Improving the efficiency of frozen semen inseminations in superovulated ewes

Summary

The key objective of this on-farm MOET study was to determine whether a single dose of frozen-thawed semen, inseminated at 52h after progesterone withdrawal, produces transferrable grade embryos as effectively as a double dose, inseminated at 40 and 46h after progesterone withdrawal. In on-farm trials using Merino and Awassi ewes, half the ewes were inseminated twice (at 40h and 46h after progesterone withdrawal) and half were inseminated once (at 52h after progesterone withdrawal). The delayed single AI increased the fertilisation rate by 14%, but decreased the proportion of embryos that were of transferable grade by 10%, compared with the standard double AI. 
 Consequently, the overall efficiency of embryo production was similar in the two treatment groups. Also, the results were similar in Merino and Awassi ewes. Importantly, the delayed single AI used half as much frozen-thawed semen, required less labour, and reduced the procedural effects on the animals, compared with the standard double AI. The cost and welfare benefits of the delayed single AI procedure are undeniable, and should promote the use of frozen-thawed ram semen in advanced breeding programs of the sheep industry.