Norgestomet implants, plasma progesterone concentrations and embryo transfer pregnancy rates in cattle.
A study was undertaken to test the hypothesis that supplementation with exogenous progestagen at the time of embryo transfer would enhance pregnancy rates in recipients. Two-hundred-and-seventy-two oestrus-synchronised crossbred heifer and cow recipients received 200 grade 1 and 72 grade 2 Simmental embryos transferred non-surgically. Heparinised blood samples were taken on day 6 and day 7 (oestrus = day 0) for the assessment of the endogenous plasma progesterone concentration. Half the recipients received an ear implant impregnated with 3 mg norgestomet on the day of embryo transfer. The pregnancy rates were 51.9 and 49.6 per cent for the norgestomet-treated and control groups, respectively. The pregnancy rate for grade 1 embryos was 56.0 per cent and for grade 2 embryos 36.1 per cent (P < 0.01). The breed of recipient, weekday of transfer, operator and condition score had no effect on pregnancy rate. The maiden heifers had a higher pregnancy rate (54.2 per cent) than the cows (46.2 per cent). The mean plasma progesterone concentrations of the pregnant and non-pregnant groups on day 6 were 6.7 ng/ml and 6.6 ng/ml, respectively, and 7.6 ng/ml in both groups on day 7.
Smith
A K
AK
Department of Animal and Feed Technology, SAC (Aberdeen).
Broadbent
P J
PJ
Dolman
D F
DF
Grimmer
S P
SP
Davies
D A
DA
Dobson
H
H
D000818:Animals; D002417:Cattle; D004343:Drug Implants; D004624:Embryo Transfer; D005260:Female; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000187:drug effects*; D011282:Pregnenediones / Q000008:administration & dosage* / Q000494:pharmacology; D011374:Progesterone / Q000097:blood*
D004343:Drug Implants; D011282:Pregnenediones; C100284:norgestomet; D011374:Progesterone