FIXED-TIME ARTIFICIAL INSEMINATION IN DAIRY EWES RAISED IN FIELD CONDITIONS IN ARGENTINA

Resumo

Modern systems of sheep production are directed towards intensification, being in this line the adoption of artificial insemination. The objective was to compare two protocols of fixed-time artificial insemination (FTAI) in dairy ewes managed under field conditions in Buenos Aires province, Argentina. Twenty four two-tooth Milchschaf x Texel ewes were synchronized with intravaginal sponges plus 300 IU eCG and cervically inseminated with fresh semen either once at 54 h (Group A) or twice at 48 and 60 h (Group B) after sponge removal. Additionally, 23 Milchschaf x Texel ewes were synchronized as previously described and estrus was detected at 6-h intervals by teaser rams. The pregnancy rate was higher in B than in A (B: 50.0% vs. A: 9.1%; P<0.05). In the group exposed to teasers, 91.3% of the ewes came into estrus from 24 to 36 h after sponge removal, with an interval to estrus averaging 30.6+-1.0 h. Based on both type of mucus mostly observed and data of estrus outcome, it could be suggested that the difference in effectiveness between protocols would be related to an earlier rather than to a double insemination. In conclusion, this study provides information on the application of FTAI in dairy ewes reared rangeland in Argentina.