Two long-term, CIDR-based estrus synchronization protocols were evaluated among @entity7040 -influenced and @entity291 beef heifers. Treatments were evaluated on the basis of estrous response and pregnancy rate resulting from fixed-time artificial insemination (FTAI), and these outcomes were analyzed retrospectively relative to @entity5860 ( @entity5860 ; Scale 1-5) at treatment initiation. Estrus was synchronized for 1139 heifers in three locations, and heifers were assigned to one of two treatments within each location based on @entity5860 . Heifers assigned to the 14-d CIDR-PG protocol received a controlled internal drug release (CIDR) insert (1.38  g @entity1420 ) on Day 0, CIDR removal on Day 14, administration of @entity22667 (PG; 25  mg im) on Day 30, and administration of @entity1176 ( @entity1176 ; 100   g im) concurrent with FTAI on Day 33, 66  h after PG. Heifers assigned to the 9-d CIDR-PG protocol received administration of PG concurrent with CIDR insertion on Day 5, administration of PG concurrent with CIDR removal on Day 14, administration of PG on Day 30, and administration of @entity1176 concurrent with FTAI on Day 33, 66  h after PG. Estrus detection aids were applied at CIDR removal on Day 14 and at PG on Day 30 to evaluate estrous response rate. Mean @entity5860 differed (P  <  0.0001) based on biological type due to higher rates of estrous cyclicity ( @entity5860 4 and 5) among @entity291 heifers (72%; 416/574) than among @entity7040 -influenced heifers (27%; 150/565). The proportion of heifers expressing estrus following CIDR removal was greater (P  =  0.01) among heifers assigned to the 14-d CIDR-PG treatment (88%; 492/559) compared to the 9-d CIDR-PG treatment (83%; 480/580). Estrous response following CIDR removal was also higher (P  <  0.0001) among @entity291 (95%; 547/574) compared to @entity7040 -influenced (75%; 425/565) heifers. Rate of estrous response prior to FTAI did not differ significantly based on treatment but was higher (P  <  0.0001) among @entity291 heifers (60%; 344/574) than among @entity7040 -influenced heifers (45%; 253/565). However, the effect of biological type on estrous response was not significant when @entity5860 was included in the model, as @entity5860 significantly (P  <  0.0001) affected the rate of estrous response both at CIDR removal and prior to FTAI. Across treatments and biological types, heifers that expressed estrus prior to AI achieved higher (P  <  0.0001) AI pregnancy rates than heifers failing to express estrus. Pregnancy rates to FTAI did not differ significantly based on treatment in either biological type. Higher rates of estrous cyclicity among @entity291 heifers resulted in higher FTAI pregnancy rates among @entity291 (51%; 290/574) compared to @entity7040 -influenced heifers (39%; 218/565). However, pregnancy rates of respective @entity5860 did not differ based on biological type. In summary, long-term CIDR-based protocols provide a simple, effective method of estrus synchronization in @entity7040 -influenced and @entity291 beef heifers. Moreover, these results highlight the importance of management practices that result in high rates of estrous cyclicity prior to protocol initiation, particularly among later maturing breeds and biological types.

Evaluation of the 14-d CIDR-PG and 9-d CIDR-PG protocols for synchronization of estrus in @entity7040 -influenced and XXXX beef heifers.

@entity1420 :: ('MESH:D011374', 'Chemical') :: ['progesterone'] @entity22667 :: ('CHEBI:15553', 'Chemical') :: ['prostaglandin F2a'] @entity5860 :: ('MESH:D060737', 'Disease') :: ['RTS', 'reproductive tract score'] @entity7040 :: ('9915', 'Species') :: ['Bos indicus'] @entity1176 :: ('MESH:D007987', 'Chemical') :: ['GnRH', 'gonadotropin-releasing hormone'] @entity291 :: ('9913', 'Species') :: ['Bos taurus']
@entity291 :: (9913,Species) :: ['Bos taurus']
