Influence of Progesterone-Treatment Length and eCG Administration on Appearance of Estrus Behavior, Ovulatory Success and Fertility in Sheep.
Authors: Martinez-Ros Paula, Rios-Abellan Alejandro, Gonzalez-Bulnes Antonio
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary Synchronising oestrus and ovulation in breeding programmes requires careful manipulation of progesterone and gonadotrophin timing, yet optimal protocols may vary between species and breeds. Martinez-Ros and colleagues investigated how CIDR (progesterone) treatment duration—five, six, seven, or fourteen days—combined with or without eCG (equine chorionic gonadotrophin) affected reproductive outcomes in Segureña ewes, measuring oestrus expression, ovulation rate, progesterone secretion, and subsequent fertility. eCG administration dramatically improved ovulatory reliability across all treatment lengths, whereas shorter CIDR protocols (5 days) without eCG achieved comparable ovulation rates (83.3%) to the longer protocol with eCG, suggesting that very brief progesterone exposure may be sufficient in certain circumstances; conversely, intermediate durations of 6–7 days without eCG resulted in poor ovulatory success (20–40%), highlighting a critical window where protocol design becomes problematic. The most consistently successful approach combined 14 days of CIDR with eCG, though this must be weighed against practical considerations and cost in commercial settings. For equine professionals advising on assisted breeding programmes or working with breeders using similar reproductive technologies, these findings underline that gonadotrophin support may justify its expense by ensuring reliable ovulation across varied treatment regimens, whilst very short progesterone priming without gonadotrophic support merits further investigation as a potentially efficient alternative.
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Practical Takeaways
- •For sheep breeding operations, selecting the right CIDR duration and eCG combination is critical—either use 14 days with eCG or 5 days without eCG for optimal fertility (83.3% success)
- •eCG administration ensures fertile ovulations regardless of CIDR duration, but without it, treatment length becomes the limiting factor for ovulatory success
- •Mid-range treatments (6-7 days without eCG) show very poor ovulatory outcomes (<40%) and should be avoided in favor of proven protocols
Key Findings
- •All treatments achieved >80% estrus display, but eCG administration resulted in earlier and more synchronized estrus onset
- •14-day CIDR treatment plus eCG showed earliest estrus onset compared to shorter treatments with eCG (p < 0.05)
- •Ovulatory success without eCG was highly dependent on treatment length: 83.3% after 5 days, but only 40% and 20% after 6-7 days respectively
- •Best fertility outcomes (83.3%) were achieved with either 14-day CIDR plus eCG or 5-day CIDR without eCG treatments