Effects of parity and season on pregnancy rates after the transfer of embryos to repeat-breeder Japanese Black beef cattle

Abstract. Repeat-breeder (RB) cows are a major source of economic waste due to their decreased fertility. Embryo transfer (ET) is an alternative tool to improve the fertility of RB cows. The aims of the present study were to evaluate the effects of recipient parity and the season on pregnancy rates following ET in RB Japanese Black beef cattle. Embryos were transferred nonsurgically to recipients, consisting of 155 heifers (< 2 years old) and 172 cows (< 8 years old), which were defined as RB cattle. Of the recipients that were presented for ET, 57 recipients received a fresh embryo and 270 recipients received a frozen embryo. There were no differences in the pregnancy rates between cattle that received fresh embryos or frozen embryos. The rates of recipients with pregnancy, abortion, stillbirth, and normal calving were similar between heifers and cows. In cows, the pregnancy rates were lower (P < 0.05) in summer (June to August) than in spring (March to May) and winter (December to February). In heifers, however, there were no differences in the pregnancy rates among the seasons. Our findings indicate that in RB Japanese Black beef cattle, the parity of the recipients does not have an effect on the pregnancy rates following the transfer of fresh and frozen embryos. However, heat stress may affect reproductive performance in RB Japanese Black cows.

Melatonin Supplementation During In Vitro Maturation and Development Supports the Development of Porcine Embryos

Melatonin has been reported to improve the in vitro development of embryos in some species. This study was conducted to investigate the effect of melatonin supplementation during in vitro maturation (IVM) and development culture on the development and quality of porcine embryos. In the first experiment, when the in vitro fertilized embryos were cultured with different concentrations of melatonin (0, 10, 25 and 50 ng/ml) for 8 days, the blastocyst formation rate of embryos cultured with 25 ng/ml melatonin (10.7%) was significantly increased (p < 0.05) compared to the control embryos cultured without melatonin (4.2%). The proportion of DNA-fragmented nuclei in blastocysts derived from embryos cultured with 50 ng/ml melatonin was significantly lower (p < 0.05) than that of embryos cultured without melatonin (2.1% vs 7.2%). In the second experiment, when oocytes were cultured in the maturation medium supplemented with different concentrations of melatonin (0, 10, 25 and 50 ng/ml), fertilized and then cultured with 25 ng/ml melatonin for 8 days, there were no significant differences in the rates of cleavage and blastocyst formation among the groups. However, the proportions (2.7-5.4%) of DNA-fragmented nuclei in blastocysts derived from oocytes matured with melatonin were significantly decreased (p < 0.05) compared to those (8.9%) from oocytes matured without melatonin, irrespective of the concentration of melatonin. Our results suggest that supplementation of the culture media with melatonin (25 ng/ml) during IVM and development has beneficial effects on the developmental competence and quality of porcine embryos.

183 ULTRASONOGRAPHIC MONITORING OF CANINE OVARIES CLAMPED AT SUBCUTANEOUS SITE AFTER FOLLICLE-STIMULATING HORMONE TREATMENT

Follicle-stimulating hormone (FSH) alone can induce oestrus in bitches, but few reports describe oestrous induction by FSH because pregnant mare serum gonadotrophin (PMSG) has been more successful than FSH for oestrus induction. Real-time ultrasonography can show canine ovarian follicle development, but no method can determine or predict ovulation accurately. Moreover, the ovary location and size complicate imaging. Using ultrasonography, we investigated FSH treatment stimulation of canine ovary follicles, with clamping of the ovaries at a subcutaneous site. Bilateral malacotomy of four 5-year-old Beagle bitches (mean weight 10.3 ± 2.0 kg) with normal oestrous cycles was done using a ventral flank abdominal approach with routine techniques and materials. Each ovary that maintained blood circulation from the suspensory ligament was clamped at a subcutaneous site through muscles of the abdomen. After about six months of bilateral malacotomy, four bitches at the anestrous (two bitches) and diestrous (two bitches) stages of the oestrous cycle were given 0.5 Armour units of FSH twice daily for 5 days. Examinations with ovarian ultrasonography with 7.5 MHz sector transducer, vaginal cytology, and serum concentrations of progesterone and oestradiol were performed daily from the day before the start of FSH treatment through 7 days after FSH treatment. After 15 days of ovarian examination, each bitch received the same FSH treatment twice continually at 15-day intervals. No serosanguineous vaginal discharge was observed during the ovarian examination. The concentrations of progesterone (<0.045–9.6 ng mL–1) and oestradiol (<9.7–81.4 pg mL–1) varied through all treatments. Comparison of the concentrations of progesterone (<0.045–7.6 ng mL–1) and oestradiol (<9.7–30.3 pg mL–1) at the start of FSH administration in each trial revealed that elevated concentrations of both progesterone and oestradiol were observed in the first treatment in 3 bitches. Regarding the second and third treatments, no elevation of concentration was found for progesterone or oestradiol. A new follicular growth was observed in 1 animal after the third FSH treatment, but no follicular growth was found for the other animals. No correlation was found between follicular development and the profile of either progesterone or oestradiol. Ultrasonography proved that FSH stimulation alone cannot induce follicular growth by a single treatment, but it might increase the levels of progesterone and oestradiol, which are not correlated with follicular development and oestrous cycles at the start of FSH treatment.

40 TRICHOSTATIN A TREATMENT EFFECTS ON IN VITRO DEVELOPMENT OF INTERSPECIES NUCLEAR TRANSFER CAT EMBRYOS DEPEND ON RECIPIENT CYTOPLASM SPECIES

The developmental ability of interspecies somatic cell nuclear transfer (iSCNT) embryos decreases as the taxonomic distance between the donor and recipient species increases. Treatment of cat iSCNT embryos using bovine oocytes with 50 nM of trichostatin A (TSA) improves in vitro embryonic development (Wittayarat et al. 2013 Cell. Reprogram. 15, 301–308). This study investigated whether the TSA treatment effects differ between the development of cat iSCNT embryos reconstructed with porcine and bovine oocytes. Porcine and bovine cumulus-oocyte complexes were in vitro matured for 44 h and 24 h, respectively. After cumulus cell removal, enucleation was performed by aspiration of the metaphase II plate and the first polar body using a piezo-driven pipette. A cat fibroblast cell was then injected into cytoplasm of successfully enucleated oocyte. Reconstructed cybrids were electrically activated by a single 1.5 kV cm–1 pulse for 100 µs (pig-cat embryos), or a 2.3 kV cm–1 pulse for 30 µs (cow-cat embryos). Pig-cat and cow-cat embryos were cultured in porcine zygote medium (PZM)-5 and modified synthetic oviducal fluid medium (mSOF), respectively. After electrical activation, pig-cat and cow-cat embryos were cultured in medium supplemented with 5 µg mL–1 cytochalasin B + 50 nM TSA (TSA group) or without TSA (control group), and the cow-cat embryo medium was also supplemented with 10 µg mL–1 cycloheximide. After 2 h, TSA-treated pig-cat and cow-cat embryos were incubated in medium supplemented with TSA for 22 h, followed by 48 h incubation without TSA. Pig-cat and cow-cat control embryos were cultured in medium without TSA for 70 h after activation. Then, all pig-cat and cow-cat embryos were cultured in porcine blastocyst medium (PBM) or mSOF medium supplemented with 5% fetal bovine serum, respectively, for 5 additional days. Four to seven replicates were performed for each experiment. Data were analysed using Student's t-test. For pig-cat embryos, no difference was observed in cleavage rates between both groups, but development to the blastocyst stage was higher in the pig control group (n = 147, 8.0%) than that of pig TSA group (n = 131, 0.7%; P < 0.05). In contrast, development to the blastocyst stage in cow-cat embryos was not observed in the cow control group (n = 125, 0%), but it was observed in cow TSA group (n = 136, 3.7%). These results indicate that TSA treatment effects are species-specific, but those effects remain to be clarified.

119 ULTRASONOGRAPHIC MONITORING OF CANINE OVARIES CLAMPED AT SUBCUTANEOUS SITE AFTER HORMONE TREATMENT

Follicular growth in bitches is usually detected indirectly through behaviour observation, vaginal smears, and hormonal assay in blood. Although real-time ultrasonography can reveal the development of canine ovarian follicles, no method has been established to determine or predict ovulation accurately. Moreover, the location and small size of the ovaries make imaging technically difficult. This study was conducted to investigate follicular waves of canine ovaries stimulated by hormone treatment, in which ovaries had been clamped at a subcutaneous site. Bilateral malacotomy of 3 bitches (4 years of age) at the anestrous (2 bitches) and proestrous (1 bitch) stages of the oestrous cycle was performed using a ventral flank abdominal approach with routine techniques and materials. Each ovary that maintained blood circulation from the suspensory ligament was clamped at a subcutaneous site through muscles of the abdomen. Oestrus was induced using subcutaneous administration of 500 IU of eCG and 1000 IU of hCG (eCG/hCG). Each bitch was given 1000 IU of hCG at 11 days after eCG/hCG administration. Examinations with ovarian ultrasonography using a 7.5-MHz sector transducer, vaginal cytology, and serum progesterone assay were performed daily until 20 days after eCG/hCG administration, and every 10 days thereafter from 20 days to 60 days. Serosanguineous vaginal discharges and vaginal cytology of 2 of the bitches were observed. Follicular growth (>1.1 mm in diameter) was observed in all bitches after eCG/hCG administration. The appearance of new follicular growth was observed on 2 days, 6 days, and 8 days after eCG/hCG administration. The mean diameter of follicles reached 4.3 to 5.5 mm, and the maximum numbers of follicles in bitches were 11 to 16. However, all follicles regressed, irrespective of hCG administration. Elevation in progesterone levels (>2 ng mL–1) after eCG/hCG administration was observed from 2 days to 12 days after eCG/hCG administration. No correlation was found between follicular development, progesterone profiles, and vaginal smear characteristics. Follicular growth clamped at the subcutaneous site can be monitored easily using ultrasound without an experienced operator. Moreover, ultrasonography proved that hormonal stimulation can induce follicular growth, but the day of appearance of new follicles varied.

158 ASTAXANTHIN EFFECTS ON MATURATION, FERTILIZATION, AND DEVELOPMENT OF PORCINE OOCYTES CULTURED UNDER HEAT STRESS

Heat stress can engender various disorders in reproductive functions such as impairment of oocyte maturation, fertilization, and embryonic development. Astaxanthin, an extremely common carotenoid, is a typical fat-soluble antioxidant that scavenges ROS and blocks lipid peroxidation. Moreover, astaxanthin has been shown to improve the development of embryos exposed to heat stress by a reduction in stress-inducible genes. This study was conducted to investigate the effects of astaxanthin supplementation on the meiotic competence, fertilization, and development of porcine oocytes exposed to high temperature (41°C) during maturation culture. Cumulus–oocyte complexes (COC) collected from ovaries were transferred into maturation medium supplemented with astaxanthin (0, 0.25, 0.5, or 1.0 ppm) and were then cultured for 46 h at 41°C or 38.5°C. After maturation culture, the COC were subjected to IVF and embryo culture to evaluate the fertility and development of oocytes. The total cell number and DNA fragmentation in the blastocysts were assessed using terminal deoxynucleotidyl transferase dUTP nick end labelling and Hoechst 33342 staining. The total numbers of oocytes matured at 41°C and 38.5°C in each treatment group were 432 to 470 and 426 to 444, respectively. Data were analysed using ANOVA, followed by Fisher's protected least significant difference test. Exposure to elevated temperatures during maturation culture significantly reduced the proportions of oocytes that reached metaphase II. When the COC were cultured in the maturation medium supplemented with 0.5 and 1.0 ppm of astaxanthin under heat stress conditions (41°C), the supplementation of astaxanthin significantly improved the proportions of maturation, fertilization, and blastocyst formation compared with the control group (0 ppm) (50–52%, 45–55%, and 11–12% v. 17, 25, and 6%, respectively). The supplementation of the maturation medium with 0.25 ppm of astaxanthin improved only blastocyst formation (9.6%). Similarly, the supplementation of astaxanthin at 1.0 ppm improved the proportions of maturation, fertilization, and blastocyst formation of oocytes matured at 38.5°C s compared with the control group (67, 57, and 18% v. 48, 33, and 12%, respectively). However, no beneficial effect of astaxanthin supplementation was found in the total cell number or DNA fragmentation in the blastocysts, irrespective of culture temperature. Our findings show that the supplementation of astaxanthin to maturation medium improves maturation, fertilization, and embryo development of porcine oocytes exposed to heat stress during maturation culture.

28 EFFECT OF TRICHOSTATIN A ON IN VITRO EMBRYO DEVELOPMENT OF INTERSPECIES NUCLEAR TRANSFER EMBRYOS RECONSTRUCTED FROM CAT DONOR NUCLEI AND BOVINE CYTOPLASM

Interspecies somatic cell nuclear transfer (iSCNT) is an invaluable tool for studying nucleus-cytoplasm interactions and may provide an alternative for cloning endangered animals whose oocytes are difficult to obtain. The developmental ability of iSCNT embryos decreases with increases in taxonomic distance between the donor and recipient species. The development of cat-bovine iSCNT embryos is reportedly blocked at the 8-cell stage (Thongphakdee et al. 2008 J. Reprod. Dev. 54, 142–147). Abnormal epigenetic reprogramming, such as DNA methylation or histone modifications, may cause low iSCNT efficiencies. The present study was conducted to evaluate the effect of the histone deacetylase inhibitor trichostatin A (TSA), previously used to enhance nuclear reprogramming following SCNT, on the developmental ability of cat iSCNT embryos using bovine oocytes matured in vitro. The matured bovine oocyte was enucleated by the glass needle and the domestic cat fetal fibroblast used as the donor nuclei was then placed into the perivitelline space adjacent to the plasma membrane of the oocyte. Couplets with bovine ooplasm were fused and activated simultaneously with a single DC pulse of 2.3 kV cm–1 for 30 µs, respectively, using an electro cell fusion generator followed by cycloheximide treatment. Reconstructed cat-bovine embryos were treated with 0, 25, 50, and 100 nM concentrations of TSA for 24 h following fusion. The percentages of embryos cleaved and embryos developed to the blastocyst stage were subjected to arc sin transformation before ANOVA. The TSA treatment at 50 nM contributed significantly higher rates of cleavage and blastocyst formation (n = 139; 84.3 and 4.6%, respectively) compared with untreated embryos (n = 187; 63.8 and 0%, respectively) and embryos treated with 100 nM TSA (n = 172; 71.4 and 0%, respectively; P < 0.05). Development to the morula stage of iSCNT embryos was observed in the TSA treatment groups, whereas no embryos developed beyond the 16-cell stage in the untreated group. In conclusion, our results indicate that TSA treatment for 24 h following fusion improves the development of iSCNT embryos. Specifically, 50 nM TSA treatment provides a beneficial effect on cleavage and development to the blastocyst stage of cat iSCNT embryos using bovine oocytes matured in vitro as recipients and domestic cat fibroblasts as donor nuclei.