Factors Affecting Fertility in the Postpartum Cow: Role of the Oocyte and Follicle in Conception Rate1

Abstract

Four experiments were designed to examine the contribution of the oocyte or the follicular, oviductal, or early uterine environments to low fertility associated with the first ovulation postpartum. At 17-25 days postpartum in experiments 1, 2, and 3, suckled beef cows were assigned at random to receive 6 mg norgestomet, via ear-implant, for 9 days (NOR) or to serve as controls (CON). Calves were weaned from all cows 7 days after assignment to treatment in order to induce estrus, an LH surge, ovulation, and subsequent formation of CL. As cows were detected to be in estrus, they were bred first by natural service and 12 h later by artificial insemination. In experiment 1, on Day 3 after estrus, the oviduct ipsilateral to the side of ovulation was removed and flushed for recovery of an embryo or oocyte. Rates of recovery (86%), fertilization (68%), and development of fertilized oocytes to the 4- to 8-cell stage (100%) did not differ between CON and NOR cows. In experiment 2, uteri were flushed nonsurgically on Day 6 after estrus. Rates of recovery of embryos from the uterus were similar between CON (86%) and NOR (71%) cows. In experiment 3, one half of the cows in each group (CON and NOR) were fed melengestrol acetate (MGA) beginning on Day 4 after estrus and continuing until Day 35. The remaining cows in each group served as controls. Treatment with NOR increased (p < 0.05) the proportion of cows that maintained pregnancy until Day 35 (9/22) as compared to controls (0/18).(ABSTRACT TRUNCATED AT 250 WORDS)

Pregnancy Rates for Embryos Transferred from Early Postpartum Beef Cows into Recipients with Normal Estrous Cycles1

“…Ovulation, fertilization, and transport of embryos into the uterus have been reported not to differ between cows with short and normal luteal phases [9]. In a previous study, pregnancy was maintained beyond Day 35 in 50% of norgestomet-pretreated cows with normal luteal phases.…”

“…First postpartum ovulation in the cow is usually followed by a short luteal phase ( 14 days) and, if accompanied by estrus and mating, is associated with low fertility [1][2][3][4][5][6][7][8][9]. The short luteal phase is caused by premature secretion of prostaglandin F 2 a (PGF 2 .)…”

Enfriamiento artificial y tasa de concepción de vaquillas holstein con estrés térmico

“…Adicionalmente, las alteraciones en el desarrollo folicular durante el estrés calóri-co pueden afectar la subsiguiente función del cuerpo lúteo y la secreción de progesterona, ya sea incrementando (Gwazdauskas et al, 1981) o disminuyendo sus niveles (Rosenberg et al, 1982), lo que resulta en alteraciones en el ambiente uterino que afectan el desarrollo del embrión (Breuel et al, 1993). Wolfenson et al (1995) reportaron que vacas lecheras bajo un sistema de enfriamiento presentaron mayores niveles de estrógenos entre el día 4-8 de la primera onda folicular comparado con vacas sin el beneficio del enfriamiento, sin embargo, los niveles de progesterona a través del ciclo estrual no fueron afectados por el enfriamiento.…”

Factors affecting embryo survival and strategies to reduce embryonic mortality in cattle

“…However, replacement therapy with progestogens at doses effective in ovariectomized cows did not maintain pregnancy in cows with short luteal phases, even though ovulation, fertilization and development to Day 6 had occurred (Breuel et al 1993). In a study to determine whether the oocytes of cows with short luteal phases were defective or the uteri of such cows hostile to embryos, Butcher et al (1992) transferred good quality embryos into the uteri of cows expected to have short or normal (norgestromet pre-treated) luteal phases.…”