家猫非繁殖季节诱导发情配种后排卵时间的确定

作者尝试在非繁殖季节应用外源促性腺激素对家猫进行人工诱导发情,并判断其较为准确的排卵时间。试验采用PMSG两次注射法对雌性家猫进行诱导发情,注射总剂量为150 IU,PMSG处理后的第6 d肌肉注射hCG（100 IU/只）并合笼配种。分别于合笼后的24、30、36 h手术法摘除家猫卵巢及输卵管部,观察记录卵巢排卵情况并对排卵侧的输卵管进行冲胚。试验结果显示,利用外源性促性腺激素可使家猫在非繁殖季节发情,且排卵时间范围为合笼配种后30 h左右。     

Artificial intravaginal insemination using fresh semen in cats

To clarify the sperm count required for fertilization by artificial intravaginal insemination (AIVI), twenty-nine female cats were examined. Six male cats aged 2-12 years with normal semen quality, copulation capability, and fertility were used. In AIVI, animals received administration of 250 iu hCG once or 100 iu twice on days 2-4 of estrus to induce ovulation, and were inseminated 15, 20, or 30 hr after the initial hCG administration. The success of ovulation was judged by elevation of the peripheral progesterone level after hCG administration. AIVI was investigated at three sperm counts, 20 x 10(6) (Experiment 1), 40 x 10(6) (Experiment 2), and 80 x 10(6) (Experiment 3), with semen collected by the artificial vagina method. Semen was infused in the vagina under general anesthesia by advancing a 9 cm-long nylon probe with 1.5 mm diameter connected to a 1 ml syringe in the vagina for 3-4 cm. Ovulation was induced in 43 of 45 animals (95.6%). One of 16 animals was fertilized (conception rate: 6.6%) by AIVI in Experiment 1. In Experiments 2 and 3, conception was obtained in six of 18 animals (33.3%) and seven of nine animals (77.8%), respectively, and the mean numbers of kits were 4.0 +/- 0.4 and 3.3 +/- 0.5, respectively, and the mean numbers of kits were 4.0 +/- 0.4 (SE) and 3.3 +/- 0.5, respectively, showing no significant difference. There were no differences in the time of insemination after hCG administration and the conception rate among these groups. Our findings showed that the number of sperm required for fertilization by AIVI of fresh semen in cats was 80 x 10(6).     

Induced ovulation in cats using porcine pituitary gland preparation during the non-breeding season

An attempt was made to induce ovulation in 19 cats during the non-breeding season by the administration of a porcine pituitary gland preparation. The dosage was 2 mg for the first day and then 1 mg for each day until estrus was induced. Studies were made to determine whether fertilization and pregnancy were possible by mating at the time of induced estrus. Estrus was induced in 89.5% (17/19) of the cats, 3-8 days after the first administration. The average number of ovulations induced by mating was 7.3 +/- 1.3 (mean +/- SE) for 16 cats (excluding one cat that failed to ovulate). The uterine horn was flushed 6-8 days after mating in 9 of the 16 ovulated cats to determine the fertilization rate. An average of 3.6 ova were recovered from 8 out of the 9 cats (including one cat from which no ovum was recovered) which gave an average recovery rate of 38.6%. Expanded blastocysts were recovered from 5 cats, while from the other 3 cats, only unfertilized ova were recovered. Pregnancy was confirmed in the other 7 cats 15-20 days after mating. In two of the 7 cats implantation was observed, but abortion occurred at 24 and 27 days of pregnancy. Plasma progesterone concentrations were lower in the estrus-induced and bred cats as compared to these in the controls, with progesterone values approaching base concentrations, approximately by day 20 in 2 cats and by day 30 in 3 cats. It was concluded that estrus could be induced in cats during the non-breeding season by administration of porcine pituitary gland preparation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Embryo transfer in the cat during the non-breeding season

Studies were conducted to investigate the possibility of embryo transfer in the cat during the non-breeding season. Estrus was induced in 19/22 (86.4%) cats using a porcine pituitary gland preparation. Uterine horns were flushed in 5 cats 6-8 days after mating with expanded blastocysts being collected from 4 cats. One to nineteen blastocysts per cat were transferred to the uterine horns of 6 recipient cats in which ovulation had been induced with HCG. The time differences between time of ovulation in donor and recipient animals were 0.5 days earlier in the recipient (2 cats), 1 day later in the recipient (3 cats), and no difference (1 cat); conception occurred in all the recipients. The ratio of fetuses to transplanted embryos were 1/1, 1/2, 2/3, 2/6, 4/7, and 2/19, respectively. Fetal death occurred in 2 cats at days 22 and 25 and abortion occurred in 3 cats at days 34, 35 and 39. There was a delay in the expulsion of placentae in the animals that experienced fetal death on days 22 and 25, expulsion occurring on days 36 and 56, respectively. One cat was treated with progesterone and carried 2 fetuses to day 66; pregnancy was terminated by cesarean section. In conclusion, it was demonstrated that embryo transfer can be performed in cats in which estrus and ovulation have been induced with porcine pituitary gland preparation during the non-breeding season. However, luteal activity needs to be supplemented by exogenous progesterone administration to maintain pregnancy.     

Early embryonic survival and embryo development in two lines of rabbits divergently selected for uterine capacity

The aim of this work is to study early embryo survival and development in 2 lines divergently selected for high and low uterine capacity throughout 10 generations. A total of 162 female rabbits from the high line and 133 from the low line were slaughtered at 25, 48, or 62 h of gestation. There were no differences in ovulation rate and fertilization rate between lines in any of the 3 stages of gestation. Embryo survival, estimated as the number of normal embryos recovered at a constant ovulation rate, was similar in both lines at 25 and 48 h. Embryo survival was greater in the high line [D (posterior mean of the difference between the high and low lines) = 0.57 embryos] at 62 h of gestation. There was no difference in embryonic stage of development at 25 h, but at 48 and 62 h of gestation, the high line, compared with the low line, had a greater percentage of early morulae (83 vs. 72%) and compacted morulae (55 vs. 38%). Divergent selection for uterine capacity appeared to modify embryo development, at least from 48 h of gestation, and embryo survival from 62 h.     

Transfer of canine embryos at various developmental stages recovered by hysterectomy or surgical uterine flushing

In dogs, embryo transfer (ET) techniques such as induciton of excessive ovulation and synchronization of estrus have not progressed well. Therefore, using embryos at various developmental stages, ET was investigated in dogs from a beagle colony in which the ovulation days were close, as estimated by the progesterone level. Embryos were, recovered 8-11 days after ovulation (4-9 days after mating) by excising the oviducts and uteri (excision method) in 16 animals and by surgical flushing of the uteri at laparotomy (surgical method) in 3 animals. In 24 dogs with -4 to +2 days of difference in the timing of ovulation between donor and recipient dogs, 1-10 embryos at the 8-cell to blastocyst stages were transferred per animal. The mean embryo recovery rate by the excision method (97.1%) was significantly higher than that by the surgical method (42.5%) (p<0.01). Twelve (57.1%) of 21 animals with -1 to +2 days difference in ovulation day became pregnant after the transfer of 8-cell to blastocyst stage embryos. Although 3 dogs with -4 to -2 days of difference of ovulation day underwent ET of morula or compacted morula, none of these dogs became pregnant. The mean ratio of the number of newborns to the number of transferred embryos was only 51.9%. The mean duration of the period between ovulation and delivery in the pregnant recipients was 65.8 days, which tended to be longer than that in natural mating. These results demonstrate that pregnancy can be induced by ET at the 8-cell to blastocyst stage in dogs with -1 to +2 days difference in ovulation day.     

Synchrony of Ovulation and Follicular Dynamics in Merino Ewes Treated with GnRH in the Breeding and Non-breeding Seasons

The effect of gonadotropin releasing hormone (GnRH) treatment on the time of ovulation and the occurrence of follicular dominance during the non-breeding and breeding seasons (experiment 1), and on fertility after artificial insemination (AI) in the non-breeding season (experiment 2), was examined in Merino ewes. Oestrus was synchronized in 40 nulliparous ewes (experiment 1; n = 20, in the non-breeding and breeding seasons) and in 79 multiparous ewes (experiment 2) using intravaginal sponges and pregnant mare serum gonadotropin. Thirty six hours after sponge removal (SR), half the ewes were injected (i.m.) with 40 microg of synthetic GnRH and the remainder used as controls. GnRH improved the synchrony of ovulation compared with the controls in the breeding (SD = 2.8 vs 5.7 days, p = 0.04) but not the non-breeding season (SD = 3.8 vs 4.4 days, p = 0.69), with ewes ovulating from 42 to 54 h (mean 50.4 +/- 4.08 h) and 42-60 h (mean 54.4 +/- 5.47 h) after SR for GnRH and control, respectively. For both treated and control ewes, ovulation occurred earlier in the non-breeding than the breeding season (50.1 vs 54.6 h; p = 0.002). GnRH had no effect on follicular dominance, as assessed by divergence (D: the time the ovulatory follicle exceeded the average size of the other non-ovulating follicles) or on the interval from D to ovulation (IDO). However, follicular dynamics differed between seasons. The mean follicle diameter increased at a faster rate up to 36 h after SR in the non-breeding compared with the breeding season and then rapidly declined, compared with a later peak (42 h after SR) in mean follicular size during the breeding season. IDO was shorter in the non-breeding than in the breeding season (26.7 +/- 4.30 h vs 39.6 +/- 4.53 h; p = 0.05). In experiment 2, ewes (n = 38 GnRH-treated, n = 40 controls) were inseminated in the uterus by laparoscopy 42 h or 48 h after SR with frozen-thawed sperm. The fertility of ewes treated with GnRH (nine of 39, 23%) was not different to the controls (eight of 38, 21%; p = 0.01). In conclusion the application of GnRH improved synchronization of ovulation but did not improve fertility rates after AI.     

Unilateral intrauterine horn insemination of fresh semen in cats

The sperm count required were investigated to obtain a conception rate of 80% by unilateral intrauterine insemination (UIUI) of fresh semen in cats. The conception rates obtained by insemination before and after ovulation were also examined. Thirty-six female cats aged 1-7 years were used in the experiments, and the number of experimental cases was 44. Seven male cats aged 2-12 years from which semen could be collected by the artificial vagina method were used. In artificial insemination, 100 iu x 2 or 250 iu of hCG was administered on days 2-4 of estrus, and sperm were introduced into the uterine horn with a greater number of ovulations (or mature follicles) 15, 20 and 30 hr after hCG administration by laparotomy. The inseminated sperm counts were 2 x 10(6) (Exp. 1). 4 x 10(6) (Exp. 2), and 8 x 10(6) (Exp. 3). As a result, ovulation was induced in 42 of 44 cases (induction rate: 95.5%) regardless of the dosage of hCG. Conception was obtained by UIUI in two of 16 animals (conception rate: 12.5%) in the Exp. 1, five of 16 animals (31.3%) in Exp. 2, and eight of 10 animals (80.0%) in Exp. 3. Regarding the relationship between the ovulation state at insemination and conception, the conception rate obtained by insemination before ovulation was clearly higher than that obtained by insemination after ovulation (p<0.05). Regarding the number of kits compared to the number of ovulations on the inseminated side, the percentages of cases in which the number of kits exceeded the number of ovulations on the inseminated side were similar in all groups inseminated with a different number of sperm. It is therefore necessary to investigate conception rates obtained by bilateral insemination to increase the fertility rate. Based on the above findings, it was shown that the sperm count required for fertilization by UIUI is 8 x 10(6).     

Relationship between time elapsed after human chorionic gonadotropin administration and developmental stage in porcine embryos collected from prepubertal gilts

We examined the relationship between the time elapsed after human chorionic gonadotropin (hCG) administration and developmental stage of porcine embryos after collection. Prepubertal gilts, 7 to 8 months old, were given 1500 IU equine chorionic gonadotropin (eCG) intramuscularly, followed by 500 IU hCG 72 h later. The treated gilts were inseminated artificially on Day 1 (Day 0=the day of hCG administration) and on Day 2. Embryos were collected surgically on Day 6 (140, 144, and 147 h after hCG administration) or on Day 7 (164, 168, and 171 h), and the developmental stages of the collected embryos were examined. From 75.2% (276/367) of the prepubertal gilts treated with hormones, we collected an average of 20.7 embryos per gilt with normal morphology. At 140 h after hCG administration, morulae (54.4%) could be collected. At 144 h, morulae and early blastocysts (57.7% and 28.9%, respectively) were collected. By 147 h, the proportion of embryos at the blastocyst to expanded blastocyst stages had increased (10.0%). From 164 h to 171 h, expanding or expanded blastocysts of more than 200 microm in diameter and hatched blastocysts could be collected. The proportion of hatched blastocysts increased from 3.2% (164 h) to 41.0% (171 h). These results suggests that although the number of ovulations differed among gilts, porcine embryos at the appropriate stages can be collected efficiently by controlling the time elapsed between hCG administration and embryo collection.     

Ovulation and embryonic developmental rate following hCG-stimulation in sows

The hCG induced ovulation in sows was studied by use of ultrasonography, and an investigation of the development and diversity of the zygotes/embryos was performed at 24 h after ovulation. Crossbred sows (N = 48) were weaned (day 0) and checked for heat twice daily from day 3 onwards. From day 4, the ovaries were transrectally scanned twice daily. On day 4, the sows were given an injection of 750 iu hCG i.m. and inseminated 27 +/- 2 h (X +/- SD) and 38 +/- 1 h later. From 38 to 48 h after the hCG injection, the ovaries were scanned at 60 to 90 min intervals. At 24 h after ovulation the oviducts were surgically flushed in 18 sows. Out of the 48 sows, 34 showed heat at 12-36 h after the hCG-treatment and 14 showed heat before the hCG treatment. In the former group of sows, 20 (59%) ovulated within the interval of 38 to 48 h after the hCG treatment, and the follicular size immediately before ovulation was 7.8 +/- 0.6 mm. Among the sows which showed heat before hCG treatment only 7 (50%) ovulated within the above interval and the preovulatory follicle size was larger (8.3 +/- 0.5, p < 0.05) than in the former group of sows, which showed heat after the hCG treatment. The flushing of 18 sows yielded a total of 243 ova, 70 (29%) 1-cell stages, 160 (66%) 2-cell stages and 13 (5%) 4-cell stages. A pronounced difference in the degree of variation in embryonic development was seen between sows: 4 animals yielded 1- to 4-cell stages, one exclusively 2-cell stage. In conclusion, the control of ovulation in sows by hCG treatment will affect the follicular growth and the exact timing of ovulation can not always be relied on. It is strongly recommended to use ultrasonography to monitor the time of ovulation if this parameter is important. Ova recovered at 24 +/- 1 h after the median time of ovulation revealed a pronounced diversity (1- to 4-cell stage) within sows. No obvious relation with this embryonic diversity and the follicular size at ovulation was seen in these data.     

Efficient production of pronuclear embryos in breeding and nonbreeding season for generating transgenic sheep overexpressing TLR4

Background: Brucella is a zoonotic Gram-negative pathogen that causes abortion and infertility in ruminants and humans. TLR4 is the receptor for LPS which can recognize Brucella and initiate antigen-presenting cell activities that affect both innate and adaptive immunity. Consequently, transgenic sheep over-expressing TLR4 are an suitable model to investigate the effects of TLR4 on preventing Brucellosis. In this study, we generated transgenic sheep overexpressing TLR4 and aimed to evaluate the effects of different seasons(breeding and non-breeding season) on superovulation and the imported exogenous gene on growth.Results: In total of 43 donor ewes and 166 recipient ewes in breeding season, 37 donor ewes and 144 recipient ewes in non-breeding season were selected for super-ovulation and injected embryo transfer to generate transgenic sheep.Our results indicated the no. of embryos recovered of donors and the rate of pronuclear embryos did not show any significant difference between breeding and non-breeding seasons(P 0.05). The positive rate of exogenous TLR4 tested were 21.21 % and 22.58 % in breeding and non-breeding season by Southern blot. The expression level of TLR4 in the transgenic sheep was 1.5 times higher than in the non-transgenic group(P 0.05). The lambs overexpressing TLR4 had similar growth performance with non-transgenic lambs, and the blood physiological parameters of transgenic and non-transgenic were both in the normal range and did not show any difference.Conclusions: Here we establish an efficient platform for the production of transgenic sheep by the microinjection of pronuclear embryos during the whole year. The over-expression of TLR4 had no adverse effect on the growth of the sheep.     

Japanese Society for Animal Reproduction: award for outstanding research 2002. The development and prevalence of the transfer technique for frozen-thawed embryos of Japanese black beef cattle in Tochigi Prefecture

The conditions of embryo transfer by the stepwise method, in which frozen-thawed embryos are transferred on day 7 (day 0=onset of estrus), were investigated with the aim of increasing pregnancy rates in frozen-thawed embryo transfer. The use of a vaginal speculum to prevent bacterial infection when passing an embryo transfer gun through the vagina yielded a pregnancy rate equal to or higher than that with application of a sheath cover to the transfer gun. Administration of a sedative, xylazine, to recipient cattle for preventing movement at the time of embryo transfer improved the pregnancy rate. The influence of the time from thawing of frozen embryos to transfer and of the transportation of the recipient by truck upon pregnancy rate was investigated. Embryo transfer within 60 minutes after aspiration into a straw or transportation of the bovine recipient, 1.5 hours each way before and after transfer, had no influence on pregnancy rate. Relations of the embryonic developmental stage and morphological quality after thawing of frozen embryos to pregnancy rate were investigated in recipients of nulliparous Holstein heifers. The pregnancy rate increased as the embryonic developmental stage advanced from compacted morula, early blastocyst, and blastocyst in that order. The pregnancy rate obtained with blastocyst stage embryos was significantly (P<0.05) higher than that with compacted morula stage embryos, and there was no significant difference in pregnancy rates between excellent morphological quality and good morphological quality for compacted morula stage embryos. When correlation of luteal function and pregnancy rate was investigated in bovine recipients, pregnancy rate showed a tendency to increase with increasing blood progesterone (P) concentration on the day before (on day 6 after estrus) and the day of embryo transfer. The pregnancy rate in bovine recipients, which showed a blood P concentration of > or =2.5 ng/ml on the day before embryo transfer, was significantly (P<0.05) higher than that in those with a blood P concentration of <2.5 ng/ml. Pregnancy rate showed a tendency to increase with decreasing blood estradiol-17beta (E2) concentration on the day of embryo transfer. Activation of luteal function by administration of human chorionic gonadotropin (hCG) in cycling cattle was investigated for its effect on increasing pregnancy rate in bovine recipients. A follicle coexisting with cyclic CL ovulated and induced CL formed after injection of hCG 1,500 IU 5 days after ovulation. The blood P concentration was significantly (P<0.05) higher in the administration group than in the control group, and the blood E2 concentration rapidly decreased, showing a lower concentration than in the control group. These results suggest the possibility that the pregnancy rate could be improved by administration of hCG. Pregnancy rate following intramuscular injection hCG 1,500 IU was comparatively investigated in parous Japanese Black beef cattle receiving frozen-thawed embryos 7 days after estrus. Pregnancy rate was 67.5% in the group in which hCG was administered on day 6 after estrus, and was significantly (P<0.05) higher than that in the control group (45.0%) and the group in which hCG was administered on day 1 after estrus (42.5%), revealing that hCG administration facilitated pregnancy. Transfer of frozen-thawed embryos in the blastocyst stage within 60 minutes after the aspiration into a straw, with a vaginal speculum after administration of xylazine is suggested as a way of improving pregnancy rate in bovine recipients with favorable luteal function and in those with luteal function activated by administration of hCG on the day before embryo transfer.     

A survey of sexual behaviour and reproduction of female cats

Details of reproductive activity among 168 breeding queens were obtained from a survey of specific information supplied by cat breeders. Puberty was reached, on average, at 9–10 months of age. The gestation period was calculated to average 65 days. Almost half the queens in the survey showed cyclic occurrence of oestrus throughout the year. Cycles were usually 21 days long. When a non-breeding season was present it generally occurred between September and the end of January, its average duration being 4 months. The data obtained from the survey are examined and discussed, and are considered to illuminate usefully a scantily reported topic.     

The effect of divergent selection for uterine capacity on prenatal survival in rabbits: maternal and embryonic genetic effects

The aim of this work was to determine whether prenatal survival depends on the genotype of the mother or of the embryo and to identify the critical periods for prenatal mortality in two lines of rabbits divergently selected by high (H) and low (L) uterine capacity. Does from H (n = 124) and L (n = 115) lines were slaughtered at 72 h of gestation. Embryos recovered at 72 h of gestation were transferred to the oviducts of recipient does from the H (n = 23) and L (n = 19) lines. Each recipient does received eight embryos from the H line into one oviduct and eight embryos from the L line into the other. Recipient does were slaughtered on d 28 of gestation. No differences were found between lines in the embryo recovery either in ovulation rate (OR) or in fertilization rate of ova recovered. Recovery rate was higher for the H line (0.80 vs. 0.72, P < 0.01). The number of embryos recovered, fitting ovulation rate as a covariate, was also higher for the H line (9.74 vs. 8.78, P < 0.05). The H line showed a more advanced embryonic stage of development, having a higher percentage of blastocysts (PB) and a lower percentage of compact morulae (PCM) (38% vs. 20%, P < 0.001 for PB, and 51% vs. 64%, P < 0.01 for PCM). The percentage of early morulae was low and similar in both lines. Neither donor nor recipient lines affected embryonic survival from 72 h to 7 d of gestation. Fetal survival was affected by the recipient line (P < 0.05). An interaction between donor and recipient was found. Embryos from the H donor line had a better fetal survival rate than embryos from the L donor line (P < 0.05) in H recipient females. Within L recipient females, embryos from H and L donor lines showed similar fetal survival. Fetal survival was divided into early (from d 7 to 17 of gestation) and late (from d 17 to 28 of gestation). The high recipient line showed a higher early fetal survival than the L recipient line (P < 0.05). The same effect was observed for late fetal survival, but the difference between H and L recipient lines was lower (P < 0.10). Thus, fetal survival depends mainly on the maternal genotype, and the embryo genotype only affects fetal survival when embryo transfer is performed to a favorable maternal environment. Selection for uterine capacity in rabbits leads to modification of early embryonic survival and of early and late fetal survival, but differences are higher for early than for late fetal survival.     

Selection for ovulation rate in rabbits: genetic parameters, direct response, and correlated response on litter size

The aim of this work was to evaluate the response to 10 generations of selection for ovulation rate. Selection was based on the phenotypic value of ovulation rate, estimated at d 12 of the second gestation by laparoscopy. Selection pressure was approximately 30%. Line size was approximately 20 males and 80 females per generation. Traits recorded were ovulation rate at the second gestation, estimated by laparoscopy as the number of corpora lutea in both ovaries; ovulation rate at the last gestation, estimated postmortem; ovulation rate, analyzed as a single trait including ovulation rate at the second gestation and ovulation rate at the last gestation; right and left ovulation rates; ovulatory difference, estimated as the difference between the right and left ovulation rates; litter size, estimated as the total number of kits born and the number of kits born alive, both recorded at each parity. Totals of 1,477 and 3,031 records from 900 females were used to analyze ovulation rate and litter size, respectively, whereas 1,471 records were used to analyze ovulatory difference, right ovulation rate, and left ovulation rate. Data were analyzed using Bayesian methodology. Heritabilities of ovulation rate, litter size, number of kits born alive, right ovulation rate, left ovulation rate, and ovulatory difference were 0.16, 0.09, 0.08, 0.09, 0.04 and 0.03, respectively. Phenotypic correlations of ovulation rate with litter size, number of kits born alive, and ovulatory difference were 0.09, 0.01, and 0.14, respectively. Genetic correlations of ovulation rate with litter size and with number of kits born alive were estimated with low accuracy, and there was not much evidence for the sign of the correlation. The genetic correlation between ovulation rate and ovulatory difference was positive (P = 0.91). In 10 generations of selection, ovulation rate increased in 1.32 oocytes, with most of the response taking place in the right ovary (1.06 oocytes), but there was no correlated response on litter size (-0.15 kits). In summary, the direct response to selection for ovulation rate was relevant, but it did not modify litter size because of an increase in prenatal mortality.     

小鼠胚胎的玻璃化冷冻研究

用不同冷冻载体(玻璃管、塑料管和0.25 mL细管)及不同冷冻方法(程序化冷冻和玻璃化冷冻)对小鼠3.5 d~4 d桑椹胚和囊胚进行冷冻保存,并与不做任何冷冻保存处理直接培养进行对比。结果表明,使用玻璃管、塑料管和0.25 mL细管作为胚胎的承载材料进行玻璃化冷冻,效果差异不显著;采用程序化冷冻与OPS玻璃化冷冻法,对小鼠胚胎进行冷冻保存可以取得较好的结果。从而得出,用不同材质的冷冻载体进行玻璃化冷冻,可以获得与程序化冷冻相同的良好效果。     

Effect of human chorionic gonadotropin on preovulatory luteinizing hormone surge and ovarian hormone secretion in gilts

The influence of varying doses of human chorionic gonadotropin (hCG) on the preovulatory luteinizing hormone (LH) surge, estradiol-17 beta (E2) and progesterone (P4) was studied in synchronized gilts. Altrenogest (AT) was fed (15 mg X head-1 X d-1) to 24 cyclic gilts for 14 d. Pregnant mares serum gonadotropin (PMSG; 750 IU) was given im on the last day of AT feeding. The gilts were then assigned to one of four groups (n = 6): saline (I), 500 IU hCG (II), 1,000 IU hCG (III) and 1,500 IU hCG (IV). Human chorionic gonadotropin or saline was injected im 72 h after PMSG. No differences in ovulation rate or time from last feeding of AT to occurrence of estrus were observed. All gilts in Groups I and II expressed a preovulatory LH surge compared with only four of six and three of six in Groups III and IV, respectively. All groups treated with hCG showed a rapid drop (P less than .01) in plasma levels of E2 11, 17, 23 h after hCG injection when compared with the control group (35 h). The hCG-treated gilts exhibited elevated P4 concentrations 12 h earlier than the control group (3.1 +/- .5, 3.4 +/- .72, 3.1 +/- .10 ng/ml in groups II, III and IV at 60 h post-hCG vs .9 +/- .08 ng/ml in group I; P less than .05). These studies demonstrate that injections of ovulatory doses of hCG (500 to 1,500 IU) had three distinct effects on events concomitant with occurrence of estrus in gilts: decreased secretion of E2 immediately after hCG administration, failure to observe a preovulatory LH surge in some treated animals and earlier production of P4 by newly developed corpora lutea.     

Luteal lifespan and fertility after estrus synchronization in goats

The present experiment aims to examine the efficiency of estrus synchronization using progesterone and equine chorionic gonadotrophin (eCG) and to look at luteal function. During the non-breeding and breeding season, 5 adult female Korean native goats were injected intramuscularly with 2.5 ml of physiological saline as the control. A progesterone impregnated intravaginal sponge was then kept in the same goats for 10 days followed, after a week, by an intramuscular injection of 500 IU eCG. Five adult female Nubian goats were mated with a fertile buck during the non-breeding season. During the non-breeding season 2 of the 5 goats showed a normal estrous cycle (ranging from 18 to 21 days) and 3 a short estrous cycle (ranging from 3 to 6 days). During the breeding season the equivalent figures were 1 and 2. The major axes of the corpus luteum (CL) were measured by means of calipers built into the ultrasonography system, and the concentrations of plasma progesterone (P₄) were determined by double antibody radioimmunoassay. The mean major axes of the CL in goats showing the short cycle (6.1 ± 0.5 mm) was significantly smaller than in those showing the normal cycle (8.9 ± 0.5 mm; p < 0.01) and also the value of P₄ in goats showing the short cycle (4.2 ± 2.1 ng/ml) was significantly lower than for those showing the normal cycle (10.3 ± 4.3 ng/ml; p < 0.05) at day 3 following ovulation. Three out of 5 Nubian goats became pregnant but only one goat carried to full term. The present experiment indicated that a combination of progesterone and eCG was effective in inducing estrus, although it resulted in a high incidence of short luteal lifespan. The low kidding rate and high incidence of embryonic loss may be due to the instability of the luteal lifespan.     

Clinical experience with native GnRH therapy to hasten follicular development and first ovulation of the breeding season

Breeding records of 48 Thoroughbred and Standardbred mares treated with native GnRH (500μg im, bid) during February—April, 1999 or 2000, on 7 farms in central Kentucky were retrospectively examined. Treated mares were classified as being in anestrus or early transition (n=42; if no signs of estrus occurred within 31/2 weeks and the largest follicle remained ≤25 mm in diameter or the first larger follicle(s) of the season regressed without ovulating), or were classified as being in late transition (n=6; if follicular growth achieved 30-40 mm diameter but ovulation had not yet occurred during the breeding season). Thirty-eight mares (38/48; 79%) ovulated in 13.7 ± 7.4 days. Interval to ovulation was negatively associated with size of follicles at onset of native GnRH therapy (P < 0.01). Per cycle pregnancy rate was 53% (19/36 mares bred). Ovulation inducing drugs were administered to 32 of the native GnRH treated mares (2500 units hCG intravenously, n = 20; deslorelin implant [Ovuplant™] subcutaneously, n=12), while 6 mares were not administered any additional drugs to induce ovulation. Per cycle pregnancy rate did not differ among mares treated only with native GnRH (2/5 mares bred; 40% PR), mares treated with native GnRH plus hCG (12/19 mares bred; 63% PR), or mares treated with native GnRH plus Ovuplant™ (5/12 mares bred; 42% PR) (P > 0.10). Additional treatment with either hCG or Ovuplant™ did not alter mean follicle size at ovulation or interovulatory interval (P > 0.10). The proportion of interovulatory intervals > 25 days was not different between mares receiving no additional treatment to induce ovulation (0/4; 0%) compared to mares receiving hCG to induce ovulation (3/8; 38%) (P > 0.10), but the proportion of interovulatory intervals > 25 days was greater for mares receiving Ovuplant™ to induce ovulation (5/7; 71%) compared to mares receiving no additional treatment to induce ovulation (P < 0.05). The proportion of mares with extended interovulatory intervals (i.e., > 25 days) did not differ between mares with follicles < 15 mm diameter (4/8, 50%) and those with follicles > 15 mm diameter (3/11, 27%) at onset of native GnRH treatment (P > 0.10). While concurrent untreated controls were not used in this study, the 79% response rate to twice daily administration of native GnRH is in agreement with other reports using pulsatile or constant infusion as methods of administration, confirming therapy can hasten follicular development and first ovulation of the breeding season. As with previous reports, follicle size at onset of treatment is an important determinant of interval from onset of native GnRH therapy to ovulation. Use of hCG or Ovuplant™ did not enhance ovulatory response in native GnRH treated mares. Use of Ovuplant™ during native GnRH therapy may increase the incidence of post-treatment anestrus in mares not becoming pregnant.     

Responses to delayed estrus after weaning in sows using oral progestagen treatment

Oral progestagen treatment extends the weaning-to-estrus interval (WEI) in weaned sows. Particularly in lower parity sows, this allows recovery from lactational catabolism and improves sow productivity. However, the optimal duration of progestagen treatment in contemporary dam-line sows is unclear. Therefore, sows (n = 749) weaned over consecutive 3-wk periods in June and July and classified as parity 2 and 3 (P2-3); 4, 5, and 6 (P4-6); or parity 7 or higher (P7+) were organized into 2 breeding groups using 1 of 3 strategies: 1) oral progestagen for 2 d before and 12 d after weaning (M14; n = 249); 2) oral progestagen for 2 d before and 5 d after weaning (M7; n = 250); or 3) no progestagen treatment (M0; n = 250). Progestagen (altrenogest) was administered directly into the sow's mouth at a dosage of 6.8 mL (15 mg of altrenogest) daily. Sows were bred using artificial insemination at first detection of estrus after weaning (M0) or altrenogest withdrawal, and every 24 h thereafter, until they no longer exhibited the standing reflex. The WEI for M0 sows was 5.1 +/- 0.1 d. Estrus was recorded sooner (P < 0.001) after withdrawing treatment in M14 than in M7 sows (6.9 +/- 0.1 vs. 7.4 +/- 0.1 d, respectively). More (P < 0.001) M14 sows (88.6 +/- 2.5%) were bred within 10 d of altrenogest withdrawal than M7 (72.8 +/- 2.8%) sows, or within 10 d of weaning in M0 sows (78.8 +/- 2.6%). Reproductive tracts were recovered after slaughter at d 30 or 50 of gestation. For P2-3 sows, ovulation rate (least squares mean +/- 95% confidence interval) in M7 (23.1 +/- 1.0) was greater (P < 0.001) than in M14 (20.7 +/- 1.0) or M0 (19.7 +/- 1.0) sows; no differences were detected in P4-6 and P7+ sows. At d 30, M7 and M14 sows had more (P < 0.01) embryos (16.4 +/- 0.6 and 15.8 +/- 0.4, respectively) than M0 (13.9 +/- 0.5) sows. At d 50 of gestation, number of fetuses in M14 sows (13.6 +/- 0.4) was greater (P < 0.001) than in M0 (11.8 +/- 0.4) and M7 (12.2 +/- 0.3) sows. Use of oral progestagen to delay the return to postweaning estrus for greater than 18 d appears to have potential for improving weaned sow productivity. Given the incidence of high ovulation rates and associated evidence of intrauterine crowding of embryos around d 30 of gestation, the changing dynamics of prenatal loss resulting from longer periods of progestagen treatment may represent an additional production advantage.