Screening of some variables influencing the results of embryo transfer in the ewe Part II: Two-day-old embryos

摘要

Each of sixty Rasa aragonesa ewes received two embryos on Days 2-3 of the estrous cycle (Day 0 = estrus) from 27 donors of the same breed that were superovulated with pFSH. The influence of several variables on fertility and prolificacy after transfer was studied by discriminant analysis. Our results showed that the main variables contributing to higher fertility were: in the donor-recipient couple, degree of estrus synchrony between them (better if donors were in estrus before recipients); in recipients, interval from FGA withdrawal to estrus onset, prolificacy in the previous lambing, age (all, better if inferior to the mean) and interval from the previous lambing (better if superior to the mean); in donors, ovulation rate (better if lower than the mean); and in embryos, developmental stage (better if superior to the mean). Likewise, the main variables contributing to higher prolificacy were: in donors, body condition score (better if higher than the mean) and weight (better if inferior to the mean); and in recipients, plasma progesterone concentration at transfer (better if inferior to the mean). The percentage of ewes correctly classified as lambing or not was 71.7% (P < 0.01), and 72.5% of the ewes were correctly classified as having one or two lambs (P < 0.05). Whether the criteria we have found for optimum results after transfer are applicable or not to conditions other than ours will need to be confirmed.