Effect of selected water temperatures used in Mycoplasma gallisepticum vaccine reconstitution on titer at selected time intervals.

Numerous methods are currently used throughout the poultry industry for the administration of vaccines. Each utilizes water for vaccine reconstitution and/or administration, including two of the three commercially available live Mycoplasma gallisepticum (MG) vaccines. Selected water temperatures were used to reconstitute and/or dilute the three commercially available live MG vaccines. Water temperatures included 4 C, 22 C (room temperature), and 32 C, and titer (color change units) was recorded at four time intervals, at point of reconstitution (time 0), 15, 30, and 60 min postreconstitution of the vaccines (time periods 15, 30, and 60, respectively). Results for F strain MG (FMG) vaccine showed significant decreases in titer from time 0 to time 15 for the 22 C and 32 C water temperatures but no significant decrease for any time period for FMG reconstituted with 4 C water. For 6/85 strain MG no significant difference in titer was noted for any of four time periods within any of the three water temperatures. For ts-11 strain MG a significant decrease was observed in titer at each of the four postdilution time periods when diluted with 32 C water. There was no significant decrease in titer at any time period for ts-11 MG vaccine when diluted with either 4 C or 22 C water.

Substrate specificity profiling and identification of a new class of inhibitor for the major protease of the SARS coronavirus.

Severe acute respiratory syndrome (SARS) is an emerging infectious disease associated with a high rate of mortality. The SARS-associated coronavirus (SARS-CoV) has been identified as the etiological agent of the disease. Although public health procedures have been effective in combating the spread of SARS, concern remains about the possibility of a recurrence. Various approaches are being pursued for the development of efficacious therapeutics. One promising approach is to develop small molecule inhibitors of the essential major polyprotein processing protease 3Clpro. Here we report a complete description of the tetrapeptide substrate specificity of 3Clpro using fully degenerate peptide libraries consisting of all 160,000 possible naturally occurring tetrapeptides. The substrate specificity data show the expected P1-Gln P2-Leu specificity and elucidate a novel preference for P1-His containing substrates equal to the expected preference for P1-Gln. These data were then used to develop optimal substrates for a high-throughput screen of a 2000 compound small-molecule inhibitor library consisting of known cysteine protease inhibitor scaffolds. We also report the 1.8 A X-ray crystal structure of 3Clpro bound to an irreversible inhibitor. This inhibitor, an alpha,beta-epoxyketone, inhibits 3Clpro with a k3/Ki of 0.002 microM(-1) s(-1) in a mode consistent with the substrate specificity data. Finally, we report the successful rational improvement of this scaffold with second generation inhibitors. These data provide the foundation for a rational small-molecule inhibitor design effort based upon the inhibitor scaffold identified, the crystal structure of the complex, and a more complete understanding of P1-P4 substrate specificity.

Stocking density and physiological adaptive responses of broilers.

Three trials were conducted to assess the effects of stocking density on physiological adaptive responses of broilers. Male broilers were reared in floor pens under conditions similar to those used commercially in the United States. Accepted indicators of adaptation to a stressor were measured on d 49 including plasma concentrations of corticosterone, glucose, cholesterol, and total nitrites as an indicator of nitric oxide, as well as heterophil:lymphocyte ratio. In trial 1, calculated stocking densities were 20, 25, 30, 35, 40, 45, 50, and 55 kg of BW/ m2 and in trials 2 and 3, stocking densities were 30, 35, 40, and 45 kg of BW/m2. Stocking densities were calculated based on a final BW of 3.3 kg. Linear trend analyses were used to assess the role of stocking density on each of the physiological parameters. Results indicate that stocking density did not cause physiological adaptive changes indicative of stress.

Comparison of Gompertz and neural network models of broiler growth.

Neural networks offer an alternative to regression analysis for biological growth modeling. Very little research has been conducted to model animal growth using artificial neural networks. Twenty-five male chicks (Ross x Ross 308) were raised in an environmental chamber. Body weights were determined daily and feed and water were provided ad libitum. The birds were fed a starter diet (23% CP and 3,200 kcal of ME/kg) from 0 to 21 d, and a grower diet (20% CP and 3,200 kcal of ME/ kg) from 22 to 70 d. Dead and female birds were not included in the study. Average BW of 18 birds were used as the data points for the growth curve to be modeled. Training data consisted of alternate-day weights starting with the first day. Validation data consisted of BW at all other age periods. Comparison was made between the modeling by the Gompertz nonlinear regression equation and neural network modeling. Neural network models were developed with the Neuroshell Predictor. Accuracy of the models was determined by mean square error (MSE), mean absolute deviation (MAD), mean absolute percentage error (MAPE), and bias. The Gompertz equation was fit for the data. Forecasting error measurements were based on the difference between the model and the observed values. For the training data, the lowest MSE, MAD, MAPE, and bias were noted for the neural-developed neural network. For the validation data, the lowest MSE and MAD were noted with the genetic algorithm-developed neural network. Lowest bias was for the neural-developed network. As measured by bias, the Gompertz equation underestimated the values whereas the neural- and genetic-developed neural networks produced little or no overestimation of the observed BW responses. Past studies have attempted to interpret the biological significance of the estimates of the parameters of an equation. However, it may be more practical to ignore the relevance of parameter estimates and focus on the ability to predict responses.

Stocking density effects on male broilers grown to 1.8 kilograms of body weight.

This study examined the effects of stocking density on live performance, physiological stress level indicators, and processing yields of male broilers grown to 1.8 kg. A total of 3,120 Ross x Ross 708 male chicks was placed into 32 floor pens (5.57 m2/pen). Stocking density treatments were 25, (75 birds/pen), 30 (90 birds/ pen), 35 (105 birds/pen), and 40 (120 birds/pen) kg of BW/m2. The BW gain, feed consumption, and feed conversion were adversely affected with increasing stocking densities by 35 d. Physiological stress indicators (plasma corticosterone, glucose, cholesterol, total nitrites, and heterophil:lymphocyte) were not affected. Litter moisture was higher as stocking density increased, which led to higher footpad lesion scores. In parallel to growth responses, carcass weight was depressed by increasing stocking density, but carcass yield, absolute and relative amounts of abdominal fat, and carcass skin defects were not affected. Increasing stocking density decreased breast fillet weight and its relative yield and breast tender weight, but not breast tender yield. As calculated stocking density increased 5 kg of BW/m2 beyond 25 kg of BW/ m2, final BW and breast fillet weight decreased by 41 and 12 g, respectively. We conclude that increasing stocking density beyond 30 kg of BW/m2 adversely affects growth responses and meat yield of broilers grown to 1.8 kg but does not alter physiological stress indicators.

Stocking density effects on growth performance and processing yields of heavy broilers.

This study examined responses of male broilers during a 49-d production cycle to 4 placement densities in 2 trials. Trials were pooled because no treatment x trial interaction occurred. In each trial, 1,488 male chicks were randomly placed into 32 floor pens to simulate final densities of 30 (37 chicks/pen), 35 (43 chicks/ pen), 40 (50 chicks/pen), and 45 (56 chicks/pen) kg of BW/m2 of floor space based on a projected final BW of 3.29 kg. Growth rate and nutrient utilization were similar (P > or = 0.05) among the treatments from 1 to 32 d of age. From 1 to 49 d, BW gain (P = 0.011) and feed consumption (P = 0.029) were adversely affected by increasing the placement density from 30 to 45 kg of BW/m2 of floor space. The reduction in cumulative BW gain due to placement density can be partially explained by less feed consumption as evidenced by 95.4% of the sums of squares of BW gain being attributable to feed consumption. Litter moisture content (P = 0.025) and foot pad lesion score (P = 0.001) increased linearly with increasing placement density. Upon processing, whole carcass and breast meat yields relative to BW were not affected (P > or = 0.05) as density increased from 30 to 45 kg/m2. The proportion of whole carcasses with scratches, but not tears, on the back and thighs increased (P = 0.021) as density increased. These results indicate that increasing the density beyond 30 kg/m2 elicited some negative effects on live performance of heavy broilers.

A self-propelled, constant-speed spray vaccinator for commercial layer chickens.

Vaccination of commercial layer chickens is labor intensive and often results in poor rates of seroconversion, which, in turn, generally correlate with decreased flock uniformity and performance. Attempts to improve the vaccination process include numerous variations of individual shop-built vaccinators in use by the layer sector of the poultry industry. Each of these vaccinators has limitations that contribute to poor vaccinations. Major problems include the nonuniform speed of the applicator system and pressure fluctuations at the spray nozzles, which contribute to sporadic dispersion of the vaccine as the vaccinator is pushed or carried past the cages. A battery-powered, self-propelled, constant-speed vaccinator was designed and constructed that operates with constant nozzle pressure. In field use, this vaccinator has resulted in both labor savings (reduction of manpower from five to one to vaccinate 75,000 chickens) and time savings (from 45 min to 7.5 min/poultry house) as well as improved vaccination results (higher positive seroconversion rates) against the poultry pathogen Mycoplasma gallisepticum (MG), a bacterium associated with losses of 15.7 eggs/hen over a 45-wk laying period in MG-infected layers as compared with layers maintained free from infection with MG.

A comparison of fitting growth models with a genetic algorithm and nonlinear regression.

A genetic algorithm (GA), an optimization procedure based on the theory of evolution, was compared with nonlinear regression for the ability of the 2 algorithms to fit the coefficients of poultry growth models. It was hypothesized that the nonlinear approach of using GA to define the parameters of growth equations would better fit the growth equations than the use of nonlinear regression. Two sets of growth data from the literature, consisting of male broiler BW grown for 168 and 170 d, were used in the study. The growth data were fit to 2 forms of the logistic model, the Gompertz, the Gompertz-Laird, and the saturated kinetic models using the SAS nonlinear algorithm (NLIN) procedure and a GA. There were no statistical differences for the comparison of the residuals (the difference between observed and predicted BWs) of growth models fit by a GA or nonlinear regression. The plotted residuals for the nonlinear regression and GA-determined growth values confirmed observations of others that the residuals have oscillations resembling sine waves that are not represented by the growth models. It was found that GA could successfully determine the coefficients of growth equations. A disadvantage of slowness in converging to the solution was found for the GA. The advantage of GA over traditional nonlinear regression is that only ranges need be specified for the parameters of the growth equations, whereas estimates of the coefficients need to be determined, and in some programs the derivatives of the growth equations need to be identified. Depending on the goal of the research, solving multivariable complex functions with an algorithm that considers several solutions at the same time in an evolutionary mode can be considered an advantage especially where there is a chance for the solution to converge on a local optimum when a global optimum is desired. It was concluded that the fitting of the growth equations was not so much a problem with the fitting methodology as it is with the form of the equation.

The power of tests for bioequivalence in feed experiments with poultry.

Several studies have compared the feeding of genetically modified (GM) grains and conventional grains to poultry. The general conclusion has been that there were no significant differences detected in the biological performance of the birds (i.e., the grains were bioequivalent). However, the question has been posed whether the experimental designs used in the studies had sufficient statistical power to detect treatment differences. The power of tests can be used to determine the ability of an experimental design to detect treatment differences. The definition of statistical power is the probability of rejecting the null hypothesis when it is false and should be rejected. The complement of statistical power is the Type II error (beta). That is, accepting the null hypothesis that there is no difference in treatments when there is one. A priori power analysis can indicate the probability at which the sampling regimen or experiment can actually detect an effect if a difference exists. Post hoc power analysis indicates the sufficiency or the sample size needed for an experiment that has already been conducted. In the current study, the power of tests for experiments published in the literature where significant and nonsignificant differences were reported between control birds and birds fed new feed grains was examined. With some exceptions, the power of tests is rarely formally considered or mentioned in poultry research. The results of the survey of the literature showed, in general, low power of statistical tests for feeding experiments involving non-GM grains or in those cases when GM and non-GM grains were compared in poultry feeding experiments. These results suggest that care needs to be taken when designing experiments for bioequivalence of grains fed to poultry.

Optimization of phase feeding of starter, grower, and finisher diets for male broilers by mixture experimental design: forty-eight-day production period.

A mixture experiment, a variant of response surface methodology, was designed to determine the proportion of time to feed broiler starter (23% protein), grower (20% protein), and finisher (18% protein) diets to optimize production and processing variables based on a total production time of 48 d. Mixture designs are useful for proportion problems where the components of the experiment (i.e., length of time the diets were fed) add up to a unity (48 d). The experiment was conducted with day-old male Ross x Ross broiler chicks. The birds were placed 50 birds per pen in each of 60 pens. The experimental design was a 10-point augmented simplex-centroid (ASC) design with 6 replicates of each point. Each design point represented the portion(s) of the 48 d that each of the diets was fed. Formulation of the diets was based on NRC standards. At 49 d, each pen of birds was evaluated for production data including BW, feed conversion, and cost of feed consumed. Then, 6 birds were randomly selected from each pen for processing data. Processing variables included live weight, hot carcass weight, dressing percentage, fat pad percentage, and breast yield (pectoralis major and pectoralis minor weights). Production and processing data were fit to simplex regression models. Model terms determined not to be significant (P > 0.05) were removed. The models were found to be statistically adequate for analysis of the response surfaces. A compromise solution was calculated based on optimal constraints designated for the production and processing data. The results indicated that broilers fed a starter and finisher diet for 30 and 18 d, respectively, would meet the production and processing constraints. Trace plots showed that the production and processing variables were not very sensitive to the grower diet.

Analysis of the nonlinear dynamics of daily broiler growth and feed intake.

Daily BW velocity (BWV) and acceleration (BWA) of individual birds have been demonstrated to be oscillatory. Daily feed intake velocity (FIV) and acceleration (FIA) were hypothesized to be oscillatory and to have a positive relationship with BWV and BWA, respectively. Forty-eight male broiler chicks were individually caged and provided a commercial starter feed ad libitum for 49 d. BW and feed intake (FI) were measured daily. Experiment 1 confirmed that, on a daily basis, BWV, BWA, FIV, and FIA were oscillatory. There was a positive correlation between BW and FI, BWV and FIV, and BWA and FIA. A Kohonen neural network (KNN) clustered BWV and FIV into two and three sequential phases. BWA and FIA analysis did not make definitive clusters. In experiment 2, it was hypothesized that correlation between BWV and FIV would increase with feeding of grower and finisher rations. It was hypothesized that KNN three phase clusters may provide more biologically ideal times of ration change (TORC) for starter, grower, and finisher rations. For 49 d, five treatments, nine birds per treatment, were fed starter, grower, and finisher rations singly or together with dietary changes according to an industry or KNN-determined TORC. Evaluation was made of BW, FI, and carcass characteristics. No significant mean differences were found. Compared to the industry group, the KNN group demonstrated significantly improved uniformity (i.e., smaller SD) of BW (bled out), FI, dressing percentage, and some of the carcass characteristics. Differences between KNN and industry TORC results might have been related to the length of time the birds were fed the starter, grower, and finisher diets.

Multiple-objective (goal) programming model for feed formulation: an example for reducing nutrient variation.

A multiple-objective programming (MOP) model was applied to the feed formulation process with the objectives of minimizing nutrient variance and minimizing ration cost. A MOP model was constructed for a broiler grower ration (3 to 6 wk) and formulated with a Microsoft Excel solver. Twenty-one ingredients with 17 nutrients were included in the formulation. Amino acids were based on digestible values. The following objectives were considered as soft constraints: (1) meeting the nutrient requirements; (2) meeting the ingredient restrictions; and (3) meeting nutrient ratios, including calcium to phosphorus and the relationship of amino acids to lysine (ideal amino acid ratios). Hard constraints considered were (1) a least-cost ration and (2) minimal nutrient variances for protein, methionine, and lysine. It was found that (1) the MOP model was more flexible in providing a compromise solution than a traditional feed formulation with a linear program, (2) the MOP model was able to handle several conflicting objectives simultaneously as compared to the traditional linear programming approach that could handle only one objective, and (3) the MOP model gave the best compromise solution that would satisfy multiple decision makers when trade-offs were made between the ration cost and minimum variances of protein and methionine. The MOP model is an efficient tool to assist the decision-making process through solving a series of linear/nonlinear programs and by interacting with decision-makers.

Active site mapping, biochemical properties and subcellular localization of rhodesain, the major cysteine protease of Trypanosoma brucei rhodesiense.

Cysteine protease activity of African trypanosome parasites is a target for new chemotherapy using synthetic protease inhibitors. To support this effort and further characterize the enzyme, we expressed and purified rhodesain, the target protease of Trypanosoma brucei rhodesiense (MVAT4 strain), in reagent quantities from Pichia pastoris. Rhodesain was secreted as an active, mature protease. Site-directed mutagenesis of a cryptic glycosylation motif not previously identified allowed production of rhodesain suitable for crystallization. An invariable ER(A/V)FNAA motif in the pro-peptide sequence of rhodesain was identified as being unique to the genus Trypanosoma. Antibodies to rhodesain localized the protease in the lysosome and identified a 40-kDa protein in long slender forms of T. b. rhodesiense and all life-cycle stages of T. b. brucei. With the latter parasite, protease expression was five times greater in short stumpy trypanosomes than in the other stages. Radiolabeled active site-directed inhibitors identified brucipain as the major cysteine protease in T. b. brucei. Peptidomimetic vinyl sulfone and epoxide inhibitors designed to interact with the S2, S1 and S' subsites of the active site cleft revealed differences between rhodesain and the related trypanosome protease cruzain. Using fluorogenic dipeptidyl substrates, rhodesain and cruzain had acid pH optima, but unlike some mammalian cathepsins retained significant activity and stability up to pH 8.0, consistent with a possible extracellular function. S2 subsite mapping of rhodesain and cruzain with fluorogenic peptidyl substrates demonstrates that the presence of alanine rather than glutamate at S2 prevents rhodesain from cleaving substrates in which P2 is arginine.

Potent second generation vinyl sulfonamide inhibitors of the trypanosomal cysteine protease cruzain.

A new family of potent N-alkoxyvinylsulfonamide inhibitors of cruzain have been developed. Inhibitor 13 has a second order inactivation rate constant of 6,480,000s(-1)M(-1) versus cruzain, and is also highly effective against Trypanosoma cruzi trypomastigotes in a tissue culture assay.

Highly diastereoselective synthesis of propargylic 1,2-anti-diol derivatives using alpha-alkoxypropargylstannanes.

Propargylic 1,2-anti-diol derivatives 2 and 10 are prepared in high yield and excellent diastereoselectivity by addition of alpha-alkoxypropargylstannanes 4a and 4b to aldehydes in the presence of BuSnCl(3). We also introduce the use of KF on Celite as a convenient and mild reagent for removal of the organotin waste products of these reactions. Reaction: see text.

Studies on the synthesis of landomycin A: synthesis and glycosidation reactions of L-rhodinosyl acetate derivatives.

An efficient, eight-step synthesis of L-rhodinosyl acetate derivative 3 is described. The synthesis originates from methyl (S)-lactate and involves a highly stereoselective, chelate-controlled addition of allyltributylstannane to the lactaldehyde derivative 7. The beta-anomeric configuration of 3 was established with high selectivity by acetylation of the pyranose precursor with Ac(2)O and Et(3)N in CH(2)Cl(2). Preliminary studies of glycosidation reactions of 3 and L-rhodinosyl acetate 10 containing a 3-O-TES ether revealed that these compounds are highly reactive glycosidating agents and that trialkylsilyl triflates are effective glycosylation promoters. The best conditions for reactions with 15 as the acceptor involved use of diethyl ether as the reaction solvent and 0.2 equiv of TES-OTf at -78 degrees C. However, the TES ether protecting group of 10 proved to be too labile under these reaction conditions, and mixtures of 16a, 17, and 18a are obtained in reactions of 10 and 15. Disaccharide 17 arises via in situ cleavage of the TES ether of disaccharide 16a, while trisaccharide 18a results from a glycosidation of in situ generated 17 (or of 16a itself) with a second equivalent of 10. These problems were largely suppressed by using 3 with a 3-O-TBS ether protecting group as the glycosyl donor and 0.2 equiv of TES-OTf as the reaction promoter. Attempts to selectively glycosylate the C(3)-OH of diol acceptors 20 or 28 gave a 70:30 mixture of 21 and 22 in the reaction of 20 and a 43:27:30 mixture of regioisomeric trisaccharides 29 and 30 and tetrasaccharide 31 from the glycosidation reaction of 28. However, excellent results were obtained in the glycosidation of differentially protected disaccharide 34 using 1.5 equiv of 3 and 0.05 equiv of TBS-OTf in CH(2)Cl(2) at -78 degrees C. The latter step is an important transformation in the recently reported synthesis of the landomycin A hexasaccharide unit.

Cathepsins X and B display distinct activity profiles that can be exploited for inhibitor design.

The carboxypeptidase and endopeptidase activities of cathepsins X and B, as well as their inhibition by E-64 derivatives, have been investigated in detail and compared. The results clearly demonstrate that cathepsins X and B do not share similar activity profiles against substrates and inhibitors. Using quenched fluorogenic substrates, we show that cathepsin X preferentially cleaves substrates through a monopeptidyl carboxypeptidase pathway, while cathepsin B displays a preference for the dipeptidyl pathway. The preference for one or the other pathway is about the same for both enzymes, i. e. approximately 2 orders of magnitude. Cleavage of a C-terminal dipeptide of a substrate by cathepsin X can be observed under conditions that preclude efficient monopeptidyl carboxypeptidase activity. In addition, an inhibitor designed to exploit the unique structural features responsible for the carboxypeptidase activity of cathepsin X has been synthesized and tested against cathepsins X, B and L. Although of moderate potency, this E-64 derivative is the first reported example of a cathepsin X-specific inhibitor. By comparison, CA074 was found to inactivate cathepsin B at least 34000-fold more efficiently than cathepsin X.

Studies on the synthesis of pectenotoxin II: synthesis of a C(11)-C(26) fragment precursor via [3 + 2]-annulation reactions of chiral allylsilanes.

[see reaction]. A synthesis of tetracycle 2 corresponding to the C(11)-C(26) fragment of pectenotoxin II is described. The synthesis features two highly stereoselective [3 + 2]-annulation reactions of chiral allylsilanes, generated via allylboration of aldehydes with the chiral gamma-silylallylborane 4 or the gamma-silylallylboronate 19, for construction of the highly substituted C and E rings.

Studies on the total synthesis of formamicin: synthesis of the C(1)-C(11) fragment.

[figure: see text] An efficient and highly concise synthesis of 6, corresponding to the C(1)-C(11) fragment of formamicin (1), has been accomplished by a route utilizing a diastereoselective lactate aldol reaction to set the C(6) tertiary ether and the TES-OTf mediated transketalization of the C(6) tertiary methoxymethyl ether and the C(25) PMB ether to set the seven-membered methylene acetal unit (see 37-->38).

Minimal number of chicken daily growth velocities for artificial neural network detection of pulmonary hypertension syndrome (PHS).

Previously, evaluation of the first 2 wk of daily growth velocity with an artificial neural network (ANN) provided an effective noninvasive approach for predicting the susceptibility of broilers to pulmonary hypertension syndrome (PHS). This study was conducted to define the minimum number of days of growth data and the type of ANN required for the best prediction of PHS susceptibility. Four experiments were conducted in which broilers were weighed daily at 0800 h. In Experiment 1, Hubbard male broilers were reared to 50 d of age, with 13 developing PHS and 33 remaining normal (N), for a PHS:N ratio of 13:33. In Experiment 2, ANAK broilers were exposed to cool temperatures (16 to 17 C) from 17 to 42 d of age, resulting in a PHS:N ratio of 16:46 for males. In Experiments 3 and 4, Hubbard male and female chicks from a base population and a PHS-resistant line were exposed to cool temperatures from 17 to 42 d (Experiment 3) or 49 d of age (Experiment 4). The PHS:N ratios were 40:68 for males and 6:96 for females in Experiment 3 and 26:91 for males and 10:58 for females in Experiment 4. Four ANN, back propagation (BP3), Ward back propagation (WardBP), probabilistic (PNN), and general regression (GRNN), were evaluated for their ability to predict PHS in the shortest number of days based on daily growth velocities (BWd+1-BWd). A 100% prediction of PHS and N birds was considered the criterion of success. Starting with 14 d of data, each ANN was trained on daily growth velocity, and the number of predictive days was reduced with each run of the ANN. The best ANN was a GRNN, which correctly diagnosed PHS and N male broilers on 4 and 6 d of growth velocity data for Experiments 1 and 2, respectively. The results were poorer with the BP3, WardBP, and PNN. The diagnostic ability of the neural network was not consistent over all four experiments. In Experiment 2, a minimum of 6 d was required for 100% PHS detection for males. In Experiment 3, the best diagnostic value for males was 93% PHS detection and 100% N detection at 15 d. For females, the 100% PHS detection occurred at a minimum of 8 d. In Experiment 4, males had 100% PHS and N detection at a minimum of 11 d. Females had a 100% PHS and N detection at a minimum of 10 d. An attempt to build a single neural network that would detect PHS susceptibility in Hubbard (Experiment 1) and ANAK (Experiment 2) broilers was unsuccessful. The application (validation) of neural networks between experiments also was not successful (data not presented). However, these studies demonstrate that within a breed or line reared under similar selection pressures for ascites, a GRNN based on the first 14 d of growth velocity can detect, with at least 93% accuracy, broilers susceptible to PHS.