Growth hormone response to growth hormone-releasing hormone in beef cows divergently selected for milk production

In dairy cattle, increased circulating growth hormone has been associated with selection for greater milk yield. This study tested the hypothesis that beef cows divergently selected for milk production would have differing GH responses to a challenge dose of GHRH. Growth hormone response to a challenge of GHRH was measured in 36 Angus-sired cows ranging from 6 to 10 yr of age. The cows were classified as high milking (n = 16) or low milking (n = 20), on the basis of their sires' milk EPD. Mean milk EPD (in kilograms) were 16.6 and -14.4 for high and low milking cows, respectively. Milk production was estimated by the weigh-suckle-weigh procedure. Blood samples were taken immediately before and 10 min after a clearance dose of 4.5 microg of GHRH/100 kg BW (injected i.v.) and, 3 h later, immediately before and 10 min after a challenge dose of either 1.5 or 4.5 microg of GHRH/100 kg BW. Each animal received both challenge doses, and the doses were randomly assigned across 2 d of blood collection. Serum concentrations of GH and IGF-I were measured by RIA. Serum IGF-I was measured in the baseline blood sample on d 1 of blood collection. A positive relationship (r = 0.35; P = 0.03) was observed between the cows' rankings for each dose of GHRH; that is, high responders to the low dose were high responders to the high dose. Growth hormone response to the 4.5 microg/100 kg BW challenge dose of GHRH was positively related to sire milk EPD (R2 = 0.09; P = 0.03). Response of GH to the 1.5 microg GHRH/100 kg BW challenge dose also tended to be related (P = 0.08) to sire milk EPD of high milking cows. In addition, IGF-I concentrations of high milking cows were inversely related (R2 = 0.24; P = 0.04) to sire milk EPD. Growth hormone response to GHRH challenge may have potential as an additional tool in the evaluation of milk production in beef cattle.     

Prevalence of faecal excretion of verocytotoxigenic Escherichia coli O157 in cattle in England and Wales

During the decade to 1999, the incidence of human infections with the zoonotic pathogen verocytotoxin-producing Escherichia coli O157 (VTEC O157) increased in England and Wales. This paper describes the results of a survey of 75 farms to determine the prevalence of faecal excretion of VTEC O157 by cattle, its primary reservoir host, in England and Wales. Faecal samples were collected from 4663 cattle between June and December 1999. The prevalence of excretion by individual cattle was 4.2 per cent (95 per cent confidence interval [CI] 2.0 to 6.4) and 10.3 per cent (95 per cent CI 5.8 to 14.8) among animals in infected herds. The within-herd prevalence on positive farms ranged from 1.1 to 51.4 per cent. At least one positive animal was identified on 29 (38.7 per cent; 95 per cent CI 28.1 to 50.4) of the farms, including dairy, suckler and fattening herds. The prevalence of excretion was least in the calves under two months of age, peaked in the calves aged between two and six months and declined thereafter. The phage types identified most widely were 4, 34 and 2, which were each found on six of the 29 positive farms.     

Effect of a 24-hour infusion of an isotonic electrolyte replacement fluid on the renal clearance of electrolytes in healthy neonatal foals

OBJECTIVE: To determine the effects of a 24-hour infusion of an isotonic electrolyte replacement fluid (IERF) on weight, serum and urine electrolyte concentrations, and other clinicopathologic variables in healthy neonatal foals. ANIMALS: 4 healthy 4-day-old foals. DESIGN: Prospective study. PROCEDURE: An IERF was administered to each foal at an estimated rate of 80 mL/kg/d (36.4 mL/lb/d) for 24 hours. Body weight was measured before and after the infusion period. Urine was collected via catheter during 4-hour periods; blood samples were collected at 4-hour intervals. Variables including urine production; urine and serum osmolalities; sodium, potassium, and chloride concentrations in urine and serum; urine and serum creatinine concentrations; urine osmolality-to-serum osmolality ratio (OsmR); transtubular potassium gradient (TTKG); and percentage creatinine clearance (Cr(cl)) of electrolytes were recorded at 0, 4, 8, 12, 16, 20, and 24 hours during the infusion period. Immediately after the study period, net fluid and whole-body electrolyte changes from baseline values were calculated. RESULTS: Compared with baseline values, urine and serum sodium and chloride serum concentrations, urine and serum osmolalities, OsmR, and percentage Cr(cl) of sodium and chloride were significantly increased at various time points during the infusion; urine production did not change significantly. After 24 hours, weight, TTKG, serum creatinine concentration, and whole-body potassium had significantly decreased from baseline values. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that administration of an IERF containing a physiologic concentration of sodium may not be appropriate for use in neonatal foals that require maintenance fluid therapy.     

Effects of long-term oral administration of levothyroxine sodium on serum thyroid hormone concentrations, clinicopathologic variables, and echocardiographic measurements in healthy adult horses

OBJECTIVE: To determine the effects of long-term oral levothyroxine sodium (L-T(4)) administration on serum thyroid hormone concentrations, thyroid gland function, clinicopathologic variables, and echocardiographic examination measurements in adult euthyroid horses. ANIMALS: 6 healthy adult mares. PROCEDURES: Horses received L-T(4) (48 mg/d) orally for 48 weeks. Every 4 weeks, physical examinations were performed; blood samples were collected for CBC, plasma biochemical analyses, and assessments of serum total triiodothyronine (tT(3)) and thyroxine (tT(4)) concentrations. Plasma creatine kinase MB activity and cardiac troponin I concentration were also measured. Echocardiographic examinations were performed before and at 16, 32, and 48 weeks during the treatment period. RESULTS: During the treatment period, mean body weight decreased significantly; heart rate varied significantly, but the pattern of variation was not consistent. Significant time effects were detected for certain clinicopathologic variables, but mean values remained within reference ranges. Cardiac troponin I was only detectable in 8 of 24 plasma samples (concentration range, 0.01 to 0.03 ng/mL). Serum creatine kinase MB activity did not change significantly over time. Compared with the pretreatment value, 5.4-, 4.0-, and 3.7-fold increases in mean serum tT(4) concentrations were detected at 16, 32, and 48 weeks, respectively. Some cardiac measurements changed significantly over time, but mean values remained within published reference ranges. Mean fractional shortening was lower than the pretreatment mean value at 16 and 32 weeks. CONCLUSIONS AND CLINICAL RELEVANCE: In horses, long-term oral administration of 48 mg of L-T(4)/d significantly increased serum tT(4) concentrations and did not appear to adversely affect health.     

Strain-associated virulence factors of Streptococcus iniae in hybrid-striped bass

Streptococcus iniae is a major fish pathogen producing invasive infections that result in economic losses in aquaculture. Development of in vitro models of S. iniae virulence may provide insight to the pathogenesis of infection in vivo. Three S. iniae strains (K288, 94-426, and 29178) were tested for virulence in a hybrid-striped bass (HSB) model using intraperitoneal injection. S. iniae strains K288 and 94-426 caused high levels of mortality in HSB (lethal dose 2x10(5)CFU) while strain 29178 was avirulent even upon IP challenge with 1000-fold higher inocula. In vitro assays were developed to test for the presence of characteristics previously associated with virulence in other species of pathogenic Streptococcus in animals and humans. In vitro differences relevant to virulence were not detected for beta-hemolysin activity, sensitivity to antimicrobial peptides, or adherence and invasion of epithelial cell layers. However, in whole-blood killing assays, the pathogenic strains were resistant to blood clearance, while 29178 was cleared (P<0.001) and more sensitive to complement (P<0.001). The avirulent strain 29178 was most efficiently phagocytosed and was most susceptible to intracellular killing (P<0.01) by the carp leukocyte cell line (CLC). When exposed to reactive oxygen species, strain 29178 was most susceptible. When the oxidative burst of CLC cells was inhibited, intracellular survival of 29178 was rescued fivefold, while no significant enhancement in survival of K288 or 94-426 was detected. Our results indicate that resistance to phagocytosis, oxidative killing, and associated phagocytic clearance is a significant factor in S. iniae virulence.     

In vitro effects of hydrochloric and lactic acids on bioelectric properties of equine gastric squamous mucosa

REASONS FOR PERFORMING STUDY: Volatile fatty acids, byproducts of carbohydrate fermentation by resident bacteria, have been implicated in causing nonglandular (NG) gastric ulcers. Lactic acid (LA), also produced by stomach bacteria, may cause gastric ulcers when exposed to the equine NG mucosa. OBJECTIVES: To investigate the in vitro effects of LA on equine NG mucosa bioelectric properties, sodium transport and tissue resistance. METHODS: Gastric tissues obtained from 13 mature horses were studied in Ussing chambers. Short-circuit current (Isc) and potential difference (PD) were measured, and electrical resistance (R) and conductance (G) calculated for tissues after addition of HCl and LA (5, 10, 20 and 40 mmol/l) in normal Ringer's solution (NRS). RESULTS: Mucosa exposed to HCl or LA (5, 10 and 20 mmol/l) in NRS (pH 1.5 and to a lesser extent pH 4.0) had a significant decrease in Isc and PD. Mucosa exposed to a high concentration of LA (40 mmol/l) in NRS (LRS) at pH 1.5 showed an increased G, but this increase was not significant. Values returned to baseline after solutions were returned to pH 7.0. Histological changes were consistent with HCl-induced (pH <4.0) acid damage. CONCLUSIONS: HCl induced alteration in bioelectric properties of equine NG mucosa whereas addition of LRS did not, other than those changes seen with HCl alone.     

Streptococcus equi Infections in Horses: Guidelines for Treatment,Control, and Prevention of Strangles—Revised Consensus Statement

This consensus statement update reflects our current published knowledge and opinion about clinical signs, pathogenesis, epidemiology, treatment, complications, and control of strangles. This updated statement emphasizes varying presentations in the context of existing underlying immunity and carrier states of strangles in the transmission of disease. The statement redefines the “gold standard” for detection of possible infection and reviews the new technologies available in polymerase chain reaction diagnosis and serology and their use in outbreak control and prevention. We reiterate the importance of judicious use of antibiotics in horses with strangles. This updated consensus statement reviews current vaccine technology and the importance of linking vaccination with currently advocated disease control and prevention programs to facilitate the eradication of endemic infections while safely maintaining herd immunity. Differentiation between immune responses to primary and repeated exposure of subclinically infected animals and responses induced by vaccination is also addressed.     

Actinomyces hordeovulneris, a canine pathogen that produces L-phase variants spontaneously with coincident calcium deposition

The spontaneous production of cell-wall-deficient filaments and protoplasts by a strain of Actinomyces hordeovulneris (UCD 81-332-9) in 10% sucrose L-form media is reported. Multiple mineral deposits were present within the variants at 48 hours. Electron microscopy revealed that these deposits were amorphous, dense, and at the inner face of the cytoplasmic membrane in wall-less protoplasts and also in filaments which had a thin wall of 10 nm. These cell-wall-deficient variants produced L-form colonies when cultured for an additional 48 hours on 10% sucrose-BYE L-form plates. The colonies were composed of only a few filaments and many vesicles which were negative with Dienes' stain. Silver substitution stains of UCD 81-332-9 cells that had been grown in L-form broth for 5 days revealed heavy calcification of all cells including protoplasts. Gram stains of L-form grown cells revealed the presence of long-beaded, infrequently branched gram-positive filaments similar to those observed in clinical specimens. The formation of cell wall-deficient variants with coincident mineralization is believed to be related to the phenomenon of sulfur granule formation in vivo.     

Effects of intravenously administrated omeprazole on gastric juice pH and gastric ulcer scores in adult horses

The study was performed to evaluate the efficacy of omeprazole powder in sterile water, administered intravenously, on gastric juice pH in adult horses with naturally occurring gastric ulcers. Omeprazole (0.5 mg/kg, IV) was administered once daily for 5 days to 6 adult horses with gastric ulcers. Gastric juice was aspirated through the biopsy channel of an endoscope and pH was measured before and 1 hour after administration of omeprazole on day 1, and then before and after administration of omeprazole on day 5. Gastric ulcer scores were recorded on day 1 before administration of omeprazole and on day 5, 23 hours after the 4th daily dose. Gastric juice pH and ulcer scores were compared between the times. When compared with the pre-injection value (2.01 +/- 0.42), mean +/- SD gastric juice pH was significantly higher when measured 1 hour after administration of the initial dose (4.35 +/- 2.31), and before (5.27 +/- 1.74) and 1 hour after (7.00 +/- 0.25) administration of omeprazole on day 5. Nonglandular gastric ulcer number score significantly decreased from a mean +/- SD of 3.2 +/- 0.80 to 2.0 +/- 1.1, but nonglandular gastric ulcer severity score remained the same. Few glandular ulcers were seen in the study, and scores did not change. Because of its potent and long duration of action on gastric juice pH, this intravenous formulation of omeprazole may show promise for treatment of equine gastric ulcer syndrome (EGUS) in horses with dysphagia, gastric reflux, or other conditions that restrict oral intake of omeprazole paste. Aspiration of gastric juice and measurement of pH can be of use to determine whether the desired pH > 4.0 has been reached after omeprazole treatment.     

In Vivo Transfection of Adult Eastern Oysters Crassostrea virginica

The eastern oyster Crassostrea virginica provides a commercially valuable industry along the eastern and Gulf coasts of the United States. Recently this industry has been damaged by disease problems, creating an interest in the use of gene transfer (transfection) to improve disease resistance. We transfected adult oysters with two genes, red-shifted green fluorescent protein ( rsGFP ), commonly used as a reporter gene, and the lytic peptide cecropin B ( cepB ), known to have antimicrobial properties. Oysters were transfected by injecting DNA mixed with SuperFect™ reagent (Qiagen Inc.) into the adductor muscle sinus. Oysters were assigned to three groups of 15: the first was injected with rsGFP complexed with transfecting reagent: the second was injected with cepB complexed with transfectlng reagent; and the third was injected with saline (control group). Hemolymph was collected at 4 and 10 d after injection. DNA was extracted for analysis by polymerase chain reaction (PCR), and hemocytes were examined by flow cytometry and fluorescence microscopy for detection of green fluorescence due to rsGFP expression. The rsGFP gene was detected by PCR in hemocytes from 14 of 15 oysters at day 4, and in 15 of 15 oysters at day 10. The cepB gene was detected by PCR in 12 of 15 oysters at day 4 and in 14 of 15 oysters at day 10. No oysters from the control group were positive for either gene at days 4 or 10. Green fluorescence was detected by flow cytometry at significantly higher levels ( P < 0.05) in oysters injected with rsGFP than in other oysters at day 4, but not at day 10. This report indicates the ability to introduce DNA into adult eastern oysters with subsequent gene expression. Future work will involve developing these techniques for enhanced disease resistance in oysters.