UNASSIGNED: The main objective of this study was to evaluate the effect of a second treatment with @entity22667 ( @entity26889 ) during Ovsynch on regression of the corpus luteum (CL) and on fertility to the timed artificial insemination. Two experiments were performed. In both experiments, @entity291 were randomized to receive (1) no additional treatments with @entity26889 =1 @entity26889 , or (2) a second @entity26889 treatment at 24h after the first @entity26889 treatment=2 @entity26889 . The first experiment (n=344 synchronized lactating dairy @entity291 that received artificial insemination at 81  3d in milk) used the Double-Ovsynch protocol for synchronizing ovulation. Blood samples were collected at the @entity26889 and final @entity1176 treatments (72 and 16h before timed artificial insemination) during the breeding Ovsynch protocol, to determine CL regression in response to the protocol. Treatment with 2 @entity26889 increased CL regression from 83.0% with 1 @entity26889 to 97.0% with 2 @entity26889 . The effect of 2 @entity26889 on CL regression was observed in both primiparous and multiparous @entity291 . @entity291 with lower (2.0 to 4.8ng/mL) versus greater (4.9 to 12.0ng/mL) circulating @entity1420 at the time of @entity26889 had lower percentage of @entity291 with complete CL regression after 1 @entity26889 (66.7 vs. 88.1%) but not after 2 @entity26889 (95.1 vs. 97.6%). Experiment 2 used 2,148 lactating dairy @entity291 on 11 dairy farms in 4 different regions of the United States. @entity291 were synchronized with Ovsynch and received timed artificial insemination at 60  3d in milk. @entity291 that received 2 @entity26889 had a tendency for increased pregnancies per artificial insemination (P/AI) compared with @entity291 with 1 @entity26889 (36.1 vs. 33.3%). This tendency for improvement in P/AI was observed in multiparous but not in primiparous @entity291 . Combining data from the 2 experiments indicated a 9.45% relative increase in P/AI for @entity291 receiving 2 compared with 1 @entity26889 (37.6 vs. 34.4%) with the increase in P/AI observed in multiparous but not in primiparous @entity291 . Thus, a second @entity26889 treatment in Ovsynch-type protocols can increase pregnancy success by about 10%, primarily due to enhanced fertility in multiparous @entity291 .

Effect of a second treatment with @entity22667 during the Ovsynch protocol on luteolysis and pregnancy in dairy XXXX .

@entity1420 :: ('MESH:D011374', 'Chemical') :: ['progesterone'] @entity22667 :: ('CHEBI:15553', 'Chemical') :: ['prostaglandin F2a'] @entity26889 :: ('MESH:D011460', 'Chemical') :: ['PGF'] @entity1176 :: ('MESH:D007987', 'Chemical') :: ['GnRH'] @entity291 :: ('9913', 'Species') :: ['Cows', 'cows']
@entity291 :: (9913,Species) :: ['cows']
