Luteal function and reproductive response in suckled beef cows after metestrus administration of a norgestomet implant and injection of estradiol valerate with various dosages of injectable norgestomet.
In an experiment replicated over 2 yr, 149 suckled beef cows were administered Syncro-Mate-B (SMB), a 6-mg Norgestomet (NOR) ear implant (in situ 9 d) in conjunction with an i.m. injection of 5 mg of estradiol valerate (EV), and either 3.0, 4.5, or 6.0 mg of NOR, 2 d after estrus. All cows were artificially inseminated at 48 h (timed insemination; TI) after implant removal (IR) and cows were reinseminated at any estrus subsequent to 24 h of TI through 30 d. Blood samples collected before treatment, every 3 d through IR, and at TI were assayed for progesterone (P4). At TI, 44, 39, and 12% of cows treated with 3.0, 4.5, or 6.0 mg of NOR, respectively, had serum concentrations of P4 greater than 1 ng/mL (3.0 and 4.5 mg vs 6.0 mg, P less than .01). Fifty-eight, 63, and 84% of cows treated with 3.0, 4.5, or 6.0 mg of NOR, respectively, exhibited a synchronized (within 5 d of IR) estrus (3.0 and 4.5 mg vs 6.0 mg, P less than .05). Pregnancy rates for the 5-d synchronized period were 38, 45, and 66% for cows treated with 3.0, 4.5, or 6.0 mg of NOR, respectively (3.0 and 4.5 mg vs 6.0 mg, P less than .05). First-service pregnancy rates were 66, 71, and 79% for cows treated with 3.0, 4.5, or 6.0 mg of NOR, respectively (P greater than .10).(ABSTRACT TRUNCATED AT 250 WORDS)
Fanning
M D
MD
Department of Animal, Dairy, and Veterinary Sciences, Clemson University, SC 29634-0361.
Spitzer
J C
JC
Burns
G L
GL
Plyler
B B
BB
D000818:Animals; D002417:Cattle / Q000502:physiology*; D003338:Corpus Luteum / Q000187:drug effects / Q000502:physiology; D004343:Drug Implants; D004958:Estradiol / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D004966:Estrogens, Conjugated (USP) / Q000008:administration & dosage / Q000494:pharmacology*; D004971:Estrus / Q000187:drug effects; D004973:Estrus Synchronization / Q000187:drug effects; D005260:Female; D005306:Fertilization / Q000187:drug effects; D007273:Injections, Intramuscular / Q000662:veterinary; D007315:Insemination, Artificial / Q000662:veterinary; D008686:Metestrus; D011282:Pregnenediones / Q000008:administration & dosage / Q000494:pharmacology*; D011374:Progesterone / Q000097:blood; D045167:Progesterone Congeners / Q000008:administration & dosage / Q000494:pharmacology*; D012098:Reproduction / Q000187:drug effects
D004343:Drug Implants; D004966:Estrogens, Conjugated (USP); D011282:Pregnenediones; D045167:Progesterone Congeners; C100284:norgestomet; D011374:Progesterone; D004958:Estradiol