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Summary

Endocrine changes in sows with ovarian cysts were determined to be comparable with those in sows in diestrus. Blood samples were collected at frequent intervals from 5 sows affected with cystic ovaries. Concentrations of serum luteinizing hormone, progesterone, estradiol-17β, and cortisol were determined by use of established radioimmunoassays. The development of ovarian cysts has been proposed to be associated with a deficiency of luteinizing hormone rather than an intrinsic ovarian abnormality. In contrast, the results of this study demonstrated that tonic and pulsatile luteinizing hormone release were not affected adversely in sows with cystic ovaries.

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To model the plasma tetracycline concentrations in swine (Sus scrofa domestica) treated with medication administered in water and determine the factors that contribute to the most accurate predictions of measured plasma drug concentrations.

Sample—Plasma tetracycline concentrations measured in blood samples from 3 populations of swine.

Procedures—Data from previous studies provided plasma tetracycline concentrations that were measured in blood samples collected from 1 swine population at 0, 4, 8, 12, 24, 32, 48, 56, 72, 80, 96, and 104 hours and from 2 swine populations at 0, 12, 24, 48, and 72 hours hours during administration of tetracycline hydrochloride dissolved in water. A 1-compartment pharmacostatistical model was used to analyze 5 potential covariate schemes and determine factors most important in predicting the plasma concentrations of tetracycline in swine.

Results—2 models most accurately predicted the tetracycline plasma concentrations in the 3 populations of swine. Factors of importance were body weight or age of pig, ambient temperature, concentration of tetracycline in water, and water use per unit of time.

Conclusions and Clinical Relevance—The factors found to be of importance, combined with knowledge of the individual pharmacokinetic and chemical properties of medications currently approved for administration in water, may be useful in more prudent administration of approved medications administered to swine. Factors found to be important in pharmacostatistical models may allow prediction of plasma concentrations of tetracycline or other commonly used medications administered in water. The ability to predict in vivo concentrations of medication in a population of food animals can be combined with bacterial minimum inhibitory concentrations to decrease the risk of developing antimicrobial resistance.

Full access
in American Journal of Veterinary Research

Abstract

Objective

To evaluate effects of endotoxemia on serum somatotropin (ST) and insulin-like growth factor I (IGF-I) concentrations in finishing pigs.

Animals

Eight female pigs (98 ± 2 kg) randomly assigned to IV administration (time 0) of saline solution (n = 4) or Escherichia coli lipopolysaccharide (LPS; 5 μg/kg of body weight; n = 4).

Procedure

Serum ST concentration was determined in serum samples obtained at 20-minute intervals for 6 hours after treatment. Serum IGF-I concentration was determined in samples collected at 1-hour intervals for 6 hours and at 12, 15, 18, 24, 48, 72, and 96 hours after treatment.

Results

One distinct pulse of ST (peak 10.5 ± 0.5 ng/ml) was observed at 40 minutes in each pig after administration of LPS. Control pigs had 2.25 ± 0.48 ST pulses during the 6 hours of frequent sample collection; however, magnitude of the ST pulses was similar between gilts given LPS and control gilts. A temporal association between ST pulses and saline administration was not evident. Serum IGF-I concentration was similar between gilts of the LPS and control groups prior to treatment. The IGF-I concentration was lower (P < 0.01) in gilts of the LPS group (44 ± 5 ng/ml) than in gilts of the control group (157 ± 4 ng/ml) at 24 hours. The difference in IGF-I concentrations between groups was evident for 96 hours.

Conclusions

Immediate release of ST was attributed to stress associated with acute endotoxemia and stimulation of the pituitary gland; immune stimulation by LPS may have contributed to the changes in IGF-I concentration. Because feed consumption was similar between the 2 groups of pigs, suppression of IGF-I concentration for 96 hours after administration of LPS was attributable to factors in addition to transient feed restriction. Thus, acute endotoxemia altered the positive association between ST and IGF-I, and provided evidence for a potential mechanism of impaired growth in endotoxemic animals. (Am J Vet Res 1997;58:1010–1013)

Free access
in American Journal of Veterinary Research

Summary

Mature boars were subjected to chronic treatment with a gonadotropin-releasing hormone (GnRH) agonist, goserelin (D-Ser[But]6, Azgly-NH210), and serum luteinizing hormone (lh) and testosterone concentrations were measured. Ten sexually mature boars were randomly assigned to treatment (n = 5) or control (n = 5) groups. On day 0, boars were implanted sc (day 0) with 2 GnRH agonist implants (1 mg of GnRH/implant) or sham implants. Blood samples were collected at 12-hour intervals on days – 2 and –1, at 6-hour intervals on days 0 through 4, and at 12-hour intervals on days 5 through 8. In addition, blood samples were collected at 15-minute intervals for 6 hours on days –1, 0, 4, and 8. Serum testosterone and (lh concentrations were determined by radioimmunoassay. Maximal (lh (7 ± 1 ng/ml) and testosterone (26 ± 3 ng/ml) concentrations were observed at 5 and 18 hours, respectively, after GnRH agonist treatment. Subsequently, (lh and testosterone concentrations decreased to pretreatment values (0.3 ± 0.1 ng/ml and 1.8 ± 0.4 ng/ml, respectively) by 24 and 48 hours, respectively, after GnRH agonist implantation. Few differences in the characteristics of pulsatile (lh release were observed between the groups. Testosterone and lh concentrations in samples collected at 6- and 12-hour intervals and pulsatile (lh release did not change after sham treatment of control boars. Whereas previous reports indicated that chronic GnRH administration suppressed serum lh and testosterone concentrations in rams, rats, and dogs, our results indicate that chronic GnRH agonist treatment induced transitory increases, without subsequent suppression, in lh and testosterone concentrations in mature boars.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate variation of drinking-water flow rates in swine finishing barns and the relationship between drinker flow rate and plasma tetracycline concentrations in pigs housed in different pens.

Design—Cross-sectional (phase 1) and cohort (phase 2) studies.

Sample Population—13 swine finishing farms (100 barns with 7,122 drinkers) in phase 1 and 100 finishing-stage pigs on 2 finishing farms (1 barn/farm) in phase 2.

Procedures—In phase 1, farms were evaluated for water-flow variation, taking into account the following variables: position of drinkers within the barn, type of drinker (swing or mounted), pig medication status, existence of designated sick pen, and existence of leakage from the waterline. In phase 2, blood samples were collected from 50 pigs/barn (40 healthy and 10 sick pigs) in 2 farms at 0, 4, 8, 24, 48, and 72 hours after initiation of water-administered tetracycline HCl (estimated dosage, 22 mg/kg [10 mg/lb]). Plasma tetracycline concentrations were measured via ultraperformance liquid chromatography.

Results—Mean farm drinker flow rates ranged from 1.44 to 2.77 L/min. Significant differences in flow rates existed according to drinker type and whether tetracycline was included in the water. Mean drinker flow rates and plasma tetracycline concentrations were significantly different between the 2 farms but were not different between healthy and sick pigs. The plasma tetracycline concentrations were typically < 0.3 μg/mL.

Conclusions and Clinical Relevance—Many factors affected drinker flow rates and therefore the amount of medication pigs might have received. Medication of pigs with tetracycline through water as performed in this study had questionable therapeutic value.

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To identify important pathogens and characterize their serologic and pathologic effects in porcine circovirus type 2 (PCV2)-infected pigs in relation to pig age and type of swine production system.

Design—Cross-sectional study.

Animals—583 conventionally reared pigs.

Procedures—3- (n = 157), 9- (149), 16- (152), and 24-week-old (125) pigs from 41 different 1-, 2-, and 3-site production systems (5 pigs/age group/farm) were euthanized and necropsied. Pigs with and without PCV2 infection were identified (via PCR assay); infection with and serologic responses to other pathogens and pathologic changes in various tissues (including lungs) were assessed. Logistic regression models were constructed for effects overall and within each age group and type of production system.

Results—Compared with PCV2-negative pigs, PCV2-positive pigs were more likely to have swine influenza virus (SIV) type A and Mycoplasma hyopneumoniae infections and sample-to-positive (S:P) ratios for SIV H1N1 from 0.50 to 0.99; also, PCV2-positive pigs had higher serum anti-porcine reproductive and respiratory syndrome virus (PRRSV) antibody titers and more severe lung tissue damage. Infection with SIV (but lower SIV H1N1 S:P ratio) was more likely in 3-week-old PCV2-positive pigs and evidence of systemic disease was greater in 16-week-old PCV2-positive pigs than in their PCV2-negative counterparts. By site type, associations of coinfections and disease effects between PCV2-positive and -negative pigs were greatest in 3-site production systems.

Conclusions and Clinical Relevance—In PCV2-positive pigs, coinfections with SIV, M hyopneumoniae, and PRRSV are important, having the greatest effect in the early to late nursery phase and in 3-site production systems.

Full access
in Journal of the American Veterinary Medical Association