Influence of Progesterone-Treatment Length and eCG Administration on Appearance of Estrus Behavior, Ovulatory Success and Fertility in Sheep.

Paula Martinez-Ros,Antonio Gonzalez-Bulnes,Alejandro Rios-Abellan

doi:10.3390/ani9010009

Paula Martinez-Ros, Antonio Gonzalez-Bulnes + Show 1 more

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https://doi.org/10.3390/ani9010009

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Abstract

Simple SummaryThis study examines the pre-ovulatory and ovulatory events (in terms of the timing of the onset of estrous and subsequent ovulation) and the yields obtained (in terms of ovulation rate, progesterone secretion, and fertility) after insertion of Controlled Internal Drug Release (CIDR) for five, six, seven, or fourteen days, with or without equine chorionic gonadotrophin (eCG).The present study characterizes, for sheep, the occurrence and timing of the onset of estrus behavior and ovulation and the yields obtained (ovulation rate, progesterone secretion, and fertility) after Controlled Internal Drug Release (CIDR) insertion for five, six, seven, or fourteen days, with or without equine chorionic gonadotrophin (eCG) in ewes of the Segureña meat breed. All the treatments showed above 80% of females displaying estrus, but the onset of estrus was earlier and more synchronized when using eCG and, among groups with eCG, onset of estrus was earlier in the sheep treated for 14 days than in the short-term treatments (p < 0.05 for all). Administration of eCG after either short- or long-term treatments assured the occurrence of fertile ovulations in all the animals. Conversely, ovulatory success without eCG was found to be dependent on treatment length, with a high percentage of animals ovulating after five days of treatment (83.3%) and very low percentages after treatment for six or seven days (40% and 20%, respectively). Ovulation rate and progesterone secretion were similar among animals ovulating, but ovulation failures predetermined the fertility yields obtained in response to the treatments. Hence, the best results were found after treatment for 14 days plus eCG, and for 5 days without eCG (83.3 for both, p < 0.05 when compared to the other groups with different treatment lengths and with or without eCG).

Highlights

Synchronization of estrus and ovulation for fixed-time artificial insemination (FTAI) in sheep is mostly based on the insertion of intravaginal devices containing either progesterone Controlled Internal Drug Release (CIDR) (ControlledInternal Drug Release) inserts or progestagens (sponges impregnated with fluorogestone acetate (FGA) or medroxyprogesterone acetate (MAP))
Treatment length affected the onset of estrus only in the groups treated with equine chorionic gonadotrophin (eCG), inducing an earlier onset in the group C14eCG than in the short-length treatments (p < 0.05 for all)
The results of the present study indicate that the administration of CIDR-based protocols, independently of the addition of eCG and the duration of the treatment, provokes the appearance of estrous behavior after device withdrawal in most of the treated sheep

Summary

Introduction

Synchronization of estrus and ovulation for fixed-time artificial insemination (FTAI) in sheep is mostly based on the insertion of intravaginal devices containing either progesterone CIDR Internal Drug Release) inserts or progestagens (sponges impregnated with fluorogestone acetate (FGA) or medroxyprogesterone acetate (MAP)). A single intramuscular injection of equine chorionic gonadotrophin (eCG) is added for inducing ovulation and synchronizing its time of appearance among animals in the same lot [1]. Administration of eCG is, essential for FTAI. There is currently a highly active movement in European countries against the use of eCG. The pressure group has forced the production of eCG to move out of the European Union and aims to get its use banned in animal production.

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