title: Induction of a new follicular wave in holstein heifers synchronized with norgestomet.
abstract: Treatments with progestin to synchronize the bovine estrous cycle in the absence of the corpus luteum, induces persistence of a dominant follicle and a reduction of fertility at doses commonly utilized. The objective of the present research was to induce a new wave of ovarian follicular development in heifers in which stage of the estrous cycle was synchronized with norgestomet. Holstein heifers (n=30) were used, in which estrus was synchronized using two doses of PGF2alpha i.m. (25 mg each) 11 days apart. Six days after estrus (day 0=day of estrus) heifers received a norgestomet implant (6 mg of norgestomet). On day 12, heifers were injected with 25 mg of PGF2alpha i.m. and assigned to treatments (T1 to T4) as follows: treatment 1, heifers received a second norgestomet implant (T1: N+N, n=6), treatment 2, received 100 microg of GnRH i.m. (T2: N+GnRH, n=6), treatment 3, 200 mg of progesterone i.m. (T3: N+P4, n=6), treatment 4, control treatment with saline solution i.m. (T4: N+SS); in the four treatments (T1 to T4) implants were removed on day 14. For treatment 5, heifers received 100 microg of GnRH i.m. on day 9 and 25 mg of PGF2alpha i.m. (T5: N+GnRH+PGF2alpha) at the time of implant removal (day 16). Ovarian evaluations using ultrasonographic techniques were performed every 48 h from days 3 to 11 and every 24 h from days 11 to 21. Blood samples were collected every 48 h to analyze for progesterone concentration. A new wave of ovarian follicular development was induced in 3/6, 6/6, 3/6, 1/6 and 6/6, and onset of estrus in 6/6, 0/6, 6/6, 6/6 and 6/6 for T1, T2, T3, T4 and T5, respectively. Heifers from T1, T3 and T4 that ovulated from a persistent follicle, showed estrus 37.5 +/- 12.10 h after implant removal and heifers that developed a new wave of ovarian follicular development showed it at 120.28 +/- 22.81 h (P<0.01). Ovulation occurred at 5.92 +/- 1.72 and 2.22 +/- 1.00 days (P<0.01), respectively. Progesterone concentration was <1 ng/ml from days 7 to 15 in T1, T2 and T4; for T3 progesterone concentration was 2.25 +/- 0.50 ng/ml on day 13 and decreased on day 15 to 0.34 +/- 0.12 ng/ml (P<0.01). For T5, progesterone concentration was 1.66 +/- 0.58 ng/ml on day 15. The more desirable results were obtained with T5, in which 100% of heifers had a new wave of ovarian follicular development induced, with onset of estrus and ovulation synchronized in a short time period.
authors.affiliation: Especialidad de Ganadería del IREGEP, Colegio de Postgraduados, KM 36.5 Carretera Mexico-Texcoco, Montecillo, Mpio de Texcoco, Edo de México CP 56230, Mexico.
authors.forename: F E O
authors.initials: FE
authors.lastname: García
authors.forename: M J L
authors.initials: MJ
authors.lastname: Cordero
authors.forename: E A
authors.initials: EA
authors.lastname: Hizarza
authors.forename: O J G
authors.initials: OJ
authors.lastname: Peralta
authors.forename: C M E
authors.initials: CM
authors.lastname: Ortega
authors.forename: M
authors.initials: M
authors.lastname: Cárdenas
authors.forename: C G
authors.initials: CG
authors.lastname: Gutierrez
authors.forename: T E M T
authors.initials: TE
authors.lastname: Sánchez
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D015237:Dinoprost / Q000008:administration & dosage; D004343:Drug Implants; D004973:Estrus Synchronization / Q000379:methods*; D005260:Female; D007273:Injections, Intramuscular; D006080:Ovarian Follicle / Q000502:physiology*; D010053:Ovary / Q000000981:diagnostic imaging; D010060:Ovulation; D011282:Pregnenediones / Q000008:administration & dosage*; D011374:Progesterone / Q000097:blood; D014463:Ultrasonography
chemical_list: D004343:Drug Implants; D011282:Pregnenediones; C100284:norgestomet; D011374:Progesterone; D015237:Dinoprost