Aggressiveness of Puccinia striiformis f. sp. tritici Isolates in the South-Central United States.

Although stripe rust, caused by Puccinia striiformis f. sp. tritici, has been an occasional problem on wheat in the south-central United States from 1941 until 1999, the disease has been consistently severe in the region since 2000. Furthermore, since 2000, the geographic range of stripe rust in the eastern United States has expanded, and the old population of races has been replaced by a new population. The objective of this study was to determine whether new isolates of the pathogen were more aggressive and better adapted to warmer temperatures than old isolates. In all, 6 old isolates (collected before 2000) and 14 new isolates (collected since 2000) were evaluated at 12 and 18°C for latent period on wheat seedlings and urediniospore germination on Noble agar. At 12°C, old and new isolates had similar latent periods and spore germination percentages. However, at 18°C, new isolates averaged 2 days less for latent period and double the spore germination compared with old isolates. Therefore, the new isolates are better adapted and, thus, more aggressive at warmer temperatures than the old isolates. These differences may have contributed to the severity of recent epidemics in the region and to the expanded geographic range for stripe rust.

Investigation of proton conductance in liver mitochondria of broilers with pulmonary hypertension syndrome.

We previously reported an impaired ability to regulate hepatic mitochondrial state 4 respiration rate in response to sequential additions of adenosine diphosphate in pulmonary hypertension syndrome (PHS). As proton conductance is a major contributor to State 4 respiration, the major goal of this study was to investigate the nature of proton conductance in hepatic mitochondria isolated from broilers with and without PHS. Broilers were placed on floor litter in environmental chambers and exposed to cold temperatures (15 degrees C) from 3 to 7 wk of age to induce PHS. Liver mitochondria were isolated from birds that exhibited PHS (cyanosis, right ventricular weight ratio > 0.30) or from birds that appeared healthy (no cyanosis, right ventricular weight ratio < 0.27). Isolated mitochondria were placed in a chamber equipped with the ability to measure oxygen content and mitochondrial membrane potential. The mitochondrial membrane potential was assessed by an ion sensitive electrode to measure the distribution of methyltriphenylphosphonium across the inner mitochondrial membrane. Proton conductance was assessed by simultaneously measuring State 4 oxygen consumption rate as respiration was progressively inhibited with increasing concentrations of malonate. The addition of cardiolipin, a lipid found in high concentrations in mitochondrial membranes that can alter proton conductance, had no affect on respiration or mitochondrial membrane potential in either group. The relationship of curves depicting State 4 respiration and mitochondrial membrane potential indicates that PHS mitochondria exhibit impaired substrate oxidation and reduced proton conductance relative to controls. These findings provide further characterization of the altered cellular oxygen utilization in broilers with PHS.

Evaluation of alternative tactics for management of insecticide-resistant horn flies (Diptera: Muscidae).

A 3-yr study was conducted to determine the efficacy of tactics that could be used to manage populations of insecticide-resistant horn flies, Hematobia irritans irritans (L.). Insecticide spray, spot-on or pour-on formulations and two IGRs in bolus formulation, 1.3- and 3.2-ha pasture rotations on different rotation schedules, 0-50% Brahman breeding, selected fly-resistant cows, and a mechanical trap were evaluated singly and in combination. Concentration-mortality tests indicated that horn flies collected from cows used in the current study were significantly less susceptible to diazinon, coumaphos, and methoxychlor than horn flies from cows at the same locations previously used to determine baseline susceptibility. During the 3-yr study at the Southeast Research and Extension Center (SEREC), the IGR-bolus significantly reduced (P < 0.05) horn fly numbers on both the continuous and rotational graze regimens, resulting in significantly (P < 0.05) greater calf weaning weights (average of 24 kg). Horn fly numbers were significantly greater on untreated cows during the 3-yr study at the Southwest Research and Extension Center (SWREC) compared with the mean fly numbers on cows that received fly-management treatments. All tactics and tactic-combinations used at SWREC on cattle having no Brahman breeding failed to significantly reduce insecticide-resistant horn fly numbers. However, the combination of Brahman breeding with the IGR-Bolus and mechanical trap significantly reduced horn fly numbers and resulted in significant increases in calf weaning weight. In addition, mean horn fly numbers decreased significantly as the percentage Brahman breeding increased with 50% Brahman breeding reducing horn fly numbers by 140 flies per cow. No significant difference was found between the mean fly numbers on the fly-resistant purebred group and the cows that had no Brahman breeding but received the IGR-Bolus or used the mechanical trap. The use of synergized zeta-cypermethrin pour-on treatment successfully complimented the use of IGR-bolus and mechanical traps in reducing insecticide-resistant horn fly numbers. Neither 1.3- nor 3.2-ha size paddocks and stocking rates used in the rotation graze regimens at SEREC and SWREC, respectively, significantly reduced horn fly numbers when compared with continuously grazed paddocks. Data indicated the importance of using tactics that reduce horn fly numbers to approximately 150 horn flies per cow. These data demonstrated the efficacy of using tactic combinations to manage insecticide-resistant horn fly populations.

Influence of the host plant on occluded virus production and lethal infectivity of a baculovirus.

Intra- and inter-specific effects of cotton, soybean, and clover on the time until death of Helicoverpa zea (Boddie) and Heliothis virescens (F.) larvae lethally infected with H. zea nucleopolyhedrovirus (HzSNPV) were evaluated in the laboratory. In the first test, on second instar only, the time until death of lethally infected larvae of both species differed with the plant tissues (vegetative or reproductive) and plant species. The total viral activity produced per larva in LC(50) units (occluded viral bodies (OBs) per larva/LC(50) in OBs/mm(2) of diet surface) was greater from H. virescens larvae fed vegetative than reproductive tissues of all host plants, but from H. zea virus production was greater only when fed vegetative tissue of soybean. In a second test that compared second and fourth instar H. virescens on cotton, total viral activity from larvae treated in both instars was greater when fed vegetative than reproductive tissues. Results of these tests suggest that the ability of host plants to influence baculovirus disease is more complex than previously believed. When examining the epizootic potential of a baculovirus, more attention must be given to the effects of the host plant on the insect-virus interactions.

Larval mortality and development of Pseudoplusia includens (Lepidoptera: Noctuidae) reared on a transgenic Bacillus thuringiensis-cotton cultivar expressing CryIAc insecticidal protein.

The effects of a transgenic Bacillus thuringiensis (Bt)-cotton cultivar (DPL 32) on three instars of the soybean looper, Pseudoplusia includens (Walker), were determined in laboratory studies. First, third, and fifth instars were fed field collected Bt-cotton leaves for 1, 2, four and 7 d or until pupation, and then transferred to artificial diet. Mortality during the larval stage increased linearly in response to an increase in the length of feeding time on Bt-cotton by first and third instars. The maximum mortality of about two out of three larvae occurred for first instars fed on Bt-cotton until pupation. For the fifth instar, there was no significant response to feeding time; however, most of these larvae reached pupation before 4 d of feeding on Bt-cotton. The length of the larval developmental period also increased linearly with an increase in feeding time on Bt-cotton in first and third instars; again, there was no significant response in the fifth instars. For both mortality and larval developmental time, the linear trend lines for the first and third instars were quite similar. Pupal weight declined linearly in the first and fifth instars in response to feeding time on Bt-cotton. Although pupal weight also declined for third instars, the response was not linear. The effect of Bt-cotton appears not to extend past pupation in that there were no significant responses in mortality and developmental time of pupae during the pupal stage. These data indicate that larvae surviving Bt-cotton are adversely affected in several ways, which should be considered in evaluating Bt-cotton suppression of soybean looper infestations.

The hepatic extraction of plasma free amino acids and response to hepatic portal venous infusion of methionine sources in anesthetized SCWL males (Gallus domesticus).

This study was conducted to investigate the hepatic extraction of plasma free amino acids in anesthetized Single Comb White Leghorn (SCWL) males (Gallus domesticus). SCWL males were anesthetized and implanted with cannulae in the carotid artery, hepatic vein, hepatic portal vein and the left hepatic duct. Free amino acids in plasma and bile were determined before, during and after 30-min infusions of Saline (control), DL-Methionine (DL-Met) or DL-2-hydroxy-4-methylthio-butanoic acid (DL-HMB) into the hepatic portal vein. Hepatic extraction rates (HER) of amino acids were calculated based on the concentration of amino acids in plasma multiplied by estimations of blood flow in the hepatic portal vein, hepatic artery and hepatic vein. For the non-essential amino acids, alanine had the highest HER (46%). The liver also removed more than 20% of hepatic inflow of tyrosine and asparagine with substantial extraction (14-18%) of serine, glycine and glutamine, also. In contrast, less than 5% of hepatic inflow of glutamate and cystine were removed by liver. For the essential amino acids, HER for methionine, histidine and phenylalanine were 30, 14 and 17%, respectively, with less than 5% for branched-chain amino acids, lysine, arginine and threonine. Biliary secretion of amino acids represented a small percentage (<0.2%) of total hepatic extraction turnover of the amino acids. Infusion of methionine sources, DL-Met and DL-HMB, had no effect on hepatic metabolism of amino acids other than methionine. The results demonstrated for the first time, the hepatic extraction of circulating free amino acids in avian species in vivo.

Electrocardiographic evaluation of broilers following unilateral occlusion of an extrapulmonary primary bronchus.

This study was conducted to provide a comprehensive evaluation of both the amplitudes and durations of the Lead II electrocardiogram (ECG) in nonascitic and ascitic broilers. At 14 d of age, male and female broiler chicks were sham-operated (SHAM, n = 27), or pulmonary hypertension was initiated by occluding one extrapulmonary primary bronchus (BRONCHUS CLAMP, n = 57). Lead II ECG and BW were recorded on Days 28 (ECG1) and 42 (ECG2), necropsies were conducted on all birds dying after Day 28, and final necropsies were conducted on Day 49. Data collected at necropsy included the presence (ASCITIC) or absence (NONASCITIC) of ascites, sex, and ventricular weights for calculating the right:total ventricular weight ratio (RV:TV), which serves as a reliable index of pulmonary hypertension. In each bird, three consecutive ECG1 and ECG2 wave cycles were quantified for both amplitude and duration of the following wave segments: Rb-R, R-S, S-R', R'-R'b, and S-T. The S wave amplitude was calculated by subtracting R-S from Rb-R and heart rate (HR) was measured from the peak of one T wave to the peak of the next. In the majority of comparisons, ASCITIC and BRONCHUS CLAMP broilers had larger S, R'-R'b, and S-T amplitudes, longer R-S, R'-R'b, and S-T durations, and a slower HR than NONASCITIC and SHAM broilers, regardless of sex. The differences in ECG wave forms and durations between ASCITIC and NONASCITIC broilers were greater on Day 42 (ECG2) than on Day 28 (ECG1), but when both ECG were used to develop a regression equation to estimate RV:TV, the R2 was 0.79. The most important Lead II ECG parameters associated with the development of ascites were an increasingly negative S wave amplitude and greater amplitudes and durations for R'-R'b and S-T as well as a decrease in the HR.

Evidence of mitochondrial dysfunction in broilers with pulmonary hypertension syndrome (Ascites): effect of t-butyl hydroperoxide on hepatic mitochondrial function, glutathione, and related thiols.

The purpose of this study was to assess mitochondrial function and glutathione (a mitochondrial antioxidant) in response to oxidative stress in mitochondria in vitro obtained from broilers with and without pulmonary hypertension syndrome (PHS). Liver mitochondria from Control and PHS broilers were incubated with 0, 1, and 5-mM tertiary-butyl hydroperoxide (tBH). Indices of mitochondrial function [the respiratory control ratio (RCR) and the adenosine diphosphate to oxygen ratio (ADP:O)], and levels of mitochondrial and extra-mitochondrial reduced (GSH) and oxidized (GSSG) glutathione, cysteine, cystine, glutamate and cysteinyl-glycine were determined following tBH treatment. Lower RCR and ADP:O values were observed in PHS mitochondria than in controls. Whereas control mitochondria remained coupled (RCR > 2.0), only 3 PHS preparations remained coupled after 60 min of incubation with 5 mM tBH, indicating a greater susceptibility to oxidative stress in PHS mitochondria. The lower RCR in PHS mitochondria was due to increased oxygen consumption during State IV respiration. Oxidative stress following tBH treatment (decreased GSH and increased GSSG) was observed, but there were no differences in GSH or GSSG between control and PHS mitochondria. The PHS mitochondria did exhibit elevated mitochondrial and extramitochondrial cystine than controls, however. The results indicate that PHS mitochondria do not lack antioxidant protection from GSH, but lower RCR and ADP:O ratios in PHS mitochondria indicate a dysfunction that may contribute to the pathophysiology of this metabolic disease in broilers.

Electrocardiographic and genetic evaluation of giant jungle fowl, broilers, and their reciprocal crosses following unilateral bronchus occlusion.

Electrocardiography is useful as a noninvasive technique for detecting right ventricular hypertrophy in birds developing pulmonary hypertension (PH) and pulmonary hypertension syndrome (PHS, ascites). The objective of this study was to identify every aspect of the Lead II ECG wave form (amplitude or duration) that can be correlated with right ventricular hypertrophy [increased right:total ventricular weight ratios (RV:TV)] indicative of PH across a broad genetic background. Sham operations were conducted, or PH was induced by occluding one extrapulmonary primary bronchus in 14-d-old chicks produced from matings of broilers (B x B), Giant Jungle Fowl (J x J), and their reciprocal crosses (B x J and J x B). Standard three-lead electrocardiograms (ECG) were recorded on Days 28 and 42, and final necropsies were conducted to evaluate the incidence of ascites, confirm sex, and obtain ventricular weights for calculating RV:TV. Ascites did not develop in the J x J, and one each of the B x J and J x B chicks developed ascites; consequently, only data from birds that did not develop ascites were compared. Heart rate was recorded, and the following amplitudes and durations were measured or calculated for three consecutive wave cycles of the Lead II ECG: base of R to the peak of R (RbR), peak of R to base of S (RS), base of S to peak of R' (SR'), S, peak of R' to base of R' (R'R'b), and base of S to peak of T (ST). Differences between the ECG of sham and bronchus clamp groups were more prominent in B x B and B x J than in J x B, and bronchus occlusion did not affect the ECG, growth, or RV:TV ratios of J x J. In contrast, sex influences were more prominent in J x J and J x B than in B x J and B x B. These observations suggest a paternal pattern of inheritance for Lead II ECG wave forms, with crosses sired by broilers (B x B, B x J) exhibiting susceptibility to PH and few ECG differences related to sex, whereas crosses sired by Giant Jungle Fowl U x J, J x B) exhibited resistance to PH and numerous ECG differences related to sex.

Effect of timing of artificial insemination on gender ratio in beef cattle.

It was recently reported that cows inseminated at approximately 10 or 20 h before an expected ovulation deliver predominately a bull or heifer calf, respectively. The objective of this study was to further investigate the effect of timing of insemination on the gender of offspring in cattle. Angus heifers (n = 41) and cows (n = 98) were used in the study. Heifers were synchronized with a 16-d treatment of melengestrol acetate followed 17 d later with an injection of PGF2alpha. Cows were synchronized with GnRH followed 7 d later with PGF2alpha. A HeatWatch electronic estrus detection system was used to determine the onset of estrus. Based on previous studies, it was assumed that ovulation occurs approximately 32 h after the onset of estrus. Therefore, animals were artificially inseminated at either 8 to 10 h (early; > or = 20 h before expected ovulation) or 20 to 25 h (late; < or = 10 h before expected ovulation) after the onset of estrus. Sixty to 80 d after insemination, ultrasonography was used to confirm pregnancy status and to determine the gender of fetuses. Gender of calves was subsequently confirmed at calving. Data were analyzed for effects of time of insemination and sire or semen batch on gender ratio, as well as any effect of length and/or intensity of estrus on conception rate and gender ratio. Twenty-nine of 41 heifers and 69 of 98 cows were detected in estrus after synchronization and were inseminated; 20 of 29 heifers and 48 of 69 cows were subsequently confirmed pregnant. Neither the length of estrus nor its intensity (number of mounts) had an effect on pregnancy rate or gender ratio (P > or = 0.418). Timing of insemination (early versus late) had no effect on gender ratio (P = 0.887). Semen from 13 sires representing 17 lots was used to inseminate the cows and heifers. No differences (P = 0.494) were detected in the gender ratios resulting from different sires or semen batches. In contrast to previous findings, our results indicate that inseminating beef cattle at approximately 20 or 10 h before an expected ovulation does not alter the gender ratio of the resultant calves.

Hepatic export of glutathione and uptake of constituent amino acids, glutamate and cysteine, in broilers in vivo.

This study was conducted to document the glutathione (GSH) cycle (interorgan circulation of GSH) in broilers in vivo. Two experiments were conducted on 36 anesthetized male broilers (n = 6 per treatment) implanted with cannulae in the carotid artery, hepatic portal, and hepatic veins. Plasma GSH, glutamate, cysteine, cystine, and cysteinylglycine levels in each vessel were monitored following a bolus injection [Experiment (Exp.) 1] or 30 min continuous infusion (Exp. 2) of GSH, or a gamma-glutamyltranspeptidase inhibitor (AT125) into the hepatic portal vein. Controls received saline alone. The GSH and AT125 treatments were used to determine the effect of increasing the prehepatic GSH load and of inhibiting systemic GSH degradation, respectively, on the GSH cycle. Hepatic export of GSH was clearly evident in all three treatment groups in both experiments (Exp.). The GSH and AT125 treatments raised amino acid levels in some or all of the vessels, whereas cysteinylglycine was elevated by AT125 and depressed by the GSH treatment compared to Controls. Hepatic uptake of glutamate, cysteine, and/or cystine was observed in Controls and GSH-treated birds, but not in birds given AT125 (Exp. 2). Neither hepatic export nor uptake of cysteinylglycine was observed in any treatment group. The results clearly demonstrate the ability of the avian liver to export GSH into the general circulation despite alterations that might arise from changes in extra-hepatic ability to utilize GSH or its constituent amino acids.

The infusion rate dependent influence of acute metabolic acidosis on pulmonary vascular resistance in broilers.

Experiments were conducted to evaluate the pulmonary vascular responses of lightly anesthetized clinically healthy male broilers during acute metabolic acidosis induced by bolus i.v. injections or constant i.v. infusions of HCl. In Experiment 1, broilers received consecutive 1.5 mL i.v. bolus injections of 2.5% mannitol (volume control) and 0.4 N, 0.8 N, and 1.2 N HCl in 2.5% mannitol. Following each injection, equivalent concentrations of mannitol or HCl were infused i.v. at a rate of 0.05 mL/min.kg BW. In Experiment 2, repeated bolus injections of 2.5% mannitol and 1.2 N HCl were administered during ongoing constant infusion of 2.5% mannitol. The following variables were evaluated: pulmonary arterial pressure, pulmonary vascular resistance, mean arterial pressure, total peripheral resistance, cardiac output, stroke volume, heart rate, respiratory rate, hematocrit (HCT), and arterial blood gas (PaO2, PaCO2, pH, HCO3-). Mannitol alone did not alter any of the variables. The HCl loading protocols acidified the arterial blood to sustained (constant infusion) or transient (bolus injection) values averaging between pH 7.2 and 7.3. In both experiments, bolus injections of 1.2 N HCl caused transient increases in pulmonary vascular resistance and pulmonary arterial pressure, coincident with decreases in mean arterial pressure and cardiac output. When HCl was infused at a constant rate in Experiment 1, the arterial blood hydrogen ion concentration, [H+], was positively correlated with pulmonary arterial pressure and cardiac output, negatively correlated with mean arterial pressure and total peripheral resistance, and was not correlated with pulmonary vascular resistance. During constant i.v. infusion of mannitol or HCl in both experiments, pulmonary arterial pressure was positively correlated with pulmonary vascular resistance and cardiac output. Overall, bolus injections of 1.2 N HCl consistently triggered transient pulmonary vasoconstriction (increased pulmonary vascular resistance), leading to a transient increase in pulmonary arterial pressure in spite of opposing changes in cardiac output and mean arterial pressure. In contrast, equivalent or greater increases in [H+] during constant i.v. infusion of HCl caused a substantially lower increment in pulmonary arterial pressure, which, in, turn was primarily attributable to increases in cardiac output rather than pulmonary vascular resistance. Increments in either pulmonary vascular resistance or cardiac output induced by metabolic acidosis would be expected to contribute to the onset of pulmonary hypertension syndrome (PHS, ascites) in broilers.

Evaluation of logistic versus linear regression models for predicting pulmonary hypertension syndrome (ascites) using cold exposure or pulmonary artery clamp models in broilers.

Syndromes such as ascites (pulmonary hypertension syndrome) present difficulties both in the interpretation of associated physiological observations and in their analyses. The ability to predict which physiological variables have the greatest influence on survival or, more importantly, which individuals are most susceptible or resistant to ascites would be very useful selection tools. When addressed in this manner, ascites data become binary data sets (healthy or affected). Binary data can be problematic in that they do not meet all of the assumptions necessary for more traditional analyses such as ANOVA and linear regression. Binary data are discrete and do not have normally distributed errors, which violates a fundamental assumption of linear models. The predictive abilities of linear and logistic regression were evaluated in two replicated experiments using two methods to induce ascites, cold exposure (COLD) and surgical clamping of one pulmonary artery (PAC). The logistic and linear predictive models were derived using the same data and variables. The first data set from PAC and COLD were used to develop the predictive models and the replicate data sets of PAC and COLD were used as "test data sets" for the prediction of ascites. The linear models developed were complex, using four or five variables and requiring up to seven different measurements. On average, the linear models predicted ascites correctly 87.6% of the time. The logistic models were simple (single variable) models that predicted ascites correctly 92.0% of the time. The variables used in the logistic models were derivations of the ratio of right ventricular weight to total ventricular weight, either corrected for age or the body weight of the bird. Although linear regression predicted the incidence of ascites almost as well as logistic regression did, logistic regression is the more appropriate test statistic to use.

Cardio-pulmonary function during acute unilateral occlusion of the pulmonary artery in broilers fed diets containing normal or high levels of arginine-HCl.

Cardio-pulmonary function was measured in male broilers reared on diets formulated to contain 1.5% arginine (NORMAL group) or 2.5% arginine (ARGININE group). A snare placed around the right pulmonary artery permitted acute shunting of the entire cardiac output (CO) through the left pulmonary artery, resulting in sustained increases in blood flow (BF) through the left lung in both groups. The unilateral increase in BF was accompanied by sustained increases in pulmonary arterial pressure (PAP) and pulmonary vascular resistance (PVR) in the NORMAL group. However, following initial transient increases in PAP and PVR in the ARGININE group, subsequent pulmonary vasodilation gradually reduced PVR, and thus PAP, in spite of the ongoing elevation of BF through the left lung. The capacity of the pulmonary vasculature in the ARGININE group to accommodate an increased BF at a normal PAP accounts for the previously reported lower incidence of pulmonary hypertension syndrome (PHS, ascites) in cold-stressed broilers fed supplemental dietary arginine. Hypoxemia and respiratory acidosis ensued rapidly in both groups after tightening the pulmonary artery snare, in spite of a compensatory increase in the respiratory rate. The gradual return of PVR and PAP to presnare levels in the ARGININE group did not eliminate the concurrent ventilation-perfusion mismatch caused by the increased rate of BF through the left lung. Tightening the pulmonary artery snare caused mean systemic arterial pressure (MAP) to drop from control levels of approximately 98 mm Hg to sustained hypotensive levels of approximately 65 mm Hg in both groups. This systemic hypotension was caused by decreases in CO and total peripheral resistance (TPR). The reduction in CO were caused by reduction in stroke volume (SV) rather than heart rate (HR), suggesting that acutely tightening the pulmonary artery snare increased PVR sufficiently to impede left ventricular filling. Accordingly, the maximum increment in PAP attainable by the right ventricle during acute increases in PVR apparently was inadequate to propel the entire CO through the pulmonary vasculature, setting the stage for the congestive right-sided pooling of blood routinely associated with PHS in broilers.

Independent and simultaneous unilateral occlusion of the pulmonary artery and extra-pulmonary primary bronchus in broilers.

Acutely tightening a snare around one pulmonary artery previously was shown to trigger a reversible ventilation-perfusion (V/Q) mismatch in broilers, as reflected by decreases in the partial pressure of oxygen in arterial blood (hypoxemia), accompanied by increases in the hydrogen ion concentration (acidosis) and partial pressure of carbon dioxide (hypercapnia). In the present study, snares were loosely implanted around the right pulmonary artery and the right extrapulmonary primary bronchus in anesthetized male broilers. These snares were tightened and released independently and then simultaneously to evaluate the possibility that directing the entire respiratory minute volume toward the left lung might attenuate the V/Q mismatch caused by forcing the entire cardiac output (CO) through the left lung. Fully reversible arterial blood hypoxemia, acidosis, and hypercapnia occurred when either snare was tightened independently. Presumably, tightening the bronchial snare restricted ventilation but not blood flow to the right lung, thereby permitting blood to perfuse poorly ventilated gas exchange surfaces. Simultaneously tightening both snares triggered arterial blood hypoxemia, acidosis, and hypercapnia similar to or greater in magnitude than the responses obtained by tightening the pulmonary artery snare independently. Tightening either snare independently or both snares simultaneously caused pulmonary arterial pressure to increase (pulmonary hypertension), and permanent obstruction of one bronchus in a separate experiment caused an increase in the right:total ventricular weight ratio, which is indicative of chronic pulmonary hypertension. The mean systemic arterial pressure decreased when the pulmonary artery snare was tightened independently or in combination with the bronchial snare, but not when the bronchial snare was tightened independently. The respiratory rate increased and the heart rate decreased when the pulmonary artery snare was tightened independently, but not when the bronchial snare was tightened independently or in combination with the pulmonary artery snare. These results demonstrate that the V/Q mismatch caused by forcing all the CO to perfuse one lung cannot be attenuated by simultaneously directing the entire respiratory minute volume toward the same lung.

The effects of selection for size in cattle on horn fly population density.

Statistically significant differences were observed in the population density of the horn fly, Haematobia irritans irritans L., on Angus cows having significantly different frame sizes. Angus cows, averaging < 112.5 cm in height at the hip, had significantly lower numbers of horn flies than Angus cows that measured 112.5-117.5 cm, 117.5-120 cm, 120-126 cm and > 126 cm in height at the hip. The Angus I cows ( < 112.5 cm in height at the hip) were significantly shorter in length (mean distance from the withers to the hip bone) and were smaller in girth than the Angus II (112.5-126 cm) and Booneville Angus cows ( > 126 cm). The estimated heritability (h2) of horn fly resistance was 0.43 +/- 0.07 and 0.95 +/- 0.31 for 1989 and 1990, respectively. Horn fly counts on the Angus I herd ( < 112.5 cm in height) was 118.1 (probable breeding value, PBV = -20.69) to 165 horn flies per cow (PBV = 26.9 flies per cow in 1989) and from 75.9 (PBV = -29.1) to 134.5 (PBV = 29.5) flies per cow in 1990. Angus I bulls had PBV = -23.7 to 13.4 and from -26.5 to 14.75 in 1989 and 1990, respectively. The Angus II cows had horn fly counts that ranged from 159.6 (PBV of -23.5) to 208.1 (PBV of 25) per cow in 1989 and from 232.3 (PBV of -56.2) to 378.7 (PBV of 90) per cow in 1990. Angus II bulls had PBVs that ranged from -17.1 to 18.9 in 1989 and from -28.1 to 48.8 in 1990. The Angus I cows had significantly (P < 0.0001) lower numbers of horn flies (mean of 63.8 horn flies per m2) than the small, medium or large Angus II cows (mean of 129.4, 149.6 and 145.5 horn flies per m2, respectively). The data indicated that some specific factor(s) associated with cow size contribute(s) to innate resistance of cattle to the horn fly.

Readability of printed sources of diet and health information.

This study surveyed nutrition education materials which are low in cost, brief and the type most used in patient education to determine which might be useful with low literacy clients. Readability of 209 pamphlets from professional health organizations, commercial organizations, government agencies, and educational institutions was assessed using three different tests. Using the Flesch and Raygor tests, materials from educational institutions had significantly lower reading levels than materials from professional organizations and government agencies. No significant differences were seen among the sources using the Fry test. Sixty-eight percent (142) of the publications were written at ninth grade level or higher. Eleven percent (24) scored at sixth grade or below on either the Fry or Raygor scale. Only two publications were written at the third grade level. Many of the publications reviewed can be read and understood by many Americans, but there were few for the millions that have limited literacy skills.

Selection of a mathematical model to generate lactation curves using daily milk yields of Holstein cows.

Mathematical descriptions of early stages of lactation were investigated using daily milk yields of 117 first, 78 second, 57 third, and 36 fourth lactations of 120 Holstein cows fitted by 10 models. The measure of fit was the error mean squares, which were replaced by ranks to perform an analysis of variance with lactation number, model, and period as factors and with cows as replicates. The interaction of model and lactation number was significant for the fit of the entire lactation. A significant interaction of model and period was obtained for the fit of three 30-d intervals. For the entire lactation, the best fit for all four lactations occurred from the diphasic logistic function, y = d1(1-tanh2(b1(nk-c1))) + d2(1-tanh2(b2(n-c2))). For the first 30 d, a modified gamma function gave the best fit for the first lactation, the inverse polynomial function for the second lactation, and the quadratic log function for the third lactation. The diphasic logistic function gave the best fit for the remaining two periods and was not significantly different from the best fitting models for the first 30-d period. Hence, this function may be useful to describe the lactation curve of Holstein cows for dairy herds in which the daily milk yield of individual cows is constantly monitored with a computer.

Effect of alpha-tocopherol on antioxidants, lipid peroxidation, and the incidence of pulmonary hypertension syndrome (ascites) in broilers.

Research has demonstrated a compromised antioxidant capacity in broilers with pulmonary hypertension syndrome (PHS). Thus, the objective of the present study was to assess the effects of vitamin E on PHS-induced mortality, tissue antioxidants, and plasma lipid peroxides in male broilers. Control broilers were provided normal ventilation but others, maintained under low ventilation conditions to induce PHS, were randomly assigned to nonimplanted (NI), placebo (PL), or vitamin E (VE) implanted groups. The VE implant released a total of 15 mg of alpha-tocopherol from 0 to 3 wk of age. Tissues and blood samples were obtained at 3 and 5 wk of age from birds with (PHS+) and without (PHS-) PHS. Five-week PHS cumulative mortality was lowered by alpha-tocopherol with mortality rates of 3.6, 4.2, 11.9, and 11.8%, for Controls, VE, NI, and PL groups, respectively. The PHS+ birds exhibited lower body weights, higher hematocrit, right ventricular hypertrophy, lower alpha-tocopherol and glutathione (GSH) concentrations in liver and lung, as well as indicators of oxidative stress, including elevated plasma lipid peroxides and lower oxidized GSH in liver and erythrocytes, at 5 wk of age. All birds exhibited lower erythrocyte catalase activity at 5 than at 3 wk of age. An improved antioxidant capacity was observed in VE birds, including higher liver and lung alpha-tocopherol at 3 and 5 wk, higher liver GSH at 3 wk, and lower plasma lipid peroxide values at 5 wk of age. Direct correlations observed between body weight and plasma lipid peroxides at 3 wk (r = .45) and between right ventricular hypertrophy and plasma lipid peroxides at 5 wk (r = .48), suggests that lipid peroxidation plays a role in the etiology of PHS. The results indicate that the VE implant was effective in lowering PHS-induced mortality in broilers apparently by attenuating processes leading to lipid peroxidation.

Problems encountered in meeting the Recommended Dietary Allowances for menus designed according to the Dietary Guidelines for Americans.

Forty-three menus that were to be used in a diet manual were designed to meet the requirements of a specific diet; provide 2,200 to 2,400 kcal, unless energy-restricted; meet the 1990 Dietary Guidelines for Americans; meet current recommendations for sodium (2g to 3 g/day), cholesterol (< or = 300 mg/day), and fiber (20g to 30 g/day); and meet or exceed the highest level for adults in the 1989 Recommended Dietary Allowances (RDAs). In addition, regular and low-fat, low-cholesterol menus for 1 week were collected from 11 hospitals throughout Arkansas. Menus were analyzed for energy, cholesterol, and 18 nutrients. Only 11% of the menus met the RDA for zinc. Half of the menus did not meet the RDA for vitamin B-6 and one third did not meet the RDA for iron. Zinc content of the menus was positively correlated (P < .001) with protein (r = .73) and with beef (r = .45). Vitamin B-6 was positively correlated with protein (r = .44, P < .001) and with all meat (r = .38, P < .01). Regular and low-fat, low-cholesterol hospital menus had the same nutrient inadequacies because they did not differ in total servings from any food group. These data indicate that the public may have difficulty choosing a diet that meets both the Dietary Guidelines and the RDAs.