Reproductive performance of commercial broodmares after induction of ovulation with HCG or Ovuplant™ (deslorelin)

Soon after Ovuplant™, the sustained-release implant containing the gonadotropin releasing hormone (GnRH) agonist deslorelin, was approved for commercial use in the United States for induction of ovulation in mares, anecdotal field observations were reported that some Ovuplant™—treated mares that did not become pregnant experienced a delayed return to estrus and prolonged inter-ovulatory interval. Although those observations have been subsequently confirmed, further data on how mares respond to Ovuplant™ compared to human chorionic gonadotropin (hCG) during the post-treatment period is needed. The objective of this study was to further evaluate the clinical use of Ovuplant™ by comparing the reproductive performance of commercial broodmares treated with hCG or Ovuplant™. This retrospective study was completed by examining the 1999 reproductive records of 106 mares treated with hCG during 134 estrous cycles and 117 mares treated with Ovuplant™ during 151 estrous cycles. There were no differences (P > 0.10) in follicle size at the time of treatment (39.4 ± 0.5 vs. 38.9 ± 0.5 mm), interval from treatment to ovulation (2.2 ± 0.1 vs. 2.2 ± 0.1 days), proportion of mares that failed to ovulate after treatment (3.0 vs. 4.6 %), or per-cycle pregnancy rate (47.7 vs. 51.4 %) between hCG-and Ovuplant™-treated mares, respectively. The interval from ovulation to return to estrus (25.8 ± 1.3 vs. 15.5 ± 0.6 days) and the inter-ovulatory interval (30.4 ± 1.5 vs. 20.8 ± 0.6 days) were longer (P<0.001) for Ovuplant™-compared to hCG-treated mares, and the proportion of non-pregnant mares that failed to return to estrus within 30 days after ovulation (31.4 vs. 1.5 %) was higher (P<0.001) for Ovuplant™-compared to hCG-treated mares, respectively. For Ovuplant™—treated mares, follicle size at the time of treatment tended (P<0.1) to be smaller for mares that failed to return to estrus within 30 days compared to mares that returned to estrus within 30 days (37.1 ± 1.1 vs. 40.1 ± 0.6 mm, respectively). Also, the average date of ovulation during the calendar year was later (P < 0.05) for Ovuplant™—treated mares that failed to return to estrus within 30 days compared to those that returned to estrus within 30 days (May 15 ± 4 vs. April 30 ± 4 days). The results of this study confirm previous reports that although the ovulatory response and fertility were not different for hCG- and Ovuplant™—treated mares, mares treated with Ovuplant™ that did not become pregnant had a significantly delayed return to estrus and prolonged inter-ovulatory interval. Based on recently published information, it appears this effect is due to Ovuplant™—induced down-regulation of the pituitary gland, which suppresses subsequent follicular growth and development. This study also demonstrated that follicle size and/or season may influence the probability that Ovuplant™—treated mares would experience a delayed return to estrus/ovulation; therefore, further work is needed to determine whether these or other factors are related to this specific outcome following Ovuplant™—treatment.     

Comparison of a central and a peripheral (cephalic vein) injection site for the measurement of cardiac output using the lithium-dilution cardiac output technique in anesthetized dogs

The objective of this study was to determine the agreement between cardiac output measured by central (cranial vena cava) versus peripheral (cephalic vein) venous injection of lithium chloride for lithium-dilution cardiac output (LiDCO) determination in the dog. Five dogs (2 males, 3 females), anesthetized with halothane, were used. With each dog, 12 alternating central and peripheral LiDCO measurements were made, resulting in 10 paired comparisons. A total of 50 comparisons were obtained, the cardiac output measurements ranging from 1.11 to 2.76 L/min. The LiDCO measurement from the cephalic vein was similar to that obtained from the recommended central venous site: the difference between the central and cephalic vein determinations for all measurements was 0.098 ± 0.336 L/min (mean ± 2 standard deviations). Linear regression analysis demonstrated a slope of 1.050 (95% confidence interval 0.904 to 1.196) and a y intercept of 0.005 (r = 0.902). Therefore, although the central venous site is recommended by the manufacturer, the cephalic vein can be used instead in the dog, eliminating the need for central venous catheterization and thus reducing time and expense.     

The Cryopreservation of Striped Bass Morone saxatilis Semen

Abstract.— Two experiments were designed to improve upon existing methods for cryopreserving striped bass Morone saxatilis , semen. In the first experiment, two extenders, two cryoprotectant concentrations, and two freezing rates were evaluated on the basis of post-thaw semen motility after 1, 7, and 30 d of storage at −196 C. Semen samples cryopreserved at a freezing rate of −40 C/m resulted in a significantly higher percentage of motile sperm ( P < 0.001) and longer duration of spermatozoa motility ( P < 0.001) than samples cryopreserved at a freezing rate of -30 Chin. Also, the cryoprotectant dimethyl-sulfoxide yielded a significantly higher percentage of motile sperm ( P < 0.001) and longer duration of spermatozoa motility ( P < 0.001) when a 5% concentration was used instead of 7.5%. In the second experiment, the two extenders from Experiment I were re-evaluated and a new extender, which was a modified version of Extender 1, was tested. The samples were cryopreserved at -40 C/min with 5% DMSO and thawed in a 25 C water bath. Spermatozoa motility and fertilization ability were evaluated, and semen cryopreserved in Extender 2 yielded the longest duration of spermatozoa motility ( P < 0.001). the highest percentage of motile sperm ( P < 0.001). and the highest percentage of fertilized eggs ( P < 0.002) in comparison to Extenders I and 3.     

Bog asphodel (Narthecium ossifragum) poisoning in cattle.

Fifteen cows among a herd of 50 suckler cows and calves rapidly lost body condition and became dull and anorexic after grazing pasture containing bog asphodel (Narthecium ossifragum) during the summer of 1989. The affected cows had evidence of kidney damage characterised by elevated plasma urea and creatinine concentrations. Eleven cows died and diffuse renal tubular necrosis was present in three cows which were examined post mortem. Similar renal lesions were reproduced experimentally by feeding bog asphodel to a healthy calf.     

Embryo transfers from mares in athletic competition

The objective of this project was to produce multiple pregnant recipient mares during one year from each of four mares which were in athletic training and competition. Twenty-six embryos were recovered from the four mares in 38 collection attempts. Each embryo was surgically transferred to one of 20 recipient mares. Nine of 10 recipient mares which were transferred to on one occasion were detected pregnant at the one week post transfer pregnancy examination and six of eight mares which were transferred to on two occasions were detected pregnant at one of the one-week post transfer pregnancy examinations. Three of the 15 pregnant recipient mares lost their pregnancies by day 150. The 12 resulting pregnant recipient mares from the four competing donor mares demonstrated that donor mares can remain in athletic competition and at the same time provide viable embryos for embryo transfer.     

Dietary molybdenum as a putative copper antagonist in the horse

Four horses were stabled and fed a diet of hay ad libitum, and 2 kg oats per animal per day, for a month. The basic diet was then supplemented with molybdenum, at a rate of 20 mg/kg dry matter for 4.5 months. For one month of this period the diet was supplemented also with sulphur at a rate of 1.2 g/kg dry matter. Analyses of jugular blood samples, obtained at intervals varying between two and 20 days, showed no evidence of a decline in total plasma copper or of an increased proportion of trichloroacetic acid (TCA) insoluble copper in plasma over this period. In separate studies, two other horses were given 99molybdenum (molybdate, 20 to 28 mg Mo, 4 mCi per animal) per os, initially while being fed the basic diet and later while maintained on the molybdenum supplemented diet. 99Molybdenum appeared rapidly in plasma, but the radioactivity was then quickly cleared (half-life 7 to 10 h). The 99molybdenum present was identified as (99Mo)-molybdate. There was no evidence of the persistent, protein-bound (99Mo)thiomolybdates which appear in ruminants. These studies indicate that increased dietary molybdenum is unlikely to interfere with copper metabolism in horses.