Synchronization of Bos indicus x Bos taurus cows for timed artificial insemination using gonadotropin-releasing hormone plus prostaglandin F2alpha in combination with melengestrol acetate.
Nonlactating Bos indicus x Bos taurus cows were used in three herds to determine the efficacy of different PGF2alpha treatments in combination with GnRH and melengestrol acetate (MGA) for a timed artificial insemination protocol. The start of the experiment was designated as d 0, at which time cows were assigned a body condition score and received 100 microg of GnRH. Cows were fed MGA (0.5 x mg x cow(-1) x d(-1)) on d 1 to 7. On d 7, cows received either a single injection of PGF2alpha (Lutalyse sterile solution; 25 mg; n = 297), a single injection of cloprostenol sodium (Estrumate; 500 microg; n = 297), or half the recommended dose of PGF2alpha (12.5 mg; n = 275) on d 7 and 8. On d 10, all cows were artificially inseminated and received 100 microg of GnRH. Pregnancy rates to the timed artificial insemination (39%) were not affected by treatment, herd, or treatment x herd. There was an effect (P < 0.01) of artificial insemination sire on timed artificial insemination pregnancy rate for one herd, but not the other two herds. Herd influenced (P < 0.05) 30-d pregnancy rates, but there were no treatment or treatment x herd effects as 72.3% of the cows became pregnant during the first 30 d of the breeding season. Results indicate that the type of PGF2alpha treatment administered 7 d after GnRH did not influence timed artificial insemination pregnancy rates in nonlactating Bos indicus x Bos taurus cows.
Department of Animal Sciences, University of Florida, Gainesville, 32611, USA.
E A
EA
Hiers
C R
CR
Barthle
M K V
MK
Dahms
G E
GE
Portillo
G A
GA
Bridges
D O
DO
Rae
W W
WW
Thatcher
J V
JV
Yelich
D000818:Animals; D001824:Body Constitution; D002417:Cattle / Q000502:physiology*; D003433:Crosses, Genetic; D015237:Dinoprost / Q000494:pharmacology*; D004973:Estrus Synchronization / Q000379:methods*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D007315:Insemination, Artificial / Q000662:veterinary; D008297:Male; D008552:Melengestrol Acetate / Q000494:pharmacology*; D011247:Pregnancy; D018873:Pregnancy Rate; D045167:Progesterone Congeners / Q000494:pharmacology*; D013997:Time Factors
D045167:Progesterone Congeners; D007987:Gonadotropin-Releasing Hormone; D008552:Melengestrol Acetate; D015237:Dinoprost