An historical look at embryo transfer.
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Anesthesia↗
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Effect on oestrus and ovulation of exposing creole goats to the male at three times of the year.
The characteristics of the oestrous and ovarian cycles of local goats were studied over 2 years, on 96 females in March, 60 in July and 100 in November. After 3 weeks of separation between sexes, the females with inactive ovaries were identified and harnessed males were introduced. Detection of oestrus was undertaken daily and the date and rate of ovulation were checked at laparoscopies. The proportion of females with non-cyclic ovaries before the mating period varied according to the season and whether the females were nulliparous or suckling. Among the females with inactive ovaries before the mating period, 97% ovulated 2 . 8 days after the introduction of males; 68% of these initial ovulations were accompanied by oestrus and 76% resulted in short luteal phases (5 . 3 days) followed by a second ovulation accompanied by oestrus 89% of the time. The proportions of initial ovulations with oestrus and of initial ovulations followed by a short luteal phase were in linear relationship with the proportion of females with non-cyclic ovaries before the mating period. For the females with cyclic ovaries before the mating period, the distribution of first oestrus during the 8 days after the introduction of males was significantly different from the expected uniform distribution. A possible luteolytic action of teasing was suspected. The fertility of females in all groups was high (greater than 79%). Litter size was not different for non-cyclic and for cyclic females.
Animals↗
Changes in pulsatile LH secretion and the positive and negative feedback actions of oestradiol after administration of a GnRH agonist in the ovariectomized ewe.
Administration of a GnRH agonist (5 micrograms) every 12 h to long-term ovariectomized ewes for 5 or 10 days during the breeding season suppressed mean LH levels from around 6 to 1 ng/ml on Days 1 and 4 after treatment; on Day 1 after treatment LH pulse frequency and amplitude were lower than pretreatment values. On Day 4 after treatment LH pulse frequency was restored to pretreatment levels (1 per h) whereas LH pulse amplitude had only slightly increased from 0.5 to 1 ng/ml, a value 25% of that before treatment. This increase in amplitude was greater the shorter the duration of treatment. Ovariectomized ewes treated with the agonist for 5 days exhibited both negative and positive feedback actions after implantation of a capsule containing oestradiol; however, compared to control ewes treated with oestradiol only, the positive and negative feedback actions of oestradiol were blunted. These results suggest that the recovery of tonic LH concentrations after GnRH agonist-induced suppression is limited primarily by changes in LH pulse amplitude. The results also demonstrate that the feedback actions of oestradiol are attenuated, but not blocked, by GnRH agonist treatment.
Animals↗
Oestrous cycles and the breeding season of the Père David's deer hind (Elaphurus davidianus).
Reproductive cycles were studied in a group of tame Père David's deer hinds. The non-pregnant hind is seasonally polyoestrous and, in animals studied over 2 years, the breeding season began in early August (2 August +/- 3.3 days; s.e.m., N = 9) and ended in mid-December (18 December +/- 5.7 days; N = 8) and early January (6 January +/- 3.2 days; N = 11) in consecutive years. During the anoestrous period, plasma progesterone concentrations were low (0.2 +/- 0.01 ng/ml) or non-detectable. There was a small, transient increase in progesterone values before the onset of the first cycle of the breeding season. In daily samples taken during an oestrous cycle in which hinds were mated by a marked vasectomized stag, progesterone concentrations remained low (less than 0.5 ng/ml) for a period of about 6 days around the time of oestrus, showed a significant increase above oestrous levels by Day 4 (Day 0 = day of oestrus) and then continued to increase for 18 +/- 2.8 days to reach mean maximum luteal levels of 3.5 +/- 0.6 ng/ml. The plasma progesterone profiles from a number of animals indicated that marking of the hinds by the vasectomized stag did not occur at each ovulation during the breeding season and therefore an estimate of the cycle length could not be determined by this method. In the following year, detection of oestrus in 5 hinds was based on behavioural observations made in the absence of the stag. A total of 19 oestrous cycles with a mean length of 19.5 +/- 0.6 days was observed.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Effects of induction of low plasma progesterone concentrations with a progesterone-releasing intravaginal device on follicular turnover and fertility in cattle.
The effects of concentration of progesterone in plasma on development and fertility of the first wave dominant follicle were studied in cattle. To identify a source of exogenous progesterone that would permit extension of the first wave dominant follicle, nonlactating Holstein cows (n = 6) received on day 8 of two successive oestrous cycles an injection of PGF2 alpha (25 mg) and a new (1.9 g of progesterone (Period 1)) or used (approximately 1.2 g of progesterone (Period 2)) CIDR-B device that was removed on day 17. Control cows (n = 6) received a new CIDR-B device on day 8 that was removed on day 17 and a PGF2 alpha injection (25 mg) on day 17. Ultrasonography and collection of blood samples were performed on alternate days throughout the experiment. Plasma concentrations of progesterone and oestradiol were different between treatments (P < 0.0001 and P < 0.05, respectively). The dominant follicle was maintained until day 17 and ovulated upon removal of the intravaginal device in 1 of 6, 6 of 6 and 0 of 6 in new CIDR-B, used CIDR-B and control groups, respectively (P < 0.01). The preovulatory dominant follicles were 14.2 +/- 1.6 mm, 20 +/- 1.3 mm and 10 +/- 1.3 mm, respectively (P < 0.001) on day 17. There were fewer 5-9 mm follicles in cows having a persistent dominant follicle (P < 0.01). The interval to onset of oestrus was negatively correlated with size of the dominant follicle on day 17 (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)
Administration, Intravaginal↗
Natural and artificial methods for inducing the luteal phase in the koala (Phascolarctos cinereus).
An experiment was conducted in which female koalas were mated for different durations of intromission and ejaculation to confirm that the luteal phase of the oestrous cycle in koalas is induced by the physical act of mating. Results showed that induction of a luteal phase in the koala usually required a complete duration of penile thrusting behaviour from the male. It is proposed that induction of a luteal phase in koalas may involve a copuloceptive reflex, triggered by the thrusting of the male's penis into the female's urogenital sinus. Although interrupted mating in koalas may be used to induce a luteal phase in preparation for an artificial insemination programme, this study showed that there is a 12.5% probability that pregnancy will result from semen prematurely emitted by the teaser male. A dose of 250 iu hCG was administered intramuscularly to eight oestrous females to determine whether it was possible to induce a luteal phase artificially. In contrast to control females, which received sterile saline injections, all females injected with hCG showed a significant increase in progestogen concentration above that of basal values, indicating that a luteal phase had been induced successfully.
Animals↗
Delayed effect of low progesterone concentrations on bovine uterine PGF(2alpha) secretion in the subsequent oestrous cycle.
Low progesterone concentrations during the bovine oestrous cycle induce enhanced responsiveness to oxytocin challenge late in the luteal phase of the same cycle. The delayed effect of low progesterone concentrations during one oestrous cycle on uterine PGF(2alpha) secretion after oxytocin challenge on day 15 or 16 of the subsequent cycle was studied by measuring the concentrations of the major PGF(2alpha) metabolite (13,14-dihydro-15-keto PGF(2alpha); PGFM) in plasma. Two experiments were conducted, differing in the type of progesterone treatment and in the shape of the low progesterone concentration curves. In Expt 1, progesterone supplementation with intravaginal progesterone inserts, with or without an active corpus luteum, was used to obtain high, or low and constant plasma progesterone concentrations, respectively. In Expt 2, untreated cows, representing high progesterone treatment, were compared with cows that had low but increasing plasma progesterone concentrations that were achieved by manipulating endogenous progesterone secretion of the corpus luteum. Neither experiment revealed any differences in plasma progesterone concentrations between the high and low progesterone groups in the subsequent oestrous cycle. In both experiments, both groups had similar basal concentrations of PGFM on day 15 (Expt 1) or 16 (Expt 2) of the subsequent oestrous cycle, 18 days after progesterone treatments had ended. In both experiments, the increases in PGFM concentrations in the low progesterone groups after an oxytocin challenge were markedly higher than in the high progesterone groups. These results indicate that low progesterone concentrations during an oestrous cycle have a delayed stimulatory effect on uterine responsiveness to oxytocin during the late luteal phase of the subsequent cycle. This resulting increase in PGF(2alpha) secretion may interfere with luteal maintenance during the early stages of pregnancy.
Animals↗
Estrous cycle characterisation and artificial insemination using frozen-thawed spermatozoa in the bottlenose dolphin (Tursiops truncatus).
The reproductive endocrinology of the bottlenose dolphin, Tursiops truncatus, was characterized to facilitate the development of artificial insemination using cryopreserved spermatozoa. Specific objectives were: (i) to determine the excretory dynamics of urinary luteinizing hormone (LH) and ovarian steroid metabolites during the estrous cycle; (ii) to evaluate the effect of an exogenously administered synthetic progesterone analog (altrenogest) on reproductive hormone excretion; (iii) to correlate follicular growth and ovulation (as determined by transabdominal ultrasound) to urinary LH and ovarian steroid metabolites; (iv) examine the in vivo fertilisation capacity of cryopreserved semen, and (v) to develop an intrauterine insemination technique. Based on urinary endocrine monitoring of natural estrous cycles (2 consecutive cycles) and nine post altrenogest cycles in ten females, estrous cycles were found to be 36 days long and comprised of an 8 day and 19 day follicular and luteal phase, respectively. Peak estrogen conjugates (EC; 5.4+/-3.8 ng/mg creatinine (Cr)) occurred 8 h prior to the LH surge (70.9+/-115.7 ng/mg Cr). The time of ovulation, as determined by ultrasonography, occurred 32.1+/-8.9 h and 24.3+/-7.0 h after the onset of the LH surge and LH peak, respectively. Mean preovulatory follicular diameter and circumference were 2.1+/-0.5 cm and 6.5+/-1.5 cm, respectively. Of the 27 estrous synchronisation attempts, 13 resulted in an ovulatory cycle, with ovulation occurring 21 days post-altrenogest treatment. Intrauterine (4 of 5) and intracornual (1 of 3) inseminations conducted across eight estrous cycles resulted in five pregnancies (63%), one pregnancy resulted from the use of liquid stored semen, whereas four were achieved using cryopreserved semen. These data provide new information on female bottlenose dolphin reproductive physiology, and demonstrate that the combination of endocrine monitoring and serial ultrasonography contributed to successful AI using liquid-stored and cryopreserved semen.
Animals↗
Procedure for successful interspecific embryo transfer from mouflon (Ovis gmelini musimon) to Spanish Merino sheep (Ovis aries).
Embryos from five anesthetized mouflons (Ovis gmelini musimon), superovulated with FSH-o (Ovagen) were transferred into preselected Spanish Merino sheep (Ovis aries). Myorelaxation was complete in four of five donor mouflons. The status of the uterus of potential recipients was evaluated by transrectal ultrasonography, and those ewes with fluid in the uterine horn were rejected. The corpus luteum in each ewe was assessed ultrasonographically the day before surgery. Plasma progesterone levels and the quality of the corpora lutea were the criteria for selection of recipients. Ten embryos were transferred to the five selected Spanish Merino recipients, resulting in four pregnancies and seven live-born lambs, including three sets of twins. This study shows that determination of plasma progesterone levels combined with ultrasonographic assessment of the corpus luteum provides information useful for screening of potential recipients.
Anesthetics, Dissociative↗
Hypothyroidism affects reproductive refractoriness and the seasonal oestrous period in Welsh Mountain ewes.
Welsh Mountain ewes (n = 6) were rendered hypothyroid by daily treatment with methylthiouracil (35 mg/kg), beginning in early August and ending in late February. Plasma thyroxine levels were reduced by mid-September to about 33% of those in untreated ewes (n = 6). The two groups of ewes were held under natural daylengths until 5 October, then on 12 h light: 12 h darkness (12L:12D) until 28 February when the photoperiod was reduced to 8L:16D. The onset of reproductive cyclicity in October was similar in both groups of ewes but the end of the reproductive period occurred later (P less than 0.05) in the hypothyroid ewes (29 January +/- 7 days (S.E.M.] than in the untreated controls (6 January +/- 7 days). As a result, the duration of the seasonal reproductive period was significantly (P less than 0.05) longer in the hypothyroid (122 +/- 9 days) than in the untreated ewes (91 +/- 10 days). The number of oestrous cycles (duration 15.4 and 15.7 days in the hypothyroid and untreated ewes respectively) was 7.0 +/- 0.6 in the hypothyroid ewes and 5.0 +/- 0.5 (P less than 0.05) in the normal ewes. Reducing the photo-period overcame the reproductive refractoriness and anoestrus in both groups, the hypothyroid ewes beginning to cycle on 13 April (+/- 0.5 days) after an anoestrous period of 72.8 +/- 7.1 days. The untreated ewes began to cycle 2 weeks later on 26 April (+/- 1.7 days) after an anoestrous period of 112.0 +/- 8.5 days (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)
Analysis of Variance↗
What is the most likely cause for the poor pregnancy rate and the distribution for stage of pregnancy in the histogram?
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Animal Husbandry↗
Use of melengestrol acetate and gonadotropins to induce fertile estrus in seasonally anestrous ewes.
Ewes of three genotypes (Hampshire, n = 59; Rambouillet, n = 36; crossbred, n = 57) were used to determine the efficiency of melengestrol acetate (MGA) and(or) PG-600 (a combination of pregnant mare's serum gonadotropin and human chorionic gonadotropin) in inducing fertile estrus in seasonally anestrus ewes. Ewes were assigned randomly, within genotype, to treatments in a 2 x 2 factorial arrangement. Treatments were control, .125 mg of MGA given twice per day for 9 d (MGA), a single 5-mL injection of PG-600 (PG-600), and the combination of treatments MGA and PG-600 (MGA/PG-600). Feeding of MGA began on May 14, 1990, and ended on May 23. Injections of PG-600 were given immediately after the last feeding of MGA or vehicle on May 23. All ewes were exposed to fertile, brisket-painted rams on May 24 (d 0) for 40 d. Ewes were checked for estrus twice daily for 9 d. Laparoscopy was performed, to assess ovulation rate (OR), on d 6 for ewes that were not detected in estrus and on d 12 for ewes that exhibited estrus. Percentage of ewes mated was increased by MGA (P less than .001). Ovulation rate of ewes exposed to rams was increased by PG-600 (P less than .01) and this effect was enhanced by MGA (P less than .05), whereas MGA alone tended to decrease OR (P less than .10). Melengestrol acetate decreased the interval to lambing by 6.5 d (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)
Anestrus↗
Norgestomet and gonadotropin-releasing hormone enhance corpus luteum function and fertility of postpartum suckled beef cows.
In Exp. 1,101 suckled beef cows were administered two injections of prostaglandin F2 alpha (PGF2 alpha) 11 d apart. Cows in Group 1 received no additional treatment. Cows in Groups 2 and 3 received 250 micrograms of GnRH plus 47-h calf removal. Cows in Group 3 also received a norgestomet ear implant that was inserted 4 d after the first PGF2 alpha injection and left in situ for 8 d. The second PGF2 alpha injection was administered approximately 28 h before the time of norgestomet implant removal. The GnRH was administered approximately 30 h after the time of norgestomet implant removal (or 58 h after the second PGF2 alpha injection). Calf removal was the period from the time of implant removal to AI. All cows were artificially inseminated once 75 h after the second PGF2 alpha injection (47 h after implant removal). Reproductive status before the time of GnRH treatment (presynchronization) was determined by multiple sampling (2, 13, and 23 d before GnRH treatment) for blood progesterone concentrations (62% anestrous and 38% cyclic). The GnRH treatment increased (P < .01) the ovulation response and norgestomet reduced (P < .01) the incidence of short luteal phases in the presynchronization anestrous cows. Norgestomet treatment increased (P < .05) the timed breeding pregnancy rates for both presynchronization anestrous and cyclic cows. In Exp. 2, 174 suckled beef cows were administered Syncro-Mate B (which includes norgestomet). Cows in Group 1 received no additional treatment, whereas cows in Group 2 received 250 micrograms of GnRH (30 h after norgestomet implant removal).(ABSTRACT TRUNCATED AT 250 WORDS)
Anestrus↗
Effects of pregnancy on digesta kinetics and ruminal fermentation in beef cows.
Four pregnant and four nonpregnant, ruminally cannulated beef cows were used to evaluate the effects of the last trimester of pregnancy on digesta kinetics and ruminal fermentation. Before breeding, cows were allotted randomly either to pregnant (PR) or to nonpregnant (NP) groups; PR cows were bred at the first estrus after synchronization. All cows were fed long-stem fescue hay at 15 g of DM/kg of BW based on BW 120 d before parturition of pregnant cows (average BW of 642 kg). Collection periods, each lasting 9 d, began at 96, 68, 41, and 10 +/- 1.3 d before parturition. Particulate passage rate was greater (P < .05) and retention times and gastrointestinal fill were less (P < .05) for PR than for NP cows. Apparent total tract DM digestion, rate and extent (96-h in situ incubation) of NDF disappearance, and ruminal fluid kinetics were not affected (P > .10) by pregnancy. A physiological state x sampling day interaction was noted (P < .05) for ruminal NH3 N, total VFA concentrations, and molar proportions of butyrate. Ruminal pH and individual VFA proportions, however, did not differ (P > .10) between PR and NP cows, except for valerate, which was less (P < .05) for PR than NP cows. Results suggest that in late pregnancy with restricted feeding, passage rate of particulates increases without substantial changes in fermentation or extent of digestion.
Ammonia↗
Effects of metestrous administration of a norgestomet implant and injection of norgestomet and estradiol valerate on luteinizing hormone release and development and function of corpora lutea in suckled beef cows.
Sixteen suckled beef cows were used to determine effects of Syncro-Mate-B (SMB) on the development and function of corpora lutea (CL) and LH release. Twelve cows were treated 2 d after estrus with the standard SMB treatment regimen, a 6-mg Norgestomet ear implant (in situ 9 d) and a 2-mL i.m. injection of 3 mg of Norgestomet and 5 mg of estradiol valerate at time of implant insertion. Four cows served as untreated controls. In cows treated with SMB with subsequently nonfunctional CL (n = 5), mean concentrations of progesterone (P4) were lower on d 9, 12 (implant removal), and 14 of the treated cycle than in control cows or in those cows treated with SMB that developed functional CL (P < .01). In cows treated with SMB that developed functional CL (n = 7), mean concentrations of P4 were lower only on d 12 of the treated cycle than those in control cows (P < .01). In cows treated with SMB with subsequently nonfunctional CL, CL were smaller from d 9 through 14 of the treated cycle than in control cows or in those cows treated with SMB that developed functional CL (P < .01). In cows treated with SMB that developed functional CL, CL were smaller on d 9 and 11 of the treated cycle than in control cows (P < .01). Regardless of subsequent CL function, mean concentrations of LH and numbers of LH pulses were lower in cows treated with SMB than in control cows on d 3 and 4 of the treated cycle (P < .01).(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Effects of ivermectin on reproductive functions in ewes.
In response to producers' concerns about possible detrimental effects of ivermectin on ewes during the breeding season, an evaluation of its effects on endocrinological, physiological, and behavioral measures of reproductive performance was made. Twenty cycling ewes were randomly assigned on d 10 (d 0 = estrus) to receive a single recommended oral dose of 200 micrograms/kg of BW of ivermectin or a control volume of water. Twelve hours after treatment, ewes received a luteolytic injection of 5 mg of PGF2 alpha and were introduced to fertile rams. On d 10 after mating, laparoscopies were performed to assess ovulation rate, and on d 18 conceptuses were surgically recovered. Blood samples were collected during the 92-h interval beginning immediately before ivermectin and control treatments and were assayed for LH. It was determined that 1) interval from PGF2 alpha-induced luteal regression to a) onset of estrus (36.1 +/- 1.4 vs 36.3 +/- 1.4 h) and b) onset of the preovulatory surge of LH (38.2 +/- 2.6 vs 44.2 +/- 2.6 h), 2) magnitude of the surge of LH (275.6 +/- 38.9 vs 199.8 +/- 38.9 ng/mL), 3) duration of the surge of LH (9.4 +/- .4 vs 9.0 +/- .4 h), 4) area under the curve of the surge of LH (54,321 +/- 7,419 vs 38,138 +/- 7,419 arbitrary units), 5) ovulation rate (2.1 +/- .4 vs 2.0 +/- .3 ovulations/ewe), 6) pregnancy rate (8/10 vs 5/10 ewes pregnant), and 7) conceptuses per ewe (1.75 +/- .37 vs 1.60 +/- .33) did not differ (all P > .1) between ivermectin- and control-treated ewes, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Histological populations and atresia of ovarian follicles in postpartum cattle treated with an agonist of gonadotropin-releasing hormone.
Surface and histological changes of ovarian follicles and degree of atresia were characterized 3 and 6 d after a treatment with a GnRH agonist (buserelin) in postpartum beef cows. Sixteen cyclic cows on d 7 of their estrous cycle and eight acyclic cows were used. On d 0 of the experimental period, eight cyclic cows were injected with 2 mL of physiological saline and the remaining eight cyclic cows and the acyclic cows were injected i.m. with 8 micrograms of buserelin. Ovaries were collected 3 or 6 d later (n = 4 cows per group per day). All follicles (> 1.57 mm) were observed microscopically, measured using routine histological techniques, and classified as either nonatretic or atretic, with early or late atresia, and grouped into Class 1, 1.57 to 3.67 mm, Class 2, 3.68 to 8.56 mm, or Class 3, > 8.56 mm. Buserelin induced formation of new corpora lutea in all cows but one (acyclic cow). Class 1 follicles decreased on d 3 but increased on d 6 (day x treatment, P < .004), whereas those of Class 2 increased (P < .07) on both d 3 and 6 after buserelin treatment. However, within Class 2 follicles, we detected an increase on d 3 and 6 in the number (P < .01) and proportion (P < .07) of atretic follicles, an increase in the number of follicles in late atresia on d 6 (day x treatment, P < .03), and a decrease in the number (P < .06) and proportion (P < .03) of nonatretic follicles on d 6 (day x treatment).(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Influence of simulated photoperiod alteration and induced estrus on reproductive performance of spring-born Columbia and Targhee ewe lambs.
The objective of this study was to test the hypothesis that a combination of induced estrus (IE) and melatonin (MEL) would increase reproductive performance in breeds characterized by late maturity more than either IE or MEL alone. Spring-born Columbia (C; n = 161; 188 to 222 d range of age at breeding; 49 to 80 kg range of BW at breeding) and Targhee (T; n = 166; 183 to 210 d range of age at breeding; 40 to 68 kg range of BW at breeding) ewe lambs were stratified randomly by breed to treatments: ambient controls (AC); IE; MEL; and MEL+IE. Melatonin (18 mg of Regulin) was implanted on September 7. Estrus induction included medroxyprogesterone acetate (MAP) pessaries inserted for 12 d and pregnant mare's serum gonadotropin (PMSG; 500 IU i.m.) at time of MAP removal. Ewe lambs were placed into two pens with five rams per pen by breed. Targhee ewes lambed at an increased rate with IE vs no IE (84.5 vs 67.9%; P < .01) and tended to lamb at an increased rate with MEL vs no MEL (82.5 vs 70.6%; P = .07). The 92.7% lambing rate observed in the Targhee ewe lambs for the combined treatment (MEL+IE) was slightly higher than an additive effect but the interaction between IE and MEL was not significant (P = .24). By contrast, none of the treatments altered (P = .5) lambing rate, number of lambs born, or number born alive for Columbia ewe lambs.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗