Resynchronization of estrus in sheep using two or three artificial inseminations with frozen semen

Abstract

This study aimed to evaluate the efficiency of two or three estrus synchronizations
followed by artificial insemination (AI) by laparoscopy with frozen semen in sheep. Santa
Inês sheep (n=147) were randomly distributed into two groups: Re-sync – 2FTAI (n=72) and
Doppler – 3FTAI (n=75), synchronized with a short protocol associated with GnRH and AI
by laparoscopy with frozen semen 50 h after removing the P4 device (D0). Two AIs were
performed in the Re-sync group, with the start of the resynchronization protocol on D23 and
gestational diagnosis on D30; the non-pregnant females were inseminated again. The sheep
were resynchronized (D10) in the Doppler group and the gestation diagnosis was made early
at 17 days using Doppler ultrasound. The open females were inseminated again, totaling
three inseminations in 42 days. Early gestation diagnoses were confirmed at 30 days. Re-sync
(29.16%) and Doppler (21.33%) were similar to each other in terms of cumulative gestation
rate (P>0.05). The indicators of the non-gestation diagnosis technique at 17 days were
sensitivity of 100%, specificity of 28%, positive predictive value of 21.3%, negative predictive
value of 100%, and accuracy of 39.8%. Early diagnosis allowed sheep to be inseminated two
to three times in the same period and was effective in diagnosing truly non-pregnant females.
Therefore, estrus resynchronization associated with AI by laparoscopy using frozen semen
can be applied in sheep, but a higher gestation rate could not be achieved with two or three
inseminations at the end of the breeding season.