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Biomedical subjects

T F Lock

Publications and source records attributed to T F Lock.

33 records · Page 2Linked to original sources
PubMed1983

The effect of method of GnRH administration and short-term calf removal on ovarian function and reproductive performance in postpartum suckled beef cows administered PGF(2)alpha for estrous synchronization.

The first experiment was a 2 x 2 factorial experiment with calf removal (none or short-term) and method of GnRH administration (intramuscularly in saline or subcutaneously in gelatin capsules) as main effects. The durations of the GnRH-induced LH surges were similar among groups but the LH surges were delayed in the cows that received GnRH subcutaneously in gelatin capsules. Calf removal enhanced the GnRH-induced LH release for cows administered GnRH subcutaneously in a gelatin capsule but not for cows administered GnRH intramuscularly in saline. In the second experiment, 191 postpartum suckled beef cows were administered two injections of prostaglandin F(2)alpha(PGF(2)alpha) 11 days apart. After the second PGF(2)alpha injection, the cows were assigned to a 2 x 2 factorial experiment as in Experiment 1 plus one control group. Short-term calf removal (47 h) began 28 h after the second PGF(2)alpha injection. GnRH was administered 30 h after the time of calf removal. The number of cows that ovulated following the time of the GnRH treatment, the number that had abnormal luteal phases and the first-service pregnancy rates among treatment groups within the anestrous and cyclic cows classifications were not significantly different. However, several effects were detected and are reported.

Journal Article↗
PubMed1982

The effect of short term calf removal in combination with GnRH treatment and the effect of limited nursing on reproductive performance of postpartum suckled beef cows administered PGF2alpha for ovulation control.

Over a two year period, postpartum suckled Hereford and Angus Cows (n=213) were administered two injections of PGF2alpha (25 mg/injection) and divided into three groups. No additional treatments were administered to cows in Group I and calves were allowed to nurse their dams ad libitum. In Group II, calves were removed for 48 hours beginning on the third day following the initial PGF2alpha injection. These cows were given a subcutaneous injection of 250 microg GnRH dissolved in 2% carboxymethylcellulose midway through the 48 hour period. In Group III, calves were allowed to nurse their dams for only one hour per day for the first 7 days after the initial PGF2alpha injection. In year 1, PGF2alpha was administered 14 days apart whereas in year 2, PGF2alpha was administered 11 days apart. Cows were artificially inseminated at 72 and 96 hours after the second injection of PGF2alpha. In year 1, the numbers of cows that conceived to the timed inseminations were similar (P>.10) for the three groups. In year 2, a higher percentage of cows in groups II (P<.10) and III (P<.05) conceived to the timed inseminations than in group I. Other reproductive performance parameters were similar (P>.10) between groups for both years 1 and 2. In summary, limited nursing and short term calf removal in conjunction with GnRH treatment may improve the pregnancy rate in cows administered PGF2alpha for ovulation control.

Journal Article↗
PubMed1982

Xylazine hydrochloride-induced hyperglycemia and hypoinsulinemia in thoroughbred horses.

The effects of intravenous xylazine (1.1 mg/kg) were studied in six thoroughbred horses (five mares and a stallion). Plasma glucose concentration increased to 168% of control at 45 min and decreased to 112% of control at 180 min. Insulin had decreased to 31% of control at 15 min. Thereafter, insulin concentration increased, reaching its highest concentration at 150 min. The mechanism for these changes is not fully understood and further investigation is indicated.

Animals↗
PubMed1982

Anthelmintic efficacy of ivermectin given intramuscularly in horses.

The anthelmintic activity of ivermectin was evaluated in 18 female horses with naturally acquired parasitic infections. Horses were treated once (IM) with vehicle only (n = 6), 200 microgram/kg of body weight (n = 6), and 300 microgram/kg (n = 6). Efficacy of both dosages of ivermectin was greater than 99% against Gasterophilus spp, 100% against Trichostrongylus axei, Habronema muscae, H majus, and Draschia megastoma, 98% to 99% against adult cyathostomes, 86% to 97% against 4th-stage cyathostomes, and 100% against adult large strongyles. Although ivermectin was incomplete in its activity against arterial stages of Strongylus vulgaris, it was effective against microfilariae of Onchocerca spp. Adverse local or systemic reactions were not observed due to treatment with ivermectin.

Animals↗
PubMed1982

Distribution of oxytetracycline in the genital tract of cows.

Pharmacokinetic parameters of the disposition of oxytetracycline (OTC) were investigated in healthy cycling dairy cows after a single IV dose of 22 mg/kg of body weight. The biological half-life of OTC was 6.5 hours. These data were used to predict an IV priming dose and a rate of constant IV infusion of OTC sufficient to approach steady-state equilibrium of the drug between a plasma concentration of approximately 5 microgram/ml and a uterine tissue concentration. After 8 hours' constant IV infusion, the mean plasma concentration of OTC was 4.86 +/- 0.68 microgram/ml and the mean uterine tissue concentration of OTC was 4.50 +/- 0.45 microgram/ml. The mean ratio of plasma-to-uterine tissue OTC concentrations was 1.08. Computer-stimulated IV multiple doses of OTC at 11 mg/kg every 12 hours and 11 mg/kg every 24 hours suggested that the former dosage regimen could provide uterine tissue concentrations greater than 5 microgram/ml during the dosage interval, whereas the latter could provide such concentrations for only the first 12 hours of a 24-hour dosage interval.

Animals↗
PubMed1981

A comparison of intrarectal Doppler and rectal abdominal palpation for pregnancy testing in goats.

Two methods of pregnancy diagnosis--rectal abdominal palpation and the intrarectal Doppler technique--were compared for accuracy in the female goat (does). Three veterinarians were given a short period of instruction as to the use of these methods, after which 38 does were evaluated by both methods by each veterinarian. The percentage of correct determination for pregnant does ranged from 94% to 100% for examiners using the intrarectal Doppler technique and from 94% to 97% for the rectal abdominal palpation. The percentage of correct determinations for nonpregnant does ranged from 25% to 75% for intrarectal Doppler technique and was 75% for rectal abdominal palpation; however, the number of nonpregnant does was small and did not allow a valid conclusion. The results indicated that both methods are reasonably accurate for pregnancy diagnosis in does at 55 days or more after breeding and can be learned with only brief training. However, rectal abdominal palpation appears to be more hazardous with respect to rectal injury and abortion and, therefore, would not be the preferred method.

Animals↗
PubMed1980

Vaccination of pregnant ponies against equine rhinopneumonitis.

Bovine herpesvirus 1247 (one dose) was given subcutaneously to five pregnant pony mares between 227 and 319 days of their gestations. There were no adverse clinical reactions, and the virus was not recovered from nasal swabs collected during a 2-week period after vaccination. Four ponies foaled full-term, live, healthy foals. The foal of the fifth mare (No. 1) was found dead, but on the basis of the pathologic and virologic examinations, the virus was not considered to be the cause of the death. At 3 weeks after vaccination, the pregnant pony mares had a 13- to 250-fold increase in serum antibody titer to equine herpesvirus-1. A virulent-virus challenge exposure of all pony mares at 208 days after vaccination resulted in antibody titers greater than those just before this exposure. Virus was recovered from nasal swabs from vaccinated mares only on postexposure day 1, whereas the one control (nonvaccinated) pony shed virus for at least 3 days after challenge exposure. The immunogenic and the nonabortifacient characteristics of the herpesvirus 1247 in pregnant pony mares indicate that it may be useful to vaccinate horses against equine herpesvirus-1.

Animals↗
PubMed1979

Equine leucoencephalomalacia (ELEM): a study of Fusarium moniliforme as an etiologic agent.

Signs and lesions characteristic of equine leucoencephalomalacia were produced in one of two donkeys given corn cultured with Fusarium moniliforme Sheldon. Gross and histopathologic lesions of the cerebrum included an extensive necrotic cavitation within one cerebral hemisphere, disruption and rarefication of the subcortical white matter, prominent perivascular hemorrhage, and some mononuclear cell perivascular cuffing. Another donkey and three rabbits fed the cultured corn did not develop characteristic signs or lesions of the toxicosis. Chick bioassay studies indicated that the cultured corn which produced the disease did not contain a monovalent salt of moniliformin.

Animals↗