Induction and synchronization of oestrus in sheep and goats

Abstract

Different methods for oestrus induction and synchronization in domestic small ruminants have been developed.Seasonality and female's status are important factors for choosing the most appropriate treatment. In the case of females during breeding season, prostaglandins can be used since functional corpus luteum must be present in the ovaries, while during non-breeding season females should be treated with progesterone-based treatments, accompanied by equine chorionic gonadotrophin (eCG), releasing hormones and other compounds. Significant spread of oestrus synchronization during and after the breeding season has been achieved by the use of intravaginal sponges impregnated with synthetic analogues of progesterone. However, the effect of hormonal drugs on the female reproductive system may manifest differently depending on the initial functional state of reproductive organs and the hormonal status, and negative consequences can be observed when drugs are wrongly administered. In addition, insufficient knowledge about the patterns of change in the reactivity of the nervous sexual centers and the corresponding reactions of the body to the administration of hormones reduces their effectiveness, which limits the widespread use. In general, the induction and synchronization of oestrus in small ruminants is an currently important direction of scientific research and an urgent problem of sheep and goat breeding, but the proposed methods require further improvement by reducing the costand increasing biosecurity and predictability of the result.

Exploring Endogenous and Exogenous Factors for Successful Artificial Insemination in Sheep: A Global Overview

“…It is administered through various methods, including the controlled internal drug-releasing (CIDR) device, medroxyprogesterone acetate (MAP), and fluorogestone acetates (FGA) to facilitate estrous synchronization [ 47 ]. Additionally, to enhance fertility, it is common practice to supplement P4-based protocols with the administration of gonadotropins like eCG, pregnant mare serum gonadotropin (PMSG), and gonadotropin-releasing hormone (GnRH) towards the end of the synchronization process [ 45 , 47 , 63 ]. The typical dosage of MAP often employed for estrous synchronization is 60 mg, although it is worth noting that doses below 40 mg can also yield effective results [ 46 , 64 ].…”

“… Exogenous factors influencing ovine artificial insemination success. Hormonal factors: [ 45 , 46 , 47 ]; semen handling and insemination techniques: [ 48 , 49 ]; heat stress: [ 50 ]; nutritional stress: [ 51 , 52 , 53 ]. …”

“…Hormonal treatments used to induce synchronization in ewes vary depending on the breeding season (Table 1). Prostaglandins are a common choice for synchronization during the breeding season, when ewes typically have a functional corpus luteum, making them responsive to this approach [45]. However, it was demonstrated that the use of prostaglandins is time-sensitive due to their role in accelerating luteal dissolution [46,63].…”

Sincronización de estros en ovejas mediante protocolo de 6 días con CIDR de primera, segunda y tercera reutilización

“…Una estrategia para reducir los efectos negativos de los progestágenos, es usar protocolos cortos de sincronización (2) mediante la aplicación de dispositivos CIDR durante 5 a 7 días, adicionando prostaglandina F2 alfa (PGF2α) que induce el control de la función lútea y gonadotropina coriónica equina (eCG), que estimula desarrollo folicular y la ovulación al aumentar tanto el número de folículos como la tasa de producción de estrógeno por los folículos estimulados (4) ; de esta manera, se obtiene un folículo con mayor capacidad de ser fertilizado durante la época reproductiva y el anestro estacional (5) .…”

Los dispositivos reutilizados en protocolos cortos de sincronización tienen el mismo efecto sobre el desempeño reproductivo y perfiles de progesterona en ovejas Pelibuey

“…La sincronización del estro con dispositivos de liberación controlada de fármacos (CIDR) se ha usado con eficiencia en varias especies animales: vacas (Bonacker et al, 2020), búfalas (Neglia et al, 2020), cabras (Skliarov et al, 2021) y ovejas (Gonzalez-Bulnes et al, 2020. Los CIDR para ovejas están impregnados con 0,3 g de progesterona natural (Wheaton et al, 1993), y generalmente son aplicados en protocolos largos de 12 a 14 días (Viñoles et al, 2001) y algunos estudios los han evaluado bajo protocolos de corta duración de 5-7 días (Menchaca y Rubianes, 2004;Martinez-Ros et al, 2019. En estos últimos se ha observado una mejor sincronización del estro y buena fertilidad con IA en ovejas comparado con protocolos largos (Cox et al, 2012;Dias et al, 2015;Santos-Neto et al, 2015;Martínez-Ros et al, 2020).…”