The aim of the study was to assess the effects of superovulatory treatment (multiple FSH-dose vs single-shot FSH treatment) and seasonality on embryo yields in fine-wool Merino ewes. Treatment based on multiple FSH-dose consisted of 200 mg of FSH (Folltropin(®)) administered in seven decreasing doses. Single-shot treatment consisted of a single dose of 70 mg of FSH + eCG. In ewes treated with multiple FSH doses, number of recovered embryos was higher (6.0 ± 0.5 vs 3.5 ± 1.0), while non-fertilization rate was lower (12.8 ± 3.9 vs 40.3 ± 9.5) during the breeding season when compared to the non-breeding season (p < 0.05); although similar values of recovered Grades 1-2 embryos were observed between seasons. During the breeding season, proportion of responding ewes (98.1 vs 57.1%), ovulation rate (13.9 ± 0.8 vs 3.2 ± 1.2), recovered structures (7.9 ± 0.6 vs 1.7 ± 0.7), total recovered embryos (6.0 ± 0.5 vs 1.2 ± 0.6) and good-quality embryos (5.1 ± 0.5 vs 0.9 ± 0.6) were higher for the multiple FSH-dose treatment than for the single-shot protocol. In a similar way, in the non-breeding season, ovulation rate (11.3 ± 1.8 vs 6.0 ± 1.1) and recovered structures (6.6 ± 1.2 vs 2.7 ± 0.6) were higher for the multiple FSH injections protocol than those for the single-shot treatment, resulting in higher recovered Grades 1-2 embryos (3.2 ± 0.9 vs 1.4 ± 0.5). Current results indicate that seasonal anestrus affected embryo yields when applying multiple FSH-dose superovulatory treatment in Merino ewes, by decreasing the number of recovered embryos although the number of recovered good-quality embryos was not affected. During both seasons, multiple FSH injections produced higher ovarian response and number of viable embryos than the single-shot treatment.
ADDITIONAL KEYWORDSSexual behavior. Buck semen. Libido. PALABRAS CLAVE ADICIONALESCapacidad de servicio. Semen caprino. Libido. RESUMENDebido a la gran población caprina y a la identidad genética del caprino Criollo de la provincia de Neuquén, en la Patagonia Argentina, se consideró la necesidad de profundizar el conocimiento sobre los aspectos reproductivos del macho. Durante un año, diez machos adultos mantenidos bajo condiciones extensivas de manejo y fotoperíodo natural (41º S) fueron evaluados en sus parámetros reproductivos. Se determinaron mensualmente las siguientes variables: peso vivo (PV), circunferencia testicular (CT), total de espermatozoides en el eyaculado (TEE), porcentaje de machos con capacidad de servicio (PMCS) y media de montas efectivas (MME). El PV y la CT presentaron un marcado incremento durante el período primavero-estival, alcanzando sus valores máximos en febrero, a los dos meses después del solsticio de verano (68,1 kg y 34 cm, respectivamente). En el período otoño-invernal, dos meses después que la circunferencia testicular alcanzara su máximo desarrollo, se evidenció el máximo valor del TEE en abril (5213 millones). El PMCS y la MME variaron a lo largo del año, alcanzando los valores medios más altos en el trimestre abril-junio (100% y 3 montas efectivas, respectivamente). Los valores medios más bajos para estas variables se presentaron en el trimestre septiembre-noviembre (53% y 1,7 montas, respectivamente). Las variables PV, CT, TEE, PMCS y MME se correlacionaron en forma positiva entre sí. La actividad reproductiva del caprino CriolloNeuquino presentó una variación estacional, evidenciando su máxima expresión en el trimestre abril-junio (otoño) y manifestando un período de baja actividad reproductiva en el trimestre septiembre-noviembre (primavera).
The aim of the study was to assess possible variations in superovulatory yields due to different FSH treatments at 2 times of the year. Superovulation and embryo recovery were performed during the breeding (n = 63) andnonbreeding (n = 46) seasons in Merino ewes located at 41°S latitude. Animals were kept under the same conditions, housed outdoors in a sheltered and covered pen, and were fed a liveweight maintenance ration. All animals received 60-mg medroxyprogesterone acetate intravaginal sponges (Progespon®, Syntex, Buenos Aires, Argentina) for 14 days. Ewes were then randomly assigned to 2 different superovulatory treatments: classic (n = 74) and one shot (n = 35) in both seasons. Classic superovulatory treatment consisted of 7 decreasing doses (2 × 48 mg, 2 × 24 mg, 2 × 20 mg, and1 × 16 mg NIH-FSH-P1)ofFSH (Folltropin®-V, Bioniche, Belleville, Ontario, Canada), administered twice daily from 48 h before to 24 h after pessary removal. A dose of eCG (300 IU; Novormon®, Syntex) was administered at progestagen removal. One shot superovulatory treatment consisted of a single dose of FSH (70 mg NIH-FSH-P1) plus 300 UI of eCG injected at pessary withdrawal. Embryo donors were inseminated by laparoscopy with frozen-thawed semen (100 × 106 spz) 12 h after the onset of estrus. Surgical embryo recovery was done on Day 7 after sponge withdrawal and embryos were graded for quality according to morphology (Grade 1 = excellent or good; Grade 2 = fair; Grade 3 = poor; and Grade 4 = dead or degenerated; IETS 1998). A 2 × 2 factorial ANOVA was used to test the main effects (season and superovulatory treatment) and interactions. There were no significant differences in the proportion of responding ewes (>3 corpora lutea), ovulation rate, and recovered Grades 1 to 2 embryos between the breeding and nonbreeding season (Table 1; P > 0.05). However, number of recovered ova/embryos and ova/embryo recovery rate were higher during the breeding season compared with the nonbreeding season, whereas the percentage of nonfertilized ova was lower in the breeding season than in the nonbreeding season (P < 0.05). Analysis of data comparing superovulatory treatments showed that the proportion of responding ewes, ovulation rate, recovered embryos, and recovered Grades 1 to 2 embryos were lower for the one shot treatment than for the classic treatment (P < 0.05). Embryo recovery rate and nonfertilization rate did not differ between treatments (P > 0.05). It was concluded that there was an increase in the number of total recovered ova/embryos during the breeding season compared with the nonbreeding season, although the number of recovered good-quality embryos was not affected. The use of multiple FSH injections produced a higher number of total recovered and viable embryos in Merino sheep than the one shot superovulatory treatment. Table 1.Embryo yields in ewes submitted to superovulation
La raza caprina Criollo-Neuquina habita la provincia de Neuquén (Argentina) y constituye la forma de vida de 1.600 crianceros del norte neuquino, debido a su alta eficiencia reproductiva y potencial productivo. En este trabajo se presenta la caracterización reproductiva de esta raza, abordando el estudio de la variación estacional de la actividad reproductiva en hembras y machos adultos, el inicio de la actividad sexual en cabritas y cabritos, el efecto macho y la dinámica folicular preovulatoria. Estas investigaciones constituyen una de las caracterizaciones reproductivas más exhaustivas de una raza de caprinos. Se determinó que el ciclo reproductivo es marcadamente estacional, con apareamientos en otoño y pariciones en primavera. Las hembras presentan un período de estros fértiles de 5 meses, entre abril y agosto; con mayores tasas de ovulación al principio de la temporada que al final (1,7 vs 1,0 ovulaciones/cabra). Los trabajos confirman la respuesta al efecto macho, presentándose una concentración de estros superior al 80 % entre los 8 a 11 días post introducción de los machos. De esta forma se valida la práctica habitual de aislar a los machos en las castronerías fuera de la época reproductiva, estacionando los servicios. La actividad sexual de los machos es estacional, presentando la mayor actividad entre marzo y junio. Los machos y hembras son precoces en su desarrollo, siendo fértiles desde su primer otoño de vida, siempre que alcancen un adecuado desarrollo corporal. La dinámica folicular preovulatoria presenta algunas de las estrategias reproductivas descriptas en razas prolíficas ovinas. Los avances en el conocimiento de la fisiología reproductiva de una raza en una determinada región constituyen estudios de referencia para establecer diferentes estrategias de manejo y mejorar su eficiencia productiva. Estos conocimientos permiten implementar un uso racional de las técnicas reproductivas para ser utilizadas en programas de conservación, difusión o mejoramiento genético.
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