Improving in vitro maturation and pregnancy outcome in cattle using a novel oocyte shipping and maturation system not requiring a CO2 gas phase.

The present work evaluated the benefit of a novel shipping and maturation medium (SMM) not requiring a CO2 gas for maturation and subsequent embryonic development of slaughterhouse and ovum pickup (OPU) bovine cumulus-oocyte complexes (COCs). Four experiments were conducted. In experiment 1, COCs were maturated for 18 hours in SMM and then incubated for 6 hours in, or 24 hours in a conventional system (control). Experiment 2 compared maturation for 24 hours in SMM versus 24 hours in the control. Experiment 3 compared three different incubation temperatures (37 °C, 38 °C, and 38.5 °C) for COCs maturation in SMM. In experiment 4, COCs obtained from 166 OPU sessions (representing two dairy and two beef breeds) in two locations (Wisconsin and California) were matured in SMM or control and evaluated relative to embryo production and pregnancy rates. Frozen semen was used for all experiments. The results for experiment 1 showed that the blastocyst rate and total embryo production rate (TE, Day-7 morulae plus all blastocysts) were higher for SMM than those in the control. However, no differences were observed for cleavage rate or blastocyst stage. In experiment 2, the blastocyst rate and TE were higher for SMM than those in the control; however, there was no difference for cleavage rate, total cell number, blastocyst stage. In experiment 3, the cleavage rate was similar, but the blastocyst rate and TE were greater for 38.5 °C than those for 38.0 °C and 37.5 °C. For experiment 4, Wisconsin OPU-derived COCs had a greater cleavage rate, blastocyst rate, TE, and blastocyst stage for SMM versus control. There were no breed effects. For the California trial, OPU-derived COCs matured in SMM had similar cleavage and pregnancy rates at Day 35 but greater blastocyst rates and transferred embryos per session than the control, which resulted in 2.2 more pregnancies per OPU session. Holstein COCs had superior embryonic development but similar pregnancy compared with Jersey. We conclude that COCs matured in SMM had greater oocyte competence than the control. Also, maturation at 38.5 °C in SMM was optimal for embryonic development. In summary, SMM resulted in greater embryonic development, similar pregnancy rates, but higher pregnancies per OPU session than the conventional maturation system.

Progesterone production in mares and echographic evaluation of the corpora lutea formed after follicular aspiration.

Ultrasound-guided follicular aspiration was performed in 26 Criollo crossbred mares, followed by the evaluation of ultrasonographic images of the Corpus luteum (CL) that was formed after puncture of follicles of different diameters (Group 25-29 mm; Group 30-35 mm and Group >35 mm). Serum progesterone (P(4) ) concentrations were measured to determine CL function. The size of the CL was measured and the CL was classified based on the following echoscore: 1- anechoic tissue; 2- poorly defined luteal structure with low echogenicity; 3- echogenicity analogous to a luteal structure. The proportion of aspirated follicles that formed a functional CL (based on P(4) concentration) 8 days after aspiration was 57.1% (4/7; CL size 25-29 mm), 75.0% (6/8; CL size 30-35 mm) and 72.7% (8/11; CL size >35 mm), respectively (p > 0.05). The echographic scores of aspirated follicles (indicating the presence or absence of a CL) were consistent with serum P(4) concentrations (p < 0.0001). Of 26 aspirations, 18 resulted in luteal function confirmed by increased progesterone concentrations ([P(4) ] > 1.0 ng/ml); 17 of these mares (94.4%) had an echoscore (2-3) compatible with luteinization (p = 0.0372). Eight days after aspiration, serum [P(4) ] > 2.0 ng/ml was associated with high (p = 0.0056) CL echoscore (3) in 15 of 17 mares (88.2%). The echoscore used in this study was valuable as a screening test to detect the presence of a functional CL after aspiration. An echoscore of 3 served as a practical and efficient method to confirm luteinization.

Luteal function induced by transvaginal ultrasonic-guided follicular aspiration in mares.

Ultrasonic-guided transvaginal follicle aspiration was performed in 58 crossbreed mares in order to determine whether aspiration of various dominant follicle diameters resulted in luteal tissue capable of producing progesterone (P(4)). The mares were randomly assigned to three groups according to follicular diameter (25-29 mm; 30-35 mm and >35 mm). Mares that had ovulations naturally served as controls. The serum progesterone (P(4)) concentrations in the aspirated mares were greater (P < 0.0001; r(2) = 0.6687; CV = 21.52) in mares with natural ovulation compared to mares with aspirated follicles regardless of groups. Serum P(4) concentration in aspired mares with follicular diameter of 25-29 mm declined 0.365 ng/ml/day (P = 0.0065) from the day of aspiration (D0) up to D8. In mares with follicle diameter of 30-35 mm, serum P(4) concentration increased (0.258 ng/ml/day; P = 0.001), as well as in the mares with follicles >35 mm diameter (0.481 ng/ml/day; P < 0.0001), and in mares with natural ovulation (1.236 ng/ml/day; P < 0.0001). Out of the 25 mares with follicular aspirations that formed Corpora hemorragica (P(4) >1 ng/ml), 23 (92%) had greater (>2 ng/ml) serum P(4) concentrations on Day 8 after aspiration. Of these 23 mares, 75% were in the 25-29 mm group, 9/10 (90%) in the 30-35 mm group, and 11/11 (100%) of the mares in the >35 mm follicular diameter group had luteinization (P(4) >2 ng/ml). These results suggest that a functional Corpus luteum can be induced in mares using follicular aspiration and that a minimum 35 mm follicular diameter is needed to reach a progesterone serum concentration compatible with that of a Corpus luteum produced by natural ovulation.

Detection and identification of plasma progesterone metabolites in the female Florida manatee (Trichechus manatus latirostris) using GC/MS/MS.

Florida manatees (Trichechus manatus latirostris) have relatively low peripheral concentrations of progesterone (P4). The objective of this study was to determine if these relatively low P4 concentrations are associated with a high ratio of progestin metabolites and to document metabolite concentrations from individual blood samples obtained from manatees during diestrus or pregnancy. Metabolites known to exist in elephants-terrestrial manatee relatives-were targeted. These included 5alpha-reduced progestins (5alpha-pregnane-3,20-dione [5alpha-DHP] and 3alpha-hydroxy-5alpha-pregnan-20-one [5alpha-P3-OH]) and 17alpha-hydroxyprogesterone (17alpha-OHP), which occurs in Asian elephants. An additional, inactive metabolite, 20alpha-hydroxyprogesterone (20alpha-OHP), indicative of P4 overproduction, was also targeted. Progesterone itself was the predominant progestin detected in pregnant and nonpregnant manatee plasma (n = 10) using gas chromatography-mass spectrometry with tandem quadrupole detectors (GC/MS/MS). Progesterone concentrations in pregnant females varied from early (moderate to high) through mid and late (low) pregnancy. Progesterone concentrations ranged from low to high in nonpregnant, nonlactating females. The most commonly detected metabolite was 5alpha-P3-OH (n = 7), which occurred in pregnant (lower limit of detection [LLOD] to high) and nonpregnant (trace to high) females. The 5alpha-DHP metabolite was also detected in pregnant (LLOD to moderate) and nonpregnant (low) females. The 17alpha-OHP metabolite was not detected in any tested female. The 20alpha-OHP metabolite was detected in one nonpregnant, nonlactating, captive female (LLOD). Metabolites were most prevalent during early pregnancy, concurrent with maximum P4 concentrations. Based on their concentrations in peripheral circulation, we inferred that these metabolites may have, opposite to elephants, a limited physiologic role during luteal, pregnant, and nonpregnant phases in the manatee.

Validation of a serum immunoassay to measure progesterone and diagnose pregnancy in the West Indian manatee (Trichechus manatus).

The objective was to validate a high-sensitivity chemiluminescent assay of serum progesterone concentrations for pregnancy diagnosis in manatees. Assay analytical sensitivity was 0.1 ng/mL, with mean intra- and inter-assay coefficients of variation of 9.7 and 9.2%, respectively, and accuracy had a mean adjusted R(2) of 0.98. Methods comparison (relative to Siemen's Coat-A-Count RIA) demonstrated r=0.98, Deming regression slope of 0.95, and an intercept of 0.01. Based on ROC analysis, a progesterone concentration >or=0.4 ng/mL was indicative of pregnancy. Assay results were not significantly altered by two freeze-thaw cycles of samples. Characteristic progesterone concentrations during pregnancy were Months 1-4 (1.7-4.7 ng/mL), 5-8 ( approximately 1.0 ng/mL), and 10 and 11 (0.3-0.5 ng/mL), whereas two late-pregnant females with impending abortion had progesterone concentrations of 0.1 ng/mL. Among pregnant females, maximum progesterone concentrations occurred in autumn (3.9+/-1.8 ng/mL), and were greater during all seasons than concentrations in non-pregnant females (0.1-0.2 ng/mL). Progesterone concentrations were also significantly higher in pregnant females than in non-pregnant females and males. This highly sensitive, specific, and diagnostic assay will be valuable for monitoring pregnancy and abortion in manatees.

Comparisons of estradiol, LH and FSH patterns in pregnant and nonpregnant beagle bitches.

To characterize plasma estradiol, LH and FSH patterns of secretion during the bitch estrous cycle, blood samples were obtained daily from 15 days before until 135 days after the LH surge in 10 pregnant and 10 nonpregnant beagle bitches. After an initial increase between days 15 and 10 and an expected proestrous peak, estradiol concentrations increased again from days 9-12 (corresponding to cytological metestrus) from basal values observed around day 9 after the LH surge, and remained significantly elevated throughout the luteal phase both in pregnant and nonpregnant animals. Concomitantly with the end of the luteal phase, plasma concentrations of estradiol returned to basal values in both groups. During the mid- to late-luteal phase, mean basal LH secretion was significantly elevated throughout in the pregnant relative to the nonpregnant animals. However, in nonpregnant animals, pulsatility was increased and peaks of higher amplitude were observed. The plasma FSH profiles, determined by a specific homologous RIA, differed significantly between pregnant and nonpregnant bitches during the last two-thirds of the luteal phase with a mean FSH level more elevated during pregnancy. The FSH level then decreased around parturition and low concentrations during lactation period were observed. The FSH concentrations remained steady in nonpregnant luteal phases from early luteal phase through mid-anestrus. The differences in pregnant and nonpregnant LH and FSH concentrations suggest pregnancy differences in regulation of the corpus luteum. Finally, the elevated estradiol concentrations observed during the luteal phase of both pregnant and nonpregnant animals suggest that an ovarian production of estrogens may be involved in overall corpus luteum regulation in dogs as in other species.

Suppression of the oestrous responses of bitches to the GnRH analogue deslorelin by progestin.

Studies were undertaken in Australia and Belgium to determine whether the initial pro-oestrous-oestrous responses of anoestrous bitches to treatment with deslorelin administered in a s.c. implant were inhibited by progestin treatment. Thirty-nine bitches of mixed breeding were treated daily with 2 mg megestrol acetate kg-1 body weight for 21 (group 1, n = 5) or 14 days (group 2, n = 10), or with 1 mg megestrol acetate kg-1 body weight for 14 days (group 3, n = 10). A deslorelin (6 mg) implant was placed s.c. on day 14 (group 1) or day 7 (groups 2 and 3) of treatment. Bitches not treated with progestin also received a deslorelin implant (group 4, n = 9) or were untreated controls (group 5, n = 9). Signs of pro-oestrus-oestrus were not observed in bitches in groups 1, 2 and 5, but were observed in bitches in groups 3 (4/10) and 4 (9/9). Four bitches in group 4 were mated, two of which became pregnant. The pregnancies failed at about day 40 of gestation and were associated with low plasma progesterone concentrations. Treatment with progestin inhibited the pro-oestrous-oestrous responses of bitches to deslorelin.

Time-related changes in canine luteal regulation: in vivo effects of LH on progesterone and prolactin during pregnancy.

The role of LH in luteal function in pregnant dogs was investigated at two different periods during pregnancy: (i) the transitional period from apparent total independence of the corpus luteum to relative hormonal dependence (days 20-35); and (ii) the period of full hormonal dependence (days 35-40). At both periods, LH neutralization, LH inhibition and LH administration studies were conducted. At both periods LH immunoneutralization had no significant effect on the secretion pattern of progesterone or prolactin. GnRH antagonist treatment (Nal-Glu) decreased plasma LH below the detection limit in all treatment periods. Nal-Glu had no effect on prolactin. When GnRH antagonist osmotic pumps were implanted, a transient decrease in plasma progesterone concentrations occurred on days 21-22 but not during the remaining implantation period. When GnRH antagonist was injected, plasma progesterone temporarily decreased (24 h) after the beginning of treatment starting on day 20, but decreased for 5 days when the treatment started on day 35. When purified pig LH was injected i.v. twice a day for 2 consecutive days either from day 30 or from day 40, plasma progesterone concentrations remained constant during treatment. However, on days 40 and 41, an increase in prolactin was observed. These results indicate that LH immunoneutralization may not impair corpus luteum function. In addition, GnRH antagonist induces dose- and time-dependent effects. Only high doses resulted in a decrease in progesterone, the duration of which increased as pregnancy progressed. Continuous GnRH antagonist administration, even when associated with complete LH inhibition, was not associated with detectable effects on progesterone. Finally, LH administration does not stimulate progesterone but may modify prolactin in the last third of pregnancy. Other studies indicated a corpus luteum prolactin dependency. The present study indicates that, in pregnant bitches, LH may not be necessary to sustain progesterone synthesis but that its role may vary in a time-dependent manner.

Comparisons of different combinations of analogues of PGF2 alpha and dopamine agonists for the termination of pregnancy in dogs.

Groups of five pregnant bitches were treated to terminate the pregnancy with four combinations of drugs, starting 28 days after the estimated surge of luteinising hormone (LH), 22 to 28 days after the first mating. The treatments were: cabergoline administered orally for 10 days at a dose of 5 micrograms/kg and a single subcutaneous injection of 2.5 micrograms/kg cloprostenol at the start of the treatment; the same dose of cabergoline plus two doses of 1 microgram/kg cloprostenol administered on days 28 and 32 after the LH surge; bromocryptine administered orally at a dose of 30 micrograms/kg three times a day for 10 days plus a single dose of 2.5 micrograms/kg cloprostenol; the same dose of bromocryptine plus two doses of 1 microgram/kg cloprostenol; and a group of five pregnant bitches was left untreated. The pregnancies were terminated in all but one of the treated bitches, in each case by resorption of the fetuses. There were few side effects in the bitches treated with two doses of 1 microgram/kg cloprostenol, and were present but acceptable in those treated with one dose of 2.5 micrograms/kg. Plasma progesterone concentrations decreased to less than 1 ng/ml within 72 hours of the start of treatment and remained low except in the bitch in which pregnancy was not terminated. In the five untreated bitches, plasma progesterone remained high and they whelped normally. In the treated groups, the intervals between successive displays of oestrus were reduced by approximately 70 days in comparison with previous cycles or with the control group, but the fertility of the dogs was not affected adversely.

Effect of stage of anestrus on the induction of estrus by the dopamine agonist cabergoline in dogs.

Beagle bitches were administered the dopamine D2 receptor agonist cabergoline in 3 groups of 5 animals each, starting on known days of the estrous cycle. Cabergoline treatment was started in either early anestrus (Days 93 to 108), mid-anestrus (Days 123 to 156), or late anestrus (Days 161 to 192) at doses of 5 ug/kg/d, per os, and was continued until the confirmation of induced proestrus or for 40 d. Reproductive parameters were compared with those in 5 control anestrous bitches (Days 90 to 150). In control bitches, the mean (+/- SEM) interval to the next proestrus (73+/-11 d) resulted in an interestrus interval (192+/-9 d) similar to that of the previous cycles (196+/-11 d). In 14 of the 15 cabergoline-treated bitches, the next proestrus occurred within 4 to 30 d, was premature in early and mid-anestrous bitches and developed with low variability within groups. The resulting intervals to proestrus in bitches treated with cabergoline in early anestrus (20+/-2 d), mid-anestrus (14+/-3 d) and late anestrus (6+/-1 d) resulted in interestrus intervals in those groups of 131+/-5, 166+/-7 and 196+/-2 d, respectively. In response to treatment, interestrus intervals were reduced (P<0.05) and more synchronous (P<0.05) in early and mid-anestrus bitches, and were more synchronous (P<0.05) in late-anestrous bitches compared with those of control bitches or those of the previous cycle. Periovulatory estradiol and progesterone profiles of induced cycles in treated bitches were similar to those of spontaneous cycles in control bitches. Four of 5 control bitches and 12 of the 14 responding cabergoline-treated bitches became pregnant and produced normal litters. Plasma prolactin concentrations at Days 2 and 5 of treatment (0.3+/-0.1 ng/mL) and at the onset of proestrus shortly before the end of treatment (0.4+/-0.1 ng/mL) were lower (P<0.05) than those present in anestrus prior to treatment (1.7+/-0.6 ng/mL) or in control bitches. Prolactin was also low at the onset of proestrus in control bitches (0.5+/-0.2 ng/mL). The results demonstrate that prolactin-lowering doses of the dopamine agonist cabergoline can terminate the normal obligate anestrus in dogs, and that the effect occurs more slowly in early anestrus than in mid or late anestrus.

Hemodynamic effects of medetomidine in the dog: a dose titration study.

OBJECTIVE: To characterize the hemodynamic effects of medetomidine administered intravenously at doses ranging from 1 to 20 microg/kg, and to determine whether these effects are dose dependent. STUDY DESIGN: Prospective randomized multidose trial. ANIMALS: Twenty-five clinically normal male beagles (5 groups of 5), aged 1 to 4 years and weighing 13.5 +/- 1.7 kg. METHODS: Medetomidine, at a dose of 1, 2, 5, 10, or 20 microg/kg, was administered intravenously at time 0. Heart rate, arterial pressure, central venous pressure, mean pulmonary arterial pressure, pulmonary capillary wedge pressure, body temperature, cardiac output, and packed cell volume were measured immediately before and at selected times after medetomidine administration (3, 7, 10, 20, 30, 40, 50, and 60 minutes in all groups, at 90 minutes for the 10 and 20 microg/kg groups, and at 120 minutes for the highest dose). Cardiac index, stroke index, rate-pressure product, systemic vascular resistance index, pulmonary vascular resistance index, and left and right ventricular stroke work indices were calculated. The degree of sedation was subjectively scored by an observer who was blinded to the treatment used. RESULTS: Heart rate, rate-pressure product, cardiac index, and left and right ventricular stroke work indices decreased below baseline values. Central venous pressure and systemic vascular resistance index increased above baseline measurements. Except in the 2 microg/kg group, after an initial and short lasting increase, a prolonged decrease in arterial pressure was observed. CONCLUSIONS: Hemodynamic changes were observed with the intravenous (IV) administration of medetomidine, at any dose. However, the two lowest doses (1 and 2 microg/kg) produced less cardiovascular depression. CLINICAL RELEVANCE: Medetomidine is an alpha-2 adrenoceptor agonist widely used in dogs, producing sedation, analgesia and cardiovascular depression. When using IV medetomidine, a reduction of the recommended dosage (ie, +/-30 to 40 microg/kg) by up to 6 times did not significantly influence the cardiovascular effects.

In vivo investigation of luteal function in dogs: effects of cabergoline, a dopamine agonist, and prolactin on progesterone secretion during mid-pregnancy and -diestrus.

The role of prolactin on luteal function in dogs was investigated in vivo. The function of prolactin in mid-luteal phase was compared in pregnant and nonpregnant dogs. A dopamine agonist, cabergoline, known for its prolactin secretion inhibitory effects, was injected subcutaneously at a dose of 5 micrograms/kg body weight in five pregnant and five nonpregnant Beagle bitches. Mean plasma prolactin and progesterone were dramatically suppressed for 4 to 5 days after injection in both groups when compared with control pregnant and non-pregnant animals, whereas no effect on luteinizing hormone (LH) secretion was observed. The decline in plasma progesterone occurred after that in prolactin, suggesting plasma progesterone was impaired by inhibition of prolactin secretion. These results confirm the luteotropic importance of prolactin in pregnant bitches, and also demonstrate its importance in luteal phase of the nonpregnant dog. Second, to demonstrate that the effects of cabergoline were mediated by prolactin inhibition and not by a direct action on the corpus luteum, concomitant administration on Day 30 of cabergoline and prolactin (375 micrograms i.v. twice daily on Days 30 and 31) or cabergoline and LH (750 micrograms i.v. twice daily on Days 30 and 31) was affected in two groups of five pregnant animals each. Results showed that only prolactin was able to reverse the negative effects of cabergoline on circulating progesterone. This confirms the indirect mode of action of the dopamine agonist, cabergoline on corpus luteum function. Third, further investigation on the precise luteotropic role of prolactin was made by IV injection of 375 micrograms pure canine prolactin twice daily in five pregnant bitches on Days 30 and 31, and in five pregnant bitches on Days 40 and 41. No direct stimulatory effect of prolactin on plasma progesterone secretion occurred. Nor was there a noticeable effect on plasma LH secretion. These results suggest that prolactin is unable to directly stimulate progesterone secretion by the corpus luteum of pregnancy. The results of this study suggest that prolactin is an essential luteotropin in the dog from mid-luteal phase in both pregnant and nonpregnant animals. However, it appears to act by sustaining corpus luteum lifespan and function rather than by direct stimulatory effects on progesterone secretion.

Effect of finasteride (Proscar MSD) on seminal composition, prostate function and fertility in male dogs.

This study reports the long-term effects and reversibility of the administration of Finasteride, a 5 alpha-reductase inhibitor, on the prostate, prostatic fluid composition and volume, sperm output and characteristic, and fertility of adult beagle dogs treated for 21 weeks at a dose of 1 mg kg-1 body weight. Finasteride was not associated with any side effects. After 5 to 15 weeks of treatment, it induced a marked decrease in the size of the prostate and a fall in its secretions and in the production of spermatozoa. Sperm concentration increased and was inversely correlated with the decrease in the volume of prostatic secretions. At maximum effect, the calculated prostate volume was reduced to 30% of the initial value, and together with the reduced prostatic secretion, no ejaculate could be collected despite normal behaviour. These effects were reversible in 6 to 8 weeks after the cessation of treatment. Matings at 20 to 22 weeks after the start of treatment were fertile, demonstrating the absence of long-term effects of this treatment on male fertility. As fertility was not impaired and prostatic benign hyperplasia successfully regressed. Finasteride treatment in this preliminary study appears to be an interesting alternative therapy in valuable breeding dogs with benign prostatic hyperplasia.

Secretion patterns of plasma prolactin and progesterone in pregnant compared with nonpregnant dioestrous beagle bitches.

The plasma concentration of prolactin has been poorly described in dogs. Published data are still controversial. In this study, plasma prolactin and progesterone concentration patterns were determined in groups of ten pregnant and ten nonpregnant beagle bitches. Blood samples were collected daily between 08:30 h and 09:30 h from day-15 to day 135 after the LH peak. Plasma concentrations of prolactin increased from day 25 after the LH surge in the pregnant animals to a peak value on day 65, the mean day of parturition. After parturition, they fell for 24-48 h, and then increased again and remained high during lactation. Variations observed in lactation were great and probably due to suckling. In the nonpregnant bitches, plasma prolactin remained constant throughout the observation period. An increase was observed at about day 70, but was not significant. Plasma prolactin patterns differed greatly, depending on whether the bitch was pregnant or not, even though the luteal phases had the same apparent duration in both cases. No significant difference was observed between progesterone concentrations of pregnant and nonpregnant bitches, even if plasma progesterone was higher from day 40 in pregnant animals. The luteal period ended abruptly in pregnant bitches on day 64, that is 1 day before parturition, and was more progressive in nonpregnant animals. Significantly higher prolactin secretion in pregnancy suggests specific luteal regulation, whereas the lower concentrations observed in nonpregnant dioestrous bitches make its role in nonpregnant luteal phases questionable.

Practical use of a combination of a dopamine agonist and a synthetic prostaglandin analogue to terminate unwanted pregnancy in dogs.

The combination of a dopamine agonist, cabergoline, and a synthetic analogue of prostaglandin F2 alpha, cloprostenol, was used to induce termination of pregnancy from day 25 after the estimated luteinising hormone surge (day 27 +/- 4 after the first mating) in five mature beagle bitches. Cabergoline was administered orally at 5 micrograms/kg daily and cloprostenol was injected subcutaneously at 1 microgram/kg every other day. Treatment efficacy, in terms of pregnancy termination, was 100 per cent. Termination always took place by resorption of the fetuses. No side effects were observed. A mean of three injections of cloprostenol and nine days of cabergoline treatment was necessary to eliminate all signs of gestation. Termination was in each case accompanied by a decline in plasma progesterone (to less than 1 ng/ml) within 72 hours of initiation of treatment. In a control group of five, untreated bitches, plasma progesterone remained elevated throughout a corresponding period (from day 25 to day 50 after the estimated luteinising hormone surge). In the treated group, interoestrous intervals (98 +/- 41 days) were reduced, compared with previous cycles (194 +/- 9 days) or with those of the control animals (205 +/- 37 days). It is concluded that the combination treatment with the anti-prolactinic agent, cabergoline (5 micrograms/kg/day), and the synthetic prostaglandin F2 alpha, cloprostenol (1 microgram/kg/two days), is an easy, practical, reliable and safe method to terminate pregnancy near and before mid-gestation in dogs.

Comparisons of intravaginal and intrauterine insemination of bitches with fresh or frozen semen.

To compare the importance of the route of insemination when using fresh or frozen semen, six groups of five bitches were inseminated either into the uterus (groups 4, 5 and 6) or the vagina (groups 1, 2 and 3) with fresh (groups 1 and 4) or frozen semen (groups 2, 3, 5 and 6). The fresh semen was collected when needed from the same dog. The frozen semen used in groups 2 and 5 was obtained from seven dogs on the same day, and pooled and processed simultaneously so that the groups were inseminated with exactly the same semen. The frozen semen used in groups 3 and 6 was obtained from different dogs and processed independently to evaluate not only the effect of the route of insemination but also the potential effect of the dog. The mean concentration of the fresh semen was 310 x 10(6) spermatozoa/ml, its motility was greater than 80 per cent and the percentage of normal live spermatozoa was 80 to 92 per cent. The mean spermatozoal concentration of the frozen semen was 200 x 10(6) spermatozoa/ml, its motility was greater than 60 per cent and the percentage of normal live spermatozoa was 80 per cent. In all the groups there were fewer than 15 per cent abnormal spermatozoa. The animals inseminated with fresh semen received significantly more spermatozoa than the others. The bitches were inseminated twice, three and five days after the estimated peak of luteinising hormone, with a total volume of 5 ml for the vaginal inseminations and 2 ml for the intrauterine inseminations. Sixty per cent of the bitches inseminated with frozen semen and 100 per cent of the bitches inseminated with fresh semen became pregnant, irrespective of the insemination technique used.

Cervical opening in relation to progesterone and oestradiol during heat in beagle bitches.

The relationship between hormonal profile and cervical opening and closure was analysed during heat in seven bitches. The bitches were studied each day from the beginning of pro-oestrus until 5 days after cytological metoestrus. Vaginography was performed using a radiopaque contrast dye injected through an insemination probe and blood samples were collected daily. The opening of the cervix was observed, in pro-oestrus, 2.6 +/- 2.8 days before the LH peak. The progesterone and oestradiol values at that time were 2.0 +/- 2.4 nmol l-1 and 171.1 +/- 133.1 pmol l-1, respectively. The opening of the cervix was observed concurrent with the day of the maximal value of the oestradiol:progesterone ratio, just before the decline of oestrogen preceding the LH peak. Differences between the oestradiol:progesterone ratio the day before, the day of and the day after opening were significant. The closure of the cervix occurred 6.7 +/- 1.4 days after the LH peak and 2.6 +/- 1 days before the first sign of cytological metoestrus. The progesterone and oestradiol concentrations at that time were 68.9 +/- 15.4 nmol l-1 and 16 +/- 10.3 pmol l-1, respectively. All bitches were in cytological oestrus when the cervix closed. These data indicate that there is a relationship between hormonal profile and cervical opening and that breeding success may also be temporarily limited, not only by oestrous behaviour, but also by cervical closure. In the beagle colony studied, a blood concentration of 60 nmol progesterone l-1 would give a good indication that no success will follow artificial vaginal insemination or natural mating.

Regulation of progesterone during pregnancy in the cat: studies on the roles of corpora lutea, placenta and prolactin secretion.

The regulation of progesterone secretion and release by the corpus luteum and/or by the placenta in cats during pregnancy has been poorly studied and the relative roles of the corpus luteum and the placenta in the release of progesterone into the plasma is not well defined. It is generally assumed that after 40-45 days of pregnancy, circulating progesterone is mainly produced by the placenta and that after 45-50 days the corpus luteum is no longer necessary to maintain pregnancy, even if remnants of corpora lutea are detected in the ovaries during the following interoestrous period. In this study, the relative roles of the placenta and ovary in progesterone production after 30 days of pregnancy have been analysed in an attempt to define the role of progesterone in pregnant cats. Different experiments involved (1) analysis of the effects of an ovariectomy performed at 30 days of pregnancy, and of megestrol acetate supplementation on plasma progesterone during the second half of pregnancy, (2) analysis of the effects of an ovariectomy performed at 45 days on plasma progesterone production and on pregnancy and (3) analysis of the effects of an antiprolactin agent (cabergoline) at days 30 and 40 of pregnancy on progesterone secretion and pregnancy. These results were all compared with the normal plasma progesterone profiles during (a) pseudopregnancy and (b) pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)

Laparoscopic vasectomy in the male dog.

A laparoscopy technique was employed to sterilize five adult male dogs. The animals were sedated with a combination of medetomidine and buprenorphine intravenously and a fragment of the ductus deferens, about 2 cm in length, was removed after having been cauterized and cut, using atraumatic forceps and a pair of scissors connected to an electrocautery unit. The procedure was easy, quick and safe. The animals had no complications after the intervention and made a good recovery.