Ovarian follicular development in cattle selected for twin ovulations and births12

Abstract

Comparisons of numbers of antral ovarian follicles and corpora lutea (CL), of blood hormone concentrations, and of follicular fluid steroid concentrations and IGFBP activity were conducted between cows selected (twinner) and unselected (control) for twin births to elucidate genetic differences in the regulation of ovarian follicular development. Ovarian follicular development was synchronized among cows by a single i.m. injection of PGF2alpha on d 18 of the estrous cycle; six cows per population were slaughtered at 0, 24, 48, and 72 h after PGF2alpha. Jugular vein blood was collected from each animal at PGF2alpha injection and at 24-h intervals until slaughter. Ovaries of twinner cows contained more small (< or = 5 mm in diameter, P < 0.05), medium (5.1 to 9.9 mm, P < 0.05), and large (> or = 10.0 mm, P < 0.01) follicles and more (P < 0.01) CL than ovaries of controls. Follicular fluid concentrations of estradiol, androstenedione, testosterone, and progesterone reflected the stage of follicular development and were similar for twinner and control follicles at the same stage. Earlier initiation of follicular development and/or selection of twin-dominant follicles in some twinner cows resulted in greater concentrations of estradiol in plasma at 0, 24, and 48 h and of estradiol, androstenedione, and testosterone in follicular fluid of large follicles at 0 h after PGF2alpha for twinner vs. control cows (follicular status x time x population, P < 0.01). Binding activities of IGFBP-5 and -4 were absent or reduced (P < 0.01) in follicular fluid of developing medium and large estro-gen-active (estradiol:progesterone ratio > 1) follicles but increased with atresia. Only preovulatory Graafian follicles lacked IGFBP-2 binding, suggesting a possible role for IGFBP-2 in selection of the dominant follicle. Concentrations of IGF-I were twofold greater (P < 0.01), but GH (P = 0.10) and cholesterol (P < 0.05) were less in blood of twinners. Three generations of selection of cattle for twin ovulations and births enhanced ovarian follicular development as manifested by increased numbers of follicles within a follicular wave and subsequent selection of twin dominant follicles. Because gonadotropin secretion and ovarian steroidogenesis were similar for control and twinner cattle, enhanced follicular development in twinners may result from decreased inhibition by the dominant follicle(s), increased ovarian sensitivity to gonadotropins, and/or increased intragonadal stimulation, possibly by increased IGF-I.

Relationships between progeny residual feed intake and dam productivity traits

“…Long-term selection for dizygotic twin births in this herd has increased twinning rate to an annual frequency of 50 to 55% (Echternkamp and Gregory 2002). These researchers (Echternkamp et al 2004) suggested that since IGF-I stimulates proliferation, differentiation, and steroidogenesis and inhibits apoptosis in ovarian follicular cells, more follicular cells are available with an increased frequency of ovulation and fertilization of two oocytes at approximately the same time. Australian researchers have reported positive phenotypic and genetic correlations (r p = 0.60; r g = 0.41) between IGF-I in the blood plasma of 6520 seedstock Angus beef cattle and RFI .…”

“…Cows that produced HIGH RFI progeny also had nearly double the rate of calf death loss (8.06 vs. 4.24 vs. 4.02%, P = 0.10) and a trend (P = 0.10) toward less calving difficulty, likely due to the lighter birth weight of twins. The physiological basis for this observation is uncertain, though higher blood and follicular fluid concentrations of insulinlike growth factor-I (IGF-I) have been observed in the MARC research herd selected for the production of twins (Echternkamp et al 2004). Long-term selection for dizygotic twin births in this herd has increased twinning rate to an annual frequency of 50 to 55% (Echternkamp and Gregory 2002).…”

The effect of polymorphism in gene of insulin-like growth factor-I on the serum periparturient concentration in Holstein dairy cows

“…Cows with higher plasma IGF-I at the first and third week postpartum tended to have a shorter interval to first ovulation after calving [9] . Concentration of IGF-I is two-fold greater in blood and follicular fluid of twinner cows [39] . Therefore, the regulatory system of ovarian folliculogenesis to enable: the activation and development of more preantral follicles, the maintenance of larger pools of small antral follicles, the recruitment of more follicles within the cohort of developing follicles, and the selection of two or more dominant follicles within a follicular wave [30] .…”

Oocyte development in cattle: physiological and genetic aspects

“…Compared with ovaries from unselected cattle, ovaries from the twinner population have more microscopic secondary follicles (Cushman et al, 2000) and more small (≥ 5 mm), medium (5.1 to 9.9 mm) and large (≥ 1.0 mm) surface follicles (Echternkamp et al, 2004). In twinner cattle, the heritability of ovulation rate is 0.35 and there is a high genetic correlation (0.75) between ovulation rate and twinning rate (Gregory et al, 1997); therefore, one can theoretically use routine ultrasound evaluation to select females that produce more follicles, more oocytes and more embryos in assisted reproduction programs (Figure 5;De Roover et al, 2005).…”