Male pheromones in ruminant species such as sheep and goats are known to reactivate quiescent ovarian function in seasonally anestrous females. We have previously shown that only a few minutes exposure to the male pheromone can accelerate the GnRH pulse generator activity immediately in the female goat. In this study the effect of 4 h continuous exposure to the male pheromone on the GnRH pulse generator activity was examined by recording the specific multiple unit acitivity (MUA) from the medial basal hypothalamus. Pooled buck hair was used as the source of male pheromone. Six ovariectomized estradiol-primed does were fitted with a nose-mask for 8 h, and during the latter 4 h period 2.0 g of pooled male hair was set in the chamber at the rostral end of the mask. As compared with the period when only an empty mask was put on, the exposure to the male hair resulted in a shortening (p<0.05) of the interval between the MUA volleys, namely the electrophysiological manifestation of the pulsatile GnRH neurosecretion. This stimulatory effect was observed throughout the time when animals were exposed to the male pheromone. This result demonstrates that the hypothalamic GnRH pulse generator of the recipient female is accelerated as long as the exposure to the male pheromone continues.

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Interferon-tau (IFNτ) is a primary factor secreted by the conceptus responsible for maternal recognition of pregnancy in ruminant animal species. Although IFNτ is well characterized in ovine and bovine species, only minute data are available for caprine IFNτ species (cIFNτ) and there is not much information available on Shiba goat IFNτ. The aim of the present investigation was to establish a new animal model system for the study of maternal-fetal communication in Shiba goats. In order to detect Shiba goat IFNτ expression, recombinant ovine IFNτ (oIFNτ) proteins were initially prepared and were used to prepare an antibody against oIFNτ in rabbits. This antiserum was used to execute immunohistochemical analysis with tissue sections prepared from Shiba goat whole uteri fixed and embedded in paraffin. Conceptus tissues exhibited distinctive staining for the presence of a protein(s) related to oIFNτ. Using the primers designed from oIFNτ cDNA, DNA sequences for potential Shiba goat IFNτ were then amplified. Nucleotide and deduced amino acid sequences of the Shiba goat equivalent were analyzed and compared to IFNτ of other species. Three kinds of nucleotide sequences close to oIFNτ and cIFNτ were identified: Two of which were almost equivalent to oIFNτ and cIFNτ, and one of which had lower homology in nucleotide and amino acid sequences. Deduced amino acid sequences of three types of clones were conserved in each position distinctive for IFNτ family. These data indicate that three types of genes identified are IFNτ homologues of Shiba goats. These data suggest that nucleotide probes derived from these genes could be used to further study biological significance and transcriptional regulation of IFNτ during periods of peri-implantation.

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Ovariectomized female rats were subcutaneously implanted with silicone capsules containing estradiol (n=11), which maintained physiological levels of plasma estradiol, or cholesterol (n=10) as control at the age of 9 weeks. Body weight, amount of food intake and water consumption were recorded twice daily during a 2 week period starting one week before the capsule implantation. Estradiol treatment induced suppression of daily food intake and body weight gain in animals carrying estradiol capsules as compared with those carrying cholesterol one, whereas there was no apparent estradiol effect on water intake. The extent of suppression of both body weight gain and food intake were indistinguishable between the light and the dark phases. The present results suggest that the mechanism which mediates the inhibition of body weight gain and the reduction of food intake is not directly linked with that generating diurnal rhythmicity.

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The present studies were designed to determine the effect of tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) during meiosis or after in vitro fertilization on early embryonic development of porcine embryos. The presence of purified ovine TIMP-1 in culture medium after in vitro fertilization did not affect the incidence of embryo cleavage or development to the blastocyst stage at 48 h or 6 days after insemination, respectively. In contrast, when various concentrations (1.25, 2.50 and 5.00 μg/ml) of purified ovine TIMP-1 were added to the culture medium during the second half (24 h) of oocyte maturation, normal cleavage rates (64 ± 3% at 1.25 μg/ml, 57 ± 5% at 2.50 μg/ml and 56 ± 1% at 5.00 μg/ml) were higher (p<0.05) as compared to controls (43 ± 2%). In addition, the incidence of embryos that developed to the blastocyst stage was increased (p<0.05) when TIMP-1 was added (34 ± 3% at 1.25 μg/ml, 32 ± 1% at 2.50 μg/ml and 28 ± 1% at 5.00 μg/ml) as compared to controls (22 ± 3%). There was no difference in the incidence (53 ± 1%) of oocytes fertilized normally. These results indicate that the presence of TIMP-1 during the second half of in vitro maturation enhanced the competence of porcine oocytes to develop to the 2- to 4-cell stages after in vitro fertilization, consequently increasing the incidence of blastocysts.

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The objectives of this research were to characterize plasma profiles of growth hormone (GH), prolactin (PRL) and insulin-like growth factor-I (IGF-I) during gestation and the lactation period in goats, as well as in their suckling growing kids. There were no obvious changes in the GH or PRL profiles during gestation, but secretion of both GH and PRL increased acutely after parturition. The elevated GH concentrations were maintained until 3 months after parturition, whereas the PRL concentrations decreased gradually after parturition. The elevated hormone concentrations are thought to be caused mainly by an increase in the secretory pulse amplitudes. In contrast to the GH and PRL profiles, the plasma IGF-I concentrations during late gestation were significantly higher than the post-parturition concentrations, and the IGF-I concentrations in late gestation decreased gradually until the day of parturition. The plasma GH, PRL and IGF-I concentrations in kids 1 week after birth were high, and concentrations of each hormone decreased thereafter. These results show that the increased secretory potencies of pituitary GH and PRL after parturition are caused mainly by an increase in the secretory pulse amplitudes and that plasma GH is inversely related to plasma IGF-I compared over gestation and the lactation period in goats.

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This study was conducted to determine the effect of accelerated lambing caused by melatonin feeding in the spring on increasing lamb production. Forty-six Suffolk ewes, which conceived last autumn and expected to give birth in February of this year, were divided into 2 groups as follows. Group 1 (treatment, n=23) and Group 2 (control, n=23) ewes were adapted to accelerated lambing and natural lambing, respectively. The accelerated lambing system composed of melatonin feeding for 60-90 days starting in late March followed by ram introduction in May and re-breeding after autumn lambing. The natural lambing system was established so that the ewes were isolated from the rams until autumn resulting in one lambing per year. In these 2 groups, the reproductive performance was evaluated. In the accelerated lambing system, 78% of the ewes (18/23) successfully produced 3 sets of lambs every 2 years. The prolificacy per year of the ewes that were involved in the accelerated lambing system was more than that in the control ewes (224% vs. 159%, p<0.01). The present results demonstrated that the accelerated lambing system with melatonin feeding only once every 2 years could result in greater lamb production than the natural lambing system.

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The present study was conducted to examine survival of fresh and frozen-thawed ovine embryos after embryo transfer (ET) using laparoscopy or in vitro culture. Embryos were collected on Day 7.5 (Day 0 =sponge removal) from donor ewes superovulated by pre-treatment of progestogen-impregnated intravaginal sponges (FGA) for 12 days and a single injection of follicle stimulating hormone (FSH) and equine chorionic gonadotrophin (eCG), at 2 days and 1 day before sponge removal. The donor ewes showed estrus between 12 h and 30 h (the mean time: 15.6 h) after sponge removal. Embryo transfer of fresh or frozen-thawed embryos was carried out on Day 7.5 in 37 recipient ewes using laparoscopic technique. Frozen-thawed morulae or blastocysts were cultured to examine their viability in a modified synthetic oviduct fluid medium (SOFM) for 24 h. The lambing rates after ET with fresh and frozen-thawed embryos were 33.3% (6/18) and 26.3% (5/19), respectively. The developmental stage (morula or blastocyst) affected the survival rate of frozen-thawed embryos transferred (54.5% and 0%, respectively). The survival rate (development to blastocyst or hatched blastocyst) of frozen-thawed embryos after 24 h in culture was 40.9% (9/22). The present results indicate that ovine ET using laparoscopy is a useful technique. But, the lambing and survival rates of both fresh and frozen-thawed embryos were low, and remained to be improved.

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Uterine luminal surface of the hamster was examined by scanning electron microscopy (SEM) to determine whether aging alters surface ultrastructure of the endometrium where implantation takes place. On Days 2 to 3, the epithelial cells of young hamsters were round and uniformly covered with microvilli. The cells of aged hamsters were polygonal in shape with microvilli of equal density. However, in about 15% of the aged uterine epithelium examined the cells had a reduced number of microvilli. The cellular protrusions appeared on the apical membrane in young uteri on Day 4, but fewer protrusions were observed in aged uteri on Day 5 and some of them were lost before implantation. Implantation was delayed in the aged females. These findings suggest that altered surface ultrastructure of the aged uterus may reflect age-related implantation failure.

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To investigate the influence of post-thawed embryonic developmental stage and post -thawed morphological quality on pregnancy rate, frozen embryos, which had been collected from Japanese Black beef cattle and qualified as morphologically excellent before freezing, were thawed by the stepwise method and transferred non-surgically to Holstein heifers on day 7 (day 0=onset of estrus). The transferred embryos ranged in development from compacted morula to blastocyst stage and were evaluated as either morphologically excellent or good quality just after thawing. Pregnancy rates of 62.0% (49/79), 66.7% (26/39), and 81.0% (34/42) were achieved in the transfers of the compacted morula, early blastocyst, and blastocyst stages, respectively, for the transfer of the excellent quality embryos. The pregnancy rate obtained with blastocyst stage embryos was significantly (P<0.05) higher than that obtained with compacted morula embryos. The pregnancy rate of morphologically excellent quality embryos of the compact morula stage was 62.0% (49/79), and that of the good quality embryos of the compacted morula stage was 58.3% (7/12) revealing no significant difference between the two morphological qualities. These results indicate that the pregnancy rate increases as the embryonic developmental stage advances from compacted morula to early blastocyst, and that post-thawed morphological qualities, excellent and good quality, have no influence on pregnancy rates for frozen-thawed embryos that are transferred to bovine recipients on day 7 of estrus.

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