Reproduction in Domestic Animals - Facultad de Ciencias Veterinarias

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16 t h International Congress on Animal Reproduction 80 Poster Abstracts P157 Role of exogenous leptin and season on thyroxine release from thyroid gland in ewes Klocek-Górka, B 1 *, Szczęsna, M 1 , Sechman, A 2 and Zięba, DA 1 1Department of Sheep and Goat Breeding, Agricultural University of Krakow, Poland; 2 Animal Physiology Dept., Agricultural University, Krakow, Poland Through its circadian release of melatonin, the pineal gland plays a key role in integrating circannual responses in day length within the neuroendocrine axis of the ewe. Leptin, which synthesis and release are sensitive to acute changes in nutritional status, acts on target sites within the brain that regulate appetite and energy balance. The pituitary-thyroid system is regulated at multiple levels, one or more of which might account for nutritional adaptation. Thyroid hormones are obligatory for the annually recurring termination of reproductive activity in a spectrum of seasonal breeders, including sheep. The presence of leptin receptors in the thyroid gland has been reported and some leptin effects may be, directly or indirectly, mediated by hypothalamo-pituitary-thyroid axis. It was shown that, in the ewe, the interaction between the thyroid gland and reproductive neuroendocrine axes changes dynamically throughout the year. The present study addresses questions related to timing of the interaction between thyroid hormone - thyroxine (T4) and leptin in seasonal breeding ewes. Studies were carried out on thyroid glands’ explants in short-term culture. Glands were collected from nine ewes selected randomly during long days (LD, i.e. Apr., May and July) and from additional nine ewes during short days (SD, i.e. Sept., Oct, Nov). The explants (approximately 30 mg) were equilibrated in 2.5 ml of RPMI/F12 medium with 0.5% FCS for 30-min, followed by a 4.5 h incubation in medium containing either 0, 50 or 100 ng/ml of recombinant ovine leptin (roleptin) with melatonin (100 ng/ml) and with or without TSH (100 ng/ml). Concentrations of T4 were determined by RIA and expressed as means ± SEM. Thyroxine concentrations in explants media were affected (P < 0.05) by season, and melatonin had inhibitory effect (P < 0.05) on T4 secretion during both long and short days. In explants cultures from thyroid glands collected during SD, roleptin in both doses together with TSH stimulated (P < 0.01) T4 release, however, those effects were diminished by melatonin. In LD, high dose of roleptin applied with TSH increased T4 secretion in comparison to control (P < 0.01), and this effect was again inhibited by melatonin. The data obtained provide an evidence for seasonal interactions between leptin and thyroxine in ewes with higher T4 secretion during long days when thyroid hormones are necessary for quiescence of the reproductive activity in ewes. P158 The use of melatonin and progestagen to advance puberty in Awassi ewe lambs Kridli, R 1 *; Jawasreh, K 2 ; Sawalha, M 1 1Department of Animal Production, Faculty of Agriculture, Jordan University of Science and Technology, Irbid 22110, Jordan 2The National Center for Agriculture Research and Extension, Baqaa, Jordan Introduction Ewes are generally culled at 6 to 7 years of age after having produced 5 to 6 lamb crops. Advancing puberty age allows ewe lambs to enter the breeding season at around 7 to 8 months of age thus obtaining one more lamb crop per female during her productive life. Attempts to breed ewe lambs at an earlier age in Jordan resulted in limited success as only 20 to 30 % of the females lambed at one year of age (personal communication). Thus, the objective of this study was to advance puberty and initiate the breeding season in Awassi ewe lambs through hormonal treatments. Methods This experiment was conducted at the Khanasry Station for Small Ruminant Development to evaluate the effect of administering hormonal treatments [melatonin, progestagen and pregnant mare\'s serum gonadotropin (PMSG)] on advancing puberty in Awassi ewe lambs. Fifty one, 6-month old ewe lambs of similar body weights (around 28 kg) were randomly assigned into four treatment groups; no hormonal treatment (CON; n=14), melatonin (M; n=13), progestagen and PMSG (PP; n=13) and melatonin plus progestagen and PMSG (MPP; n=11). Ewe lambs in the PP and MPP groups were treated with intravaginal progestagen sponges for 14 days. Four hundred IU PMSG were administered to each of these ewe lambs on the day of sponge removal. Ewe lambs in the M and MPP groups received subcutaneous melatonin implants (Regulin®, 18 mg melatonin) 36 days before sponge insertion. The melatonin implants were applied in mid May, around 6 to 7 weeks before the natural breeding season for Awassi. Fertile, harnessed Awassi rams were introduced at the time of sponge removal. Results Hormonal treatment had no effect on body weight. Estrus expression tended to be greater (P = 0.1) in the M, PP and MPP compared with CON ewe lambs (92%, 92%, 100% and 71%, respectively). The duration from ram introduction to onset of estrus was shorter (P < 0.001) in PP and MPP than in M and CON ewe lambs (12±3.5, 5.7±3.7, 23.9±3.5 and 26.5±3.9 d, respectively). Pregnancy rate (evaluated by ultrasonography 60 days post ram introduction) was similar among treatments although being numerically greater in the MPP group (50%, 61.5%, 53.8% and 81% in CON, M, PP and MPP ewe lambs, respectively). Conclusion Results indicate that a combination of melatonin, progestagen and PMSG appears to be effective in advancing puberty in Awassi ewe lambs. The lack of significant differences in estrus expression and pregnancy rate may be attributed to the low number of animals. P159 Luteinizing hormone (LH) and Follicle stimulating hormone (FSH) induce the expression of Cyclooxygenase -2 mRNA in cervical tissue of non-pregnant ewes Leethongdee, S 1,2 *, Khalid, M 1 and Scaramuzzi, RJ 1 1The Royal Veterinary College, University of London, United Kingdom; 2Faculty of Veterinary Medicine and Animal Sciences, Mahasarakham University, Thailand Introduction The ovine cervix contains both LH and FSH receptors and their concentrations are greatest at oestrus indicating physiological roles in relaxation of the cervix. Cervical relaxation at oestrus is mediated by prostaglandin E 2 whose synthesis is regulated by the inducible enzyme, COX-2. Consequently, the high level of FSH and LH during the peri-ovulatory period may stimulate COX-2 regulated PGE 2 synthesis leading to cervical relaxation at oestrus. Our objective was to determine the effect of intra-cervical LH and FSH on the expression of COX-2 mRNA in the cervix of the ewe during oestrus. Methods Eighteen ewes were assigned to 4 groups of 5 (groups 1 and 2) or 4 ewes (groups 3 and 4). Oestrus was synchronised using progestagen pessaries and 500 IU PMSG at pessary removal. Intracervical hormone was applied 24h after pessary removal: Group 1: FSH 2 mg; Group 2: LH 2 mg; Group 3: Vehicle; Group 4: Control. Cervices were collected 54h after sponge removal or 30 h after hormone treatment and divided transversely into 6 sections; alternate sections were formalin fixed, wax embedded and sectioned at 7μm. The expression of COX-2 mRNA was determined by In situ hybridization using a digoxigenin-11-UTP labelled riboprobe. COX-2 expression in cervical tissue was analysed in five tissue layers (epithelium, stroma, circular, longitudinal and transverse muscle) and three cervical regions (vaginal end, middle region and uterine end). Results The expression of COX-2 mRNA in cervical tissue of ewes treated with FSH was greater than in the gum vehicle (P = 0.004) and control (P = 0.003) groups. Similarly, the expression of COX-2 mRNA in cervical tissues of ewes treated with LH was also greater than in the gum vehicle (P = 0.007) and control (P = 0.006) groups. The highest expression of the COX-2 mRNA was at the vaginal end of the cervix. The expression of COX-2 mRNA at the vaginal end and the middle region were significantly greater than at the uterine end (both P < 0.001).There was no difference in COX-2 mRNA expression between the vaginal end and the middle region (P = 0.683). Among the tissue layers expression was highest in the luminal epithelium and lowest in the stroma. The expression of COX-2 mRNA in smooth muscle and luminal epithelium were higher than in the stromal layer (both, P < 0.001).
16 t h International Congress on Animal Reproduction Poster Abstracts 81 Conclusions The results show that both FSH and LH stimulated COX-2 mRNA in the sheep cervix at oestrus. The increased COX-2 induced by FSH and LH is probably associated with increased PGE 2 synthesis and cervical relaxation during the peri-ovulatory period. P160 Synchronization with progestagen affects LH receptor and function of corpus luteum in sheep Letelier, C 1,2 *; Garcia, RA 3 ; Contreras, I 1 ; Garcia-Palencia, P 3 ; Sanchez, B 3 ; Sanchez, MA 3 ; Gonzalez-Bulnes, A 1 ; Flores, JM 3 1Reproducción Animal, INIA, Spain; 2 Facultad Cs. Veterinarias, UACh, Chile 3Facultad de Veterinaria, UCM, Spain Introduction Pregnancy in mammals is the consequence of an adequate equilibrium between embryo and maternal factors; mainly luteal activity, in terms of progesterone (P) secretion. The gonadotrophin LH is the primary luteotropic hormone, supporting the development and function of the CL, through LH receptors expressed in ovary. Thus, we aimed to discern possible effects of synchronization treatment on LH secretion and/or LH receptors expression around the implantation. Methods Oestrus was synchronized in 30 Manchega sheep; half of the animals were treated with three injections of prostaglandin, 10 days apart (group, PGF), and the remaining 15 ewes, were synchronized with intravaginal progestagens, applied for 14 days (group FGA). Appearance of oestrus behaviour was detected with rams and considered Day 0. Number and size of all CL were determined daily by 7.5 MHz transrectal ultrasonography until Day 13, 15 and 17 of pregnancy. Blood samples were taken coincidentally and plasma progesterone concentration and LH concentration were measured by radioimmunoassay and ELISA, respectively. Ovaries with corpora lutea of PGF and FGA group were collected on days 13, 15, 17 post mating, routinely processed in 4% paraformaldehyde and paraffin-embeded. The corpora lutea (n= 45) were studied using conventional immunohistochemical techniques for determining LH receptor (LHr) expression. Results In both groups, the total luteal tissue in sheep showed a linear growth (p
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Reproduction in Domestic Animals - Facultad de Ciencias Veterinarias

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