title: Superovulation and embryo quality in beef cows using PMSG and a monoclonal anti-PMSG.
abstract: The long half-life of pregnant mare serum gonadotrophin (PMSG) reduces its application in the superovulation of cattle; thus, a monoclonal antibody to PMSG (anti-PMSG) was administered at the onset of estrus to increase the number of transferable embryos. Angus, Hereford and Angus x Hereford cows (n = 149) 3 to 9 yr old were assigned randomly to one of three dosages of PMSG (1500, 3000 or 6000 IU) with or without an equivalent dosage of anti-PMSG. Embryos were collected nonsurgically on Day 8 (estrus = Day 0), and all cows were ovariectomized on Day 9. The percentage of cows exhibiting estrus and ovulating decreased (P<0.05) with an increasing dosage of PMSG (82, 76 and 44% for 1500, 3000 and 6000 IU, respectively). Ovarian and total corpora lutea (CL) weight increased (P<0.001) linearly as PMSG dosage increased, but were reduced (P<0.001) curvilinearly by anti-PMSG, resulting in a PMSG by anti-PMSG interaction (P<0.001); the interaction was also significant (P<0.05) for ovulation rate (14.0 vs 14.3, 21.5 vs 24.4 and 29.2 vs 6.6 CL for 1500, 3000 and 6000 IU PMSG, without vs with anti-PMSG, respectively). Anti-PMSG increased (P<0.001) the number of small ovarian follicles (1 to 3 mm diameter) and decreased (P<0.001) the number of large follicles (>10 mm) at ovariectomy; the number of large follicles increased (P<0.001) with PMSG dosage. The number of total and transferable embryos recovered did not differ among PMSG and anti-PMSG dosages; however, the percentage of transferable embryos decreased (P<0.01) with increasing PMSG dosage. In general, neither PMSG dosage nor anti-PMSG influenced embryo quality.
authors.affiliation: USDA, ARS, Roman L. Hruska US Meat Animal Research Center, P.O. Box 166, Clay Center, NE 68933, USA.
authors.forename: M M
authors.initials: MM
authors.lastname: Zeitoun
authors.forename: A M
authors.initials: AM
authors.lastname: Yassen
authors.forename: A A
authors.initials: AA
authors.lastname: Hassan
authors.forename: A Z
authors.initials: AZ
authors.lastname: Fathelbab
authors.forename: S E
authors.initials: SE
authors.lastname: Echternkamp
authors.forename: T H
authors.initials: TH
authors.lastname: Wise
authors.forename: R R
authors.initials: RR
authors.lastname: Maurer