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(Abstracted from Ultrasound Obstet Gynecol2020;56:215–224)In recent years, the use of combined first-trimester screening (CFTS) and cell-free DNA (cfDNA) screening has increased. With the rise of CFTS and cfDNA prenatal testing, there has been a dramatic decrease in the number of invasive diagnostic tests performed during pregnancy.

Pathogenic bacteria can live asymptomatically within and on cattle and can enter the food chain but also can be transmitted to humans by fecal or direct animal contact. Reducing pathogenic bacterial incidence and populations within live cattle represents an important step in improving food safety. A broad range of preslaughter intervention strategies are being developed, which can be loosely classified as 1) directly antipathogen strategies, 2) competitive enhancement strategies (that use the microbiome's competitive nature against pathogens), and 3) animal management strategies. Included within these broad categories are such diverse methods as vaccination against foodborne pathogens, probiotics and prebiotics, bacterial viruses (i.e., bacteriophages), sodium chlorate feeding, and dietary and management changes that specifically alter the microbiome. The simultaneous application of 1 or more preharvest strategies has the potential to reduce human foodborne illnesses by erecting multiple hurdles preventing entry into humans. However, economic factors that govern producer profitability must be kept in mind while improving food safety.

Dried distiller's grains (DG) produced from ethanol fermentations dosed with 0 (control), 2, or 20 mg/kg virginiamycin-based product or spiked with virginiamycin (VM) postfermentation were fed to cattle and effects on antimicrobial susceptibility, and prevalence of antimicrobial resistance genes in commensal bacteria was examined. Biological activity assays of DG (from each fermentation) indicated a concentration of 0, 0.7, and 8.9 mg/kg VM, respectively. Twenty-four crossbred beef steers were fed 1 of 4 diets (containing 8% of each of the different batches of DG) and a fourth using 8% of the control DG (0 mg/kg VM) + 0.025 g/kg V-Max50 (positive control) for 7 wk. Fecal samples were collected weekly throughout the experimental period and cultured for Escherichia coliand Enterococcus, and isolates were examined for antimicrobial susceptibility, antimicrobial resistance genes (vatE, ermB, and msrCin Enterococcus), and integrons (E. coli). No treatment differences (P> 0.05) were observed in antimicrobial susceptibility of the E. coliisolates. Enterococcusisolates were resistant to more antimicrobials; however, this was influenced by the species of Enterococcusand not treatment (P> 0.10). The prevalence of ermBwas greater (P< 0.05) in the control isolates after 4 and 6 wk while at wk 7, prevalence was greater (P< 0.01) in the 0.7 and 8.9 mg/kg VM treatments. Taken together, the minor treatment differences observed for the presence of ermBcoupled with the lack of effect on antimicrobial susceptibility patterns suggest that feeding DG containing VM residues should have minimal if any impact on prevalence of antimicrobial resistance.

Dietary components and changes cause shifts in the gastrointestinal microbial ecology that can play a role in animal health and productivity. However, most information about the microbial populations in the gut of livestock species has not been quantitative. In the present study, we utilized a new molecular method, bacterial tag-encoded FLX amplicon pyrosequencing (bTEFAP) that can perform diversity analyses of gastrointestinal bacterial populations. In the present study, cattle (n = 6) were fed a basal feedlot diet and were subsequently randomly assigned to 1 of 3 diets (n = 2 cows per diet). In each diet, 0, 25, or 50% of the concentrate portion of the ration was replaced with dried distillers grain (DDGS). Ruminal and fecal bacterial populations were different when animals were fed DDGS compared with controls; ruminal and fecal Firmicute:Bacteroidetes ratios were smaller (P= 0.07) in the 25 and 50% DDG diets compared with controls. Ruminal pH was decreased (P< 0.05) in ruminal fluid from cattle fed diets containing 50% compared with 0% DDGS. Using bTEFAP, the normal microbiota of cattle were examined using modern molecular methods to understand how diets affect gastrointestinal ecology and the gastrointestinal contribution of the microbiome to animal health and production.

Salmonellacauses an estimated 1.3 million human foodborne illnesses and more than 500 deaths each year in the United States, representing an annual estimated cost to the economy of approximately $2.4 billion. Salmonella entericacomprises more than 2,500 serotypes. With this genetic and environmental diversity, serotypes are adapted to live in a variety of hosts, which may or may not manifest with clinical illness. Thus, Salmonellapresents a multifaceted threat to food production and safety. Salmonellahave been isolated from all food animals and can cause morbidity and mortality in swine, cattle, sheep, and poultry. The link between human salmonellosis and host animals is most clear in poultry. During the early part of the 20th century, a successful campaign was waged to eliminate fowl typhoid caused by SalmonellaGallinarum/Pullorum. Microbial ecology is much like macroecology; environmental niches are filled by adapted and specialized species. Elimination of S. Gallinarum cleared a niche in the on-farm and intestinal microbial ecology that was quickly exploited by SalmonellaEnteritidis and other serotypes that live in other hosts, such as rodents. In the years since, human salmonellosis cases linked to poultry have increased to the point that uncooked chicken and eggs are regarded as toxic in the zeitgeist. Salmonellosis caused by poultry products have increased significantly in the past 5 yr, leading to a USDA Food Safety and Inspection Service “SalmonellaAttack Plan” that aims to reduce the incidence of Salmonellain chickens below the current 19%. The prevalence of Salmonellain swine and cattle is lower, but still poses a threat to food safety and production efficiency. Thus, approaches to reducing Salmonellain animals must take into consideration that the microbial ecology of the animal is a critical factor that should be accounted for when designing intervention strategies. Use of competitive exclusion, sodium chlorate, vaccination, and bacteriophage are all strategies that can reduce Salmonellain the live animal, but it is vital to understand how they function so that we do not invoke the law of unintended consequences.

Objectives: To examine the ability of flavophospholipol to inhibit bacterial conjugation between Escherichia coli donor and recipient pairs in vitro and in day-of-hatch chickens.Methods: In vitro donor cultures were incubated in the presence of 0, 2, 4, 8, 16, 32 and 64 mg/L flavophospholipol during primary overnight mono-cultures only, secondary conjugation cultures only, or throughout primary and secondary cultures. Transconjugants were selected using oxytetracycline and nalidixic acid. Treatment groups A–G (n = 20) of day-of-hatch broiler chickens received 0, 2, 4, 8, 16, 32 and 64 g/ton flavophospholipol, respectively, in their feed throughout the experiment. On day 4, all treatment groups were given 0.25 mL of donor and recipient E. coli at 7.0 and 9.0 log10 cfu/mL, respectively. On day 10, the birds were euthanized and the caecal contents were cultured on selective medium (oxytetracycline and nalidixic acid).Results: A dose-dependent reduction in transconjugant populations was observed in vitro when flavophospholipol was present in the secondary conjugation culture. The susceptibility profiles of transconjugants obtained from in vitro studies were identical to the predicted profile of the donor and recipient combination. There was no significant difference (P ≥ 0.05) in the number of transconjugants isolated from chickens among any of the flavophospholipol treatment groups when compared with the controls. The susceptibility profiles of chicken transconjugants suggested acquisition of naturally occurring plasmids.Conclusions: Flavophospholipol strongly inhibited conjugation in vitro, but did not prevent recipient E. coli from acquiring resistance determinants in vivo.

A reactive extrusion process was developed improving the rheological properties of PET via the coaddition of a dianhydride and polyol. Specifically, the coaddition of pyromellitic dianhydride (PMDA) with pentaerythritol resulted in a gel‐free polyester with superior melt strengths and viscosities compared to the addition of PMDA alone. The enhancement in rheological properties were dependent on the relative amounts of dianhydride and polyol with the resultant polyester structurally stable in the melt. These results are consistent with the formation of a hyperbranched polyester with long chain branches. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3646–3652, 2006

Objectives: To characterize a multidrug-resistant Aeromonas hydrophila isolate (CVM861) that possesses a high-level macrolide inactivation gene cluster (mphA-mrx-mphR), previously only reported in Escherichia coli.Methods: PCR fragment length mapping, gene sequencing and Southern blotting were used to map the mphA-mrx-mphR gene cluster and flanking elements in CVM861. Conjugation experiments were done to determine whether the multidrug resistance genetic element was mobile.Results: The mphA-mrx-mphR gene cluster mapped downstream of a class 1 integron and upstream of an aph(3′) gene, and was present on a Tn21-like element. The gene order determined by sequencing was intI1-dhfrXII-orfF-aadA2-qacΔE-sul1-orf5Δ178-tnpA-mphR-mrx-mphA. Horizontal transmission of high-level macrolide resistance from CVM861 to E. coli 47011 was inconsistent; however, a composite plasmid possessing the mphA gene cluster was transferred at a conjugation frequency of 2.02 × 10−5 per recipient.Conclusions: An mphA-mrx-mphR gene cluster was present downstream of the In2 integron located on a Tn21-like transposon in an A. hydrophila isolate. Whether this recombination event resulted in the truncation of the orf5 sequence is unknown. The presence of other resistance genes downstream of the mphA-mrx-mphR gene cluster suggests that multiple recombination events have occurred on this genetic element. This is the first known report of the mphA-mrx-mphR gene cluster carried by A. hydrophila and the first known isolation of this cluster in the United States.

Mortality and morbidity associated with Escherichia colicause economic losses to the swine industry. Enterotoxigenic strains of E. coliaffecting nursery-age pigs have become more difficult to treat because of increased antibiotic resistance, and alternatives to antibiotics are currently being sought. Our laboratory developed a defined culture of commensal bacteria of porcine gastrointestinal tract origin, maintained it in continuous-flow culture for 3 yr, and designated it as RPCF. Laboratory studies have shown that RPCF-treated pigs had decreased mortality and bacterial shedding compared with controls when challenged with enterotoxigenic strains of E. coli. The objective of the present study was to evaluate the practicality, safety, and efficacy of RPCF to protect nursery-age pigs in commercial swine operations from field challenge by enterotoxigenic strains of E. coli. In field studies involving six geographically separated farms with a history of high mortality from K-88 and F-18 strains of E. coli, piglets were administered RPCF within 24 h of birth and monitored throughout the nursery period. A total of 21,467 piglets were treated with RPCF, and a similar number of piglets on the same farms served as untreated controls. On five of six farms, mortality in RPCF-treated pigs decreased by an average of 2.6% compared with untreated pigs. Differences in mortality were not observed in RPCF-treated pigs compared with controls on one Minnesota farm. When projected to an annual basis, the economic benefits from decreased medication costs and mortality averaged $24,663 per farm. These studies suggest that under commercial conditions, RPCF tended to control disease induced by enterotoxigenic E. coli, and that RPCF may be a viable alternative to the use of antibiotics.

Abstract: A commercial-feed-grade form of zinc propionate was examined as a potential feed amendment at a concentration of 1% zinc to induce molt in 90-wk-old hens. Dietary treatments consisted, of 4 treatment groups of 28 birds each randomly assigned to either (1) molted conventionally by feed withdrawal, (2) 1% zinc as Zn acetate, (3) 1% zinc as Zn propionate, or (4) nonmolted control for 9 d. Ovary weights of hens fed Zn acetate or Zn propionate were not significantly different from each other, but hens fed Zn acetate or Zn propionate were significantly (p<0.05) lighter than the ovary weight of nonmolted control hens. Zinc concentrations in the kidney and liver were significantly (p<0.05) increased in both Zn acetate- and Zn propionate-molted hens when compared to either nonmolted control-fed hens or feed-withdrawal molted hens. Over the entire 3-mo postmolt period, there were no significant differences in interior or exterior egg qualities among the four treatments Egg production of hens fed Zn acetate was significantly lower than feed-withdrawal hens, Zn propionate-fed hens, or nonmolted control hens (p<0.05). The data of the current study demonstrated that feeding a feed grade of Zn propionate (1% Zn)-supplemented diet can induce molt and retain postmolt egg quality and production comparable to hens molted by feed withdrawal.

Abstract: Zinc is an important nutrient in animal metabolism. In poultry, zinc serves not only as a nutrient but can also be used as a dietary supplement to manipulate the reproductive system of the bird. This article summarizes the general biochemistry, physiology, and nutritional aspects of zinc metabolism to provide a brief overview on what is known regarding zinc. The potential role of zinc in poultry immune response, Salmonella infection, and molting are emphasized.

Mature, healthy lactating dairy cattle were sampled on two farms in the southwestern United States to examine the effects of heat stress (Experiment I) and stage of lactation (Experiment II) on the fecal shedding of E. coli O157:H7 and Salmonella. To examine the effects of heat stress, fecal samples were collected from 45 cows at 7:00 AM (coolest part of the day) and 5:00 PM (hottest part of the day) in August 2002 on a 250 cow dairy. The study was replicated one month later (n = 170 total samples). A temperature-heat index (THI) was calculated for each sampling time. In Experiment II, stage of lactation was examined by sampling lactating dairy cattle early [<60 days in milk (DIM)] and late (>150 DIM) in the lactation cycle in the summer of 2001. The study was replicated the following summer (60 cows/group/replicate; n = 240 total samples). For Experiment I, THI averaged 75 and 82 for the AM and PM samplings, respectively, indicating the cows were beginning to experience heat stress in the morning and by afternoon were in severe heat stress. The shedding of E. coli O157:H7 tended to be higher (p = 0.09) in the afternoon sampling of the first replicate, however was not different in the second replicate or when both replicates were pooled (p > 0.10). Salmonella shedding was not different (p > 0.10) at any sampling time with nearly 100% of the cows positive. Stage of lactation had no effect on the number of cows shedding E. coli O157:H7 (p > 0.10). Salmonella shedding tended to be higher (p = 0.09) in early lactation cows in the first replicate, while in the second replicate more late lactation cows were shedding Salmonella (p < 0.05); however, there were no differences due to stage of lactation when replicates were pooled (p > 0.10). While further research is needed, results of this research highlight the variability in pathogen shedding in healthy dairy cattle and indicate that environmental factors and/or production demands may influence shedding patterns of E. coli O157:H7 and Salmonella.

Many human foodborne illnesses can be caused by consumption of foodstuffs (including meat products) contaminated with pathogenic bacteria from animal intestinal contents or hides. Steps that have been taken in the slaughter plant to decrease the spread of foodborne pathogenic bacteria (e.g., hazard analysis and critical control point methods) have been very effective; however, meat products are still the source of foodborne bacterial human illnesses. Increasing numbers of human Escherichia coliO157:H7 illnesses have also been related to contact with animals or to water supplies contaminated by run-off from cattle farms. Thus, strategies that specifically target foodborne pathogenic bacteria in the animal at the farm or feedlot level have great potential to improve food safety and decrease human illnesses. In this review, we describe a broad range of live-animal intervention strategies, both probiotic and antipathogen. Additionally, we examine some of the effects of diet and management strategies on foodborne pathogenic bacterial populations. The use of antibiotics in food animals to decrease foodborne pathogens also will be briefly examined. Overall, the concurrent use of several of these preslaughter intervention strategies could synergistically decrease human illnesses by providing for additional barriers in a multiple-hurdle approach to improving food safety.

Food-borne pathogenic bacteria sicken more than 76 million Americans annually. Many of these illnesses are caused by consumption of foodstuffs produced from animals. Postslaughter intervention strategies effectively reduce bacterial contamination level from the abattoir to the table. However, in spite of these effective strategies, food-borne illnesses and food-related deaths still occur far too frequently. Therefore, strategies that expand the continuum of intervention from the abattoir back to the farm have the greatest potential to reduce pathogenic contamination of meats and resultant human illnesses. A broad range of preslaughter intervention strategies have been contemplated and are currently under investigation. Potential strategies to be discussed include vaccination, competitive exclusion, substrate-adapted competitive exclusion, and the use of pro- and prebiotics (e.g., fructooligosaccharides). Other strategies such as the use of bacteriophage to specifically target certain pathogenic bacteria, and the exploitation of the physiology of specific pathogens will be described. Additionally, the use of antibiotics to specifically reduce pathogens will be examined, as well as the risks incurred by antibiotic usage. The effects of management strategies (e.g., dietary changes), transportation, and stress on food-borne pathogenic bacterial populations of food animals will also be discussed. The parallel application of one or more of these preslaughter strategies has the potential to synergistically reduce the incidence of human food-borne illnesses by erecting multiple hurdles against entry of pathogens into the food chain.

Virulence gene expression in Salmonella is triggered by a variety of environmental factors including changes in the gastrointestinal environment of birds during different dietary regimes. The objective of this study was to determine if growth of specific microorganisms alters the environmental conditions sufficiently to signalSalmonella Typhimurium virulence response. Spent media was obtained from aSalmonella TyphimuriumhilA:lacZY fusion strain, a poultrySalmonella Typhimurium strain, Eschcrichia coli K12, andLactobacillus caseii Spent media samples were collected after 2, 4, 8 and 24 h of growth in brain heart infusion broth (BHI) and M9 media, β‐galactosidase assays were performed on the samples to determine virulence expression. Virulence response to Salmonella, spent media was 2‐fold greater than Lactobacillus spent media at 4, 8 and 24 h growth (P < 0.05). Virulence expression almost doubled when exposed to Salmonella Typhimurium (NONA) spent media compared to mixed culture spent media at 4 h, andSalmonella Typhimurium (NONA) was significantly higher than mixed culture spent media at 24 h (P < 0.05). Based on these results, it appears that growth of similar bacterial species may alter the composition of rich media sufficiently to influence virulence.

Cattle are a natural reservoir of the food-borne pathogen Escherichia coli O157:H7. Therefore, strategies that reduce E. coli O157:H7 prior to slaughter will reduce human exposures to this virulent pathogen. When bacteria that can anaerobically respire on nitrate (e.g., E. coli) are exposed to chlorate, they die because the intracellular enzyme nitrate reductase converts nitrate to nitrite, but also co-metabolically reduces chlorate to cytotoxic chlorite. Because chlorate is bactericidal only against nitrate reductase-positive bacteria, it has been suggested that chlorate supplementation be used as a strategy to reduce E. coli O157:H7 populations in cattle prior to harvest. Cattle (n = 8) were fed a feedlot-style high-grain diet experimentally infected with three strains of E. coli O157:H7. Cattle were given access to drinking water supplemented with 2.5 mM KNO3 and 100 mM NaCl (controls; n = 4) or 2.5 mM KNO3 and 100 mM NaClO3 (chlorate-treated; n = 4). Sodium chlorate treatment for 24 h reduced the population of all E. coli O157:H7 strains approximately two logs (10(4) to 10(2)) in the rumen and three logs (10(6) to 10(3)) in the feces. Chlorate treatment reduced total coliforms and generic E. coli from 106 to 10(4) in the rumen and by two logs throughout the rest of the gastrointestinal tract (ileum, cecum, colon, and rectum). Chlorate treatment reduced E. coli O157:H7 counts throughout the intestinal tract but did not alter total culturable anaerobic bacterial counts or the ruminal fermentation pattern. Therefore, it appears that chlorate supplementation is a viable potential strategy to reduce E. coli O157:H7 populations in cattle prior to harvest.

A survey was conducted to establish the prevalence of Campylobacterin pigs from an integrated commercial hog farm. This study was carried out in four different groups of pigs: 1) adult gilts (50); 2) pregnant sows (9); 3) piglets at day-of-birth (73); 4) weaned piglets (20). Rectal and/or caecal samples were collected from each pig.Campylobacterwas cultured and enumerated from such samples using Bolton enrichment broth and Campy-Cephex agar plates. Both biochemical and serological tests were used to determine Campylobacterspecies. Gilts had a 76 per cent incidence ofCampylobacterwith a mean of 76·3 per cent for C. jejuni, 21 per cent for C. coliand 2·6 per cent for C. lari. Pregnant sows had a 100 per cent incidence of Campylobacterwith a mean of 87 per cent forC. jejuniand 13 per cent for C. coli. Newborn piglets had a 57·8 per cent incidence ofCampylobacter, rising to 100 per cent by the time of weaning. Thus it appears that pigs, from the day of birth, are highly susceptible to colonisation by Campylobacter.

We present 16 cases, 10 de novoand 6 familial, in which extra structurally abnormal chromosomes (ESACs) were diagnosed prenatally and identified by fluorescence in situhybridization (FISH) studies with follow up from birth. We review the literature on prenatally diagnosed ESACs arising de novoand suggest a management protocol for these cases. Copyright © 1999 John Wiley & Sons, Ltd.

We present 16 cases, 10 de novo and 6 familial, in which extra structurally abnormal chromosomes (ESACs) were diagnosed prenatally and identified by fluorescence in situ hybridization (FISH) studies with follow up from birth. We review the literature on prenatally diagnosed ESACs arising de novo and suggest a management protocol for these cases. Copyright © 1999 John Wiley & Sons, Ltd.

The objective of this study was to examine the effects of a Saccharomyces cerevisiaeculture (YEA-SACC) on lactate utilization by the predominant luminal bacterium Selenomonas ruminantium.Lactate uptake was stimulated by YEA-SACC concentrations between 2.5 and 10 g/liter, and the 5-g/liter level increased uptake 3.8-fold. When YEA-SACC concentrations were increased above the 5-g/liter level lactate uptake was decreased, but 10 g/liter still stimulated uptake more than threefold. A filter-sterilized YEA-SACC filtrate also increased lactate uptake more than fourfold at all concentrations tested (10 to 100 μl/ml), and the 25-μl/ml level increased uptake ninefold. Growth of S. ruminantiumin medium that contained 2 g/liter of DL-lactate was stimulated more than twofold by either 2 or 5%(vol/vol) YEA-SACC filtrate after 24 h. The YEA-SACC filtrate also increased the production of acetate, propionate, total VFA, and YLACTATE(grams of cells/mole of lactate) from lactate-grown cells. Because the increase in propionate production was greater relative to acetate, a decrease in the acetate:propionate ratio was observed. Growth on lactate and uptake of radiolabeled lactate by S. ruminantiumwas stimulated by a filtersterilized YEA-SACC filtrate. The concentration of L-malic acid in the YEA-SACC filtrate was 4.9 mM,and it seemed that L-malic acid played a role in the stimulation of growth on lactate as well as lactate uptake by S. ruminantiumtreated with YEA-SACC.

The objective of this study was to examine the effects of Aspergillus oryzaefermentation extract (Amaferm) on the in vitro ruminal fermentation of coastal bermudagrass, soluble starch and amino acids. Mixed ruminal microorganisms were incubated in anaerobic media for either 24 h (Amaferm alone, soluble starch, amino acids) or 48 h (bermudagrass). Amaferm was added to the incubation bottles (n = 4) at concentrations of 0, .4 or 1.0 g/liter. When mixed ruminal microorganisms were incubated with only Amaferm, the 1.0 g/liter concentration increased the production of hydrogen (H2; P< .001), methane (CH4; P< .01), acetate (P< .05), butyrate (P< .01), total VFA (P< .05) and NH3(P< .05). Addition of both levels of Amaferm to soluble-starch fermentations tended to enhance the production of H2(P< .11), CH4(P< .15), acetate (P< .29) and total VFA (P< .19); propionate production was increased (P< .10) by 1.0 g/liter Amaferm, resulting in a decrease (P< .05) in the acetate:propionate ratio. Fermentation of amino acids plus 1.0 g/liter Amaferm enhanced the production of acetate (P< .05), propionate (P< .05), valerate (P< .01) and total VFA (P< .10) and decreased the acetate:propionate ratio (P< .05). In addition, NH3production tended (P< .19) to increase with both levels of Amaferm. When bermudagrass was the substrate, few changes in fermentation products were observed with Amaferm treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Selenomonas ruminantium is one of the more prominent and functionally diverse bacteria present in the rumen and can survive under a wide range of nutritional fluctuations. Selenomonas is not a degrader of complex polysaccharides associated with dietary plant cell wall components, but is important in die utilization of soluble carbohydrates released from initial hydrolysis of these polymers by other ruminal bacteria. Selenomonads have multiple carbon flow routes for carbohydrate catabolism and ATP generation, and subspecies differ in dieir ability to use lactate. Some soluble carbohydrates (glucose, sucrose) appear to be transported via the phosphoenolpyruvate phosphotransferase system, while arabinose and xylose are transported by proton symport. High cell yields and the presence of electron transport components in Selenomonas strains has been documented repeatedly and this may partially account for the energy partitioning observed between energy consumed for growth and maintenance functions. Most strains can utilize ammonia, protein, and/or amino acids as a nitrogen source. Some strains can hydrolyze urea and/or reduce nitrate and use the ammonia for the biosynthesis of amino acids. Experimental evidence suggests that ammonia assimilatory enzymes in some strains may possess unique properties with respect to other presumably similar bacteria. Little is known about the genetics of ruminal selenomonads. Plasmid DNA has been isolated from some strains, but it is unknown what physiological functions may be encoded on these extrachromosomal elements. Due to the predominance of S. ruminantium in the rumen, it is an ideal candidate for genetic manipulation. Once the genetics of this bacterium are better understood, it may be possible to amplify its role in the rumen.

The fortuitous occurrence of cases of jaagsiekte (sheep pulmonary adenomatosis) in a group of young Scottish Blackface sheep exposed to experimental cold stress is described. The incidence (11/62 cases) was high and the age of onset early (less than 20 months) by comparison with the authors' local experience of the disease. There was also some indication that males were more susceptible (9/26) than females (2/36). The results are not conclusive, but suggest the need for similar cold stress experiments in animals deliberately infected with the disease.

Poultry litter is a potentially valuable crude protein feedstuff for ruminants but must be treated to kill pathogens before feeding. Composting effectively kills pathogens but risks losses of ammonia during uric acid degradation. Presently, 250-g portions of used wood chip litter (WCL, 73% dry matter) were treated with 125 mL 0.4 M phosphate buffer (pH 6.5) containing Chinook or Galena hop extracts to achieve 0.03 g beta-acid/g WCL. Control WCL was treated with buffer alone. The WCL was distributed (11 g) to 50-mL tubes (3 tubes/treatment per sampling day), inoculated with a marked challenge strain of SalmonellaTyphimurium (ST) then capped and incubated at successive 3-day increments at 22oC, 37oC and 42oC. Repeated measures analysis of variance of ammonia, urea and uric acid measured in samples collected on days 0, 3, 6 and 9 revealed a main effect of day on uric acid (P< 0.05), which increased from day 0 to 3 (a high of 9.4 µmol/g) and declined thereafter to its low (4.1 µmol/g) on day 9. A day x treatment interaction was observed (P< 0.05) on ammonia accumulations which increased steadily, accumulating more on day 9 with Galena hops-treated WCL than with control- or Chinook hops-treated WCL (7.3, 6.6 and 5.6 µmol/g, respectively). A main effect of treatment but not day or their interaction was observed on urea accumulations, highest for control, lowest for Galena- and intermediate for Chinook hops-treated WCL (1.7, 0.5 and 1.0 µmol/g, respectively). Analysis of bacterial concentrations revealed little effect of treatment on bacterial counts; however, main effects of day on ST and E. coliwere observed (P< 0.05) with both being decreased below detection limits (1 log10CFU/g) by day 9. These results indicate that composting combined with Chinook hops-treatment may help safely preserve crude protein of WCL.

Poultry litter (PL) contains uric acid which makes it a good crude protein supplement for ruminants. However, PL must be treated to kill pathogens before feeding. Composting effectively kills pathogens but risks loss of ammonia due to uric acid degradation. Because tannins possess antimicrobial activity and can inhibit uric acid metabolism, we tested their ability to preserve uric acid and reduce pathogens during PL composting. Used PL (76% DM) was mixed 2:1 with 0.4 M phosphate buffer (pH 6.5) and distributed (11 g) to 50-mL tubes (3/treatment per sample day) amended with 1 mL buffer alone or containing pine bark, quebracho, chestnut or mimosa tannins to achieve 1.5% wt/vol. Tubes were inoculated with a novobiocin- and naladixic acid-resistant Salmonella Typhimurium (STNN), closed with caps and incubated at successive 3 day increments at 22oC, 37oC and 42oC, respectively. Repeated measures analysis of variance of bacterial numbers enumerated in contents collected on days 0, 6 and 9 revealed a main effect of day (P < 0.0001) but not treatment (P > 0.05) on all populations, with initial counts of E. coli and STNN being decreased from 4.3 and 3.6 log10 CFU/g to below detection limits (1 log10 CFU/g) by day 9. A tendency for a day x treatment interaction was observed on STNN populations (P = 0.09), with STNN being decreased 0.4 log10 CFU/g on day 6 in quebracho-treated litter compared to being increased 0.6 log10 CFU/g in control PL. Analysis of ammonia, urea and uric acid concentrations revealed an effect of day (P < 0.05) but not treatment or their interaction, with concentrations increasing 36, 32 and 27% from initial values (2.9, 3.3 and 4.4 µmol/mL, respectively). Results confirm that composting was an effective pathogen control treatment but revealed little additional benefit due to tannin treatment under the conditions studied here.

Poultry litter (PL) is a valuable nitrogen feed source for ruminants whose gut microbes transform the nitrogen in uric acid into microbial protein. Evidence indicates that nitro-treatment may improve the feed value of composted PL by inhibiting degradation of its nonprotein nitrogen (NPN) during composting but it is not known what effect residual nitrocompounds may have on ruminal NPN metabolism. In this study, freshly collected ruminal fluid from a pasture-reared cow was incubated anaerobically (10 mL/tube) at 39oC in closed-culture tubes supplemented with 0.2 g ground alfalfa, 0.15 g of one-year-old PL and with or without 20 mM 3-nitropropionate (NPA) or ethyl nitroacetate (ENA), concentrations previously shown to be inhibitory of uric acid degradation. Analysis of uric acid, urea and ammonia concentrations measured at 0, 6 and 24 h revealed rates of uric acid and urea disappearance in nitro-treated cultures did not differ from controls (0.10, 0.07 and 0.19 µmol urea 0.09, 0.05 and 0.07 µmol uric acid per mL incubation fluid for controls, NPA- and ENA-treated cultures, respectively). Rates of ammonia accumulations in NPA-treated cultures were similar to controls but lower in ENA-treated cultures (0.16, 0.17 and 0.09 µmol/mL, respectively). Effects of nitro-treatment were observed on headspace gas accumulations, although this was not unexpected as the nitrocompounds are known methane-inhibitors. Less gas volume accumulated in NPA- and ENA-treated cultures compared to controls (26, 21 and 18 mL, respectively) and methane production was lower in NPA- and ENA-treated cultures than controls (0.7, 0.5 and 21 µmol/mL, respectively). Hydrogen accumulations were similar between NPA-treated cultures and controls but higher in ENA-treated cultures (0.1, 0.4 and 0.9 µmol/mL, respectively). These results indicate that residual nitrocompounds in nitro-treated PL will have little if any adverse effect on ruminal NPN metabolism and may beneficially contribute to lowering methane emissions.

Forced molting of laying hens increases enteric foodborne pathogens in the reproductive tract, leading to contaminated eggs and progeny of infected hens. Currently, we lack a complete understanding of how conditions such as molting affect the immune system. Previous reports have shown that alfalfa is effective in inducing a molt as well as in producing protection against Salmonella Enteritidis organ invasion. Our laboratory has also shown that immune functions are significantly reduced during molting. The present investigation evaluates a specific parameter of immune function, heterophil function, during an induced molt in hens fed alfalfa. Three replicate experiments used hens older than 65 wk of age that were divided into 6 groups of 12 hens each and placed in individual laying cages. Two weeks before dietary changes, hens were placed on an 8L:16D photoperiod that continued for the 12-d experiment. Peripheral blood samples were taken from hens on d 0, 2, 6, and 12 of molt. Hens were randomly placed into 3 treatment groups: nonfed hens, fully fed hens, and alfalfa-fed hens. To evaluate heterophil functions, the production of an oxidative burst as well as cellular degranulation assays were performed. In addition, total and differential peripheral blood leukocyte counts were performed. When compared with the nonfed control, alfalfa-fed birds showed significantly (P < 0.05) higher oxidative burst and degranulation activities. The data confirm previous observations that heterophil functions are significantly decreased in nonfed birds and the data show that birds fed alfalfa had numerically increased heterophil functions over a 12-d molting period when compared with heterophils of nonfed controls. Commercial integrators should consider using alfalfa when developing new molting programs.

Australian mosquitoes were evaluated for their ability to become infected with and transmit a Torres Strait strain of Japanese encephalitis virus. Mosquitoes, which were obtained from either laboratory colonies and collected using Centers for Disease Control and Prevention light traps baited with CO2 and octenol or reared from larvae, were infected by feeding on a blood/sucrose solution containing 104.5±0.1 porcine stable-equine kidney (PS-EK) tissue culture infectious dose50/mosquito of the TS3306 virus strain. After 14 d, infection and transmission rates of 100% and 81%, respectively, were obtained for a southeast Queensland strain of Culex annulirostris Skuse, and 93% and 61%, respectively, for a far north Queensland strain. After 13 or more days, infection and transmission rates of >90% and =50%, respectively, were obtained for southeast Queensland strains of Culex sitiens Wiedemann and Culex quinquefasciatus Say, and a far north Queensland strain of Culex gelidus Theobald. Although infection rates were >55%, only 17% of Ochlerotatus vigilax (Skuse) and no Cx. quinquefasciatus, collected from far north Queensland, transmitted virus. North Queensland strains of Aedes aegypti L., Ochlerotatus kochi (Dönitz), and Verrallina funerea (Theobald) were relatively refractory to infection. Vertical transmission was not detected among 673 F1 progeny of Oc. vigilax. Results of the current vector competence study, coupled with high field isolation rates, host feeding patterns and widespread distribution, confirm the status of Cx. annulirostris as the major vector of Japanese encephalitis virus in northern Australia. The relative roles of other species in potential Japanese encephalitis virus transmission cycles in northern Australia are discussed.

Exposure of newly hatched chicks in the hatchery to salmonellae results in the establishment of seeder chicks with fecal shedding and the transmission of salmonellae to other contact chicks in the broiler house during growout. This study investigated the protective effect of treatment with a characterized competitive exclusion culture, CF3 on the transmission of Salmonella from seeder to contact chicks when CF3 treatment occurred simultaneously with seeder challenge or when treatment was delayed until 24 hr after challenge. Delayed treatment failed to prevent the establishment of seeder chicks, but did significantly (P=.005) reduce the spread of Salmonella from seeder to non-challenged contact chicks. Simultaneous Salmonella challenge and CF3 treatment significantly (P=.005) decreased the establishment of seeders and was highly effective in preventing the spread of Salmonella from seeder to contact chicks. The results demonstrated that treatment on the day of hatch can significantly help to reduce seeder establishment and the spread of Salmonella from seeders to highly susceptible contact chicks.

Broiler breeder flocks and hatcheries have been identified as reservoirs of salmonellae and potential sources of Salmonella infection for highly susceptible day-old chicks. Once salmonellae have colonized the gastrointestinal tract of the chick, the bacteria replicate and are shed into the environment to contaminate it and to colonize other chicks. Salmonella will continue to cycle throughout the broiler flock via bird to bird contact, and any facilities that have house the flock will become a potential reservoir for future flocks. The present studies were conducted to evaluate horizontal transmission of Salmonella typhimurium from challenged chicks (seeders) to non-challenged broiler chicks (contacts). Data from the present study suggest that the spread of Salmonella from seeder chicks to contact chicks is dependent on the Salmonella challenge dose and not the number of chicks originally exposed. Horizontal transmission of Salmonella to unchallenged contact chicks from seeders initially challenged with 100 Salmonella or more will limit the effectiveness of any post-hatchery Salmonella control program after they leave the hatchery.