The effect of Gonadotropin releasing hormone administration on fertility and embryonic loss in goats during the anoestrus period

Following the induction of oestrus out of season in small ruminants, low fertility and variations in fertility rates are associated with embryonic losses. One of the main causes of embryonic loss is luteal dysfunction. Gonadotropin Releasing Hormone (GnRH) supports the luteal structure, and increasing progesterone levels may be beneficial in terms of promoting embryonic life. The main objective of the present study was to evaluate the efficacy of GnRH administration following an oestrus induction protocol in the anoestrus season for preventing embryonic loss in goats having failure to conceive during the season. In the study, 106 Damascus goats aged 3-5 years and weighing 45-60 kg were used. The oestrus of 106 goats in the anoestrous group was stimulated with progesterone and pregnant mare serum gonadotropin (PMSG) treatment. Out of breeding season, goats were divided into the 4 following groups: GnRH0 (n = 27), GnRH7 (n = 26), GnRH0+7 (n = 27) and control (n = 26). In each goat, an intravaginal sponge (IS) containing 20 mg of fluorogestone acetate (FGA) was placed into the vagina and left for 9 days. With the withdrawal of the sponge, 550IU PMSG and 125 µg of d-cloprostenol were injected intramuscularly. Oestrus detection was made via teaser bucks for 3 days starting 24 h after withdrawal of the IS. Eighteen bucks known to be fertile were used for breeding. Goats in the oestrus period were mated via natural breeding. The GnRH analogue lecirelin was injected intramuscularly at breeding in the GnRH0 group, on day 7 post-breeding in the GnRH7 group, and both at breeding and on day 7 post-breeding in the GnRH0+7 group. No injections were given to the control group. Blood samples for progesterone measurement were taken by jugular vena puncturing on days 3, 6, 7, 10, 13, 16, and 19 after breeding from 10 randomly chosen goats in all groups. The goats with a level of > 3.5 ng/mL of progesterone on day 21 post-breeding were evaluated as pregnant. Pregnancy was also viewed on day 50 after breeding by real-time ultrasonography (USG) with a 5-7.5 MHz convex probe. The oestrus rate was 96.23% (102/106) in the goats. The rates of onset of oestrus between 36-48 h, 48-60 h and 60 h and beyond were 38.7% (41/106), 21.7% (23/106) and 35.8% (38/106), respectively. The total pregnancy rate was 35.8% (38/106). There were no statistically significant differences (P > 0.05) found for the pregnancy rate, embryonic death rate or progesterone concentration of the groups. However, serum progesterone levels were statistically different in the GnRH7 group compared with the control group (P < 0.05). After synchronisation, various anti-luteolytic strategies can be used to support corpus luteum development and elevate progesterone concentration in the luteal phase to decrease embryonic loss and increase reproductive performance. Therefore, application of GnRH to support the luteal structure and to increase progesterone levels may be beneficial in terms of supporting embryonic life. The results showed that GnRH treatment on the day 7 post-breeding following oestrus induction, including FGA and PMSG, can increase serum progesterone levels in Damascus goats in the anoestrus period. However, following oestrus induction in the anoestrus period, it was seen that GnRH treatment at breeding or on day 7 after breeding did not have any positive effect on embryonic loss or reproductive performance. In conclusion, it was considered that this protocol could be implemented successfully, yielding a 35% pregnancy rate in Damascus goats in the anoestrus period, but embryonic loss must be deeply studied in detail.(AU)

O uso do cloridrato de piridoxina para induzir estro em cadelas / The use of pyridoxine chloridrate to induce estrus in female dogs

Os agonistas dopaminérgicos são utilizados para induzir estro em cadelas, pois atuam na síntese e liberação de prolactina. Objetivou-se avaliar o efeito da piridoxina como indutor de estro em cadelas por agir na neurotransmissão dopaminérgica. Foram selecionadas 40 cadelas em anestro, divididas em quatro grupos experimentais, tratadas com 10mg/kg/dia (G1) e 50mg/kg/dia (G2) de cloridrato de piridoxina, 5µg/kg/dia (G3) de cabergolina e grupo controle/placebo (G4) por até 20 dias. Foram realizadas citologias vaginais a cada 24h para acompanhamento do ciclo estral e análises hormonais (FSH, LH e PRL) no dia zero e 120h do início do tratamento. As cadelas do G3 (100%) manifestaram proestro após 12 dias de tratamento aproximadamente, tempo inferior aos demais grupos (P<0,05). Apenas uma cadela do G1 e uma do G2 ficaram gestantes contra oito fêmeas do G3 e nenhuma do G4 (P<0,05). As concentrações plasmáticas de prolactina foram reduzidas nas fêmeas do G2 e G3 (P<0,05). As demais avaliações hormonais não sofreram influência do tratamento (P>0,05). O cloridrato de piridoxina foi ineficiente para induzir estro em cadelas, mas foi capaz de suprimir a prolactina, de forma semelhante à cabergolina, quando utilizado na dose de 50mg/kg/dia.(AU)

Dopaminergic agonists are used to induce estrus in female dogs as they act in the synthesis and release of prolactin. The objective of this study was to evaluate the effect of pyridoxine as an inducer of estrus by acting on dopaminergic neurotransmission. A total of 40 female dogs in anestrous were divided into four experimental groups treated with 10mg/kg/day (G1) and 50mg/kg/day (G2) of pyridoxine hydrochloride, 5µg/kg/day (G3) of cabergoline and control group/placebo (G4) for up to 20 days. Vaginal cytologies were performed every 24h for follow-up of the estrous cycle and hormonal analyzes (FSH, LH and PRL) on day zero and 120 hours after the start of treatment. The female dogs from G3 (100%) showed proestrus after 12 days of treatment, less time than the other groups (P< 0.05). Only one female from G1 and one from G2 were pregnant against eight from G3 and none from G4 (P< 0.05). Plasma concentrations of prolactin were reduced by treatment in females from G2 and G3 (P< 0.05). The other hormonal evaluations were not influenced by the treatment (P> 0.05). Pyridoxine chloridrate was inefficient to induce estrus in female dogs but was able to suppress prolactin when used at a dose of 50mg/kg/day.(AU)

Immunoexpression of vascular endothelial growth factor and B-cell lymphoma 2 in the uterine tissue of rats treated with melatonin in the estrus phase

Abstract Purpose: To investigate the effect of melatonin on uterine tissue in the ovariectomized rat model. Methods: Fourty Wistar albino rats were divided into four groups for histologic and immunohistochemical examination. The rats were first numbered randomly and then randomly divided into 4 equal groups: control (group 1), torsion (group 2), torsion+detorsion (group 3) and torsion+detorsion+melatonin (group 4) groups. In addition, four Wistar albino rats were used for western blot analysis in each group. And also, malondialdehyde (MDA) levels were measured biochemically in all rats. Results: The histopathological examination of the uterine tissue in rats ovarectomized showed a degeneration in uterine glands, dilation of blood vessels in the internal layer with a thrombosis and bleeding, abnormal nucleuses and vacuolated cytoplasm above and below the nucleus. In torsion group, the apoptotic cells increased in luminal epithelium and gland cells. In the melatonin group showed that the Bcl2 negative effect on the uterine epithelium and did not lead to apoptotic cells. Conclusion: The increase in vascular endothelial growth factor expression resulted in the rearrangement of endothelial cell growth and the induction of angiogenesis.

Comparison between two progesterone sources and two oestradiol formulations in a Heatsynch protocol for postpartum cycling dairy cows in pasture

To compare an injectable progesterone (MAD-4) with an intravaginal device (IPD), and natural O17 with synthetic oestradiol (OB) in a synchronisation protocol, 51 cows were divided into four groups. Each group was treated with one of the two sources of progesterone and one of the two oestradiol formulations. Oestrus behaviour, follicle diameter, and pregnancy rates were evaluated. Oestrus behaviour (p = 0.902), numbers of cows in oestrus (p = 0.917), follicle diameter (p = 0.416), and pregnancy rates (p = 0.873) were similar among the four groups. More cows in the group treated with the IPD and OB scored > 200 oestrus behaviour points compared to the other groups (p = 0.038). A longer interval between the end of treatment and oestrus was observed among cows treated with MAD-4 than cows given the IPD (p = 0.030), but no differences were found between animals receiving the two oestradiol formulations (OB and O17). While the use of MAD-4 requires further testing, similar responses to natural oestradiol observed in the present study could allow the use of this formulation in reproductive protocols because it is not associated with the potential human health risks of OB.

Evaluation of the effect of a 3rd GnRH injection administered six days after the 2nd GnRH injection of Ovsynch on the reproductive performance of Japanese black cows

This study was designed to evaluate the reproductive performance of Japanese black cows following the 3rd injection of gonadotropin releasing hormone (GnRH) analogue administered concurrently with Ovsynch-based treatment on day 6 (day 1 = the day of ovulation). In Experiment 1, 12 cows were allocated into three groups: a control group that was subjected to Ovsynch treatment and then injected with a placebo on day 6; group 1 (Ovsynch + GnRH), which was subjected to Ovsynch treatment and was injected with GnRH analogue on day 6, and group 2 (Ovsynch + controlled internal drug-release (CIDR) + GnRH), which received Ovsynch-CIDR treatment and was injected with GnRH analogue on day 6. Blood collection and ultrasonographic observation of the ovaries were conducted daily. Both treatments induced the formation of an accessory corpus luteum and significantly increased the cross-sectional area of the luteal tissue when compared to the control. However, plasma progesterone (P(4)) was significantly higher in the treatment groups than in the control group on days 11, 12, 17 and 18 in the group 1 and from day 10 to 21 in the group 2. In Experiment 2, 41 cows were assigned to the same three groups described above and then artificially inseminated on day 1. The pregnancy rates on day 45 did not differ among groups. In conclusion, administration of GnRH analogue on day 6 following Ovsynch-based treatment did not improve the reproductive performance of Japanese black cows, even though the P(4) concentration was higher in groups that received the GnRH.

Progesterone restores stress induced inhibition of estrous behavior in rat.

Exposure to a stressor (mild electrical shocks to foot, five times per episode, at 1800, 1830, 1900 and 1930 hrs of proestrus) coinciding with period of pre-ovulatory progesterone secretion in rats abolished estrous behavior as shown by the absence of lordosis response and a significant increase in rejection quotient compared to controls. These rats did not show spermatozoa in the vaginal smear next day morning in contrast to their presence in controls. On the other hand, rats treated with progesterone (a single injection, 500 microg in 0.1 ml olive oil at 1800 hr of proestrus) prior to exposure to stressor showed normal estrous behavior, as shown by significantly lower rejection quotient than rats exposed to stress alone, lordosis quotient similar to controls and presence of spermatozoa in the vaginal smear next day. The results, albeit indirectly, to the best of our knowledge, first time indicate that stress induced impaired steroidogenesis leads to suppression of estrous behavior.

Effects of selenium toxicity on oestrous cyclicity, ovarian follicles, ovulation and foetal survival in rats.

Effects of intraperitoneal injections of sodium selenite (2.0 and 4.0 mg/kg body weight) to normally cycling female albino Wistar rats daily for 30 days, and of single injection either during proestrous or oestrous and at each stage of the 4-day oestrous cycle were determined on oestrous cyclicity, ovarian follicles, ovulation, implantation and pregnancy outcome on day 14 of gestation. Administration of selenite for 30 days had no effect on the duration of first two oestrous cycles but afterwards the rats remained at the dioestrus stage. Their ovaries developed cystic follicles. Selenite treatments during the oestrous cycle preceding mating affects the implantation and pregnancy outcome in a dose-related manner. Its single dose containing 2.0 mg/kg body weight administered either at proestrous or oestrous, though had no effect on different reproductive parameters investigated in this study but its daily dose during the 4 day oestrous cycle reduced the number of corpora lutea and implantations as compared to saline injected control female rats. Similar effects of a single dose of selenite (4.0 mg/kg body weight) when injected at proestrous were recorded. Higher dose of selenite at oestrous or throughout the cycle decreased the number of implantations, but in addition, also increased the resorption rate/litter on day 14 of gestation. The present studies clearly show that high selenium levels in the body during the oestrous cycle preceding mating affects the number of ovulations, implantations and live embryos depending upon its dose and stage of administration.

Effect of methyl parathion formulation on estrous cycle and reproductive performance in albino rats.

The animals were injected intraperitoneally with graded doses of methyl parathion at 1.5 to 3 mg/kg body weight for 15 days from the day of estrus. Results indicated that the methyl parathion treatment showed irregular estrous cycles, affect the duration of each estrous cycle, proestrus and diestrus were significantly changed in 2.5 and 3 mg treatment groups. But there was no significant change in the number and duration of each estrous cycle, duration of proestrus and diestrus in 1.5 and 2 mg methyl parathion treatment groups. However, there was a significant decrease in the duration of estrus, while there was no significant change in the duration of metestrus in all methyl parathion treatment rats when compared with those of the corresponding parameters of the control. There was no significant effect on number of live pups on day 1 and 5 except in 3 mg methyl parathion treatment group where it was significantly decreased. There was no significant change in reproductive indices like pregnancy, parturition, live birth and viability in all the methyl parathion treatment rats except the viability index in the highest dose.

Effect of graded doses of nicotine on ovarian and uterine activities in albino rats.

Nicotine (2 and 4 mg/kg body weight, i.p.) administered to albino rats for 20 days decreased the number of healthy follicles and increased the number of regressing follicles in the ovary. Uterine weight, its diameter, thickness of myometrium and endometrium and height of epithelium were reduced. Increase in the ovarian cholesterol level and decrease in glycogen content in nicotine treated rats indicate the inhibition brought in the steroidogenesis which is dependent on pituitary gonadotrophins. Decreased protein content of the ovary and uterus may be due to their retarded growth. Reduced number of estrous cycle with prolonged metaestrus and diestrus also supports the decreased estrogen synthesis responsible for cornification of vaginal smear in nicotine treated rats.

Morphological aspects of the endometrium of persistent estrous rats induced by continuos light submitted to ooforectomy and treated with oestrogen and progesterone

Los principales objetivos de este trabajo son analizar las modificaciones que ocurren en el endométrio de ratas en estros persistentes inducida por luz contínua y observar la respuesta endometrial a administración de estrógenos y/o progestágenos sobre el endometrio, en esas condiciones experimentales. Los resultados mostraron que el estroma endometrial de ratas sometidas a luz continua presentaba característica típicas de la fase de estro, siendo que los epitelios superficial y glandular presentaban áreas de estratificación, dependientes de las hormonas ováricas y que tales características desaparecen después de la ooforectomía. La ooforectomía no bloquea el efecto inducido por la luz, ya que después de la administración del estrógeno, el endometrio presentaba las mismas características de los animales en estro persistente. Cuando se administró el acetato de medroxiprogesterona juntamente con el estrógeno, hubo un bloqueo de las áreas de estratificación, indicando que la progesterona es moduladora del estrogeno. En este trabajo cloncluimos que el estro persistente inducido por la luz continua, depende de las hormonas ováricas y que la principal hormona es estrógeno. También se observó que la progesterona bloquea las inducciones provocadas por el estrógeno

Fluid balance: changes in cycling rats treated with difluoro-methyl-ornithine [DFMO] during the pro-oestrus.

Plasma vesopressin levels have been shown to fluctuate through out the rat oestrus cycle and following ovariectomy. To determine how these fluctuations in vesopressin are related to fluid regulations during the rat oestrus cycle. Studies have been carried out in cycling females rats using a specific inhibitor of Ornithine Decarboxylase [ODC], Di-fluoro-methyl Ornithine [DFMO 20 mg/100g body weight], the animals were housed in individual metabolism cages under 12 hours light/12 hour dark regimen with free access to food and water. Urine samples were collected to determine the osmolality and sodium concentration at 8.00 and 17.00-18.00 hours. The results of this study indicate a significant decrease in urine osmolality and sodium retention in the cycling pro-oestrus rats treated with DFMO as compared to the controls. The result of this study indicates that cause of fluid retention in the cycling rats during pro-oestrus may be the oestradiol dependent increased levels of vesopressin and the increase in the ODC activity in the Magno-cellular neurons is the part of mechanism underlying the oestradiol induced Vesopressin release

Comparative study on the efficacy of prostaglandin F[2] and short-term norgestomet treatments as luteolytic agents in buffaloes

Induction of luteolysis in suboesterous buffaloes with palpable and functional cor pora lutea was applied. Different doses of prostaglandin F[2]alpha [lutalyse] were used through intramuscular [25 mg] and vaginal submucosa [12.5 and 7.5 mg] routes. Short-term [9-10 days] norgestomet [Synchro-Met-B] ear implants were also administered for comparison. The results showed that intramuscular injection of 25 mg PGF[2] alpha during summer inducd luteolysis in 70% of the treated animals, while injection of 12.5 mg PGF[2]alpha into vaginal submucosa of suboestrous buffaloes during summer also, resulted in luteolysis in 87.5%. Injection of 7.5 mg PGF[2] alpha into vaginal submucosa in suboestrus buffaloes during winter improved the rsponse [88.89%]. Application of Synchro-Met-B ear implants led to luteolysis in 90.90% of the treated buffaloes. In conclusion, injection of PGF[2] alpha into submucosa proved to be effective, economic and easily applied treatment of suboestrous and/or synchronization of oestrus in buffaloes

Atropine and testosterone propionate induced atretic changes in granulosa cells of house rat (Rattus rattus) ovary.

Degenerative changes in membrana granulosa of ovaries in R. rattus have been studied using scanning electron microscopy. Ovaries from rats treated with atropine (300 mg/kg body weight) and testosterone propionate (10 IU) were used to study sequential course of atresia in granulosa cells. Granulosa cells undergoing atresia showed degenerative changes in following order i) loosening of intercellular matrix, ii) changed morphology and texture of secretory granules, iii) destabilization of granulosa cell membranes, iv) erosion of cell membrane, v) formation of specific degenerative belts, vi) pycnosis, vii) ghost cell formation and their subsequent mixing in hazzy follicular fluid of cyst. Phenomenon of atresia, its duration, course and underlying causes have been discussed.

Efecto de la dosis reducida de un análogo de la prostanglandina (luprostiol) por vía submucosa intravulvar en la luteólisis y la manifestación en vacas Suizo Pardo / Effect of reduce dose of prostaglandin via intravulva submucosal on the luteolytic effect and the estrous cycle in brown swiss cows

El objetivo del estudio fue evaluar si la dosis reducida de un análogo de la prostaglandina (Luprostiol) (LP) por vía submucosa intravulvar (SMIV) e ipsilateral al cuerpo lúteo (IPL) inducen la luteólisis y la manifestación del estro. Se utilizaron 39 vacas de la raza Suizo Pardo en producción con ciclos estrales regulares, las cuales fueron asignadas a los siguientes tratamientos: 15 mg de LP por vía intramuscular (n=13); T1, 11.2 mg de LP por vía SMIV e IPL (n=13); T2, 7.5 mg de LP por vía SMIV e IPL (n=13). Se tomaron muestras sanguíneas para medir la concentración plasmática de progesterona (P4) a la 0 h y posteriormente cada 12 h, hasta las 72 h postratamiento. Se consideró la luteólisis (LUT) cuando las concentraciones de P4 fueron menores de 1 ng/ml y se mantuvieron hasta las 72 h postratamiento. A las 0 h, inicio de los tratamientos, la concentración de P4 fue de 3.22 ng/ml, después de las 24 h los niveles de P4 fueron menores de 1 ng/ml y se mantuvieron hasta las 72 h postratamiento, sin mostrar diferencia entre los grupos tratados (P>0.05). El porcentaje total del estro (PTE) (84.1 por ciento) y el intervalo tratamiento-manifestación del estro (ITE) (86.4 h) fueron similares entre tratamientos (P>0.05). El peso corporal, el nivel de producción láctea, el número de parto y el intervalo parto-tratamiento no fueron determinantes para efectuar la LUT, el ITE y el PTE (P>0.05). Las vacas que recibieron dosis reducidas de LP por vía SMIV e IPL tuvieron LUT, ITE y PTE similares a los observados en vacas con una dosis completa y por vía intramuscular

Cambios en el efecto ansiolítico de los agonistas 5-HT 1A de acuerdo con la especie, la edad, el género y el estado endócrino del individuo / Changes in the anxiolitic effect of 5-HT1A agonists according to species, age, gender and endocrinous state of the individual

En este trabajo se analiza la importancia que puede tener el género, la especie, la edad y algunos factores endócrinos de los orgnaismos en el efecto de ciertos fármacos con propiedades ansiolíticas como son los agonistas del receptor 5-HT1A buspirona, indorrenato, 8-OH-DPAT e ipsapirona. Aunque hay en la actualidad muchos modelos animales para evaluar la ansiedad experimental, en este caso se utilizó el paradigma de la conducta defensiva de enterramiento con el propósito de hacer comparables los resultados derivados de las diferentes condiciones experimentales antes mencionadas. Así, se muestra que en las ratas, los ratones y los hamsters, los agonistas 5-HT1A producen un efecto claramente ansiolítico: sin embargo, el mecanismo de acción subyacente a dicho efecto parece ser diferente dependiendo de la especie estudiada. En el caso de los ratones y los hamsters, la neurotransmisión serotoninérgica participa directamente en la mediación del efecto ansiolítico producido por los compuestos antes mencionados, mientras que en las ratas este efecto parece estar regulado prodominantemente por el sistema noradenérgico. También se hace notar que el efecto de estos fármacos varía en función de la edad de los sujetos experimentales, de manera que en los animales jóvenes, los ansiolíticos serotonínergicos no inducen efecto alguno, mientras que en animales adultos (9-13 semanas) se observa una clara acción ansiolítica. No obstante, este efecto se va perdiendo conforme avanza la edad del animal (21 semanas). En relación al efecto de los fármacos administrados en hembras y machos, los ansiolíticos no mostraron diferencias. Sin embargo, se manifestó una marcada sensibilidad de las ratas machos a los efectos tranquilizantes de la benzodiacepina "diacepam" en comparación con las hembras. La diferencia más notable se encontró entre los machos y las hembras que se encontraban en la etapa de metaestro del ciclo estral. Al respecto, es interesante mencionar que durante el ciclo endócrino de la rata se encontraron diferentes niveles basales de ansiedad, siendo más bajos durante el proestro y más altos durante el metaestro y diestro. En este caso, el efecto de los fármacos antes mencionados no fue influido por las diferentes etapas del ciclo estral. Sin embargo, la capacidad de respuesta de los animales (es decir la reactividad) disminuyó en el grupo de mahcos después de la administración de indorrenato e ipsapirona, al igual que con el diacepam. En el caso de las hembras...

Timely administration of extract of Ferula jaeschkeana causes luteolysis in the ovary of cyclic guineapig.

Effect of hexane extract of Ferula jaeschkeana has been studied on corpora lutea of adult cyclic guinea-pigs. Administration of extract showed duration dependent luteolytic changes in the corpora lutea. Its administration for first three days from the onset of estrus caused significant decrease in the diameter of corpora lutea in the ovary at day 10 of cycle. Ovarian wet weight, proteins and glycogen contents were decreased while the activity of acid phosphatase in the ovary was increased. These luteolytic changes in the ovary have also been observed in the histological findings. Administration of extract for other durations (4-6, 7-9 or 10-12 of cycle) did not cause any change at 10th and 16th day.

Sincronización de estros en ovejas mediante un tratamiento corto con acetato de melengestrol (MGA) combinado con cipionato de estradiol (ECP) / Synchronization of estrus in ewes with a short treatment of melengestrol acetate (MGA) combined with oestradiol cipionate

El objetivo de este trabajo fue evaluar la dosis óptima de un tratamiento corto a base de acetato de melengestrol (MGA) y el efecto del cipionato de estradiol (ECP), para la sincronización del estro en borregas. El trabajo se realizó durante la época reproductiva (agosto a octubre). Se utilizaron 96 borregas, las que fueron sometidas a la detección del celo con la yuda de machos vasectomizados 18 días antes de iniciar el experimento, se encontró que el 91 por ciento mostró celo. Las borregas fueron distribuidas en 5 grupos: MGA22-ECP (n = 19); MGA11-ECP (n = 20). Los dos primeros recibieron en el concentrado 0.22 mg de MGA/borrega/día durante 9 días; el tercero y cuarto grupo recibieron 0.11 mg de MGA/borrega/día por 9 días. Adicionalmente el primer y tercer grupo recibieron 0.5 mg de cipionato de estradiol al inicio del tratamiento para provocar la regresión del cuerpo lúteo. Durante los primeros 6 días postratamiento, el porcentaje de presentación de estros fue significativamente menor (P < 0.05), (Ji-cuadrada) en el grupo testigo (42 por ciento), que en los grupos MGA-22-ECP (74 por ciento), MGA22 (90 por ciento), MGA11-ECP (65 por ciento) y MGA11 (67 por ciento). La máxima sincronización en un periodo de 72 horas también fue significativamente menor (P < 0.05) en el grupo testigo (37 por ciento) que en los grupos MGA22-ECP (63 por ciento), MGA22 (79 por ciento), MGA11-ECP (50 por ciento) y MGA11 (56 por ciento). Las borregas fueron inseminadas con semen fresco diluido 12 horas después del inicio del estro. Aunque las diferencias en porcentaje de concepción a primer servicio no fueron significativas, dichos porcentajes fueron menores en los grupos MGA22.ECP (22 por ciento) y MGA11-ECP (15 por ciento) que en los grupos MGA22 (53 por ciento), MGA11 (65 por ciento) y testigo (42 por ciento), lo que surgió un efecto detrimental del ECP sobre la fertilidad. La administración oral de MGA durante nueve días constituye un método sumamente eficiente, práctico y de bajo costo para efectuar la sincronización de estros en ovejas. La combinación de MGA y ECP no mejora la sincronización y parece que ejerce efecto negativo sobre la fertilidad

Ovarian sensitivity to exogenous gonadotrophins in phenobarbital treated unilaterally ovariectomized albino rats.

Adult cycling female rats were hemispayed and administered with 7.5 mg phenobarbital/100 gm body weight for 15 days. 5IU FSH or FSH+LH per 100 gm body weight was administered from day 13 to 15 to the hemispayed phenobarbital treated rats. Phenobarbital inhibits the ovarian compensatory hypertrophy significantly and increases the cholesterol and lipid levels in the ovary. Administration of FSH alone or in combination with LH restores the ovarian compensatory hypertrophy and decreases cholesterol and lipid levels significantly but LH alone is not much effective. These results suggest that the inhibition of ovarian growth may be due to the lack of availability of pituitary gonadotrophins in phenobarbital treated rats and these actions can be rectified by the administration of exogenous gonadotrophins which indicate that the ovary has not lost its sensitivity due to phenobarbital treatment.