Abstract
ABSTRACT The objective of the present research was to determine the effect of long synchronization protocols based on reused progesterone devices (controlled internal drug release [CIDR]) associated with different doses of equine chorionic gonadotropin (eCG) on reproductive variables in crossbred sheep (Suffolk × Kathadin × Dorset). The CIDR were used for eleven days in a previous study in sheep from the same herd and were washed and disinfected before reusing. Sixty-four sheep, in the reproductive season, were randomly assigned to four experimental groups (n = 16). Treatments consisted of a group with 10 d CIDR and 300 IU eCG; a group with 10 d CIDR and 400 IU of eCG; a group with 12 d CIDR and 300 IU of eCG; and a group with 12 d CIDR and 400 IU of eCG. A completely randomized design was used. There was an estrous presentation rate of 100% in all treatments. The begining of estrous, gestation rate, fertility rate, type of parturition, and prolificacy index were equal between groups. Progesterone serum concentration was higher in sheep from the 10 d CIDR groups. The CIDR, reused for the second time, associated with 300 or 400 IU of eCG for estrous synchronization in sheep, are effective to obtain good pregnancy rates and ensures higher prolificacy rates.
Highlights
The most used hormonal treatments in estrous syncronization protocols for sheep are those based on progesterone or its analogues (Abecia et al, 2012)
The objective of the present research was to determine the effect of long synchronization protocols based on reused progesterone devices associated with different doses of equine chorionic gonadotropin on reproductive variables in crossbred sheep (Suffolk × Kathadin × Dorset)
Once the device is removed, an injection of equine chorionic gonadotropin is applied (Abecia et al, 2011), which has an effect of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) to enhance ovulation (Quintero-Elisea et al, 2011; Martinez-Ros et al, 2018)
Summary
The most used hormonal treatments in estrous syncronization protocols for sheep are those based on progesterone or its analogues (Abecia et al, 2012). Controlled internal drug release (CIDR) is an intravaginal device impregnated with 0.3 g of natural progesterone (Wheaton et al, 1993) designed for use between 12 and 14 days in sheep (Viñoles et al, 2001). Once the device is removed, an injection of equine chorionic gonadotropin (eCG) is applied (Abecia et al, 2011), which has an effect of follicle-stimulating hormone (FSH) and LH to enhance ovulation (Quintero-Elisea et al, 2011; Martinez-Ros et al, 2018). The results indicate that the cost of CIDR is reduced when reusing it in long protocols (Swelum et al, 2019), which
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