to suppression before binocular summation of signals in human vision.

Visual mechanisms in primary visual cortex are suppressed by the superposition of gratings perpendicular to their preferred orientations. A clear picture of this process is needed to (i) inform functional architecture of image-processing models, (ii) identify the pathways available to support binocular rivalry, and (iii) generally advance our understanding of early vision. Here we use monoptic sine-wave gratings and cross-orientation masking (XOM) to reveal two cross-oriented suppressive pathways in humans, both of which occur before full binocular summation of signals. One is a within-eye (ipsiocular) pathway that is spatially broadband, immune to contrast adaptation and has a suppressive weight that tends to decrease with stimulus duration. The other pathway operates between the eyes (interocular), is spatially tuned, desensitizes with contrast adaptation and has a suppressive weight that increases with stimulus duration. When cross-oriented masks are presented to both eyes, masking is enhanced or diminished for conditions in which either ipsiocular or interocular pathways dominate masking, respectively. We propose that ipsiocular suppression precedes the influence of interocular suppression and tentatively associate the two effects with the lateral geniculate nucleus (or retina) and the visual cortex respectively. The interocular route is a good candidate for the initial pathway involved in binocular rivalry and predicts that interocular cross-orientation suppression should be found in cortical cells with predominantly ipsiocular drive.

Oral N-acetyl-L-cysteine is a safe and effective precursor of cysteine.

Relative bioavailability and toxicity of N-acetyl-l-Cys (NAC) were evaluated in 9-d chick growth assays. The bioavailability of NAC relative to Cys was determined by feeding young chicks a highly purified crystalline AA diet singly deficient in Cys. Bio-availability estimates were obtained using standard slope-ratio methodology. N-Acetyl-l-cysteine was shown to be as effective as Cys in supporting chick growth, and was assigned a relative bioavailability value of 100%. To assess toxicity, a nutritionally adequate corn-soybean meal diet was supplemented with graded concentrations of NAC (isomolar to 10, 20, 30, or 40 g/kg of Cys, as-fed). When NAC supplied 10 or 20 g/kg of Cys, chick growth performance was unaffected, but NAC supplying 30 or 40 g/kg of Cys reduced (P < 0.05) BW gain by 13 and 34%, respectively, relative to the unsupplemented control diet. Only plasma-free NAC was substantially increased (P < 0.05) because of excess dietary NAC; plasma-free Cys was unaltered. We concluded that dietary NAC is efficacious in supplying Cys in support of chick growth, and only large excesses of NAC are growth depressing. Hence, the human clinical benefits of oral NAC likely result from its ability to deliver Cys safely and effectively to the portal circulation.

An Escherichia coli phytase expressed in yeast effectively replaces inorganic phosphorus for finishing pigs and laying hens.

Two experiments determined the efficacy of an Escherichia coli phytase (ECP) added to P-deficient, corn-soybean meal diets fed to finishing pigs and second-cycle laying hens. Sixty finishing pigs (49 +/- 0.9 kg) were formed into blocks within sex based on weight and ancestry and allotted to a P-deficient diet unsupplemented or supplemented with 0.10% inorganic P (iP) from KH2PO4 or ECP at 250, 500, 1,000, or 10,000 phytase units (FTU)/kg. Individually fed pigs were allowed ad libitum access to the experimental diets until a BW of 120 +/- 3 kg was achieved, at which time the pigs were euthanized and the left fibula and fourth metatarsal were excised for determination of bone ash. Pigs were fed a 2-phase diet program for early- and late-finishing pigs; available P in the basal diets was set 0.10% below the requirement. Dietary supplementation of iP or ECP increased weight gain (P < 0.10) and G:F (P < 0.01); performance was not different (P > 0.13) among the phytase-supplemented groups. Fibula ash was greatest (P < 0.01) for pigs fed diets containing 10,000 FTU of ECP/kg. Two hundred forty second-cycle hens were allotted to a P-deficient diet or a P-deficient diet supplemented with 0.10% iP or ECP at 150, 300, or 10,000 FTU/kg for a 12-wk experiment. The basal diet was a corn-soybean meal diet with no added iP (17% CP, 3.8% Ca, 0.10% available P). Hens fed the P-deficient diet were removed from the experiment after 4 wk due to poor egg production. Supplementation of iP or ECP resulted in increased (P < 0.01) feed intake, egg weight, and egg production during the first 4 wk. During the entire 12-wk period, there were no differences (P > 0.28) between the iP- and ECP-supplemented groups in feed intake, egg weight, or egg production. These experiments reveal that ECP was as efficacious as supplemental iP and that supplementation of an excess dose of ECP was efficacious and without negative effects in finishing pigs and laying hens.

Variations in the digestible sulfur amino acid requirement of broiler chickens due to sex, growth criteria, rearing environment, and processing yield characteristics.

Four experiments (Exp.) were conducted with Cobb 500 chicks to evaluate variations in the estimated digestible sulfur amino acid (DSAA) requirement of broilers due to rearing environment, sex, or growth performance during the starter period (7 to 19 d), and live performance response and carcass yield characteristics during the grower period (21 to 42 d). In the first 3 experiments conducted during the starter period, chicks were allocated to battery or floor pens, and in the fourth experiment birds were reared in floor pens. For Exp. 1, 2, and 3 a sulfur amino acid deficient corn-soybean meal-corn gluten meal basal diet and for the grower experiment a corn-soybean meal-peanut meal basal diet was formulated to be isocaloric and isonitrogenous within experiment. Graded levels of DSAA ranged from 0.54 to 0.94% in Exp. 1, 0.53 to 1.03% in Exp. 2, 0.49 to 0.89% in Exp. 3, and 0.43 to 0.83% in Exp. 4. True digestibility of the diets was determined using the precision-fed rooster assay. The DSAA requirements were estimated using 1-slope broken-line methodology. During the starter period, the average DSAA requirement of males and females was similar when based on the gain to feed ratio (G:F; 0.71 and 0.71%, respectively) and BW gain (BWG; 0.67 and 0.67%, respectively). In Exp. 3 involving battery and floor pens, males and females had similar DSAA requirement estimates, but the DSAA requirement based on maximal G:F (0.68%) was higher than the maximal BWG requirement (0.61%). In the grower period, the estimated DSAA requirement for males based on G:F was higher than that based on BWG, but the BWG and G:F requirements were similar for females. The DSAA requirement estimates were similar for males and females based on BWG (0.55%), but the DSAA requirement based on G:F was higher for males than females. The DSAA requirement for maximum breast meat yield was similar for males (0.55%) and females (0.56%), and the requirement for maximal breast meat yield was similar to that for maximal BWG. The DSAA requirements were similar based on sex, rearing environment, or both; however, there was a difference in the estimated DSAA requirements between growth and carcass responses.

Excess dietary lysine increases growth of chicks fed niacin-deficient diets, but dietary quinolinic acid has no niacin-sparing activity.

Catabolism of Trp and Lys produces alpha-ketoadipic acid as an intermediary metabolite. An alternate pathway of Trp turnover leads to NAD synthesis. We hypothesized that excess Lys might improve the conversion of Trp to niacin by causing a buildup of alpha-ketoadipic acid, thereby endproduct inhibiting the main Trp catabolic pathway and resulting in more niacin synthesis from Trp. Six bioassays were carried out in which 12 to 20 chicks were fed each experimental diet from d 8 to d 20 or 21 posthatching. The basal diet (4 mg/kg of bioavailable niacin) used for all assays was a semipurified corn gluten meal diet fortified with crystalline amino acids to 22.5% CP and 0.96% true digestible Lys. Assay 1 through 3 established the requirements for digestible Trp (0.16%) and bioavailable niacin (19.5 mg/kg) and showed that 0.96% digestible Lys was adequate for chick growth in the presence of adequate Trp and niacin. The fourth assay was done to determine the effect of 1% Lys (1.25% food-grade L-Lys x HCl) on niacin utilization. Excess Lys improved (P < 0.01) weight gain of niacin-deficient chicks. The fifth assay showed that 1% excess food-grade Lys improved weight gain in niacin-deficient (4 mg/kg) chicks but depressed weight gain in niacin-adequate (24 mg/kg) chicks (niacin x Lys interaction, P < 0.01). In assay 6, chicks fed 6 mg/kg of niacin gained faster (P < 0.01) than control chicks, but neither quinolinic acid (100 mg/kg) nor picolinic acid (4,200 mg/kg) elicited a response. These results suggest that excess Lys leads to an accumulation of alpha-ketoadipic acid, which causes endproduct inhibition of the main Trp catabolic pathway to CO(2), therefore increasing flux of 2-amino-3-carboxymuconate semialdehyde to NAD.

Effect of reciprocating dietary lysine fluctuations on chick growth and carcass yield.

Three experiments (Exp) were conducted to study the effect of reciprocating (i.e., back-and-forth) fluctuations in dietary Lys concentration on growth performance of male broiler chicks. The Lys, CP, and ME concentrations were fluctuated in Exp 1 by varying corn and soybean meal concentrations. Corn-peanut meal diets in Exp 2 and 3 contained a constant calorie-protein ratio, but Lys concentrations were fluctuated by varying supplemental L-Lys x HCl. During 7-d feeding periods from d 8 to 43 posthatch, chicks fed the fluctuating regimen were provided diets with nutrient concentrations arranged in the following order (relative to control diets at any given point): excess-deficient-excess-deficient-adequate. In each Exp, differences in feed intake and gain:feed were observed during the first 7 d. Weight gain was never affected by dietary regimen. Overall, chicks fed the fluctuating regimen showed similar weight gain and feed intakes relative to chicks fed the control regimen. Additionally, efficiency of feed, Lys, CP, and ME utilization over the 35-d growth period of Exp 2 and 3 were not affected by dietary regimen. An increase in carcass yield (dressed, carcass weight as a percentage of live weight) of birds fed the fluctuating regimen was observed, but there were no differences in abdominal fat yield (as a percentage of dressed, carcass weight). These data support the conclusion that reciprocating 7-d periods of nutrient excess and deficiency do not affect overall growth performance of growing chicks.

Effect of a novel phytase on growth performance, bone ash, and mineral digestibility in nursery and grower-finisher pigs.

To compare the effectiveness of 2 phytase enzymes (Phyzyme and Natuphos), growth performance, fibula ash, and Ca and P digestibilities were evaluated in 4 studies. The first 3 studies used 832 pigs (i.e., 288 in the nursery phase, initial BW 8.1 kg; 288 in the grower phase, initial BW 24.2 kg; and 256 in the finisher phase, initial BW 57.8 kg) and were carried out over periods of 28, 42, and 60 d, respectively. Dietary treatments in each study consisted of a positive control [available P (aP) at requirement level]; negative control (Ca remained as in the positive control, and aP at 66, 56, and 40% of the requirement for the nursery, grower, and finisher studies, respectively); negative control plus graded levels of Phyzyme [250, 500, 750, or 1,000; measured as phytase units (FTU)/kg] or Natuphos (250 and 500 FTU/kg for the nursery and grower studies, or 500 and 1,000 FTU/kg for the finisher study) plus a very high dose of Phyzyme (tolerance level, at 10,000 FTU/kg) in the nursery and grower experiments. Across the 3 studies, there was no effect of any dietary treatment on ADFI, but the negative control reduced ADG (10%), G:F (7%), and bone ash (8%) compared with the positive control. In the nursery study, phytase addition increased G:F and bone ash linearly (P < 0.01). In the grower study, phytase increased ADG, G:F, and bone ash linearly (P < 0.01). In the finisher study, phytase addition increased ADG and bone ash linearly (P < 0.01) and increased G:F quadratically (P < 0.05); G:F was, on average, 5% greater (P < 0.05) with Phyzyme than with Natuphos. The fourth study was conducted to investigate the P-releasing efficacy of the 2 phytases. The apparent fecal digestibility of P, measured with chromic oxide as an external marker in 35 pigs (55.9 kg of BW), showed that aP increased (P < 0.001) by 0.17 and 0.06 g (+/- 0.023) per 100 FTU consumed for Phyzyme and Natuphos, respectively. Also, Phyzyme at 10,000 FTU/kg was not detrimental to animal health or growth performance. At doses intended for commercial conditions, Phyzyme proved to be effective in releasing phytate bound P from diets, with an efficacy superior to a commercially available enzyme.

Effect of microbial phytase and citric acid on phosphorus bioavailability, apparent metabolizable energy, and amino acid digestibility in distillers dried grains with solubles in chicks.

Three experiments were conducted to evaluate the effectiveness of OptiPhos phytase and citric acid for releasing the P that is not bioavailable in distillers dried grains with solubles (DDGS). The effect of OptiPhos phytate on AME(n) and amino acid digestibility was also determined. New Hampshire x Columbian chicks were fed experimental diets from 8 to 21 d of age. For Experiment 1, a basal P-deficient diet contained 40% DDGS plus supplemental amino acids, and DDGS was the only source of P. The basal diet was then supplemented with 1,000 or 10,000 phytase units (FTU)/kg of OptiPhos phytase or with 0.2% of P from KH2PO4. In Experiment 2, a slope-ratio chick growth and tibia ash assay used a P-deficient soybean meal basal diet, and it was found that the bioavailability of P in DDGS was 67%. For Experiment 3, a P-deficient basal diet with 30% DDGS plus supplemental amino acids was supplemented with 0.05 or 0.1% P from KH2PO4, with 3% citric acid, or with 1,000 or 10,000 FTU/kg of OptiPhos phytase. In Experiment 1, both 1,000 and 10,000 FTU/kg of phytase increased tibia ash but had no effect on AME(n). Both 10,000 phytase units (FTU)/kg of phytase and supplemental P increased digestibility of amino acids. In Experiment 3, supplemental phytase and citric acid increased tibia ash (mg/tibia), and it was estimated that phytase and citric acid could release from 0.04 to 0.07% P from DDGS. In terms of bioavailability coefficients, the bioavailability of the P in DDGS was increased from 62 to 72%. These results indicate that phytase and citric acid increase the bioavailability of P in DDGS, but phytase at 1,000 FTU/kg had no consistent effect on AME(n) and amino acid digestibility.

Variations in the digestible lysine requirement of broiler chickens due to sex, performance parameters, rearing environment, and processing yield characteristics.

Four experiments were conducted to evaluate variations in the digestible lysine (DLYS) requirement estimates of broilers due to rearing environment, sex, or growth performance during the starter period (7 to 21 d) and due to sex, growth, and carcass yield characteristics during the grower period (21 to 38 d). In the first 3 experiments, chicks were allocated to either battery or floor pens. The fourth experiment was conducted during the grower period with birds reared in floor pens only. All the studies used a lysine-deficient corn-soybean meal-corn gluten meal basal diet formulated to be isonitrogenous and isocaloric. Treatments consisted of 5 graded levels of DLYS varying from 0.70 to 1.21% in the first 3 experiments and from 0.73 to 1.13% in the fourth experiment. The DLYS requirement was estimated by broken-line methodology based on body weight gain (BWG) and gain:feed ratio (G:F) for the starter period, and the same variables plus breast meat yield for the grower period. During the starter period, the average DLYS requirement of males based on BWG was slightly higher than that of females reared in battery (0.96 vs. 0.94%) or floor pens (0.98 vs. 0.93%). However, based on G:F, the average DLYS requirement of females was slightly higher than that of males reared in both battery (0.99 vs. 0.96%) and floor pens (1.01 vs. 0.99). The DLYS requirement based on G:F was higher than that based on BWG only for females in both rearing environments. Rearing environment did not affect the DLYS requirement of broilers during the starter period. In the grower period, the DLYS requirement of males was higher than that of females based on BWG (0.97 vs. 0.93%), but for G:F it was similar for both sexes (0.96%). The DLYS requirement for females based on G:F was higher than that based on BWG. The DLYS requirement for maximum breast meat yield of males (0.98%) or females (0.90%) was similar to the estimate for maximal growth performance.

Citric acid improves phytate phosphorus utilization in crossbred and commercial broiler chicks.

Previous research in our laboratory has shown that citric acid (CA) improves phytate P utilization in New Hampshire x Columbian (NHC) crossbred chicks fed a P-deficient corn-soybean meal diet. The current study was conducted to determine if CA is also effective in commercial broiler chicks (Ross x Ross). In 3 experiments, 4 replicate groups of 5 male NHC chicks and male commercial chicks were fed corn-soybean meal diets varying in CA and nonphytate P (NPP) from 8 to 22 d of age. In experiment 1, a 2 x 2 x 2 factorial treatment arrangement was used to evaluate the effect of 2 levels of CA (0 and 3%) and NPP (0.13 and 0.28%) in NHC chicks and commercial chicks. The commercial chicks, but not the NHC chicks, fed the 0.13% NPP diet had to be removed from the experiment after 3 to 5 d due to very poor growth and severe leg problems. Chick weight gain and tibia ash were significantly increased (P < 0.05) by CA in both types of chicks. In experiment 2, the same 2 x 2 x 2 factorial treatment arrangement was again used except that the NPP levels were 0.18 and 0.28%. Tibia ash was increased significantly (P < 0.05) with the addition of CA in both breeds of chicks; response was greater at 0.18% NPP than at 0.28% NPP. In experiment 3, graded levels of CA (0, 1, 2, 3, and 4%) were evaluated in commercial chicks fed diets containing 0.18% NPP. Tibia ash increased linearly (P < 0.05) as CA increased from 0 to 4%. The average increase in bone ash resulting from 3% CA supplementation in experiments 2 and 3 was 41%. These results indicate that CA markedly improved phytate P utilization in NHC and Ross x Ross commercial broiler chicks.

Effects of different cereal grains and ractopamine hydrochloride on performance, carcass characteristics, and fat quality in late-finishing pigs.

Forty-eight barrows and forty-eight gilts (PIC 337 sires x PIC C22 dams) were evaluated to determine the effects of feeding ractopamine hydrochloride (RAC) and different cereal grains on the carcass and fat quality in late finishing pigs. The study was carried out using four replicates with 24 animals in each replicate (four pigs per pen, six pens per replicate, two replicates per slaughter date, 12 pens per slaughter date). Treatments for the experiment included corn, wheat, and barley (early finisher period); and corn, corn + RAC, wheat, wheat + RAC, barley, and barley + RAC for the late finisher period. Ractopamine was fed at the level of 10 mg/kg (as-fed basis) of feed. Pigs were allotted to early finisher period treatments at approximately 45 kg BW. Pigs were then given late finisher period treatments at approximately 80 kg BW and fed for 28 d. The dietary digestible lysine level for all diets was maintained at 2.7 g/Mcal of ME. Pigs fed the wheat and corn diets during the late finisher period had a greater (P <0.05) G:F than those fed the barley diets. Pigs fed diets with RAC had lower (P <0.05) leaf fat weights, 10th-rib fat, last-rib fat, and belly firmness and had improved (P <0.05) dressing percents and loin muscle areas compared with those not receiving RAC. Pigs fed the wheat diets had a greater (P <0.05) dressing percent than those receiving the barley diets, but pigs fed the barley diets had a higher (P <0.05) Minolta L* for fat color than pigs fed wheat. Pigs fed diets containing RAC produced pork that was less tender (P <0.05) compared with pigs that did not receive RAC. Linoleic acid percent values were higher (P <0.05) for pigs fed diets with RAC than in those that did not. Feeding RAC improved G:F and lowered feed intake of pigs during the late finisher period (P <0.05). Feeding diets equal in lysine (2.7 g/Mcal of ME) but varying in ME, whether based on corn, wheat, or barley with or without RAC, had little to no effect on carcass, meat, or fat quality attributes.

Tolerance for excess basic zinc chloride and basic copper chloride in chicks.

(1) Four chick experiments were conducted to determine toxicity estimates for basic zinc chloride (BZC) and basic copper chloride (BCC), now being used as sources for these minerals. (2) In experiment 1, New Hampshire x Columbian crossbred chicks were fed 0, 500, 1000, 1500, 3000 and 5000 mg Zn/kg from BZC (Zn5Cl2(OH)8). Broken-line regression analysis showed that the minimal toxic break points for chick weight gain and gain:food were 1720 and 2115 mg Zn/kg, respectively. (3) Crossbred chicks were fed 0, 150, 250, 500, 750 and 1000 mg Cu/kg from BCC (Cu2(OH)3C) in experiment 2. Regression analysis indicated that the minimal toxic break points for chick weight gain and gain:food were 642 and 781 mg Cu/kg, respectively. (4) In experiment 3, commercial broiler chicks were fed 0, 1500, 2000 and 2500 mg supplemental Zn/kg from BZC or 0, 500, 650 and 800 mg supplemental Cu/kg from BCC. Broiler chicks fed those high inclusion rates of Zn did not show reduced weight gain in comparison to chicks fed no supplemental Zn. All high concentrations of supplemental Cu depressed chick weight gain in comparison to control chicks. (5) Experiment 4 involved two separate 4 x 2 factorial designs with supplemental Zn (0, 2500, 3500 and 4500 mg/kg) or Cu (0, 500, 750 and 1000 mg/kg) and two breeds of chicks (crossbred and commercial). Significant interactions for weight gain, food intake, gain:food and liver Cu suggested that the crossbred and commercial chicks responded differently to high concentrations of supplementary dietary Cu.

Vitamin E supplementation does not mitigate the acute morbidity effects of porcine reproductive and respiratory syndrome virus in nursery pigs.

The objective of this study was to determine whether feeding a vitamin E-rich diet would benefit nursery pigs infected with porcine reproductive and respiratory syndrome virus (PRRSV). Sixty-four pigs were subjected to one of four treatment combinations (2 x 2 factorial) of dietary vitamin E (adequate or excess) and PRRSV (medium or inoculation with VR-2385 isolate P-129). Pigs were fed experimental diets during a 3-wk period before inoculation as well as during a 12-d period after inoculation. Growth performance was determined throughout the study, and lipid peroxidation in liver, glutathione peroxidase (GPX) activity in serum, circulating white blood cells, and serum interleukin-1beta (IL-1beta) and interferon-gamma (IFN-gamma) were determined in samples collected from pigs killed 4 or 12 d after inoculation. Infection by PRRSV (P < 0.001) induced a marked decrease in both ADFI and ADG, but neither the main effect of diet nor the diet x PRRSV interaction was significant. Neither diet nor PRRSV affected feed efficiency. At 12 d after inoculation, lipid peroxidation in liver and GPX activity in serum were lower in pigs fed excess vitamin E than in those fed adequate vitamin E (P < 0.01), suggesting that the diet high in vitamin E bolstered the antioxidant status of the pigs. However, PRRSV did not affect lipid peroxidation in liver or serum GPX activity, and the diet x PRRSV interaction was not significant. White blood cell counts were decreased and IFN-gamma, and IL-1beta were increased (P < 0.05) 4 and 12 d after inoculation in PRRSV-infected pigs, but neither diet nor the diet x PRRSV interaction was significant. Collectively, these results indicate that increasing antioxidant defenses by feeding high levels of vitamin E did not ameliorate the effects of PRRSV on decreased growth, leukopenia, and increased serum IL-1beta and IFN-gamma. Thus, feeding nursery pigs a diet high in vitamin E may not be useful for mitigating the acute morbidity effects of PRRSV infection.