Synchronization of ovulation and fixed time intrauterine insemination in ewes

A novel method for oestrus-ovulation synchronization in sheep followed by fixed time insemination is presented herewith. Mature dry ewes (n = 28) of Karagouniko breed being at an unknown stage of the oestrous cycle, were used during the middle of breeding season. The treatment protocol consisted of an initial administration of a GnRH analogue followed 5 days later by a prostaglandin F2alpha injection. Thirty-six hours later a second GnRH injection was administered to synchronize ovulation, and laparoscopic intrauterine insemination was performed 12-14 h later. Three days after insemination, fertile rams were introduced into the flock twice daily and oestrus-mating detection was carried out. For progesterone (P-4) determination, blood samples were collected on alternate days, starting 2 days before the first GnRH injection and continuing for 17 days after insemination. An additional sample was taken on the day of insemination. Pregnancy diagnosis was carried out by trans-abdominal ultrasonography. Fourteen ewes (50%) conceived at insemination and maintained pregnancy; from the remainder 14 ewes 10 became pregnant at natural service, while four, although they mated at least two to three times, failed to conceive. In response to the first GnRH, P-4 concentration increased at higher levels in ewes that conceived at AI compared with those that failed to conceive (47.54 and 22.44%, respectively; p < 0.05). Significant differences (p < 0.05) in mean P-4 concentration between pregnant and non-pregnant animals were detected 1 day before AI (0.17 +/- 0.06 and 0.26 +/- 0.14 ng/ml, respectively) on the day of AI (0.15 +/- 0.04 and 0.24 +/- 0.08 ng/ml, respectively) as well as 9 and 11 days thereafter (0.48 +/- 0.12 and 0.38 +/- 0.12 ng/ml; 0.68 +/- 0.14 and 0.50 +/- 0.18 ng/ml, respectively). These results indicate that using the proposed protocol, an acceptable conception rate can be achieved which could be further improved by modifying the time intervals between interventions

Gonadotrofina coriônica eqüina: purificação, caracterização e resposta ovariana em ovinos e suínos Equine chorionic gonadotrophin: purification, characterization and ovarian activity in ewes and gilts

A gonadotrofina coriônica equina (eCG) foi purificada e caracterizada com respeito ao grau de pureza e atividade biológica. A pureza de quatro preparações foi determinada por eletroforese e a atividade biológica pelo incremento do peso ovariano de ratas imaturas (40 - 50g) e pela indução de ovulação em ovelhas e leitoas. A análise eletroforética revelou a presença de três bandas polipeptídicas. A atividade biológica media foi de 313 UI/mg de proteína. Sessenta e cinco (65) ovelhas, fora da estação reprodutiva, foram divididas ao acaso em dois grupos os quais receberam implantes vaginais de esponjas impregnadas com acetato de medroxiprogesterona por um período de l l a 14 dias. No grupo I (55 ovelhas), foram injetadas (IM) 500UI do eCG purificado no momento da retirada das esponjas, enquanto que no grupo II (10 ovelhas) foram injetadas 500UI de eCG comercial. Uma semana após a aplicação do eCG as ovelhas foram submetidas a um exame laparoscópico para avaliar o número de ovulações. Obteve-se uma média de 2,1 &plusmn; 0,3 e 1,8 &plusmn; 0,3 ovulações (P>0,05) para as ovelhas dos grupos I e II, respectivamente. De 120 leitoas pré-púberes, com peso médio de 87,2 kg, 90 (grupo I) foram injetadas com 500UI do eCG purificado e, às 72 horas, 500UI de hCG (gonadotrofina coriônica humana), e 30 leitoas (grupo II) não receberam injeção hormonal. Observou-se a presença de 25,9 &plusmn; 22,2 e 0,0 corpora lutea (P<0,001), nos grupos I e II, respectivamente. Estes resultados demonstraram que o PMSG purificado apresenta pureza e atividade biológica similares ao produto comercial utilizado como controle e que é eficiente para induzir atividade ovariana em ovinos e suínos.<br>Equine chorionic gonadotrophin (eCG) was purified and characterized with respect to its purity and bionological activity. The purity of four preparations was determined by electrophoresis, and the biological activity by increasing of the ovarian weight ot immature female rats (40-50g) and induction ot ovulation of ewes and gilts. Electrophoretic analysis revealed three polipeptidic bands. The mean biological activity was 313UI/mg of protein. Sixty-five ewes, not in reproductive season, were divided randomly in two groups that received vaginal pessaries impregnated with medroxiprogesterone acetato for 11 to 14 days. In treatment I, ewes (n = 55) were injected (IM) with 500UI of puritied eCG at the moment of pessaries withdraw, while in treatment II, the ewes (n = 10) received 500UI of comercial eCG. The results observed were 2.1 &plusmn; 0.3 and 1.8 &plusmn; 0.3 ovulations (P > 0.05) for treatments I and II, respectively. One hundred-twenty gilts, with mean weight of 87.2kg, were divided m two treatments. The animals in treatment I (90 gilts) received 500UI of puntied eCG and, 72 hours later, 500UI of hCG (human chorionic gonadotrophin). In treatment II hormones were not injected. The results observed were 25.9 &plusmn; 22.2 and 0.0 corpora lutea (P < 0.001) for treatments I and II, respectively. These results demonstrated that the eCG purified has purity and biological activity similar to the comercial product used as control, and that it is efficient in inducing ovarian activity in ewes and gilts

Luteal stage dependence of pituitary response to gonadotrophin-releasing hormone in cyclic dairy ewes subjected to synchronisation of ovulation

Possible hormonal aberrations precluding conception or maintenance of pregnancy in dairy ewes subjected to ovulation synchronisation were investigated in this study. The pituitary response to exogenous gonadotrophin-releasing hormone ( GnRH) was tested at different luteal stages in 36 ewes. Oestruses were synchronised by using progestagen-impregnated sponges and the animals were randomly allotted into one of three treatment groups ( A, B and C; n= 12 for each). Treatments commenced on Days 4, 9 and 14 of the new cycle ( oestrus was defined as Day 0). Ewes were given two GnRH injections, 5 days before and 36 h after a prostaglandin F-2 alpha (PGF(2 alpha)) injection, and the animals were inseminated 12-14 h after the second GnRH injection ( modified OVSYNCH). For luteinising hormone ( LH) determination blood samples were withdrawn from six ewes of each group at the time of GnRH administration, and 30, 90, 180, 270 and 360 min later. Progesterone was assayed in samples taken every other day starting from oestrus and for 17 days after the second GnRH injection, and in an additional sample collected on the day of insemination. After the first GnRH injection, the LH concentration was higher in Group C than in Groups B and A (mean +/- s.d.: 64.8 +/- 10.0 ngmL(-1), 41.3 +/- 3.7 ngmL(-1) and 24.6 +/- 9.0 ngmL(-1), respectively; P < 0.05), whereas after the second GnRH injection a uniform LH release was found in all groups. PGF2 alpha caused a significant decrease in progesterone (P-4) concentration in all groups; however, at artificial insemination ewes that conceived had significantly lower P-4 concentration in comparison with those that failed to conceive. As early as Day 5, pregnant animals had higher P-4 concentrations than non- pregnant animals. Overall, 21 animals conceived ( seven, nine and five ewes from Groups A, B and C, respectively). These results indicate that the proposed protocol is equally effective in inducing a preovulatory LH surge at any stage of the luteal phase, and that elevated P-4 concentration along with a delayed P-4 increase should be considered as a causative factor for inability to conceive