title: Effects of progestagen exposure duration on estrus synchronization and conception rates of crossbreed ewes undergoing fixed time artificial insemination.
abstract: Synchronization of estrus and ovulation are of paramount importance in modern livestock improvement programs. These methods are critical for assisted reproduction technologies, including artificial insemination and embryo transfer, that can increase productivity. In the current study, subcutaneous implants containing norgestomet were placed for long (14 days), medium (9 days), and short (5 days) periods of time in 70 crossbred ewes undergoing fixed-time artificial insemination. The resulting effects on estrus synchronization and conception rates were subsequently evaluated. Among the synchronized ewes, 85.7% (60/70) underwent estrus over a period of 72 h after progestagen treatment ceased. The shortest mean interval between withdrawal of the device and onset of estrus (34.2 ± 8.9 h) was observed in the G14 days of P4 group (p < 0.05). The conception rate of the G14 days of P4 group was statistically higher than that of the other groups (83.3% vs. 60.9% vs. 47.8%; p < 0.05). In conclusion, 14 days of norgestomet treatment produced higher conception rates and a greater number of pregnancies at the beginning of the breeding season.
authors: Laboratory of Animal Reproduction, Londrina State University, Londrina PR 86051-990, Brazil.
authors: Wanessa
authors: W
authors: Blaschi
authors: Paula A
authors: PA
authors: Lunardelli
authors: Luciana S R
authors: LS
authors: Marinho
authors: Marilu C
authors: MC
authors: Max
authors: Gustavo M G
authors: GM
authors: Santos
authors: Katia C
authors: KC
authors: Silva-Santos
authors: Fabiana A
authors: FA
authors: Melo-Sterza
authors: Hernan
authors: H
authors: Baldassarre
authors: Thales R
authors: TR
authors: Rigo
authors: Marcelo M
authors: MM
authors: Seneda
mesh_terms: D000818:Animals; D004343:Drug Implants / Q000627:therapeutic use; D004973:Estrus Synchronization / Q000187:drug effects / Q000379:methods*; D005260:Female; D005306:Fertilization / Q000187:drug effects; D007315:Insemination, Artificial / Q000379:methods / Q000662:veterinary*; D011282:Pregnenediones / Q000008:administration & dosage / Q000494:pharmacology*; D012756:Sheep
chemical_list: D004343:Drug Implants; D011282:Pregnenediones; C100284:norgestomet
keywords: estrus synchronization; norgestomet; ovine; pregnancy; progesterone